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Ruby Land: The Gems and Geology of Myanmar's Mogok

Stone Tract by AMNH on 08/11/2014 03:42 pm FROM THE FIELD POSTS

Mogok, an historic city in northern Myanmar (Burma), lies in a valley 50 miles west of the snaking Irrawaddy River, about 3,500 feet above sea level. The shrub- and flower-covered hills rising above are dotted with small towns, villages, and garden plots, and adorned with well-tended Buddhist shrines. The spires of these gold-leaf-covered pagodas reach skyward, like gilded sculptures arising from rock-outcroppings along not just the area’s one major highway but also its dirt roads and walking paths.

Buddhist Myanmar is dotted with shrines and gold-leaf-covered pagodas, like these at Kyauk-

Pyat-That monastery, rising from the rocks.

Image Credit: J.Newman

Mogok is best known for its gemstones, including ruby, sapphire, spinel, peridot, and moonstone. For centuries, the Mogok Stone Tract’s hills were legendary for such amazing abundance that locals were said to come upon gems just glinting in the grass in their gardens. The area is still world-famous for gems: A sign along the highway reads “Welcome to Ruby Land,” as about 1,000 working mines and diggings are found there today; most of the world’s finest gem rubies come from Myanmar, most of these from Mogok.

These women use bamboo baskets to concentrate gems, like gold miners panning for gold,

from the outwash of a gem processing plant.

Image Credit: J. Newman

“Geologically, Mogok is an unusual place,” says Curator George Harlow, who specializes in minerals and gems. Dr. Harlow has visited the country’s mineral-rich regions three times since his first trip in 1997-8—a trip that the not-prone-to-hyperbole curator described as “a jaw-dropping experience. I don’t know anyother place on the entire planet that has such a diverse suite of minerals.” Harlow is one of the lucky few to have traveled to Myanmar over the last few decades, however. Until 2011, the country was ruled by a military junta, and travel was greatly restricted, even for researchers. Since a government transition, a series of political reforms in this Buddhist nation of about 56 million people is gradually opening its borders to scientists, businesspeople, and even more so to tourists, in some places.

In November 2013, a group of Museum geologists finally got a long-awaited opportunity: to travel to Mogok to study the complex geological evolution of “Ruby Land.” Why was it that the region was so rich in gem-quality minerals, which are, by definition, rare? Harlow was joined by Curator James Webster, who studies magma processes, and Senior Scientific Assistant Jamie Newman, on a Constantine S. Niarchos expedition supported by the Stavros Niarchos Foundation.

During the trip, mineralogist George Harlow and geologist James Webster (right) collected more

than 200 pounds of specimens, making notes at every collecting stop.

Image Credit: J.Newman

Unlike other mineral resources, gemstones do not generally form in large ore deposits. Instead, the deposits are usually small and found only in certain geologic environments. The Mogok Stone Tract is unique because it contains several very different environments, offering one clue as to why the region is so gem-rich. These sources include igneous (formed from magma) intrusions called pegmatites that can form large gem pockets inside other rocks. Magmas reacted with preexisting rock (which researchers call country rock) to form sapphire, moonstone, and certain rare gemstones. Metamorphism by heat, pressure, and passing fluid transformed limestone to marble and created Mogok rubies and spinels, a related red gem, during mountain-building as long ago as 200 million years. Weathering of all these rocks created river and cavern concentrations of gems, historically the richest deposits of all.

Sapphires in the Morgan Memorial Hall of Gems

AMNH/D.Finnin

Another explanation for the presence of certain gems in Mogok, says Dr. Webster, could be the ancient circulation of extremely hot watery fluids through Earth’s crust, which might have helped minerals dissolve and re-form in veins or at contacts between

different types of rock. “It’s really about hot water,” says Webster. “At one time, it must have dissolved certain things out of the rock—changing minerals to other minerals.” One hypothesis is that a portion of the Mogok deposits of the mineral corundum—a very hard mineral, second only to diamond, known to us in its red form as ruby and in many other colors as sapphire—formed in this way about 15 to 25 million years ago. Read more about the expedition here. This story is adapted from an article in the Summer 2014 issue of Rotunda, the Member magazine. Tags: From the Field, Geology http://www.amnh.org/explore/news-blogs/from-the-field-posts/ruby-land-a-museum-expedition-to-mogok

Ruby Land: A Museum Expedition to Mogok by AMNH on 08/14/2014 04:30 pm FROM THE FIELD POSTS

In November 2013 a group of Museum scientists including Curators James Webster and George Harlow and Senior Scientific Assistant Jamie Newman traveled to Mogok, a historic city in northern Myanmar (Burma), to study the region's complex geological evolution on a Constantine S. Niarchos Expedition supported by the Stavros Niarchos Foundation. Read the first part of this story here. In Myanmar, Museum scientists worked with Dr. Kyaw Thu, a Burmese geologist, mineralogist, and gem dealer who helped arrange visits to 19 mines over 9 days in Mogok. Traveling by jeep or by foot from their home base at the Golden Butterfly Hotel, the geologists concentrated on collecting—not rubies, since these cannot be imported from Myanmar to the United States due to an embargo, but other gems and rocks to be analyzed back at the Museum.

Museum Curators George Harlow (left) and James Webster (right) with Dr. Kyaw Thu (center)

overlook the gem-rich Mogok Valley.

Image Credit: J. Newman

Most of the mines in the region are large, employing hundreds of workers and using mechanized earth-moving equipment and high-pressure hoses to blast apart the sediments from open pits. Others are more basic, but at each spot the rocks researchers collected around the mines were clues—sometimes heavy ones—to the larger context of the geology that created the gems. One day, for instance, they visited the Pandaw pegmatite mine. Setting off from the hotel, the team walked downhill for an hour or so on a path used for walking or, for intrepid miners, motorcycles, with birds calling in the distance through the foliage. At the bottom of the hill they finally came to a small mine, a pegmatite pocket—barely big enough for a person to wiggle into—that was mostly hand-dug.

Most of the 1,000 working mines in Mogok are industrial, but some are accessible only by remote

paths.

Image Credit: J.Newman

Accompanied by miners, Harlow and Webster crawled into the mine and collected rock samples. To add to their yield, the mine owner offered them a variety of mineral and rock samples as well. Then, with full rucksacks weighing perhaps 50 pounds, the researchers slowly walked back up the track to reach their vehicle, a trek that took more than an hour. “For some reason,” says Webster, dryly, “the mines always seemed to be at the bottom of the hill.” Geologists are used to hauling their specimens: they collect rocks on expeditions all the time. But being allowed to do so in Mogok, Myanmar, remains for Westerners a special privilege. By the end of their three-week trip, the Museum team had collected 121 kilograms (266 pounds) of rocks for studying the context of this mineral-rich area. Using X-ray diffraction, scanning electron microscopy, mass spectrometry, and other techniques back in New York, the team hopes to be able to tease out answers to Mogok’s mineralogy.

Harlow, Webster, and colleagues investigate the geology of Mogok.

Image Credit: J. Newman

For instance, Harlow is working to understand how the mineral peridot—the gem form of forsterite, the common form of the mineral olivine—formed in Mogok, and whether these exquisite green gems were formed via similar processes to other known peridot deposits. Perhaps the most important part of the trip happened not in the field, however, but in Myanmar’s universities and geological societies. There, the Museum team met and exchanged ideas with Burmese researchers who have been limited in their international collaborations and hampered in their access to modern scientific equipment. During their visit, the team met local scientists and gave presentations in Yangon and at the geology department of the University of Mandalay.

“Helping our colleagues in Myanmar and developing collaborations should be beneificial to them, the Museum, and Myanmar as well,” says Harlow. He and Webster hope that young scientists from Myanmar will be able to travel to the Museum in the not-too-distant future to train with researchers in the Department of Earth and Planetary Sciences, and that Museum postdocs will have opportunities to travel to Myanmar for field work—in Ruby Land and beyond. This Constantine S. Niarchos Expedition was generously supported by the Stavros Niarchos Foundation. This story is adapted from an article in the Summer 2014 issue of Rotunda, the Member magazine. Tags: From the Field, Geology

http://www.lotusgemology.com/index.php/library/articles/159-rock-talk-a-mogok-geology-primer

Mogok Geology Primer • Rock Talk • Lotus Gemology

by Wilawan Atichat & Richard W. Hughes

A look at the geology of Myanmar's Mogok Stone Tract, home to pigeon's blood

rubies and so much more…

The Mogok Stone Tract is situated in Myanmar’s Mandalay province, some 200

km northeast of Mandalay. Home to the world’s premier ruby mines, it is also one

of the richest mineral concentrations on Earth. Aside from ruby, Mogok produces

a potpourri of gems, including sapphire, spinel, peridot, topaz and moonstone, to

name but a few. One of Mogok’s gems, painite, is found nowhere else on the

planet. With over fifty different gem species mined at Mogok, in terms of

gemological diversity, perhaps only Sri Lanka can compare.

Bend me, stretch me…

During certain periods in the Earth’s history, tectonic activity produced large-

scale deformation of the surface. This stress resulted in fantastic zones of

mineral formation, where mundane minerals mutated into artistic wonders of

singular beauty. Geologists call this rock recycling process “metamorphism” and

the resulting bow-shaped regions “orogenic” belts. Most of the world’s greatest

ruby and sapphire mines fall into one of two such zones.

The Pan-African orogeny (Figure 1) occurred 750–450 million years ago, and

gave rise to deposits in Kenya, Tanzania, Mozambique, Madagascar, Sri Lanka

and southern India. Many of these corundums are genetically related.

Figure 1. The former supercontinent, Gondwana, showing the proximity of the important ruby and

sapphire deposits of East Africa, Madagascar, Sri Lanka and southern India some 750–500 million

years ago. From Hughes et al., 2014.

In contrast, the Himalayan orogeny took place just 45–5 million years ago, a

result of the Indian subcontinent speeding north from Gondwana and colliding

with the Asian plate (Figure 2). In geologic terms, this was a continental train

wreck as India dove some 2000 km under and into Central Asia. This resulted in

not just the greatest mountains on the planet, but furious mineral-forming activity,

including a string of ruby and sapphire deposits that stretch all the way from

Afghanistan and Tajikistan in Central Asia, through Pakistan, northern India,

Nepal and Myanmar, to China and Vietnam in the East. Together with the Pan-

African orogeny, these two events are responsible for virtually all of the finest

rubies and sapphires thus far discovered on Planet Earth.

Figure 2. South and Central Asia, showing the major faults associated with the collision between the

Indian subcontinent and the Eurasian mainland. One of the results was the formation of ruby, as

limestone metamorphosed into marble, creating the world’s premier ruby deposits. From West to

East: Jegdalek (Afghanistan), Kukurt (Tajikistan), Hunza and Nangimali (Pakistan), Chumar (Nepal),

Mogok and Mong Hsu (Burma), Yuanjiang (China) and Luc Yen (Vietnam). The Himalayan orogeny

took place during the period between 45–5 million years ago, making these rubies more than ten

times younger than their Mozambique belt cousins. From Hughes et al., 2014.

While marble-hosted ruby deposits have been studied in some detail elsewhere

(Garnier et al., 2008), political instability has left Myanmar’s mines as somewhat

of an enigma.

All across the Himalayan belt, ruby is found in marble. According to Harlow and

Bender (2013):

The present model for the formation of rubies hosted in marble from the

Himalayan arc is a closed-system metamorphism of former clays from

evaporitic/organic-rich shale units in margin basins. Mogok has still not

been fully included in this model. Involvement of igneous intrusions and the

formation of skarn with the marble has been an outstanding topic.

In plain English, an ocean (the Tethys Sea) once separated the Indian

subcontinent from Asia. Oceans are typically filled with sea creatures whose

skeletons are rich in calcium and carbon. As fish and coral die, those bones end

up in sediments on the sea’s floor, eventually forming a sedimentary rock we call

limestone.

When the Indian subcontinent slammed into Asia, this former seafloor was raised

up, in places so high that bits of it can be found even on the summit of Mount

Everest. Extreme pressures from this collision caused recrystallization of the

limestone into a metamorphic rock called marble.

So now we understand how the marble formed, but where did the ruby come

from? Ruby consists of aluminum (Al) joined to oxygen (Al2O3), with a dash of

chromium (Cr3+). Neither aluminum nor chromium is normally present in

limestone. It is thought that these elements entered the marble system when

clays metamorphosed into shale at margin basins. This alteration of an otherwise

pure rock by hydrothermal solutions is termed “metasomatism” and is thought to

be the mechanism by which aluminum and chromium (and vanadium) entered

the marble (Figure 3).

Marbles come in two flavors. Some are simply made of calcite – CaCO3, while

others are composed of dolomite – CaMg(CO3)2. When Al and Cr join together

with magnesium (Mg), the result is spinel. Only when the Mg is exhausted does

ruby grow. This explains why far more red spinels than rubies are found at

Mogok.

Figure 3. Ruby miners preparing to set an explosive charge in the marble at Sagyin, just north of

Mandalay. Note the clay band cutting through the marble. Hydrothermal fluids from this clay are

thought to have supplied the aluminum and chromium necessary for the growth of ruby and spinel in

marble. Photo: E. Billie Hughes

Figure 4. Ruby is not the only gem found in marble at Mogok. Spectacular red spinels are even more

common. Some of these octahedral crystals are so perfect that they are termed nat-twe (angel

polished). The photo shows a completely natural spinel crystal mounted in a ring, along with a

natural spinel octahedron in the marble mother rock. Specimens courtesy of Dr. Saw Naung U

family; Photo: Wimon Manorotkul

Skarn

But what’s the skarn mentioned above? In the current sense, skarn refers to a

rock formed by metasomatism, where an igneous rock (such as a granite) comes

in contact with a carbonate (such as a marble). And herein lies the uncertainty.

The accepted geologic model for formation of ruby in marble cannot explain

certain ruby specimens that have been found in the Mogok area that show

evidence of having formed in a skarn. Thus much more work remains to be done

before the occurrence of ruby at Mogok is fully understood.

Karst topography

One of the first things a visitor notices upon entering the Mogok region is the

presence of eerie black rock pinnacles rising from the surrounding valleys and

hills. That black rock is weathered marble and the weathering process in the area

has produced something geologists call a “karst topography.” China’s Guilin

region is perhaps the most famous example of this. It is produced by mildly acidic

water dissolving the weakly soluble limestone/marble.

Breaking open one of those black rocks at Mogok will reveal a bright white

marble within (and if the gods are smiling, a ruby or spinel). Mogok’s marble is

extremely coarse-grained, meaning the individual calcite and dolomite crystals

within the rock body are quite large, testimony to an exceedingly slow

crystallization process. When a crystal grows slowly, it grows larger and with

greater perfection, one of the clues as to why we find so many fine gems in the

Mogok area.

Among the benefits of the processes that produce karst topography is that those

same acidic waters also free the gems in the marble. Mogok is riddled with caves

and narrow underground passages as millions of years of weathering have eaten

away the weak places in the marble. Those gems settle in the cave bottoms; the

Burmese term these places lu-dwin, and they are home to some of the richest

concentrations of ruby and spinel.

Figure 5. The karst topography of the Mogok area is on display at Kyauk-Pyat-That, where a temple

sits atop weathered marble like a fairyland castle. Photo: R.W. Hughes

Geologic Jigsaw Puzzle

Geologically, the Mogok Stone Tract lies in what geologists call the Mogok

metamorphic belt, a 40 km-wide swath stretching from Moulmein in the south to

Putao, some 1450 km to the north. This belt contains a variety of andalusite and

sillimanite-bearing metamorphic rocks, pre-collisional granites and granodiorites,

and post-collision garnet + tourmaline-bearing leucogranites (Searleet al., 2007).

Figure 6. Map of Myanmar showing the location of Mogok and the Mogok Belt. Map: Richard W.

Hughes

Via phlogopite inclusions, the Mogok marble emplacement has been dated at

approximately 18.7 million years (Garnier et al., 2006). In the Mogok area there

are also schist and quartz veins cutting across the marble units.

Another important rock type is the so-called Mogok gneiss, which is composed

mainly of sillimanite-garnet gneiss, in which is found patches of calc-silicate rock.

Ultramafic rocks found in Mogok include dunite and harzburgite, both featuring

chromite. Pegmatite veins and graphic granite dykes cut into these ultramafic

rocks (Mitchell et al., 2007).

Intrusive igneous rocks in Mogok are predominantly nepheline syenite. Dating

granite in the Mogok area by 40Ar/39Ar in biotite gave an emplacement age of 15.8

million years. Dating metamorphic rock using biotite revealed the age of 19.5–

16.5 million years. The U-Pb dating using inclusions of zircon in ruby revealed

the age to be 32–31 million years old (cited in Yui et al., 2008).

Exploration and petrogenesis studies suggest that corundum deposits in this

area involve high-grade metamorphism at temperatures of about 600–650° C,

with pressures of approximately 4.5 kbar (Barley et al., 2003).

Correlation studies between the metamorphic and igneous rocks reveal that

there were two metamorphic processes, namely Early Jurassic regional

metamorphism and Early Tertiary metamorphism. These high-grade

metamorphic processes likely occurred during the collision of Indian and

Eurasian plates at 65–55 million year ago. This was later followed by igneous

intrusions (primarily syenite and leucogranite) during the period of 35–23 million

years ago (Maung Thein, 1973; Barley et al., 2003).

Both primary and secondary deposits are mined in the Mogok area. Ruby and

sapphire in such primary deposits are mainly hosted in white marble intercalated

with other metasediments of the Mogok metamorphic belt. The corundum-

bearing marbles are always in contact with either mica-rich granite gneiss or

calc-silicate rocks.

In Mogok, certain localities produce only ruby or only sapphire, but others host

both ruby and sapphire. One example of the latter is Baw Mar, where mine owner

Tint Lwin told us that both ruby and sapphire are found. During our explorations

at Baw Mar in July 2013, we found no evidence of the existence of both ruby and

sapphire within the same marble bed. Hence, it is clear that detailed research

work is required to unravel this mystery (GIT, 2013a, b).

By now it should be clear that the geology of the Mogok area is extremely

complex, with formation processes including metamorphism, igneous intrusion

and skarn reactions. Such processes have produced ruby-bearing marbles,

sapphire-bearing pegmatites, nepheline syenites, and a host of other rocks. It’s

almost as if Mother Nature took all of her leftovers and dumped them into this

remote region of Myanmar. The result is a spectacular gem assemblage, unique

on Planet Earth.

References

Barley, M.E., Pickard, A.L. et al. (2003) Jurassic to Miocene magmatism and

metamorphism in the Mogok metamorphic belt and the India-Eurasia collision

in Myanmar. Tectonics, Vol. 22, No. 3, pp. 4-1–4-11.

Garnier, V., Maluski, H. et al. (2006) Ar–Ar and U–Pb ages of marble-hosted

ruby deposits from central and southeast Asia.Canadian Journal of Earth

Sciences, Vol. 43, No. 4, pp. 509–532.

Garnier, V., Giuliani, G. et al. (2008) Marble-hosted ruby deposits from

Central and Southeast Asia: Towards a new genetic model.Ore Geology

Reviews, Vol. 34, No. 1–2, pp. 169–191.

GIT (2013a) GIT Exploring Ruby and Sapphire Deposits of the Mogok Stone

Tract, Myanmar. Bangkok, Gem and Jewelry Institute of Thailand (Public

Organization), git.or.th, 6 pp.

GIT (2013b) The Study Project on Potential and Accessibility to Sources of

Raw Gem Materials in ASEAN Countries (Cambodia, Laos, Myanmar,

Vietnam) (In Thai), Bangkok, Gem and Jewelry Institute of Thailand (Public

Organization), 176 pp.

Harlow, G.E. and Bender, W. (2013) A study of ruby (corundum) compositions

from the Mogok Belt, Myanmar: Searching for chemical fingerprints. American

Mineralogist, Vol. 98, pp. 1120–1132.

Hughes, R.W., Manorotkul, W. et al. (2014) Ruby & Sapphire: A Collector's

Guide. Bangkok, Gem and Jewelry Institute of Thailand, 384 pp.

Maung Thein (1973) A preliminary synthesis of the geological evolution of

Burma with reference to the tectonic development of Southeast

Asia. Geological Society of Malaysia Bulletin, Vol. 6, pp. 87–116.

Mitchell, A.H.G., Htay, M.T. et al. (2007) Rock relationships in the Mogok

metamorphic belt, Tatkon to Mandalay, central Myanmar.Journal of Asian

Earth Sciences, Vol. 29, No. 5–6, pp. 891–910.

Searle, M.P., Noble, S.R. et al. (2007) Tectonic evolution of the Mogok

metamorphic belt, Burma (Myanmar) constrained by U-Th-Pb dating of

metamorphic and magmatic rocks. Tectonics, Vol. 26, TC3014, 24 pp.

Yui, T.-F., Zaw, K. et al. (2008) A preliminary stable isotope study on Mogok

ruby, Myanmar. Ore Geology Reviews, Vol. 34, No. 1–2, pp. 192–199.

Acknowledgments

The authors would like to thank the following individuals for their assistance:

Hpone-Phyo Kan-Nyunt of Gübelin Gem Lab for helping to organize our latest

visit to Mogok in July 2013; Dr. Ei Ei, who helped guide us in Mogok; Saw Sanda

Soe, who shared her stories of growing up in Mogok; Ko Ye Aung Myo, Ko Than

Htwe, U Thein Htay, U Win Maung, all of Mogok. Finally, a special thank you to

GIT for financial support.

About the authors

Wilawan Atichat is the former director of the Gem and Jewelry Institute of

Thailand. She currently works as an advisor for the GIT Gem Testing Laboratory.

Richard W. Hughes is the author of the classic Ruby & Sapphire and over 170

articles on various aspects of gemology. Many of his writings can be found

at www.lotusgemology.com and www.ruby-sapphire.com. His latest book is Ruby

& Sapphire: A Collector's Guide (2014).

Notes

First published in InColor magazine, Fall/Winter 2013, pp. 46–50.

http://www.minelinks.com/alluvial/ruby2.html

PRECIOUS STONES

RUBY

RUBY AS A GEM

The facets of a cut ruby are ground on a rotating iron disc precisely as in the diamond.

The use of diamond-powder as a grinding material is now very general in Europe since it considerably expedites the process. That of polishing follows the operation of

grinding, which is effected on a copper disc charged with tripolite moistened with water.

The forms of cutting adopted for the ruby are those generally used for the diamond.

The brilliant form is frequently chosen, since this displays the beauties of the stone to the best possible advantage. In order to increase the transparency of the ruby,

however, the brilliant is cut thinner and flatter than is allowable in the case of the

diamond. Owing to the strong refraction of the ruby, the rays of light which enter the stone by its front facets are totally reflected by the back facets and pass out by the

front of the stone, the fine red color of the ruby having been imparted to them during

their passage through it. It is this coloring of the rays of light, together with the brilliant

luster of the stone, which gives the ruby its effectiveness. Owing to the small dispersion of corundum, the magnificent play of prismatic colors characteristic of the diamond is

almost absent in the ruby. This being so, the step-cut or trap-cut form of cutting is just

as effective as the brilliant for the ruby, or indeed for any colored stone which shows no play of prismatic colors. The mixed-cut, of which the upper portion consists of brilliant

facets and the lower those of the step-cut, is also an effective form. Table-stones,

point-stones, and similar forms are scarcely ever cut now; the few examples met with are the work of former times. Flat and thin rubies are usually cut as roses (rosettes),

since this form involves little loss of material and, at the same time, produces a good

effect. Very small stones are irregularly faceted; they are used to form a contrasting

border round some larger precious stone.

In Burma, the chief home of the ruby, the stones are cut en cabochon, that is to say

with a rounded surface, before they come on the market. When this form of cutting

does not display the beauties of a stone to the best advantage it is recut in Europe. It is obviously to the purchaser's advantage to buy a ruby cut en cabochon rather than an

uncut stone, since in the former case it will be possible to detect any faults in the

interior. With the exception of the asterias or star-rubies, this gem is seldom in Europe cut en cabochon; in the exceptional case mentioned, the rounded form of cutting is

obviously the most suitable for displaying the six-rayed chatoyant star for which the

stone is peculiar.

Clear and transparent stones of a full deep color are usually mounted in open settings

(a jour); those of poorer quality are often backed by a foil of gold or copper or red glass, which materially improves their appearance. In Burma it is customary, instead of

setting such a stone on a foil, to hollow out the underside and fill it in with gold.

Besides being faceted and cut en cabochon, rubies are sometimes engraved with

inscriptions or figures, this being most frequently done in the East. Such antique gems

of ruby engraved with the head of Jupiter Serapis and a figure of Minerva are known.

Map of occurrence of ruby and sapphire in Burma and Siam.

(Scale, 1:15,000,000.)

OCCURRENCE

While the poorer qualities of ruby are widely distributed, clear, transparent material suitable for cutting is found in but few countries, of which Burma, Siam, and Ceylon are

alone of commercial importance at the present time.

Now, just as in former times, Upper Burma furnishes us not only with the finest but also

with the largest supply of rubies. The distribution of precious stones (ruby, red tourmaline, jadeite, and amber) in this country is shown on the map above. The ruby

mines of Upper Burma were worked at least as early as the fifteenth century and have

ever since supplied the greater part of the material used in jewelry, including the finest

stones known. The majority of the rubies, which are now put on the market, come from Burma. It is probable; however, that part of this supply is the gradually accumulated

stock of former times, and that the yield of the mines is now smaller than formerly.

The Burmese ruby mines were mentioned long ago by Tavernier. According to his

account, which, however, was not based on personal observation but en second-hand information, they were situated in the "Capelan Mountains", in Pegu, twelve days

journey in a north-east direction from the town of Syriam, now a small village close to

Rangoon. The yield at that time (second half of the seventeenth century) was apparently not very great, and was estimated at 100,000 ecus ($2,445,000) per annum

by Tavernier, who adds that he found the importation of rubies from Europe into India a

lucrative business.

Tavernier's error in describing the locality of the ruby mines has been repeated again and again, and is even now current in the text-books of the present day. There is not

the least doubt that the mines referred to are those which are still being worked in

Upper Burma, and which are very much further removed from Syriam than Tavernier stated them to be. The distance from here to Mandalay is at least thirty-six days

journey, and from Mandalay to the principal ruby district of Mogok is another eight days

journey, the less important district of the Sagyin Hills lying, however, a little nearer. For a long time the exact location of these mines was a secret jealously guarded by the

Burmese. Since the annexation of the country in 1886 by Britain, more detailed

information has been obtainable, and a part of the workings has been taken over by

Europeans. The district was officially visited and reported upon in 1888 by Mr. C. Barrington Brown. The rocks and minerals collected there were examined by Professor

J. W. Judd, the result of their joint examination being published in 1896 in the

Philosophical Transactions of the Royal Society of London.

The district of Mogok is the most important "ruby tract", or "stone tract", and embraces an area of forty-five square miles, or, if some abandoned mines are included, sixty six

square miles. The ruby-bearing area is, in all probability, much greater than this,

extending to the south and east into the independent Shan States, and has been estimated by Lockhart, who for two years was resident engineer to the Burma Ruby

Mining Company, at 400 square miles. This opinion is supported by the recent discovery

of an old ruby mine in the river gravels of the Nampai valley, near Namseka village, in the Mainglon State. The district, which is mountainous, and scored by deep valleys, lies

to the east of the Irrawaddy, from which it is separated by a plain thirty miles in width,

in which a few unimportant ruby mines are worked by the natives.

This district has formed a part of the kingdom of Burma since 1637; its chief town and center of the trade in precious stones is Mogok, latitude 22° 55' N., longitude 96° 30' E.

of Greenwich, thirty-four miles in a straight line (but fifty-eight by road) from the river,

and ninety miles north-north-east of Mandalay. A little below Mandalay is Ava, formerly known as Ratanapura (city of gems), the old capital of Burma, round which the trade in

precious stones of the whole country centers. Mogok stands at an elevation of 4,100

feet above sea level, while the highest point of the district has an elevation of 7,775 feet. In spite of this the country is covered with thick forests, and is unhealthy both for

Europeans and natives. The principal mines are situated in the valleys in which stand

the towns of Kathay and Kyatpyen (Kapyun). The mountains surrounding the latter

town have been conclusively proved by Prinsep to be identical with the "Capelan

Mountains" of Tavernier.

The mother-rock of the ruby and of the minerals, such as spinel, with which it is

associated, is a white, dolomitic, granular limestone or marble, which forms whole

mountain ranges in this district, and which, according to the investigations of Dr. F. Noetling, of the Indian Geological Survey, is of Upper Carboniferous age. These rocks

were originally compact limestones of the ordinary kind, which have been altered by

contact with intrusive masses of molten igneous rock; this caused the calcium carbonate to re-crystallize out as pure calcite, while the impurities contained in the

original limestone crystallized out separately as ruby and its associated minerals.

Geologists know the alteration of rocks by contact with a mass of molten igneous material as contact-metamorphism; the results of the process are frequently to be

observed in all parts of the world, but, although corundum is often to be found in such

altered rocks, fine ruby of gem-quality is only rarely met with. Such were the conclusions as to the geology of the district and the mode of origin of the ruby arrived

at by Professor Max Bauer, from information and specimens supplied to him by Dr. F.

Noetling, and published in a scientific journal in 1896. The point of view adopted by Mr. C. Barrington Brown and Professor J. W. Judd must not, however, be passed over

without notice.

These authors describe the white crystalline limestone, which alone contains the ruby

and spinel, as occurring in thick bands interfoliated with gneisses. These gneisses are

usually of intermediate chemical composition; but sometimes of more acid, and at other times of more basic character; the crystalline limestones are more intimately associated

with the basic gneisses (pyroxene-gneisses and pyroxene-granulites, with pyroxenites

and amphibolites). These contain crystals of calcite, and as the proportion of calcite present increases, they merge gradually in the limestones. It is concluded, on these

grounds, that the limestones have been derived by the alteration of the lime-feldspar in

these basic rocks. This feldspar (anorthite), being a silicate of calcium and aluminum, would, on alteration, give rise to calcium carbonate and hydrated aluminum silicates,

the former being deposited as calcite, and the latter as silica (opal), and various

aluminum hydroxides (diaspore, gibbsite, bauxite, etc.). Under other conditions of temperature and pressure these may have been afterwards converted into crystallized

anhydrous alumina, that is ruby.

In the masses of crystallized limestone occurring in situ precious stones are only

sparingly present, being found in much greater abundance in the clayey and sandy weathered products of the mother-rock, which lie on the sides of the hills, fill up the

bottom of the valleys, and are often overlain by similar detrital material containing no

precious stones. This secondary gem-bearing bed consists of brown or yellow, more or less firm, clayey, and at times sandy, material, known to the Burmese as "byon", which

may be regarded as the residue after the solution of the limestones by weathering

processes. It contains beside ruby, sapphire, and other color-varieties of corundum, spinel (Tavernier's "mother of ruby"), tourmaline, large fragments of quartz, grains of

variously colored feldspars, nodules of weathered iron-pyrites, and other minerals of

more or less value, together with fragments of the rocks which occur in situ in the

neighborhood. Sometimes in the river alluvium, instead of clayey and sandy material,

there are pure gem-sands consisting mainly of minute sparkling grains of ruby.

The gem-bearing layer lies on a soft decomposed rock of characteristic appearance.

When the natives reach this level in their excavations they know that the "byon"

extends no further down, and that work at that spot must be abandoned. The "byon" lies about 15 to 20 feet below the surface of the floor of the valleys, and is from 4 to 5

feet in thickness, though occasionally it may thin off to a few inches. On the sides of the

hills the bed of "byan" may be 15 to 20 feet thick, and sometimes as much as 50 feet.

https://en.wikipedia.org/wiki/Mogok

Mogok (Burmese: မ ိုုးကုတ်, pronounced: [móɡoʊʔ]; Shan: မ ိူငိ်ုးၵတု််ႈ) is a city in the Pyin Oo Lwin District of

the Mandalay Region ofMyanmar, located 200 km north of Mandalay and 148 km north-east

of Shwebo. Mogok was in Shan State and after British, the town was put in Mandalay Region along

with Pyin Oo Lwin.

Geography

At 1170 meters in elevation, the city has a fairly temperate climate year-round, and is home to

mostly Bamar, with large minorities ofShan, Lisu, Palaung, and Karen ethnic groups, as well

as Chinese, Indians and Gurkhas. The city is composed of two towns, Mogok and Kyat Pyin. Mogok

is four miles long and two miles wide. It is situated in a valley surrounded by a large number of

mountains. Kyat Pyin lies about 12 miles from Mogok. Tourist travel to the area is not permitted.

Repute for gemstones

Mogok and other villages nearby have been famous since ancient times for its gemstones,

especially ruby and sapphire, but semi-precious stones such as lapis

lazuli, garnet, moonstone, peridot and chrysoberyl are also found. The gems are found

in alluvial marble gravels by means of panning, tunneling and digging pits by hand. There is little

mechanization of the mining. The gravels derive from the metamorphosed limestones (marbles) of

the Mogok metamorphic belt

Gems are sold in markets in Mogok; however, foreigners require special permits to visit the town,

and purchase/export of gems from Myanmar at non-government licensed dealers is illegal.

90% of the world's rubies come from Myanmar. The red stones from there are prized for their purity

and hue. Thailand buys the majority of Myanmar's gems. The "Valley of Rubies", the mountainous

Mogok area, 200 km (120 mi) north of Mandalay, is noted as the original source of ruby including the

world's finest "pigeon's blood" rubies as well as the most world's most beautiful sapphires in "royal"

blue.

Notes

1. Jump up^ "Pyin Oo Lwin / Mogoke Map" Myanmar Information Management Unit (MIMU)

2. Jump

up^ http://www.myanmartourism.org/index.php?option=com_content&view=article&id=351&

Itemid=289

3. Jump up^ Searle, D. L.; Ba Than Haq (1964) "The Mogok belt of Burma and its relationship

to the Himalayan orogeny" Proceedings of the 22nd International Geological Conference,

Delhi 11: pp. 132–161

4. Jump up^ Iyer, Lakshinarayanpuran Anantkrishna Narayana (1953) The geology and gem-stones of the Mogok Stone Tract, BurmaGeological Survey of India Memoir 82, Government of India Press, Calcutta, OCLC 6526679 ; reprinted in 2007 by White Lotus, Bangkok, ISBN 978-974-480-123-4

https://en.wikipedia.org/wiki/Ruby

Ruby A ruby is a pink to blood-red colored gemstone, a variety of the mineral corundum (aluminium

oxide). The red color is caused mainly by the presence of the element chromium. Its name comes

from ruber, Latin for red. Other varieties of gem-quality corundum are called sapphires. Ruby is

considered one of the four precious stones, together with sapphire, emerald and diamond.[3]

Prices of rubies are primarily determined by color. The brightest and most valuable "red" called

blood-red or "pigeon blood", commands a large premium over other rubies of similar quality. After

color follows clarity: similar to diamonds, a clear stone will command a premium, but a ruby without

any needle-like rutile inclusions may indicate that the stone has been treated. Cut and carat (weight)

are also an important factor in determining the price. Ruby is the traditional birthstone for July and is

usually more pink than garnet, although some rhodolitegarnets have a similar pinkish hue to most

rubies. The world's most expensive ruby is the Sunrise Ruby.

Physical properties

Crystal structure of rubies

Rubies have a hardness of 9.0 on the Mohs scale of mineral hardness. Among the natural gems

onlymoissanite and diamond are harder, with diamond having a Mohs hardness of 10.0 and

moissanite falling somewhere in between corundum (ruby) and diamond in hardness. Sapphire,

ruby, and pure corundum are α-alumina, the most stable form of Al2O3, in which 3 electrons leave

each aluminum ion to join the regular octahedral group of six nearby O2− ions; in pure corundum this

leaves all of the aluminum ions with a very stable configuration of no unpaired electrons or unfilled

energy levels, and the crystal is perfectly colorless.

When a chromium atom replaces an occasional aluminum atom, it too loses 3 electrons to become a

chromium3+ ion to maintain the charge balance of the Al2O3 crystal. However the Cr3+ ions are larger

and have electron orbitals in different directions than aluminum. The octahedral arrangement of the

O2− ions is distorted, and the energy levels of the different orbitals of those Cr3+ ions are slightly

altered because of the directions to the O2− ions.[4] Those energy differences correspond to

absorption in the ultraviolet, violet, and yellow-green regions of the spectrum.

Transmittance of ruby in optical and near-IR spectra. Note the two broad violet and yellow-green

absorption bands and one narrow absorption band at the wavelength of 694 nm, which is the

wavelength of the ruby laser.

If one percent of the aluminum ions are replaced by chromium in ruby, the yellow-green absorption

results in a red color for the gem. Additionally, absorption at any of the above wavelengths

stimulates fluorescent emission of 694-nanometer-wavelength red light, which adds to its red color

and perceived luster.

After absorbing short-wavelength light, there is an interval of time when the crystal lattice of ruby is

in an excited state before fluorescence is actually emitted. If 694-nanometer photons pass through

the crystal during that time, they can stimulate more fluorescence photons to be emitted in-phase

with them, thus strengthening the intensity of that red light. By arranging mirrors or other means to

pass emitted light repeatedly through the crystal, a ruby laser in this way produces a very high

intensity of coherent red light.

All natural rubies have imperfections in them, including color impurities and inclusions

of rutile needles known as "silk". Gemologists use these needle inclusions found in natural rubies to

distinguish them from synthetics, simulants, or substitutes. Usually the rough stone is heated before

cutting. Almost all rubies today are treated in some form, with heat treatment being the most

common practice. However, rubies that are completely untreated but still of excellent quality

command a large premium.

Some rubies show a three-point or six-point asterism or "star". These rubies are cut

into cabochons to display the effect properly. Asterisms are best visible with a single-light source,

and move across the stone as the light moves or the stone is rotated. Such effects occur when light

is reflected off the "silk" (the structurally oriented rutile needle inclusions) in a certain way. This is

one example where inclusions increase the value of a gemstone. Furthermore, rubies can show

color changes—though this occurs very rarely—as well as chatoyancy or the "cat's eye" effect.

Ruby vs. pink sapphire

Generally, gemstone-quality corundum in all shades of red, including pink, are called

rubies.[5][6] However, in the United States, a minimum color saturation must be met to be called a

ruby, otherwise the stone will be called a pink sapphire.[5] This distinction between rubies and pink

sapphires is relatively new, having arisen sometime in the 20th century. If a distinction is made, the

line separating a ruby from a pink sapphire is not clear and highly debated.[7] As a result of the

difficulty and subjectiveness of such distinctions, trade organizations such as the International

Colored Gemstone Association (ICGA) have adopted the broader definition for ruby which

encompasses its lighter shades, including pink.

Natural occurrence

The Mogok Valley in Upper Myanmar (Burma) was for centuries the world's main source for rubies.

That region has produced some of the finest rubies ever mined, but in recent years very few good

rubies have been found there. The very best color in Myanmar rubies is sometimes described as

"pigeon's blood." In central Myanmar, the area of Mong Hsu began producing rubies during the

1990s and rapidly became the world's main ruby mining area. The most recently found ruby deposit

in Myanmar is in Namya (Namyazeik) located in the northern state of Kachin.

Rubies have historically been mined in Thailand, the Pailin and Samlout

District of Cambodia, Burma, India, Afghanistan, Australia, Namibia, Colombia,Japan, Scotland, Bra

zil and in Pakistan. In Sri Lanka, lighter shades of rubies (often "pink sapphires") are more commonly

found. After the Second World War ruby deposits were found

in Tanzania, Madagascar, Vietnam, Nepal, Tajikistan, and Pakistan.[10]

A few rubies have been found in the U.S. states of Montana, North Carolina, South

Carolina and Wyoming. While searching for aluminous schists in Wyoming, geologist Dan

Hausel noted an association of vermiculite with ruby and sapphire and located six previously

undocumented deposits.[11]

More recently, large ruby deposits have been found under the receding ice shelf of Greenland.[citation

needed]

Republic of Macedonia is the only country in mainland Europe to have naturally occurring rubies.

They can mainly be found around the city of Prilep. Macedonian ruby has a unique raspberry color.

The ruby is also included on the Macedonian Coat of Arms.

In 2002 rubies were found in the Waseges River area of Kenya. There are reports of a large deposit

of rubies found in 2009 in Mozambique, in Nanhumbir in the Cabo Delgado district ofMontepuez.[12]

Spinel, another red gemstone, is sometimes found along with rubies in the same gem gravel or

marble. Red spinel may be mistaken for ruby by those lacking experience with gems. However, the

finest red spinels can have a value approaching that of the average ruby.

Factors affecting value

Diamonds are graded using criteria that have become known as the four Cs, namely color, cut,

clarity and carat weight. Similarly natural rubies can be evaluated using the four Cs together with

their size and geographic origin.

Color: In the evaluation of colored gemstones, color is the most important factor. Color divides into

three components: hue, saturation and tone. Hue refers to "color" as we normally use the term.

Transparent gemstones occur in the following primary hues: red, orange, yellow, green, blue, violet.

These are known as pure spectral hues.[14] In nature, there are rarely pure hues, so when speaking

of the hue of a gemstone, we speak of primary and secondary and sometimes tertiary hues. In ruby,

the primary hue must be red. All other hues of the gem species corundum are called sapphire. Ruby

may exhibit a range of secondary hues. Orange, purple, violet and pink are possible.

A naturally occurring ruby crystal

Natural ruby with inclusions

Rubies set in jewelry

A cut pink ruby

The finest ruby is best described as being a vivid medium-dark toned red. Secondary hues add an

additional complication. Pink, orange, and purple are the normal secondary hues in ruby. Of the

three, purple is preferred because, firstly, the purple reinforces the red, making it appear

richer.[14] Secondly, purple occupies a position on the color wheel halfway between red and blue. In

Burma where the term 'pigeon blood' originated, rubies are set in pure gold. Pure gold is itself a

highly saturated yellow. When a purplish-red ruby is set in yellow, the yellow neutralizes its

complement blue, leaving the stone appearing to be pure red in the setting.

Treatments and enhancements

Improving the quality of gemstones by treating them is common practice. Some treatments are used

in almost all cases and are therefore considered acceptable. During the late 1990s, a large supply of

low-cost materials caused a sudden surge in supply of heat-treated rubies, leading to a downward

pressure on ruby prices.

Improvements used include color alteration, improving transparency by dissolving rutile inclusions,

healing of fractures (cracks) or even completely filling them.

The most common treatment is the application of heat. Most, if not all, rubies at the lower end of the

market are heat treated on the rough stones to improve color, remove purple tinge, blue patches and

silk. These heat treatments typically occur around temperatures of 1800 °C (3300 °F).[15] Some

rubies undergo a process of low tube heat, when the stone is heated over charcoal of a temperature

of about 1300 °C (2400 °F) for 20 to 30 minutes. The silk is only partially broken as the color is

improved.

Another treatment, which has become more frequent in recent years, is lead glass filling. Filling the

fractures inside the ruby with lead glass (or a similar material) dramatically improves the

transparency of the stone, making previously unsuitable rubies fit for applications in jewelry.[16] The

process is done in four steps:

1. The rough stones are pre-polished to eradicate all surface impurities that may affect the

process

2. The rough is cleaned with hydrogen fluoride

3. The first heating process during which no fillers are added. The heating process eradicates

impurities inside the fractures. Although this can be done at temperatures up to 1400 °C

(2500 °F) it most likely occurs at a temperature of around 900 °C (1600 °F) since the rutile

silk is still intact.

4. The second heating process in an electrical oven with different chemical additives. Different

solutions and mixes have shown to be successful, however mostly lead-containing glass-

powder is used at present. The ruby is dipped into oils, then covered with powder,

embedded on a tile and placed in the oven where it is heated at around 900 °C (1600 °F) for

one hour in an oxidizing atmosphere. The orange colored powder transforms upon heating

into a transparent to yellow-colored paste, which fills all fractures. After cooling the color of

the paste is fully transparent and dramatically improves the overall transparency of the

ruby.[17]

If a color needs to be added, the glass powder can be "enhanced" with copper or other metal oxides

as well as elements such as sodium, calcium, potassium etc.

The second heating process can be repeated three to four times, even applying different

mixtures.[18] When jewelry containing rubies is heated (for repairs) it should not be coated with

boracic acid or any other substance, as this can etch the surface; it does not have to be "protected"

like a diamond.

The treatment can easily be determined using a 10x loupe and determination focuses on finding

bubbles either in the cavities or in the fractures that were filled with glass.[19]

Synthetic and imitation rubies

Artificial ruby under a normal light (top) and under a green laser light (bottom). Red light is emitted

In 1837 Gaudin made the first synthetic rubies by fusing potash alum at a high temperature with a

little chromium as a pigment. In 1847 Ebelmen made white sapphire by fusing alumina in boric acid.

In 1877 Frenic and Freil made crystal corundum from which small stones could be cut. Frimy

and Auguste Verneuil manufactured artificial ruby by fusing BaF2 and Al2O3 with a little chromium

at red heat. In 1903 Verneuil announced he could produce synthetic rubies on a commercial scale

using this flame fusion process.[20] By 1910, Verneuil's laboratory had expanded into a 30 furnace

production facility, with annual gemstone production having reached 1,000 kilograms (2,000 lb) in

1907.

Other processes in which synthetic rubies can be produced are through Czochralski's pulling

process, flux process, and the hydrothermal process. Most synthetic rubies originate from flame

fusion, due to the low costs involved. Synthetic rubies may have no imperfections visible to the

naked eye but magnification may reveal curves, striae and gas bubbles. The fewer the number and

the less obvious the imperfections, the more valuable the ruby is; unless there are no imperfections

(i.e., a "perfect" ruby), in which case it will be suspected of being artificial. Dopants are added to

some manufactured rubies so they can be identified as synthetic, but most need gemological testing

to determine their origin.

Synthetic rubies have technological uses as well as gemological ones. Rods of synthetic ruby are

used to make ruby lasers and masers. The first working laser was made by Theodore H. Maiman in

1960[21] at Hughes Research Laboratories in Malibu, California, beating several research teams

including those of Charles H. Townes at Columbia University, Arthur Schawlow at Bell Labs,[22] and

Gould at a company called TRG (Technical Research Group). Maiman used a solid-state light-

pumped synthetic ruby to produce red laser light at a wavelength of 694 nanometers (nm). Ruby

lasers are still in use. Rubies are also used in applications where high hardness is required such as

at wear exposed locations in modern mechanical clockworks, or as scanning probe tips in

a coordinate measuring machine.

Imitation rubies are also marketed. Red spinels, red garnets, and colored glass have been falsely

claimed to be rubies. Imitations go back to Roman times and already in the 17th century techniques

were developed to color foil red—by burning scarlet wool in the bottom part of the furnace—which

was then placed under the imitation stone.[23]Trade terms such as balas ruby for red spinel

and rubellite for red tourmaline can mislead unsuspecting buyers. Such terms are therefore

discouraged from use by many gemological associations such as the Laboratory Manual

Harmonisation Committee (LMHC).

Records and famous rubies

Rubies at the National Museum of Natural History, Washington, D.C., USA

The Smithsonian's National Museum of Natural History in Washington, D.C. has received one of

the world's largest and finest ruby gemstones. The 23.1 carats (4.62 g) Burmese ruby, set in a

platinum ring with diamonds, was donated by businessman and philanthropist Peter Buck in

memory of his late wife Carmen Lúcia. This gemstone displays a richly saturated red color

combined with an exceptional transparency. The finely proportioned cut provides vivid red

reflections. The stone was mined from the Mogok region of Burma (now Myanmar) in the 1930s.

In 2007 the London jeweler Garrard & Co featured on their website a heart-shaped 40.63-carat

ruby.

On December 13/14, 2011 Elizabeth Taylor's complete jewellery collection was auctioned

by Christie's. Several ruby-set pieces were included in the sale, notably a ring set with an 8.24 ct

gem that broke the 'price-per-carat' record for rubies ($512,925 per carat, i.e. over $4.2 million in

total), and a necklace that sold for over $3.7 million.

The Liberty Bell Ruby is the largest mined ruby in the world. It was stolen in a heist in 2011.[28]

The Sunrise Ruby is the world's most expensive ruby, most expensive coloured gemstone, and

most expensive gemstone other than a diamond. In May 2015, it sold at auction in Switzerland

to an anonymous buyer for US$30 million.

A synthetic ruby crystal became the gain medium in the world's first optical laser, conceived,

designed and constructed by Theodore H. "Ted" Maiman, on the 16th of May, 1961 at Hughes

Research Laboratories.[30][31] The concept of electromagnetic radiation amplification through the

mechanism of Stimulated Emission had already been successfully demonstrated in the

laboratory by way of the Maser, using other materials such as ammonia and indeed, later, ruby,

but the Ruby Laser was the first device to work at optical (694.3 nm) wavelengths. Maiman's

prototype laser is still in working order.

Historical and cultural references

In Job 28:18 and Proverbs 3:15, wisdom is more valuable than rubies. In Proverbs 31:10, a wife

of noble character is worth more than rubies.

An early recorded transport and trading of rubies arises in the literature on the North Silk

Road of China, wherein about 200 BC rubies were carried along this ancient trackway moving

westward from China.

Rubies have always been held in high esteem in Asian countries. They were used to ornament

armor, scabbards, and harnesses of noblemen in India and China. Rubies were laid beneath the

foundation of buildings to secure good fortune to the structure.[

References

1. Ruby on Gemdat.org

2. Jump up^ Precious Stones, Max Bauer, p. 2

3. ^ Jump up to:a b "Ruby: causes of color". Retrieved 28 Mar 2016.

4. ^ Jump up to:a b Matlins, Antoinette Leonard (2010). Colored Gemstones. Gemstone Press.

p. 203. ISBN 0-943763-72-X.

5. Jump up^ Reed, Peter (1991). Gemmology. Butterworth-Heinemann. p. 337. ISBN 0-7506-

6449-5.

6. Jump up^ Wise, Richard G. "Gemstone Connoisseurship; The Finer Points, Part II".

7. Jump up^ Hughes, Richard W. "Walking the line in ruby & sapphire". ruby-sapphire.com.

8. Jump up^ Federman, David. "Pink Sapphire". Modern Jeweler.

9. Jump up^ http://www.gemsociety.org/article/ruby-sapphire-identifying-origin-understanding-

value-rarity-gem-corundum/

10. Jump up^ Hausel, W. Dan (2009). Gems, Minerals and Rocks of Wyoming. Book Surge.

p. 176.ISBN 1-4392-1856-0.

11. Jump up^ Mozambique: Police Seize Boat With 96 Illegal Immigrants. AllAfrica. 4

November 2010

12. Jump up^ Wenk, Hans-Rudolf; Bulakh, A. G. (2004). Minerals: their constitution and origin.

Cambridge, U.K.: Cambridge University Press. pp. 539–541. ISBN 0-521-52958-1.

13. ^ Jump up to:a b Wise, Richard W. (2006). Secrets Of The Gem Trade, The Connoisseur's

Guide To Precious Gemstones. Brunswick House Press. pp. 18–22. ISBN 0-9728223-8-0.

14. Jump up^ The Heat Treatment of Ruby and Sapphire. Bangkok, Thailand: Gemlab Inc.

1992.ISBN 0940965100.

15. Jump up^ Vincent Pardieu Lead Glass Filled/Repaired Rubies. Asian Institute of

Gemological Sciences Gem Testing Laboratory. February 2005

16. Jump up^ Richard W. Hughes (1997), Ruby & Sapphire, Boulder, CO, RWH

Publishing, ISBN 978-0-9645097-6-4

17. Jump up^ Milisenda, C C (2005). "Rubine mit bleihaltigen Glasern gefullt". Zeitschrift der

Deutschen Gemmologischen Gesellschaft (in German) (Deutschen Gemmologischen

Gesellschaft) 54 (1): 35–41.

18. Jump up^ "Lead Glass-Filled Rubies". GIA Global Dispatch (Gemological Institute of

America). 2012.

19. Jump up^ "Bahadur: a Handbook of Precious Stones". 1943. Retrieved 2007-08-19.

20. Jump up^ Maiman, T.H. (1960). "Stimulated optical radiation in ruby". Nature 187 (4736):

493–494. Bibcode:1960Natur.187..493M. doi:10.1038/187493a0.

21. Jump up^ Hecht, Jeff (2005). Beam: The Race to Make the Laser. Oxford University

Press.ISBN 0-19-514210-1.

22. Jump up^ "Thomas Nicols: A Lapidary or History of Gemstones". 1652. Retrieved 2007-08-

19.

23. Jump up^ "The Carmen Lúcia Ruby". Exhibitions. Retrieved 2008-02-28.

24. Jump up^ "Garrards – Treasures (large and important jewelry pieces)". Retrieved 2010-11-

08.

25. Jump up^ The Legendary Jewels, Evening Sale & Jewelry (Sessions II and III) | Press

Release | Christie's. Christies.com (2011-12-14). Retrieved on 2012-07-11.

26. Jump up^ Elizabeth Taylor's ruby and diamond necklace. News.yahoo.com (2011-09-07).

Retrieved on 2012-07-11.

27. Jump up^ http://philadelphia.cbslocal.com/2012/01/09/irreplaceable-2-million-ruby-stolen-

in-wilmington-jewelry-heist/

28. Jump up^ "World's most expensive coloured gem sells for $30m". BBC. 13 May 2015.

Retrieved 13 May 2015.

29. Jump up^ Maiman, T.H. (1960) "Stimulated Optical Radiation in Ruby". Nature, 187 4736,

pp. 493-494.

30. Jump up^ "Laser inventor Maiman dies; tribute to be held on anniversary of first laser".

Laser Focus World. 2007-05-09. Retrieved 2007-05-14.

31. Jump up^ C. Michael Hogan, Silk Road, North China, The Megalithic Portal. 19 November

2007

32. Jump up^ Smith, Henry G. (1896). "Chapter 2, Sapphires, Rubies". Gems and Precious Stones. Charles Potter Government Printer, Australia.

http://discovermagazine.com/

2004/nov/geology-of-rubies

The Geology of...Rubies A ruby's dazzling color masks the mysterious origins of its

birth.

2. By Anne Sasso|Thursday, November 25, 2004

3. RELATED TAGS: EARTH SCIENCE

4. Sometimes George Harlow looks more like a medieval magician than the curator of

gems and minerals at the American Museum of Natural History. Sweeping an

ultraviolet light wand over a box of rocks in a darkened room at the museum, he

ignites the stones—uncut rubies—in a burst of fiery red light that is otherworldly.

“It’s like Day-Glo colors,” he says. “They are brighter than they should be. You look at

them and say: ‘Wow! Look at that red! What’s going on?’ ”

5. That remarkable radiance—caused by any ultraviolet light, including UV rays from

the sun—has given rubies a special place in history. Long before Marco Polo found

his way to Asia, Burmese warriors were embedding the stones under their skin to

make them invincible in battle. Sanskrit medical texts were prescribing rubies as a

cure for flatulence and biliousness. And Hindu lore was preaching that a ruby’s light

could not be extinguished nor hidden by clothing. Geologists can explain the glow:

Ultraviolet light causes the chromium in rubies to fluoresce. But there is much about

rubies that scientists cannot account for. The biggest question, the one that has

geologists on both sides of the Atlantic at odds with each other, is how rubies formed

in the first place. Geologists simply do not know. That rubies even exist, says Peter

Heaney, geosciences professor at Penn State University, is something of a “minor

geological miracle.”

6. Rubies are a type of corundum, a rare mineral made up of densely packed aluminum

and oxygen atoms, which are normally colorless. When other atoms are substituted

for a few of the aluminum ones, bright hues emerge. Small amounts of chromium

impart the deep red color of ruby, traces of titanium and iron produce the stunning

blue of sapphire, and chromium and ferric iron create the delicate orange shades of

the extremely rare and costly padparadscha.

7. None of this can take place, however, if silica or large amounts of iron are present.

And therein lies the mystery. Since silica is one of the most abundant elements in

Earth’s crust, how is it that rubies managed to avoid it but at the same time connect

with the exceedingly rare chromium? And how did rubies avoid iron, another

common element? Sapphires and padparadscha need some iron, but rubies, by

definition, have very little at all. “The fluorescence [of a ruby] is tied to its

composition, to the low iron. That’s hard to do in geology, to get the iron that low,”

says Harlow. “Corundum is rare enough as it is. So, adding all these things together,

ruby is very rare.”

8. The majority of the world’s ruby deposits (but not necessarily the best) are in a

discontinuous band of marble that stretches 1,800 miles along the southern slope of

the Himalayas from Tajikistan through Afghanistan, Pakistan, Kashmir, Nepal, and

on into China and Vietnam. The model of ruby formation that many geologists,

including Harlow, accept involves tectonics: two continents—India and Asia—

smashing together to form the Himalayas.

9. Around 50 million years ago, the Indian subcontinent moved toward Asia,

constricting the Tethys Sea, an ancient ocean that lay between. On the floor of the

Tethys were deposits of limestone, sedimentary rocks of calcium carbonate (the stuff

of Tums). “It turns out that many limestones are dirty,” says Heaney. The Tethyan

limestone was composed of every mineral that washed off the rocks of the

surrounding land, including all the ingredients necessary for rubies: aluminum,

oxygen, and chromium, plus silica.

10. As the Tethys closed up, its limestones were pushed deep into the earth, where they

were cooked and squeezed at inferno-like temperatures (1,112 to 1,238 degrees

Fahrenheit) and pressures (3 to 6 kilobars). The result? They metamorphosed into

sparkly marble—the kind Michelangelo loved to work with. At the same time, molten

granite intruded into the marble, releasing fluids that percolated up through the

rock. That process, called metasomatism, removed the silica but left the alumina

behind. For the next 40 million to 45 million years, the two continents slowly

squeezed together, raising the Himalayas. Erosion eventually exposed a necklace of

ruby deposits along the scar where the two plates collided.

11. Studies done in France by Gaston Giuliani of the Institute of Research and

Development, along with Virginie Garnier and Daniel Ohnenstetter of the

Petrographical and Geochemical Research Center, back up the traditional view—in

part. They link the timing of ruby formation to the rise of the Himalayas. “When we

dated the ruby deposits, we noticed that they were directly related to the continental

collision and to the Himalayan orogeny [mountain building],” says Giuliani. “So the

ruby is in effect an ideal marker of this continental collision.”

12. But the French team also noticed that while the Himalayas’ ruby-hosting marbles

extend over large areas, the rubies themselves occur only erratically in patches. “The

occurrence of ruby is very isolated and localized. We don’t find rubies everywhere

that there is marble. So then we had to ask, why do we only find ruby in certain

locations? Because if it’s a metamorphic phenomenon, normally it affects the whole

ensemble of marble,” says Giuliani. “But that wasn’t the case, so there’s a big secret

here.”

13. The secret, the French believe, is salt. Not only were the limestones dirty, they were

salty as well. The Tethys, they say, was so shallow in places that it would occasionally

dry out, leaving behind a thin rind of salt from evaporated seawater. The salt mixed

with detritus washing off the land to form the unique limestone that gave birth to

rubies. Once heated, the salt acted like a flux, assuring that the aluminum became

mobile enough to mix with the chromium.

14. Further clues to salt’s role lie deep within the microscopic world of the ruby crystal.

There Garnier found tiny drops of fluid, immortalized snapshots of the liquids

swirling within the marble when the rubies crystallized. Minuscule crystals of sodium

chloride and anhydrite (found in sea salt) float within the liquid. But what of ruby’s

enemy, silica? Garnier claims that there wasn’t enough present in the original rocks

to do much damage. And what of the role of granite? Giuliani says it had no role at

all.

15. Harlow disagrees. “The fundamental issue is, if you metamorphose a marble, the

silica content is much greater than that of aluminum, and you’re never going to make

corundum—although we all know that there are marble-hosted corundum deposits.

So how do you do it?” he asks. “Simple. You need a fluid. You need some transport

mechanism to reduce the silica in the rock.” Intrusions, like granites, offer a

convenient source of fluids. “It’s a simple mechanism, even though it’s not yet proven

for rubies,” he adds.

16. No model of ruby formation will be considered definitive until geologists can explain

the legendary stones of the famed Mogok mine in Myanmar (formerly Burma),

source of some of the world’s finest rubies and spinels. While Mogok gems are

indeed hosted in marble, they often grow alongside beautiful topaz and moonstone,

minerals that are igneous (crystallized from rising magmas) rather than

metamorphic in origin. The huge size of these crystals implies a type of magma called

pegmatite, a juicy water-rich melt that provides unusual conditions, allowing

minerals to grow to enormous sizes. This suggests that different processes than those

hypothesized for the creation of other rubies were at work. “The minerals blew my

mind,” Harlow says. “I started seeing things that really challenged the concept that

rubies are metamorphic.”

17. Sadly, it may be some time before geologists can sort this out. Politics in Myanmar

have long blocked scientists —especially Western scientists—from entering the

country to take a look. “The fundamental problem with Myanmar is that you can’t get

in there to do anything,” Harlow says. “And the people who have done the geology

are Myanmar geologists who, unfortunately, are suffering with being 40 years behind

in science.”

18. If Western scientists were allowed complete access to Mogok, would they find an

answer to the question of how rubies formed? Harlow isn’t sure. “Yes, Mogok’s

special,” he says. “But is it going to defy the other models or defy other

interpretations? I don’t think fundamentally it will. There’s astrong similarity among

a lot of the deposits, even though the details tend to be different. I think we’re still a

ways away from answering these questions.”

http://www.ruby-sapphire.com/r-s-bk-burma.htm

The quest for precious stones does not rank high on humankind's list of

worthy or redeeming activities. You'll find no mention of it in the Boy Scout

handbook. And you'll not see it prescribed by priests as a path towards

forgiveness, for in the struggle to possess the earth's booty, far too many a

sinner is born and even more falsehoods are fabricated. We cannot look to

gemstone mining for useful homilies. There is no lesson via process, no

consolation in the journey. The only reward is the reward itself – to

possess, to claim as one's own. Gem mining's attraction is thus: grasp the

purest of the pure, tap God's current, the power of all creation. Hold the

earth's bounty in one's own hand… and damn anyone who shall stand in

your way.

Anonymous

Figure 1. Dust jacket from the 1960 English edition of

Joseph Kessel's Mogok: The Valley of Rubies.

Burma (Myanmar)

Corundum has been found in a number of different areas of Burma. These include Sagyin

(near Mandalay), Thabeitkyin, Naniazeik (near Myitkyina), Mogok and, most recently, Möng

Hsu (central Shan state). Most famous is the Mogok Stone Tract, which has remained the

world's premier source of ruby for more than 800 years.

Far away in a remote corner of the earth is a town of mushroom growth, called Mogok… It has

but one industry, the recovery of rubies from mud and sand. You may be ever so hungry or

thirsty, the first things offered or mentioned to you are rubies. No matter what business may have

brought you to Mogok, the natives all assume you are there for rubies – rubies, nothing but

rubies… It is said that a king would be ruling at Mandalay today if it had not been for rubies…

Anonymous, 1905, A city built on rubies

Figure 2. Kipling called it a "beautiful winking

wonder." It is Rangoon's Shwedagon Pagoda,

symbol of Burma, theGolden Land. Ralph Fitch, the

great English traveler of the 16th century, described

it thus:

"…it is called Dogonne, and is of a wonderfull

bignesse, and all gilded from the foot to the toppe…

It is the fairest place, as I suppose, that is in the

world."

In addition to the numerous solid gold plates, the

upper reaches are embedded with literally

thousands of diamonds and other precious stones.

Atop it all rests a 76-ct diamond orb. (Photo by the

author, 1980)

When one speaks of ruby, the Mogok Stone Tract in Upper Burma immediately

springs to mind. Lying approximately 644 km (400 miles) north of Rangoon, Mogok

has for the past 800 years been the premier source of fine rubies. It is an area

steeped in legend and its story embraces not only gems, but also the early

exploration and expansion of the European colonial empires into Asia.

The town of Mogok (1500 m) is located in the Katha district of Upper Burma.

Consisting of heavily-jungled hills rising to a height of 2347 m (7700 ft) above sea

level, the ruby mines district covers about 400 sq miles, although only a portion

(70 sq miles) is gem bearing. Considered one of the most scenic areas in Burma, it

is home to a number of colorful ethnic groups, as well as a variety of wildlife,

including elephants, tiger, bear and leopard.

Figure 3. Pigeon's Blood

Left: The 196-ct Hixon Ruby of the Los Angeles County Museum of Natural History is one of the

finest Burmese ruby crystals on public display. Unfortunately, such crystals are all too rare – most

are immediately cut, since the market for cut stones is far larger than that for mineral specimens.

Right: These extraordinary rubies, at 5.56 and 5.25 ct., represent a lifetime's toil. They are

mounted in the traditional Burmese manner, with the gold setting improving the stones' color, as

well as acting as a mirror to increase the gems' brilliance.

Figure 4. Map of Southeast Asia, showing the important gem localities, particularly those of

Burma.

Timeline of ruby and sapphire in Burma

Middle Pleistocene

Ruby is probably discovered in the Mogok region by stone-age humans inhabiting the area.

6th Century AD

One of the seven sons of Kun-Lung, founder of the Shan dynasty, is said to rule a state,

probably Momeit, a near which ruby mines existed. His tribute to the central government

was two viss b yearly (G.S. Streeter, 1889a).

1200s

Talaing chronicles speak of a kingdom of Kanpalan [Kyatpyin?] (Mason, 1850; Halford-

Watkins, 1934).

1419–1444

Nicolò di Conti visits Ava (Penzer, 1929).

1495–1496

Hieronimo di Santo Stefano, a Genoese merchant, visits Pegu. Ava is described as a land

lying fifteen days' journey from Pegu. Rubies and many other precious stones are said to

"grow" there (Major, 1857).

1500–1517

Duarte Barbosa does not visit, but describes Ava and Capelam [Kyatpyin?] and the ruby

trade (Dames, 1918).

1502–1508

Ludovico di Varthema visits Pegu and describes the source of rubies as Capellan. In return

for a present of coral, di Varthema received from the king of Pegu about 200 rubies in

return: "Take these for the liberality you have exercised towards me" (Temple, 1928).

1563

Cæsar Fredericke visits Pegu, describes the ruby trade, and buys rubies for later sale in

Ceylon (Hakluyt, 1903–05).

1586

Ralph Fitch, the first Englishman to reach Burma, visits Pegu and describes the ruby trade.

He mentions Caplan as the source (Hakluyt, 1903–05).

1597

Burmese king, Nuha-Thura Maha Dhama-Yaza forces the Momeik sawbwa (prince) to trade

Mogok and Kyatpyin for Tagaungmyo (George, 1915).

1617

The British East India Company makes its first contact with Burma, when Henry Forrest and

John Staveley are sent to recover the goods of a company servant who had died at Syriam

(Stewart, 1972).

1629–1637

Fray Sebastien Manrique visits Arakan, where he said the market was well-stocked in such

things as rubies, sapphires and even "gray" amber (Luard, 1926–27).

1631–1668

Jean-Baptiste Tavernier makes six separate voyages to Asia. Although he does not visit

Burma, his memoirs mention that ruby comes from Capelan (Ball, 1925).

1780

King Bodawpaya sends thousands of captives from the Manipur war to Mogok, to work the

mines. Thereafter the mines become a quasi-penal colony (Halford-Watkins, 1932).

1783

King Bodawpaya extends the tract boundaries to encompass Mogok, Kyatpyin and Kathé

(Brown, 1927).

1795

Michael Symes visits Ava, and mentions ruby mines at a mountain called Woobolootaun

opposite to Keoum-meoum (Symes, 1800).

1824–1826

The first Anglo-Burmese war is won by Britain. The treaty of Yandabo cedes Arakan, Assam

and Tenasserim to the East India Company (Stewart, 1972).

1830

A runaway English sailor in the employ of King Phagyidoa is sent to blast a rock at a royal

ruby mine at Tapambin. He either died at the mines or slipped quietly away, for nothing was

heard of him again (G.S. Streeter, 1889).

1833

Père Giuseppe d'Amato, an Italian Jesuit, visits Chia-ppièn [Kyatpyin] and describes the ruby

mines. His account (published posthumously in 1833) is the first documented eyewitness

description of the ruby mines (d'Amato, 1833).

1852–1853

Britain annexes Pegu, which is taken with few losses in the second Anglo-Burmese war

(Stewart, 1972).

1853

Henry Yule's mission to Ava. He describes, but does not visit, the ruby mines (Yule, 1858).

1853–1878

The reign of King Mindon Min. In 1863, payments in silver are offered Mindon Min for the

sole rights to purchase gems at Mogok. This forced increasing persecution of miners,

resulting in large-scale depopulation of the area by the time of the British annexation

(George, 1915; Halford-Watkins, 1932).

1870

A German mining engineer named Bredemeyer is put in charge of the ruby mines at Sagyin,

near Mandalay (E.W. Streeter, 1892).

1878

King Thebaw takes the throne upon the death of Mindon Min (Stewart, 1972).

1879

Rival members of the royal family are murdered in Mandalay. Britain withdraws its resident

(Stewart, 1972).

1881

A party of Frenchmen under an engineer in Thebaw's employ visit Mogok (G.S. Streeter,

1889).

1882

April: Burmese mission to Simla, in British India, declares to the French Consul from Calcutta

that a Frenchman just obtained from King Thebaw the concession for the Burma ruby mines.

This was probably just a proposal (Preschez, 1967; trans. by Olivier Galibert, June, 1994).

1883–1885

French and Italian speculators negotiate with Thebaw for mining concessions at Mogok. In

Feb., 1884, a French engineer, Alexandre Izambert, goes to Mandalay to solicit concession

for the ruby mines of "Monieh and Rapyen." He offers Rs300,000 for the concession, which

would cover 750 m on both sides of the road between Mandalay and the mines that his

company proposes to build. The deal falls apart, due to a secret agreement between a

Burmese minister and an Italian consular agent (Preschez, 1967; trans. by O. Galibert, June,

1994). Further massacres in Mandalay (Stewart, 1972; Keeton, 1974).

1885

Britain uses the pretext of Mandalay palace massacres and a timber dispute between the

Burmese government and the Bombay-Burma Trading Corp. to invade Upper Burma. The

real reason was fear of French influence in an area thought vital to British interests.

Mandalay is taken on Nov. 29. In December, Edwin W. Streeter becomes interested in

obtaining the concession for the mines (Stewart, 1972; E.W. Streeter, 1892).

1886: Jan. 1

Britain formally annexes Upper Burma. Shortly thereafter, E.W. Streeter forms a syndicate

with Charles Bill and Reginald Beech. They approach the India Office to obtain the

concession for the Mogok mines. Lord Dufferin puts the lease out to tender, which the

Streeter syndicate wins with a bid of Rs400,000 (E.W. Streeter, 1892).

1886: Dec. 26

British military force reaches Mogok area. On Jan. 27, 1887 they enter the town of Mogok.

Accompanying the expedition were G.S. Streeter (E.W. Streeter's son), Col. Charles Bill,

Reginald Beech and engineer Robert Gordon (G.S. Streeter, 1887a). The period between

annexation and the first arrival of British troops is the golden age of local mining. For the

first time in centuries, mining is free and stones can be sold without restrictions (George,

1915).

1887

C. Barrington Brown is sent to Mogok by the Secretary of State for India to determine the

value and conditions of the mines. His report represents the first systematic description of

the deposits (Brown and Judd, 1896).

1889

The Streeter syndicate joins with the Rothschilds to form the Burma Ruby Mines Ltd, which

is floated on Feb. 26. Pandemonium reigns as the offer is oversubscribed fourteen times and

ordinary shares rise to a 400% premium. The £1 founders' shares trade at £350 (P.

Streeter, 1993).

1895

Warth examines ruby mines at Naniazeik, some 80 km west of Myitkyina (Kachin State)

(Penzer, 1922).

1889–1896

Period of the Burma Ruby Mines Ltd first lease, with a profit shown only during 1895–1896

(Brown, 1927).

1897–1904

Period of the second lease, generally profitable (except 1897–98 and 1903) (Brown, 1927).

1905–1912

Period of the third lease, generally profitable (except 1909). A.H. Morgan's drainage tunnel

is finished in 1908, allowing mining of once-flooded alluvials (Brown, 1927).

1913–1925

Period of the supplementary agreement. Losses mount as rich areas are exhausted and the

market slumps due to World War I. Profit is shown only in 1913, 1918 and 1920. Morgan's

drainage tunnel is damaged in 1925 and never reopened. The company goes into voluntary

liquidation on Nov. 20, 1925 (Brown, 1927).

1926–1931

No buyers take the lease. The company continues small-scale mining until June 30, 1931,

when the lease is surrendered (Halford-Watkins, 1932a).

1926–1947

Mining is performed largely by native methods. European-style mining is limited to a few

leased mines.

1938

U Khin Maung Gyi (1938) reports on the Thabeitkyin stone tract west of Mogok. Sporadic

mining had apparently been done for at least 50–60 years previously.

1942: 7 May

Japanese occupy Mogok. Organized mining stops until the British reoccupation (March 15,

1945), but small-scale digging continues (Ehrmann, 1957b).

1948: Jan. 5

Burma achieves independence from British.

1962

General Ne Win stages a military coup, plunging Burma into isolation. Thus begins one of the

20th century's cruelest and longest-running dictatorships, where Ne Win rules in a manner

akin to the 19th-century Burmese kings.

1969: March 12

Burmese Ministry of Mines bans exploration and mining of gems, effectively nationalizing the

country's gem mines. Ruby and jade mining licenses previously issued to prospectors are

revoked (Mining Journal, Annual Review, June, 1970).

1968–1980s

Smuggling increases, with only a fraction of the total output ending up in government

coffers. More Burmese gems are on offer in Bangkok than Rangoon.

1988

Anti-government riots wrack the country. The government crushes the opposition, with

thousands gunned down in Rangoon, Mandalay and other cities.

1989–94

To quell mounting discontent, the military junta begins to liberalize the economy (including

mining) while still maintaining total political control. The name Burma is changed to

Myanmar; Rangoon is changed to Yangon.c

1990: March 9

Private/government mining joint ventures are opened for tender at Mogok (Kane and

Kammerling, 1992). However, smuggling remains widespread as the government's share of

profits is 51.4%.

1991

Rubies are found at Möng Hsu (Shan State). The Thai border town of Mae Sai becomes the

main smuggling point for these gems (Hlaing, 1991). The first foreign gemologists in over 25

years visit Mogok (Ward, 1991).

1994

The government reduces the export tax on gemstones to 15% (U Hla Win, pers. comm., May

2, 1994).

1995

Dismayed by the continued smuggling of Möng Hsu rubies, the Burmese government closes

all ruby markets at Taunggyi, moving legal trading to Rangoon (U Hla Win, pers. comm., 14

Mar., 1995).

1997–Present

Governement policy on gemstone trading vascillates between openness and repression, with

constant policy flip-flops.

a. Möng Mit state is often written as Momeit or Momeik.

b. In those days all payments were made in roughly cast discs of silver, with rupee

coins not coming into general use until about 1874. One viss of silver weighed 3.6

lb (1.6 kg), and was then worth about Rs100. It was subdivided into 100 ticals

(Halford-Watkins, 1934).

c. A common Asian belief is that a change of name will help put a stop to a run of

bad luck, the idea being that the bad spirits cannot find something with a new

name. Thus Ne Win, a notoriously superstitious man, ordered the names of the

capital and country changed after the riots. Of course if those spirits are as smart as

some give them credit for, a name change shouldn't phase them a bit, but that is

another matter for another day.

History

The exact date when rubies were first discovered in Mogok is unknown. No doubt

the first humans to settle the area found rubies and spinels in the rivers and

streams. Kunz (1915) mentions a Burmese legend from the ruby mines.

According to this legend, in the first century of our era three eggs were laid by a female naga,

or serpent; out of the first was born Pyusawti, a king of Pagan; out of the second came an

Emperor of China, and out of the third were emitted the rubies of the Ruby Mines.

Taw Sein Ko, as told to G.F. Kunz (1915)

A similar story is related by Tin and Luce (1960):

At that time spirits carried away a certain hunter. When they reached the place where the

Naga had laid her egg, the hunter finding the egg bore it away joyfully. But while he was

crossing a stream, swollen by a heavy shower of rain till it overflowed its banks, he dropped it

from his hand. And one golden egg broke in the land of Mogok Kyappyin and became iron and

ruby in that country.

P.E.M. Tin & G.H. Luce, 1960

The Glass Palace Chronicle of the Kings of Burma

Early humans at Mogok

Vague references (Ehrmann, 1957) exist suggesting, on the basis of stone relics

unearthed, that the area was first settled by Mongolians about 3000 bc. However it

is likely that humans moved into the area long before that date. Halford-Watkins

(1934) stated that stone, bronze and iron-age tools fashioned from a variety of

jadeite have been found in alluvial diggings throughout the Mogok area.

The karst (sink-hole) topography, with its numerous underground caves, makes

the Mogok area interesting for students of ancient man and prehistoric animal life.

Karst topography has yielded important finds of Peking Man and younger extinct

human types in China, as well as many fossil anthropoid apes. While no important

archeological finds have been found at Mogok, this probably has more to do with

the xenophobic attitude of the Burmese government since 1962 (and the

subsequent decline in all types of academic activity), rather than a lack of study

material. Interesting animal specimens did come to light before the area was closed

off to outside study and it seems likely that further work will reveal further

discoveries (de Terra, 1943).

Hellmut de Terra (1943) made a detailed report on the Pleistocene in the Mogok

area in 1937–38 as part of a study on early man in Burma. No Pleistocene fossils

were found, mainly because intensive mining had not spared even the smallest

limestone fissures. However, in one cave a lower human jaw was found, believed to

be that of a female human prehistoric cave-dweller dating well before the present

people settled the Mogok area. Many Neolithic stone implements were also found,

from the surface of old lake terraces approximately 3.2 km (2 miles) east of the

town of Mogok, or from cave entrances. Certain caves were found to be inhabited

by Buddhist hermits, who had installed shrines in them. One cave was even used

as a cemetery. According to De Terra, "There is no question that the first people to

settle in this area took refuge in the caves, because most of them face a valley that

must have offered a most favorable habitat in prehistoric times. A lake, several

streams and plenty of game, in addition to fertile loamy soils covering several

square miles of flat ground at the valley bottom, would have offered plenty of

inducement to early settlers. Here the chase could have been combined either with

food-gathering or with agricultural practices."

The dragons of Mogok

In the vicinity of the Mogok Caves the

inhabitants relate many tales of buried

dragons and underground spirits, which at

one time are supposed to have taken

refuge underground. The association of

these beasts with the cavities presumably

traces back to some sort of worship, but

today the people are chiefly after gem-

bearing deposits: cave loam and sand. In

the course of these mining operations the

miners often find fossils, teeth of elephants

and deer, or other bones belonging to

animals now extinct. To the local people

fossils are known as "nagá ajó" or dragon

bones. They distinguish several types of

dragons, although none of these seem to

fall within the range of zoölogical

nomenclature. A miner upon finding a

fossil will present his find as a sort of

religious offering to a near-by monastery

or Buddhist shrine, and here it will be

placed before an image. In some cases I

learned that fossil teeth of large size, such

as elephant molars, are worshipped as

"Buddha's teeth," but the monks themselves do not approve of this practice…. Quite

possibly the magic cult came from China where "dragon bones" continue to play an

important role in native pharmacology and superstitious customs….

During my stay at Mogok, it was generally believed by the natives that I had come to

search for a special kind of dragon bone. The result was that after a week's stay, prices for

fossil bones soared, until an elephant's molar was valued as highly as a five-carat ruby! This

attitude did not make it easy for us to acquire much of the cave fauna. At Leu Village,

where I made an attempt to excavate one of the larger caves, the headman told me that

Figure 5. Tunnelling into the limestone in

search of rubies at the Linyaungchi mine in

the Mogok area. (Photo: Thomas Frieden)

years ago, near Pinpyit, miners had come across large bones. They had been so frightened

at the sight of the huge animal remains that they gave up their work, closing the entrance

with a stone wall so that the dragon might not walk out and ravage their village!

Hellmut de Terra, 1943

The Pleistocene of Burma

Transactions of the American Philosophical Society

It is unlikely that any human could live in the Mogok area for long, particularly in

caves, and not discover the gems which have made the area so famous. No doubt,

the first gems collected would be the well-formed red spinel crystals today

termed anyan-nat-thwe (`spirit polished') by locals. Such lustrous crystals need no

fashioning to display their beauty and could not help but attract attention.

Modern history of Mogok

According to G.S. Streeter (1889a), one of the sons of Kun-Lung, founder of the

Shan Dynasty, is said to have governed a state in the 6th century AD, near which

there were ruby mines, and to have paid an annual tribute of 2 viss (about 3.3 kgs)

of rubies to the central government. However, this has not been documented.

Ehrmann (1957) describes a local legend stating that modern Mogok was founded

in 579 AD by headhunting tribesmen from nearby Möng Mit (Momeik). After losing

their way they discovered a "mountain break full of beautiful rubies" when

investigating a commotion made by many birds. This story is similar to that told of

many gem deposits and is believed to derive from Sinbad the Sailor's "Valley of

Precious Stones" in Sri Lanka, or perhaps al-Kazwini's relation of Alexander's valley

of serpents and diamonds in India (Kunz, 1913). In the Burmese version, a fever-

and serpent-ridden valley was found teeming with rubies. Far too dangerous for

mere mortals to enter, the stones were obtained by casting lumps of fresh meat

into the abyss. This attracted large birds of prey who snatched up the meat and

brought it out, along with the rubies adhering to it. They were then retrieved from

the birds' nests and droppings (see box, 'The Valley of Serpents,' Chapter 11).

Figure 6. Spoils of the jungle

A variety of wild game is found in the heavy forest surrounding the Mogok ruby and sapphire mines.

Here Burmese miners return from the hunt with a slain leopard. (From O'Connor, 1905)

The first Europeans arrive

From the earliest times of European contact with East Asia, Burma has been

associated with rubies. Nicolò di Conti, the first European visitor to Ava, described

the king of Ava thus:

The King rideth upon a white Elephant, which hath a chayne of golde about his necke, being

long unto his féete, set full of many precious stones.

Nicolò de' Conti, 1419–1444

from Frampton's Elizabethan translation (Penzer, 1929)

Ludovico di Varthema visited Pegu between 1502 and 1508:

The sole merchandise of these people is jewels, that is, rubies, which come from another city

called Capellan [Ruby Mines District in Burma], which is distant from this thirty days' journey;

not that I have seen it, but by what I have heard from merchants…. Do not imagine that the

King of Pego enjoys as great a reputation as the King of Calicut, although he is so humane and

domestic that an infant might speak to him, and he wears more rubies on him than the value

a very large city, and he wears them on all his toes. And on his legs he wears certain great

rings of gold, all full of the most beautiful rubies; also his arms and his fingers all full. His ears

hand down half a palm, through the great weight of the many jewels he wears there, so that

seeing the person of the king by a light at night, he shines so much that he appears to be a

sun.

Ludovico di Varthema of Bologna (Temple, 1928)

Di Varthema and his party offered the king coral as a gift. This act of generosity

so impressed the king that he gave them over 200 rubies (Temple, 1928).

Duarte Barbosa, visiting Burma about the same time, gave one of the best

accounts of rubies:

Capelam

And yet further inland beyond this city [Ava] and Kingdom there is another Heathen city whith

its own King, who nevertheless is subject and under the lordship of Ava; which city or

Kingdom they call Capelam. Around it are found many rubies which are brought in for sale to

the Ava market, and are much finer than those of that place.

Of Rubies

In the first place rubies are produced in the Land of India and are found chiefly on a river

called Pegu. These are the best and finest, and are called Numpuclo* by the Malabares, and

when they are clean and without flaw they fetch a good price. To test their quality the Indians

put them on the tongue; those which are finest and hardest are held to be the best. To test

their transparency they fix them with wax on a very sharp point and looking towards the sun

they can find any blemish however slight. They are also found in certain deep pits in the

mountains beyond the said river.

In Pegu they know how to clean but not how to polish them, and they therefore convey them

to other countries, especially to Paleacate, Narsinga, Calicut and the whole of Malabar, where there

are excellent craftsmen who cut and mount them.

Dames' annotations

* Pegu Rubies. The name Numpuclo here stated to be used for the Pegu rubies in Malabar is

explained by Mgr. Dalgado in his Glossario. He considers that the initial letter is wrongly given

owing to a copyist's mistake, and that the word should be read chumpuclo, as in Malayalam

the name of the ruby is chuvappukallu from kallu "stone" and chuvappu "ruby," literally "ruby-

stone." For the places where these rubies are found see p. 107 and p. 108.

Duarte Barbosa, ca. 1500–1517 (from Dames, 1858)

The first Englishman to visit Burma

was Ralph Fitch, in 1586, whose

journey led to the founding of the

British East India Company. He said:

Caplan is the place where they finde the

rubies, saphires, and spinelles: it

standeth sixe dayes journey from Ava in

the Kingdome of Pegu. There are many

great high hilles out of which they digge

them. None may go to the pits but onely

those which digge them.

Ralph Fitch, 1586 (in Hakluyt, 1903–05)

Not only did Fitch comment upon

the rubies, but also told of a curious

local custom mentioned by many of

the early European travelers to the area:

In Pegu, and in all the countreys of Ava, Langeiannes, Siam, and the Bramas, the men weare

bunches or little round balles in their privy members: some of them weare two and some

three. They cut the skin and so put them in, one into one side and another into the other side;

which they do when they be 25 or 30 years old, and at their pleasure they take one or more of

them out as they thinke good… The bunches aforesayd be of divers sorts: the least be as big

as a litle walnut, and very round: the greatest are as big as a litle hennes egge: some are of

brasse and some of silver: but those of silver be for the king and his noble men. They were

invented because they should not abuse the male sexe for in times past all those countries

were so given to that villany, that they were very scarse of people.

Ralph Fitch, 1586 (in Hakluyt, 1903–05)

Just how such balls would prevent masturbation or homosexuality is unclear.

But the custom continues into the present day. During one 1980s visit to Burma,

William Spengler met a man who claimed that he had pearls implanted in his

genitals, to heighten sexual pleasure (very pers. comm., 20 March, 1995).

Alexander Hamilton (1744), who traveled to India and Burma in the 18th

century, also had some interesting remarks about the Burmese. In reference to the

sarongs worn by ladies, he said:

Figure 7. A stunning 1734-ct Mogok ruby crystal

sits atop the marble which nurtured it into

existence. (Photo: Thomas Frieden)

Under the Frock they have a Scarf or `Lungee' doubled fourfold, made fast about their Middle,

which reaches almost to the Ancle, so contrived, that at every Step they make, as they walk, it

opens before, and shews the right Leg and Part of the Thigh.

This Fashion of Petticoats, they say, is very ancient, and was first contrived by a certain Queen

of that Country, who was grieved to see the Men so much addicted to `Sodomy,' that they

neglected the pretty Ladies. She thought that by the Sight of a pretty Leg and plump Thigh, the

Men might be allured from that abominable Custom, and place their Affections on proper Objects,

and according to the ingeiuous Queen's Conjecture, that Dress of the `Lungee' had its desired End,

and now the Name of Sodomy is hardly known in that Country.

Alexander Hamilton, 1744

Hamilton also mentioned the products of Burma:

The Product of the Country is Timber for building, Elephants, Elephants Teeth, Bees-wax,

Stick-lack, Iron, Tin, Oyl of the Earth, Wood-oyl, Rubies the best in the World, Diamonds, but

they are small, and are only found in the Craws of Poultry and Pheasants, and one Family has

only the Indulgence to sell them, and none dare open the Ground to dig for them… About

twenty Sail of Ships find their Account in Trade for the limited Commodities, but the

Armenians have got the Monopoly of the rubies, which turns to a good Account in their Trade;

and I have seen some blue Sapphires there, that I was told were found on some Mountains of

this Country.

Alexander Hamilton, 1744

Figure 8. One of the earliest European

maps to show the position of the ruby

mines, based on information provided by

a Burmese slave to Francis Hamilton in

1824. Roman numerals indicate the

average number of stages (walking days)

between points. Although the distances

are relatively accurate, Mogok (`Mogouk')

actually lies further east from Amarapura

(near present-day Mandalay). (Redrawn

by the author from Hamilton, 1824)

Such tales certainly contributed to the European

view of the Orient as a place of wonder and exotic

mystery. But these were nothing compared to that

related by the famous French traveler and diamond

merchant, Jean-Baptiste Tavernier, about the King

of Bhutan.

There is no King in the World more fear'd and more

respected by his Subjects then the King of Boutan; being in

a manner ador'd by them…. One thing they told me for truth,

that when the King has done the deeds of nature, they

diligently preserve the ordure, dry it and powder it, like

sneezing-powder: and then putting it into Boxes, they go

every Market-day, and present it to the chief Merchants, and

rich Farmers, who recompence them for their kindness: that

those people also carry it home, as a great rarity, and when

they feast their Friends, strew it upon their meat. Two Boutan Merchants shew'd me their

Boxes, and the Powder that was in them.

Jean-Baptiste Tavernier, 1677–8

That is one banquet in which this beggar would decline to partake.Down

Satan! But it is interesting that the passage was apparently so shocking to Victorian

British that it was removed from the later editions edited by Valentine Ball.

Men of the cloth

Figure 9. Native gem diggers at

Mogok about the turn of the

century. (From O'Connor, 1905)

Cæsar Fredericke of Venice, who journeyed to Asia in

1563, gave one of the earliest accounts of the

fascinating Asian technique of negotiating prices in

secret by covering the hands of the buyer and seller

with a cloth.

There are many Marchants that stand by at the

making of the bargaine, and because they shall

not understand howe the Jewels be solde, the

Broker and the Marchants have their hands

under a cloth, and by touching of fingers and

nipping the joynts they know what is done, what

is bidden, and what is asked. So that the

standers by knowe not what is demaunded for

them, although it be for a thousand or 10.

thousand duckets. For every joynt and every

finger hath its signification. For if the Marchants

that stande by should understand the bargaine,

it would breede great controversie amongst

them.

Cæsar Fredericke, 1563, (in Hakluyt, 1903–05)

Figure 10. Traders offer jadeite,

sapphires and rubies in Rangoon's

Shwebontha Street gem market.

(Photo by the author, 1992)

Of the many accounts of the gems of Pegu, as Burma was then known, perhaps

most interesting was that of Cæsar Fredericke of Venice, who journeyed to Asia in

1563. The following is his description of the gem trade in Pegu.

…it is a thing to bee noted in the buying of jewels in Pegu, that he that hath no knowledge

shall have as good jewels, and as good cheap, as he that hath practized there a long time.

There are in Pegu foure men of good reputation, which are called Tareghe, or brokers of

Jewels… through the hands of these foure men passe all the Rubies: for they have such

quantitie, that they knowe not what to doe with them, but sell them at most vile and base

prices. When the Marchant hath broken his mind to one of these brokers or Tareghe, they cary

him home to one of their Shops, although he hath no knowledge in Jewels: and when the

Jewellers perceive that hee will employ a good round summe, they will make a bargaine, and

if not, they let him alone… when any Marchant hath bought any great quantitie of Rubies, and

hath agreed for them, hee carieth them home to his house, let them be of what value they

will, he shall have space to looke on them and peruse them two or three dayes: and if he hath

no knowledge in them, he shall alwayes have many Marchants in that Citie that have very

good knowledge in Jewels; with whom he may alwayes conferre and take counsell, and may

shew them unto whom he will; and if he finde that hee hath not employed his money well, hee

may returne his Jewels backe to them who hee had them of, without any losse at all. Which

thing is such a shame to the Tareghe to have his Jewels returne, that he had rather beare a

blow on the face then that it should be thought that he solde them so deere to have them

returned.

Cæsar Fredericke, 1563 (in Hakluyt, 1903–05)

Thus "spake" Cæsar Fredericke. After reading his tale, one can only wish and

sigh that modern-day gem merchants would be so understanding. Perhaps

businessmen haven't really changed all that much. Fredericke was no doubt just an

example of a species still in flourish. Had he made his journey in the present day,

Fredericke may have returned to Europe with wooden elephants – in addition to his

gem purchases.

Guiseppe d'Amato's description of Mogok

From 1597 AD onwards, Mogok was part of Burma proper. The first European to actually

visit the mines in the Mogok area and write about them was a Portuguese priest, Giuseppe

d'Amato, sometime before 1833. D'Amato arrived in Burma sometime in 1784, and spent

the rest of his life there. He resided at Moun-lha (Mon-lhá), some 30 miles (48 km)

northwest of Ava, where he died in 1832 (Burney, 1832). His brief account of the ruby

workings at Kyatpyin was published posthumously in the Journal of the Asiatic Society of

Bengal and is reproduced in its entirety below:

IV.--Short Description of the Mines of Precious Stones, in the District of Kyat-

pyen, in the Kingdom of Ava.

[Translated from the original of Père Giuseppe d'Amato]

The territory of Kyat-pyen * (written Chia-ppièn by d'Amato) is situated to the

east, and a little to the south of the town of Mon-lhá , distant 30 or 40 Burman

leagues, each league being 1000taa**, of seven cubits the taa |; say 70 miles [113

km]. It is surrounded by nine mountains. The soil is uneven and full of marshes, which

form seventeen small lakes, each having a particular name. It is this soil which is so

rich in mineral treasures. It should be noticed, however, that the ground which

remains dry is that alone which is mined, or perforated with the wells whence the

precious stones are extracted. The mineral district is divided into 50 or 60 parts,

which, beside the general name of "mine," have each a different appellation.

The miners, who work at the spot, dig square wells, to the depth of 15 or 20

cubits, and to prevent the wells from falling in, they prop them with perpendicular

piles, four or three on each side of the square, according to the dimensions of the

shaft, supported by cross pieces between the opposite piles.

When the whole is secure, the miner descends, and with his hands extracts the

loose soil, digging in a horizontal direction. The gravelly ore is brought to the surface

in a ratan basket raised by a cord, as water from a well. From this mass all the

precious stones and any other minerals possessing value are picked out, and washed

in the brooks descending from the neighbouring hills.

Besides the regular duty which the miners pay to the Prince, in kind, they are

obliged to give up to him gratuitously all jewels of more than a certain size or of

extraordinary value. Of this sort was the tornallina (tourmaline?) presented by the

Burman monarch to Colonel Symes. It was originally purchased clandestinely by the

Chinese on the spot; the Burmese court, being apprized of the circumstance,

instituted a strict search for the jewel, and the sellers, to hush up the affair, were

obliged to buy it back at double price, and present it to the king.

You*** may ask me, to what distance the miners carry their excavations? I reply,

that ordinarily they continue perforating laterally, until the workmen from different

mines meet one another. I asked the man who gave

me this information, whether this did not endanger the falling in of the vaults, and

consequent destruction of the workmen? but he replied, that there were very few

instances of such accidents. Sometimes the miners are forced to abandon a level

before working to day-light, by the oozing in of water, which floods the lower parts of

the works.

The precious stones found in the mines of Kyat-pyen , generally speaking, are

rubies, sapphires, topazes, and other crystals of the same family, (the precious

corundum .) Emeralds are very rare, and of an inferior sort and value. They

sometimes find, I am told, a species of diamond, but of bad quality****.

The Chinese and Tartar merchants come yearly to Kyat-pyen , to purchase

precious stones and other minerals. They generally barter for them carpets, coloured

cloths, cloves, nutmegs and other drugs. The natives of the country also pay yearly

visits to the royal city of Ava, to sell the rough stones. I have avoided repeating any of

the fabulous stories told by the Burmans of the origin of the jewels of Kyat-pyen .

There is another locality, a little to the north of this place, called Mookop , in

which also abundant mines of the same precious gems occur.

Note .--While I am writing this brief notice, an anecdote is related to me by a

person of the highest credit, regarding the discovery of two stones, or, to express

myself better, of two masses ( amas ) of rubies of an extraordinary size, at Kyat-

pyen . One weighed 80 biches*****, Burmese weight, equivalent to more than 80

lbs.! the second was of the same size as that given to Colonel Symes. When the

people were about to convey them to the capital to present them to the king, a party

of bandits attacked Kyat-pyen for the second time, and set the whole town on fire. Of

the two jewels, the brigands only succeeded in carrying off the smaller one; but the

larger one was injured by the flames: the centre of the stone, still in good order, was

brought to the king. I learned this from a Christian soldier of my village of Mon-lhá ,

who was on guard at the palace when the bearer of the gem arrived there.

Prinsep's annotations

* The Kyat-pyen mountains are doubtless the Capelan mountains mentioned as the

locality of the ruby, in Phillips' Mineralogy--"60 miles from Pegue, a city in Ceylon ."

Though it might well have puzzled a geographer to identify them without the clue of

their mineral riches.

** Estimating the cubit at 1 1 / 2 feet, the league will be 10,500 feet, or nearly

two miles;--about an Indian kos . [The cubit is an ancient measure of length based on

the forearm]

*** The letter seems to have been intended for some scientific friend in Italy.

**** Probably the turmali or transparent zircon, which is sold as an inferior

diamond in Ceylon. [Vide vol. i. page 357.]

***** The Père d'Amato's biche is the bisse of Mendez Pinto, and the old

travellers, and the biswa or vis of Natives of India. The Burmese word is Peik-tha ,

which is equivalent to 3 1 / 2 lbs., and to a weight on the Coast of Coromandel

called vis . B.

Père Giuseppe d'Amato, 1833 (with notes from James Prinsep)

Ralph Fitch also mentioned the Tareghe, and said that if they failed to pay a

merchant in a timely fashion, the merchant could "take [the Tareghe's] wife and

children and his slaves, and binde them at your doore, and set them in the Sunne;

for that is the law of the countrey." (Hakluyt, 1907) A noble custom, and perhaps

one which could be applied today to politicians, tax collectors and sundry dictators.

In the year 1597 AD, the Burmese King Nuha-Thura Maha Dhama-Yaza ratified

a royal edict exchanging small parts of Burma under his control for the Mogok

Stone Tract, previously under the control of a Shan saopha (Burmese = sawbwa; or

prince). Both the Burmese text of this order and an English translation are

reproduced in Figure 11 (George, 1915).

According to Halford-Watkins (1934), the town of Mogok did not exist at that

date, the name merely being applied to a mining area and series of paddy fields

situated some five miles (8 km) from Thapanbin village. Due to the difficult nature

of the country, the journey between the two places could not be completed before

nightfall, which is mochok in Burmese. Thus the name Mochok (`nightfall camping

ground'), which was later corrupted to Mogok. Another possible derivation of the

name is that it is the place where the mountains meet the sky, in allusion to the

mountain tops being hidden in the clouds during the rainy season.

Figure 11. The Royal edict of 1597 AD transferring the Mogok Stone Tract from a

Shan saopha (sawbwa in Burmese) to the Burmese King. (From George, 1915)

Translation

Shwe-Wa-myo (Ava) was established on 12th Tawthalin Labyigyaw of 959 B.E. It is

the Ratna Pura (Ratna=Gem, and Pura=City). Mogok and Kyatpyin are names for

Gem. They should be included in the Shwewamyo. These two were part of Momeik

Sawbwa's State but should be excluded and Tagaung Myo with its surrounding

villages be included in the State instead.

It is ordered that the Momeik Sawbwa take possession of Tagaungmyo and that

Mogok and Kyatpyin be given over to Shwewamyo. The Wuns concerned must take over

the rubies with a list of all descriptions (big and small) and pay into the Government

Treasury.

No appointments whatever are therefore to be made by the Sawbwa to Mogok and

Kyatpyin which have been given to Shwewamyo in exchange for Tagaungmyo.

nakhandawpyawgyima

5th Thadingyut Labyigyaw, 959 B.E.

One might wonder why the Shan saopha would agree to such a one-sided deal,

where a relatively worthless piece of land was traded for the world's greatest ruby

mines. It is indeed strange what people will do with a knife at their throat.

Burmese monarchs worked the Stone

Tract as a royal monopoly, in a

thoroughly despotic manner. All rubies

above the value of Rs2000 were

considered Crown property and failure

to surrender them was punishable by

torture and death. Father Sangermano,

an Italian priest who lived in Ava

between 1783 and 1806, discussed this:

With regard to precious stones, a few inferior

sapphires and topazes are sometimes found;

but it is the rubies of the Burmese Empire

which are its greatest boast, as both in

brilliancy and clearness they are the best in the world. The mines that contain them are

situated between the countries of Palaon and the Koè. The Emperor employs inspectors and

guards to watch these mines, and appropriates to himself all the stones above a certain

weight and size; the penalty of death is denounced against any one who shall conceal, or sell,

or buy any of these reserved jewels.

Father Sangermano, 1893

The Burmese Empire a Hundred Years Ago

But conceal them they did. The story of the Nga Mauk Ruby provides an example. Nga Mauk,

a poor miner, uncovered a large fine ruby which was later divided into two excellent pieces along

an incipient flaw. One half was given to the king, but the other secretly sold. The king learned of

the deception when he proudly showed his half to the dealer who had bought the other part

(Keely, 1982). Enraged, he sent his minions to exact punishment. All area villagers were placed

into a makeshift stable and burned alive. Even today, some 150 years later, the remains of this

horrible cremation can be seen at a spot called Laung Zin, which means "fiery platform."1 Daw

Nann, his wife, is said to have watched his blazing death from a hill near Kyatpyin which is today

called Daw Nann Kyi Taung (`the hill from where Daw Nann looked down'). As for the famous

Nga Mauk ruby, it disappeared from the palace the night the British conquered Ava in 1885

(Keely, 1982; E.W. Streeter, 1892; Clark, 1991).2

Figure 12. "An' I seed her first a-smokin' of a

whackin' white cheroot…"

(Rudyard Kipling, Mandalay ) (Photo: Thomas

Frieden)

In wars with the neighboring kingdoms of

Manipur and Assam, prisoners were taken.

During the latter part of the 19th century,

production from Mogok declined drastically

due to the despotic rule and heavy handed

policies of the Burmese monarchs' agents.

In their quest to extract as much tax as

possible, they effectively drove people from

the area.

Empire building

On the road to Mandalay, where the old Flotilla

lay,

With our sick beneath the awnings when we went

to Mandalay!

Oh the road to Mandalay, where the flyin'-fishes

play,

An' the dawn comes up like thunder outer China

'crost the Bay!

Rudyard Kipling, 1892, Mandalay

The British move into Burma came slowly, but inevitably. Disputes on the

border with British India led to the first Anglo-Burmese war in 1824–6. As a result,

Arakan, Assam and Tenasserim were ceded to the East India Company. Pegu was

annexed after the British won the second Anglo-Burmese war of 1852–3. In 1885,

commercial disputes and reported corruption and massacres at the Court gave the

British the needed excuse to annex all of Upper Burma, including the Mogok Stone

Tract.

Mandalay was taken on Nov. 29, 1885. While the British expedition quickly took

the capital, it was over one year before Mogok was occupied and five long years of

skirmishes before the rest of Upper Burma was secured.

Unfortunately, the fabulous jewels of King Thebaw were never recovered. When

the British took Mandalay, they sealed the palace, but Thebaw's ministers

Figure 13. A native miner at a twin-lon

mine, near Mogok, Burma.

(From O'Connor, 1905)

requested permission for Queen Supayalat's ladies to come and go as they wished.

General Prendergast, leader of the British expedition, agreed over the objections of

G.S. White. White wrote: "Colonel Sladen… sent me word that the ladies might be

allowed to come and go freely. I entered a protest that everything of small size and

great value would be passed out by the ladies…. [as a result] thousands of pounds

of booty were, I am sure, lost to the army." (Stewart, 1972)

Halford-Watkins (1934) felt the magnitude of

the royal treasure was highly exaggerated,

pointing out that there is not a single written

first-hand description of these gems:

…[the monarchs'] persons were regarded as being so

very sacred that such regalia had to be viewed from

a very respectful distance, so that it was quite

impossible for anyone even to judge of the genuine

nature of the stones, much less to estimate their

value. [I have] talked with several of the old officials

and habitués of the palace of the times of both King

Mindoon Min and Thebaw, and has been assured that

the majority of these tales are pure invention, and

that most of the stones worn were of quite ordinary

quality, and sometimes very poor, quality; while

many of the large gems attached to the robes and

other regal paraphernalia were merely coloured glass.

This rather calls to mind the stories of the valuable ruby trousers buttons worn by my friend

the Sawbwa of Momeit during his visit to London, which were made so much of at the time by a

certain section of the press. The Sawbwa invariably wears his native costume, in which his trousers

do not possess a single button of any kind, much less ruby ones.

Figure 14. King Thebaw and Queen

Supayalat, the last monarchs of Burma.

(From theIllustrated London News, 16

Jan., 1886)

The fact that only a

comparatively few gems of any

importance were found in the

possession of King Thebaw at

the taking of Mandalay confirms

the statements made by these

old officials. And it is a known

fact that when Queen Supayalat

left she carried with her all her

personal gems wrapped in a

handkerchief which was so small

that she dropped it as she was

boarding the steamer, and did

not miss it until it was returned

by a soldier who had picked it

up. Of course it was said that

the majority of the treasure had

been buried as the British

advanced, and there has since been much excavating and searching done in and around the

square mile of Fort Dufferin, in some of which [I have] taken an active part. But so far the result

has been a total blank, as the old officials always said that it would be, owing to nothing having

been buried, and but comparatively little stolen, for the simple reason that it was not there to be

made away with.

J.F. Halford-Watkins, 1934

Shortly after the annexation of Upper Burma in December, 1885, London

jeweler, Edwin Streeter, was breakfasting in Paris and happened to overhear two

men discussing the Burma ruby mines. After introducing himself, he found that a

French firm, Bouveillein & Co., had arranged a provisional lease of the ruby mines

from King Thebaw. With the British annexation, this lease was then worthless.

Upon his return to London, Streeter contacted the India Office with the prospect

of obtaining the lease. A syndicate was formed, consisting of Streeter, Charles Bill,

Reginald Beech and Streeter's son, George Skelton Streeter. Captain Aubrey Patton

was selected to travel to Rangoon for negotiations. He departed from London in

January, 1886. On Patton's arrival in Burma, it was found that Gillanders,

Arbuthnot & Co. of Calcutta and Rangoon, in conjunction with an unknown London

jewel broker, had already offered two lakhs3 of rupees for the lease. The Streeter

Figure 15. British camp at Mogok. (From theIllustrated

London News, 19 Feb, 1887)

syndicate countered with an offer of three lakhs, which Gillanders, Arbuthnot & Co

met. The government then decided to offer the lease for public tender. In respect

of the further competition, Streeter increased the offer to four lakhs (£30,000) for

a five-year lease, which was provisionally accepted, pending investigation into

native mining rights (E.W. Streeter, 1892; Times of London, Aug. 17, 1887).

Meanwhile, as per the British Indian government's suggestion, Streeter dispatched

his son, along with Bill, Beech and Rangoon engineer, Robert Gordon, to

accompany the British military expedition to Mogok, which left Mandalay in

November, 1886 (E.W. Streeter, 1892).

Figure 16. Geological map of the Mogok Stone Tract in Upper Burma. Most gems are recovered

from alluvial deposits situated near the towns of Mogok and Kathé. (Modified from Iyer, 1953)

Mogok was occupied by British troops in December, 1886. In February, 1887, Mr.

F. Atlay arrived at the mines to act as agent for the Streeter syndicate. He

subsequently became mine manager, a position he continued to hold under the

Burma Ruby Mines Ltd.

It was not until 1889 that the lease actually began. The reasons for the delay

were entirely political. Edward Moylan, a disbarred barrister, managed to convince

many in London that the lease holder, E.W. Streeter, had acquired it through

dishonest means (such as bribery). Moylan, who was then Burma correspondent for

the Times of London, succeeded in raising enough questions to cause the lease to

be reexamined. In the end, his true motive was revealed; he was working for

Gillanders, Arbuthnot & Co, who hoped to win the lease themselves4 (Stewart,

1972).

At this point, enter one Moritz Unger, a Paris jeweler. He claimed to represent a

powerful European syndicate with the London Rothschilds at the head, and in

March, 1886, applied for the lease. Unfortunately, he could produce no evidence of

this syndicate's existence, and soon disappeared from the scene

(London Times, Aug. 17, 1887).

In light of the controversy surrounding the lease, the British government

decided to send a trained geologist to report on the mines. C. Barrington Brown

reached Mogok on January 10, 1888. His was the first detailed geologic study of

the Mogok area (Brown & Judd, 1896). Brown's report was eventually received by

the Secretary of State and the lease was put up for renewed tender (E.W. Streeter,

1892).

By this time, the London Rothschilds were involved. N.M. Rothschild and Sons,

through their Exploration Co subsidiary, had written to the Secretary for India,

asking if they could bid for the mines. Eventually the Streeter syndicate joined with

N.M. Rothschild and the Exploration Co., and together they floated the Burma Ruby

Mines, Ltd. A fresh offer was tendered and was accepted on Nov. 27, 1888. The

lease was signed on February 22, 1889, giving the company seven years, with a

renewal option, at an annual rent of Rs400,000, plus one sixth of net profits (E.W.

Streeter, 1892; P. Streeter, 1993). Streeter and his associates later sold the lease

to the Burma Ruby Mines, Limited for £55,000 (Brown, 1927).

Notes

1. George (1915) has reported that the name Kyatpyin, from which the Capelan of

early European travellers is derived, comes from the fact that the people slept on

platforms, with fires underneath to keep them warm at night.

One lakh equals 100,000 rupees. A Mr. Danson was reportedly sent to Mogok

at one stage to report on the mines for Gillanders, Arbuthnot & Co. (George, 1915). This page is http://www.ruby-sapphire.com/r-s-bk-burma.htm v. 1.0

Page updated 7 March, 2013

Burma Continued from Part 1

The Burma Ruby Mines, Ltd.

The Times of London published the prospectus for

the company on Feb. 27, 1889. That morning,

extraordinary scenes were witnessed at the

company's offices, as the following extract shows:

If St. Swithin's Lane had been a ruby mine

itself the scene witnessed there yesterday

morning could not have been more

remarkable. The crowd around New Court was

so dense that Lord Rothschild and other

members of the house were unable to get in by

the door. So a ladder had to be got, and the

spectacle was seen of a number of great

financiers entering their own office in a

burglarious fashion. The clerks had to be

smuggled in by a back entrance behind the

Mansion House. The surging crowd in front

drove a telegraph boy right through the

window of a baker's shop opposite, the poor

fellow being rather severely hurt. The fortunate possessors of Ruby Mine

application forms, which were being hawked at five shillings, had to pass

between files of policemen to hand in their applications. The next time the

Figure 17. Edwin Streeter, the

London jeweler and author who

was involved in the early history

of the Burma Ruby Mines, Limited.

(From Streeter, 1892)

Messrs. Rothschild make an issue, it would be well for the police to arrive on

the scene before the stags.

Financial News, London, Feb. 28, 1889

Within hours, the issue sold out. General public and company directors alike

were under the mistaken impression that fabulous riches were just waiting to be

unearthed in Mogok. No one gave a thought to the difficulties of mining gems in

such an inhospitable and remote location. Instead, they could see but one thing--

rubies--pigeon's blood rubies.

London Mine Gambling

London has periodical investment or gambling crazes. At one time it is

railway "securities," so called, at another the bonds of some bankrupt State,

at still another some South Sea bubble in the shape of Indian or African gold

mines. At present the fever is African and Burmese….

The latest London craze was finely exhibited at the recent allotment of

shares in the Burmese ruby mines, concerning which our well-informed London

correspondent wrote us February 15th: "The mines may be immensely valuable,

or perhaps not; no one can tell as to this until a year's work has been done

upon them." All London rushed to get the prospectus, and the crowd began to

collect in front of theRothschild's offices long before they were open in the

morning. The £1 shares went immediately to £4, and the total amount of stock

offered was applied for many times over.

These shares are "a pure gamble," even more than is usual in mining,

though they have this advantage over most of the London mining stocks, that

there is a possibility that they will pay, and pay largely, while the average

London mining stock is absolutely certain never to pay anything.

Editorial, Engineering and Mining Journal

New York, March 16, 1889

The Company started its career with a paid up capital of £150,000 and a highly

exaggerated view of potential production. All kinds of unforeseen difficulties were

encountered during the first years, with an unusual amount of time spent in

preliminary operations. The annual rental fee to be paid to the Government of India

was originally fixed at the high sum of £30,000 per year plus 30% of any profits

made, in return for the sole rights to mine with machinery. Native mining was also

allowed by native methods in areas not utilized by the Company, for which a tax of

30% on all finds was collected. This tax soon proved unworkable and so a fee per

workman was charged instead. Revenue from native workings later became an

important source of funds, but in the beginning little was collected.

Mogok--A city built on rubies

Mogok has always been known as the city of rubies.

Just how true this is was brought home when

geologists and engineers first began to study the gem

deposits of the area. They found that some of the

richest alluvials lay right beneath the town itself and

so in 1902, and again in 1908 and 1909, parts of the

town were purchased and the people resettled

elsewhere (Brown, 1933).

Figure 18. High street in Mogok about 1905 (From

O'Connor, 1905)

Tremendous difficulties were encountered from the outset. First, a road had to be

constructed from Thabeitkyin to Mogok, through nearly 100 kms of densely-jungled

hills 5 (George, 1915). Machinery had to be imported; diseases took their toll of

men and livestock; flooding was common in the rainy season; these were but a few

of the problems. Power generation was yet another obstacle. Coal was not practical

as it would have had to have been brought from Thabeitkyin (Talbot, 1920). Steam

pumps were used at first, but required too much timber. Since Mogok had plenty of

water, it was decided to construct a hydroelectric plant. This was completed in

1898, the first of its kind in that part of Asia (Brown, 1933).

Although water helped in electricity

generation, it remained the nemesis

of miners at Mogok, continually

flooding the workings. The

company's engineer, A.H. Morgan,

proposed a tunnel through the rock

some 100 ft (30 m) below the

surface and more than a mile (1.6

km) in length. Construction began in

1904 and finished in 1908. The

tunnel was immediately successful in

dewatering the

diggings.6 Unfortunately, its

completion coincided with a

downturn in the gem market, in part brought about by the development of

Verneuil's synthetic ruby.

Introduction of cheap Verneuil synthetic rubies hurt sales, as did the economic

downturn resulting from World War I. With losses mounting, the Company

renegotiated its lease with the Government several times, but it was not enough.

In 1925, faced with mounting losses, the Company went into voluntary liquidation.

No buyers were forthcoming and so in 1931 the lease was surrendered. Thus ended

the first attempt at mechanized mining of the world's richest ruby deposits.

Company postmortem

Many have speculated about the reasons for the Company's failure (Halford-

Watkins, 1932a-d), most concluding that it was just not meant to be, the

difficulties being too great to surmount. But evidence uncovered by the author

suggests the Company owed its failure less to the difficulty of the task and more to

that old devil we know--human greed. In a confidential report written to the

Government of India on the future of mining at Mogok, the head of the Geological

Survey of India, J. Coggin Brown, pointed his finger straight at the De Beers

diamond cartel:

Figure 19. Bottom of the ramp at the Burma Ruby

Mines Ltd. mine at Mogok, with both British and

native workers. (From Claremont, 1906)

At this juncture I cannot refrain from writing an opinion which I have

already expressed verbally, that the influence of the De Beers diamond

concern has had more to do with the present [1927] position of mining for

coloured gems in Burma than appears on the surface. The reasons for this

are obvious, and it is significant that there has always been a powerful

representative of the Great South African concern on the Board of the

Burma Ruby Mines, Limited.

J. Coggin Brown, 1927

Gem Mining in the Mogok Stone Tract… (confidential report)

Brown was referring to the competition for a share of the gem market between

De Beers and the Burma Ruby Mines Ltd. Apparently, he believed that the Burma

Ruby Mines Ltd. was sabotaged by De Beers. This idea is not as far-fetched as it

might seem. De Beers was not always the huge and powerful monopoly of today. It

has taken over eighty years of monopolistic practices and masterful marketing to

reach such a position of dominance.

Marching on Mogok

It was anticipated that we should not reach this unknown country without meeting with

some opposition, and on Nov. 15th [1886] a force of Shans was found stockaded in our

front on the Kodan River. The ground they had chosen was a spot on which two years

previously an army of Theebaw's had been completely routed. A successful flanking

movement, however, cleared them out completely in a little over an hour, several dead

and wounded men being left behind.

No more opposition being met with, Sagadoun at the foot of the hills was reached

and occupied, and a halt was made for a few days. From here, 6000 feet above us,

glittering in the sun, could be seen the peaks of Shwee-ov-Toun, which were promptly

christened Sheba's breasts, from their supposed likeness to the hills that guarded King

Solomon's mines, and lesser peaks covered with jungle forest, from which peeped out a

native village or a green patch of cultivation.

On Dec. 18th the march up the hills began. The only transport that could be used

along these mountain tracks was that of pack mules and ponies, and hard work these

poor beasts found it, often ascending 2000 feet in a day, and many a man wondered as

he tramped along if his kit and food would reach him before midnight. At each camp new

and curious views would open themselves out before us; at one point the plains and hills

between us and Bhamo could be seen stretching for miles and miles in the bright

evening sunlight; next morning the same country would be covered with white clouds

floating far below our position, appearing like some huge snow field. Again, at another

camp would be discovered away to the east some mountain range of Yunnan veiled in

blue mist.

As the force proceeded, the Shans and Dacoits fell back, evacuating one strong

stockade after another, till at last, on the morning before Christmas Day, we reached a

point at the end of a narrow valley where the hills rose high above us, and through

which two narrow passes lead directly into the Ruby Mine district. It was found that

these passes were strongly stockaded, and held by the enemy in force.

General Stewart determined to attack the position on our right front first, as it would

otherwise command our flank. A few shells were first dropped into it, and then an

attacking party moved forward; in about an hour a ringing cheer informed us that the

stockade was taken, and soon its former occupants could be seen scuttling over the

hills, conspicuous in their white jackets and large straw hats. It was too late, however,

to give proper attention to the stockade on our left which commanded the road to

Mogok; so camp was pitched, and on the order bugle sounding it was found that we

were to spend a quiet Christmas Day, for the last few days' work had exhausted both

men and beasts. At an elevation of about 6000 feet, the morning of Dec. 25th dawned in

quite an English fashion; a heavy white frost covered the ground, and bitter were the

complaints at the coldness of the night. The popular Padre of the force held divine

service and the day passed quietly. Next morning the column started early, but only to

discover that the series of stockades on our left had been abandoned: they had been

most carefully constructed and cleverly masked, and would, properly held, have formed

a very formidable obstacle to the advance….

…[Due to the head man absconding with the payroll], the opposition against us

evaporated and we entered the Ruby Mine valleys of Burma without firing another shot.

On the morning of January 27th the last ridge overlooking Mogok was reached and the

town lay at our feet.

G. Skelton Streeter, Mogok, March 8, 1887

(From Streeter, 1887a, Murray's Magazine)

Early in the 20th century the diamond market faced the real problem of oversupply,

due to discovery of vast new deposits in South Africa. It takes no great leap of faith

to see that, from De Beers' perspective, the potential success of the Burma Ruby

Mines Ltd. represented a substantial threat. Of course, one cannot sell rubies if

they are not being mined and effectively marketed. According to Brown, poor

decisions taken by the Board of Directors of the Burma Ruby Mines Ltd. greatly

contributed to the venture's eventual failure.7

In his summary, Brown discussed the future potential of ruby mining in Burma:

The operations of the Company, apart from an abortive attempt to mine

gems from the limestone, and one or two half-hearted efforts to prove the

hill deposits, have consisted entirely in working the valley alluvials, confining

their attentions to the Mogok, Kyatpyin and Kathe Valleys. There are,

however, other valleys in the stone tract and the question arises whether

these have been sufficiently explored. It is exceedingly doubtful if they

have, in particular the Kin and Khabine [Kabaing] deposits. It is notoriously

difficult to prospect this type of mineral deposit and no two geologists of

experience would agree as to the reliability of the results so obtained. But it

was surely the duty of the Company to put these questions beyond doubt.

This has not been done, not through any fault of the local technical

command but owing to the inhanition of the Board of Control…

It has been stated to me repeatedly, and I see no reason to doubt the fact

from my own view as a geologist, that there are great possibilities in the hillside

deposits. They will certainly be more difficult to evaluate and occasional failures

might result, but, in a speculative business like gem mining perhaps this does

not matter much…. The history of the Company proves that time after time the

selection of a field for a new enterprise instead of being a matter of scientific

certainty, has been a pure speculation, based for the most part on reports and

rumours of the success of native miners.

J. Coggin Brown, 1927

Gem mining in the Mogok Stone Tract… (confidential report)

Burma after the company

In the years after the failure of the Company, the working of the mines reverted to

the age-old methods of native miners. Company machinery lay fallow and

eventually became useless. The fantastic drainage tunnel designed by A.H. Morgan

was damaged by heavy flooding in 1925 and never repaired, resulting in the

formation of two large lakes which today dominate the landscape of Mogok.

New rules for mining took effect in 1930, which allowed homesteading upon

payment of a Rs10 per miner fee (Ehrmann, 1957b). The result was a

proliferation of small mines. Some machinery and the electric plant were sold to

A.H. Morgan and a Mr. Nichols (or Nicols; Meen, 1962). Morgan later died, but

Nichols continued to supply electricity to the area at least through 1962. By 1957,

some 1200 individual mines were in operation, employing anywhere from 2–50

people each. Miners were also shareholders, splitting the profits with mine owners,

which helped to eliminate theft (Ehrmann, 1957b).8

In 1962, a military coup brought General Ne Win to power and plunged the

country into isolation. Ne Win called the new direction the "Burmese road to

socialism," but many thought the "Burmese road to poverty" a more apt label. With

the exception of roadside food stalls, most industries were nationalized.

Gem mining was fully nationalized in 1969 ( Mining Journal, June, 1970) and

private trading of gems outlawed. In fact, mere possession of loose stones was a

crime.9 After nationalization, the government worked the mines in a rather

desultory fashion. Mechanized mines were operated, but with little success, as the

generals placed their military cronies in positions of power, rather than trained

engineers and administrators. The little output that did fall into government hands

was sold at the annual auction in Rangoon, operated by the state-run Myanma

Gems Enterprise (MGE).10 Illegal mining also took place and accounted for the

lion's share of production. These stones eventually found their way onto the world

market through the porous borders of Thailand, China and India.

Smuggling became the norm, so much so that the black market was dubbed the

"brown market" by Burmese, due to its ubiquity. At Mandalay's night market one

could find all manner of smuggled foreign goods openly on sale, while, at the jade

mining and trading town of Hpakan, the goods offered were even more exclusive.

French cognac and champagne, American cigarettes, perfume from Paris, all were

readily available for those willing to pay the price (Lintner, 1989).

Burma today

In 1988, anti-government riots wracked the

country and were ruthlessly crushed.

Realizing the degree of popular discontent,

the years following the riots have seen an

ever-so gradual loosening of controls on the

country's economy. In 1989, MGE began to

accept privately-owned gem and jewelry

consignments for offer at the annual

auction and at its retail shops. Private-

government joint ventures in gem mining

were started, as were joint ventures with

foreign companies for jewelry manufacture.

The holding of foreign currency was also

legalized, eliminating the need for sacks of

the local kyat, which is available in small

denominations only. In April, 1994, the

gem export tax was reduced to a near-

reasonable 15% (U Hla Win, pers. comm., May 2, 1994). But in today's highly

competitive business climate, only when such restrictions are entirely eliminated

can smuggling be erased.

Today, the seed of a local jewelry-manufacturing industry in Burma has been

planted, but it will take years to bear fruit. As of the present writing, Burmese

jewelry cannot compete with that manufactured elsewhere; most foreign buyers of

Burmese jewelry are strictly interested in the gems, with the settings being used

for scrap once out of the country.

From the developments of the past few years, it is clear that big changes are

afoot in Burma's gem and jewelry industry. The world will certainly welcome such

moves if they lead to true economic and political freedom.

The current situation in Mogok

Figure 20. The search for crimson infects

both young and old. Inn Gaung (`Big Hole

Mine'), Mogok. (Photo: Thomas Frieden)

Prior to 1991, information on Mogok's mining situation was difficult to obtain. The

biggest problem was the totalitarian nature of the Burmese government, which

regards even mundane details about the country as state secrets. Until 1991,

foreigners were not permitted to travel to Mogok. E.J. Gübelin (1963, 1965, 1966)

was one of the last foreign gemologists to visit the area, in the early 1960s.

During the mid-1980s, the author had a chance to discuss the, then current,

mining situation with a longtime resident of Mogok. Photographs were also

obtained, revealing that little had changed in Mogok since the early 1960s. Private

mining had long been banned throughout Burma, but in a town of several thousand

people whose sole means of income is mining gems, the government was forced to

turn a blind eye. Just as in former times, a gem market was held once a week in

Mogok at the parade grounds and traders came from far and near to attend.

Cheaper goods were displayed openly, while more expensive stones were sold

behind closed doors in small sheds which lined the edges of the grounds.

Beginning in 1991, foreigners were again allowed to visit Mogok (Ward, 1991;

Kane & Kammerling, 1992). What they found was little changed from the time of

the Burma Ruby Mines Ltd. Today, just as in the time of the company, mechanized

mines coexist with traditional workings, and smuggling continues to be a big

problem.

Borderlands

Burma is home to one of the planet's richest sources of gem mineral wealth. Since 1962,

it has also achieved notoriety of a different sort--home to one of the planet's most

repressive regimes.

The country today known as Myanmar (Burma) was, before the British colonial

period, a patchwork of tributary states populated by diverse ethnic groups, including

Shan, Kachin, Karen, Karenni, Pa-O, Mon, Wa and others, loosely ruled by the Burmese

monarch. Under the Burmese monarchs, such groups paid tribute, but the capital had

little direct influence. British rule succeeded in uniting the country, but when it became

clear that colonialism was at an end, long-simmering dreams of ethnic independence

quickly boiled over. In order to prevent fragmentation of the country, a constitution was

drawn up allowing any of the member states to secede from the Union of Burma if they

felt it necessary. It was only by adding this clause that the non-Burmese ethnic states

agreed to join the Union.

Independence came in 1948, but problems arose almost immediately, with the

ethnic states feeling neglected in terms of development money and support. The Karens

were the first to resort to armed struggle, shortly after independence. In 1958, the

Shans followed, and, in 1961, the Kachins. This was the beginning of the still-ongoing

civil war (Lintner, 1990). Many rebel groups use smuggling to raise revenue. Whether by

foot, road, river, rail, elephant or mule, manufactured goods from Thailand and

elsewhere travel into Burma, while gems, narcotics, gold, silver and other raw materials

move outward in a never-ending stream.

Smuggling routes from Burma's gem mines to the outside world are varied and

constantly changing. From Mogok, gems may pass by road east through Kengtung, to

reach Mae Sai in northern Thailand. This route has, of late, become particularly popular

for the new ruby from Möng Hsu. Another popular route, which has been eclipsed to

some degree, takes one by rail or road to Moulmein, south of Rangoon. From here, it is

but a short 1–2 day walk to Mae Sot in Thailand's Tak province. Still another route leads

westward into India or Bangladesh.

With the opening up of China's economy, much jade now proceeds directly from the

mines in Kachin State, to Kunming, capital of China's Yunnan province. And reports have

it that rubies and sapphires are also finding their way along this route (Robert Frey,

stolid comm., May 3, 1994).

Current government policy is to make peace with the ethnic guerilla groups. As of

May, 1994, a number of them had laid down their arms (Lintner, 1994a-b).

Figure 21. The Moei river separating Thailand from Burma, at

Wang Kha, near Mae Sot in Thailand. On the opposite bank, the

bamboo blind hid a bustling market with close to 1000 people

from all over Asia. Wang Kha was one of several smuggling

camps operated by Karen rebels along the Thai-Burma frontier.

Figure 22. Porters leave Wang Kha, bound for Moulmein with

Thai manufactured goods. This camp was once a major transit

point for Burmese gems smuggled into Thailand, but several

years after this photo was taken the Burmese military attacked

the site and burned it to the ground. All that remains today are a

few charred timbers amidst the ever-encroaching jungle.

Figure 23. Elephants arrive at Wang Kha. After this photo was

taken, the two mahouts climbed down off their rides and undid

their longyis (sarongs), revealing special cotton belts with slots

containing silver bars. (Photos by the author, 1979–81).

Mining areas

It is somewhat fruitless to describe precise mining areas because the situation is

constantly in flux. As with most mining areas, mines continually close and new ones

open, as deposits are exhausted and new ones discovered. Illegal mining (and

cutting) generally takes place in more inaccessible regions and is sometimes

supported by armed rebel groups. As of 1992, the Burmese government was

operating eight mechanized mines in the Mogok area, seven for ruby/sapphire and

one for peridot. Both open cast and tunneling are being used. MGE operates two

tunneling operations, one at Lin Yaung Chi for ruby and another at Thurein Taung

for sapphire. Byon from the various mines is either separated on site, or

transported to the MGE Central Washing Plant (Kane & Kammerling, 1992).

Figure 24. Photo of Albert

Ramsay, who purchased and cut

In addition to government mines, since 1990,

the government has allowed private/government

joint ventures, which as of 1992 numbered in the

hundreds. A number of joint-venture primary-source mines operate near Kyauk

Saung, as well one at Dattaw (Dat Taw).11 The later is famous as the source of the

SLORC ruby (Kane & Kammerling, 1992).

The mine at Myintada, near the town of Mogok, is famous for fine quality star

rubies and sapphires, with facetable ruby and fancy spinels also being found in

quantity. Near the town of Kathé (famous for sapphires) is the government mine at

Pingu Taung (`Spider Mountain'), where fine sapphires are found. To the west of

Pingu Taung is another government mine at Kyaukpyatthat-ashe. In addition to

sapphire and ruby, a number of other gems, and even uranium, are also mined.

These are but a few of the localities where mining is proceeding today. Rubies

are found in virtually all of these localities, along with spinels and zircons.

Other gems from the Mogok area

Other than corundum, the Mogok area produces fine gems of many species. In this

regard, Mogok is, next to Sri Lanka, probably the most prolific source of gems in

the world. Chief among these is the spinel, which historically was often confused

with ruby. Although occurring in many colors, Mogok produces the world's finest

reds (including pink) and oranges, bar none. Not only are the cut stones

magnificent, but the area also furnishes the world's finest crystal specimens.

Locally termedam nyunt-nat-thwe (`spirit polished'), the perfection of these

crystals is such that they are often set into jewelry as is. At Kabaing, pink spinels

are mined, while just south from Kabaing, at Sakangyi, hot pink rubies are

obtained. Near the town of Kyatpyin are obtained the world's finest red spinels,

while many ilometers north, at Pandaw, the best pink spinels are found.

Some of the world's finest peridot is mined at Pyaung Gaung, near Bernardmyo,

with cut gems sometimes larger than one hundred carats, while the world's rarest

gem mineral, painite (named after its finder, longtime Mogok resident, A.C.D.

Pain), has been found near Ongaing.

the Gem of the Jungle.(From

Ramsay, 1925)

The following are among the species mined in the Mogok Stone Tract, based on

the author's own research, on Kammerling & Scarratt et al. (1994), and U Hla Win

(pers. comm., Feb. 1994). In parentheses are the Burmese names for the gems.

Gem species of the Mogok Stone Tract

Gem type

Amblygonite/montebrasite – colorless, yellow

Andalusite – orange

Apatite – green, yellow and light blue, including cat's eyes

Beryl – aquamarine

Chrysoberyl – alexandrite, colorless, yellow

Cordierite (iolite) – good violetish blue colors

Corundum – all colors, including stars and color-change gems

Danburite – colorless, fine yellow and, rarely, pink and green

Diamond – found north of Mogok, near Momeik

Diopside – green, including cat's eyes

Enstatite – green to yellow (including brown), cat's eyes

Epidote

Feldspar (myaw myo kyauk )

o Albite – colorless, white, yellow and cat's eye

o Moonstone (myaw ) – near colorless, with distinctive rainbow or blue

schiller,found east of Mogok

o Orthoclase, pink, transparent

Fluorite – violet/purple, green, yellow

Garnet (u daung ) – pyrope, almandine, spessartine and hessonite (grossular)

Jeremejevite – near colorless

Johachidolite – pale yellow, only one specimen to date (possibly from Mogok)

Kornerupine – green, yellow-green, blue and stars

Kyanite – blue

Lazurite (Lapis Lazuli) (pa la dote hta) – blue

Painite – dark red-brown; very rare (only four crystals found to date, two from

Ongaing)

Pargasite – gray; rare

Peridot (pyaung gaung sein ) – green; world's finest and largest, from

Bernardmyo

Phenakite – colorless, has been found

Poudretteite – pink to purple; rare

Quartz (sa lin ) – colorless, yellow (sa lin wa), brown (sa lin nyo ), violet (sa

lin swe )and rose (formerly thu yaung; today termed sa lin nhin zee )

Scapolite (myaw-ni ) – colorless, pink, yellow and violet cat's eyes and faceted

gems

Sillimanite (fibrolite) – fine blue gems, including cat's eyes

Sinhalite – yellow-brown; rare

Sodalite – blue

Sphene – orange-brown

Spinel (am nyunt pan; from am nyunt – 'poor – in reference to spinel's lower

hardness compared to corundum) – the world's finest red, pink and orange

spinels, plus fancy colors and stars

Spodumene – colorless

Taaffeite – colorless, pale violet; rare

Topaz (hatat ta ya) – colorless and other colors

Tourmaline (pa ye u) – yellow, red, brown, orange, green and colorless

Wadeite – yellow-green; rare

Zircon (gaw meik) – yellow, green, orange and red

Figure 25. Rubies are not the only gem found in

Mogok. Grab bag lots such as this contain mainly

spinels, plus a smattering of other gems. Did I hear

someone say painite? (Author's photo, April 1996,

Mogok)

Mining methods

The rubies of Mogok occur in a crystalline limestone (marble) matrix believed to

result from a combination of both contact and regional metamorphism. In contrast,

the sapphires are derived from a number of different igneous rocks, including

biotite gneisses, urtite veins intruded into marble (Kane & Kammerling, 1992), or

pegmatites (Iyer, 1953). Weathering has transported both rubies and sapphires

down from the hills to the valley floors where they have settled in the bottom of the

streams and rivers to form part of the alluvium. It is from these ancient river

gravels that the majority of the stones have been recovered.

Four traditional types of mines exist

in Mogok:

The Twin-lon, or pit method,

for mining the valley alluvials.

The Hmyaw-dwin, or open

trench method, for excavating

hillside deposits.

The Lu-dwin system for the

extraction of gem-bearing

materials that fill limestone

caves and fissures.

Quarrying (tunneling) directly into the host rock to extract rubies and

sapphires.

Since the time of the Burma Ruby Mines Ltd., these have been supplemented by

open-cast mechanized mines.

Twin-lon

Twin-lon or "twin" mining involves the sinking of a small round shaft or hole down

to the gem-bearing gravel, which is locally termed byon. Miners believe that an

area is rich in rubies where big chunks of quartz are found in the byon (Iyer,

1953). Each mine is generally worked by two to three men, similar to traditional

gem mining in Thailand and Sri Lanka. Two of the men take turns digging the shaft

while the third stands above-ground lowering a small basket to haul up the earth.

This basket is attached to the end of a long bamboo pole with a counterweight, or a

hand-cranked winch, to assist in lifting the earth. Depths of these twins vary with

Figure 26. Twin-lon mines and native miners at

Mogok, Burma. (From Iyer, 1953)

the depth of the gravel and range from 3–24 m (10–80 ft). Light is provided by

ingenious manipulation of a looking glass or reflector at the shaft's mouth so that a

beam is thrown down to the bottom. Candles may also be used.

Once a layer of byon is reached, horizontal

tunnels are driven for distances of up to 9

m (30 ft) to remove as much paydirt as

possible. Shallow shafts need no shoring

up, but the deeper ones are firmed with

posts. Even with these precautions cave-ins

do occur on occasion and may be fatal.

Flooding from groundwater is a constant

problem and the first job each day is to

remove the previous night's accumulation

of water. Ingenious pumps made from

bamboo have been devised for this

purpose. Today these are supplemented by

diesel-powered pumps. Generally, twin-lon

operations can only be carried on in the dry

season (Nov.-May).

Larger excavations, shored up by

timber, twigs and leaves, are

termedlebin and kobin, and the

biggest, inbye. These are used in areas where the earth is not compact enough for

twinlons. The inbye is rarely seen due to the expense of the timber needed

(George, 1915, p. 77).

Hmyaw-dwin

Hmyaw-dwin mining consists of open cuttings on the sides of hills. J. Coggin Brown

was earlier quoted as feeling that great potential still remained for this type of

mining. A stream of water, sometimes brought from great distances via bamboo or

plastic channels, is directed to the upper end of the working under pressure. This

carries the mud into the tail race of the excavation, with the lighter material being

Figure 27. Raising gravel from a lebin

(square pit) at Mogok's Inn Gaung (`Big

Hole Mine'). Note the foil reflector at the pit

entrance, which is designed to direct light

to the pit's bottom. (Photo: Thomas

Frieden)

swept away. The heavier concentrate is then carried to a suitable site for washing.

As this method requires plenty of water, it is used mainly in the rainy season

(June-October).

Lu-dwin

The lu-dwin ('loo') is the least common of

the three traditional methods of mining in

Mogok. These are excavations into the

sides of the hills, following the gem-bearing

material through the crevices and caves in

the limestone. It is within these caverns

and crevices that some of the richest finds

have been made. One cavern proved so

vast in size and the depth of the byon so

great, that hmyaw-dwin and twin were

actually set up inside the cavern itself.

Unfortunately the roof caved in, putting an

early halt to the proceedings (Halford-

Watkins, 1932a). According to George (1915, p. 76), the danger attending this

method was overstated. However, just before Kane and Kammerling's 1992 visit,

they were told that several miners had died in a cave-in at a lu-dwin at Than Ta

Yar.

Such caves form as a result of impurities in the limestone. Groundwater

dissolves the limestone, forming cavities. More resistant minerals, such as rubies

and other gems, concentrate in the loamy soil on the cave bottoms. Miners will

crawl through tiny crevices in the limestone to reach concentrations of byon. This

will then be hauled to the surface for washing. One particularly rich lu-dwin near

Bobedaung (Bawpadan) was termed the "Royal Loo"12 because it produced a

number of stones of such high quality that they had to be turned over to the king.

In 1996, the author was given a grand tour of the now-abandoned Royal Loo at

Bawpadan. The entrance consists of a narrow tunnel into which one must crawl.

Figure 28. A Burmese miner at Mogok

dewatering an excavation using an

ingenious bamboo pump. (From O'Connor,

1905)

Figure 29. Although hillside deposits were largely ignored

during the British period, today they represent virgin

ground. Here, at Inn Gaung (`Big Hole Mine'), in the Mogok

area of Burma, miners tunnel like ants, occupying an entire

hillside in their quest for the red stone. This drama has been

played out throughout human history, a continuum of our

species' pursuit of dreams, ego, wealth and power. Some

make it big; too many others are left with only the dream.

(Photo: Thomas Frieden)

Quarrying

C. Barrington Brown (Brown and Judd, 1896) described a fourth method of mining

– quarrying or tunneling into the host rock itself, which is a slight variation on the

lu-dwin. At the time of Brown's visit in 1887, miners were using a gunpowder of

local manufacture. However, this often damaged the gems. Today, more

sophisticated types of blasting are used to extract both ruby and sapphire from

their host rock (Kane & Kammerling, 1992).

Mechanized mining

During the time of the Burma Ruby Mines Ltd., mechanized mines were operated at

a number of different locations, and this continues today. The largest, at Mogok's

Shwebontha mine, opened in April, 1894, and operated for years thereafter. These

were generally open cuts, with the excavations being made by hand. First, a pit 10

sq ft (0.93 sq m) was sunk to a depth of 25 ft (7.62 m). This served as a water

sump, and a centrifugal pump was lowered into position to remove the water. Near

this hole coolies would attack the byon by digging a hole and working outward on

all sides, breaking down the walls and loading the earth into trucks. As the hole

widened, it became possible to sink lower and lower. Workers dug away at the toe

of the wall, and as the bank caved in, transferred the earth to trucks, with water

being diverted to the pump pit. The trucks were hitched to an endless rope, which

would haul the earth up a ramp to the washing plant, where it is tipped into

screens and falls into the washing pans (Talbot, 1920).

At Shwebontha, this simple process developed into a huge gaping hole in the

surface of the valley nearly a mile (1.6 km) in length. While not deep, it was mining

on a grand scale. From January, 1895 to February, 1904, 4,820,000 truck-loads of

byon were taken out of the ground at Shwebontha, and its extension at

Schwelimpan. These resulted in gems worth over •'485,000 (Talbot, 1920).

Figure 30. French gem dealer, Olivier

Galibert, descending into a lu-dwin at

Kadoktut, near Bawpadan. We asked the

miners how deep it was. They answered

that their rope was 5000 ft. long and it did

Washing the byon

Once sufficient byon has been obtained, it

is transported to the washing area. A

shallow circular enclosure is formed with big rocks, the floor of which slopes slightly

at one end. Into this the byon is placed and a stream of water directed onto it while

the whole mass is stirred. Water and lighter debris flow out a small opening at the

lower end, leaving behind the gems and heavier material. Eventually the opening

becomes clogged with heavy gravel. This gravel is then removed for further

washing on circular bamboo trays, similar to the method used in panning for gold

(Halford-Watkins, 1932b). Today, byon is often stockpiled in the dry season, for

washing in the wet season, when workings become flooded.

Output from mechanized mines goes to a washing plant, to be separated by

machine. In the days of the Burma Ruby Mines Ltd., two separate washing plants

were operated at Shwebontha, three at the Redhill mine, and one at Padansho,

near Kyauklongyi (Brown, 1933). Today, the government operates a washing plant,

where byon from government mines which do not have a plant on site is washed.

The kanase (kanes) custom

Almost inevitably, some of the gems escape

and are carried away to the tailings.

According to local custom, these tailings

may be searched through by anyone, with

any stones found becoming the property of

the finder. Under the Company, however,

this was later restricted to women only;

any man who raised a stone from the

ground, unless a worker or license holder,

was subject to imprisonment. Thus, it is the

women who search in this way. They are

termed kanase women. According to

Halford-Watkins (1932b), this custom

resulted in the wholesale theft of large

numbers of stones from Company mines, as well as providing a convenient method

not reach the bottom. (Author's photo, May

1996)

Figure 31. Native kanase women washing

ruby gravel at Mogok, Burma, ca. 1905.

(From Anonymous, 1905a, Booklovers

Magazine)

for the disposal of stolen goods. The way it worked was as follows: a dishonest

workman may catch sight of a stone. He would then pass it secretly to a nearby

kanase woman or tell her where to search for it. Moments later, there is a shout of

joy from the woman as she has just "uncovered" a stone which, by custom, is hers

to keep. The Company went to great lengths to prevent the theft of stones,

enclosing the sorting areas, requiring workers to wear steel masks so that stones

could not be swallowed, etc. However, all this was to no avail because of the

kanase custom.

Sorting and trading

Final sorting of the gravel is normally done

by the mine owner, his relatives or other

trusted staff, with another person present

to keep him honest. All others are kept

away. As stones are found they are placed

into a bamboo container, or today, a plastic

bag. At the end of the day, the contents are

put into a packet, which is sealed on the

spot if the owner has partners who are not

present. This seal will only be broken in the

presence of all the partners, again to keep

everyone honest.

In the morning, stones found during the

previous day's work are placed onto a

polished brass plate for grading in direct

sunlight. First the inferior material, termed sonzi, is removed and separated into

three types: ruby, sapphire and spinel. This is later crushed for use as abrasive

(Halford-Watkins, 1932b).

Those left on the plate are now graded roughly, by hand or sieve, according to

size. The owner himself removes the best stones, for personal grading at a later

time, with the remainder graded by sorters. First, lower qualities are arranged in

small piles, then better stones. In the end, all are passed to the owner for final

Figure 32. Kanesé girl washing gem

gravels in a stream in Burma's Mogok

Stone Tract. (Photo by the author, May

1996)

classification, assisted by the ubiquitous brokers, who play an important role in the

valuation and sale. Valuations and bids are all done with the secret hand language

so quaintly described earlier by Cæsar Frederick.

To catch a thief

In a gem mining operation, it is

absolutely vital that theft be kept to a

minimum (it can never be eliminated

entirely). If a significant portion of the

production is stolen, these stones will

appear in the marketplace, always

undercutting the prices asked for

legitimate production. The author was

once told of one unique method of

dealing with this problem. Two brothers

purchased a gem mine in Africa. While

one brother handled the daily affairs at

the mine, the other set himself up

incognito at the nearby town as a gem

buyer, purchasing all of the stones

stolen by his workers. Although they

were buying stones that were rightfully

theirs, the brothers were happy with the

arrangement for it allowed them to

control the entire production of the

mine, and thus, to better influence the

price.

Figure 33. Native workers under British

supervision at the Company mines at Mogok,

Burma. Despite close watch, theft was a

constant problem. (From O'Connor, 1905)

The role of brokers is important,

both at Mogok and further north at

the Hpakan jade mines. Each dealer

employs them to act as his eyes and

ears. Their job is not only to assist

in valuations and sales, but also to

obtain intelligence about what

valuable stones have been recently

mined, who the owners are, and,

just as importantly, who the stones

are being offered to and the prices

bid. Owners of valuable stones do

their best to keep details secret, for if a piece is bid upon, when the spies of other

dealers learn of the bid, no one will offer more (Halford-Watkins, 1932b; W.K. Ho,

pers. comm., ca. 1982). In other words, if one dealer believes it is worth only

50,000 Kyat, then why offer more? This situation results in purchases taking place

in a cloak-and-dagger atmosphere as both buyer and seller seek to conceal their

activities. Stolen stones in particular may be offered at remote jungle rendezvous',

sometimes in the dead of the night with only a hand torch as illumination.

Legitimate goods may also be offered in this way, being represented as stolen in

the hope that this would increase the buyer's feeling that he is getting a steal of a

deal (Halford-Watkins, 1932b).

Perhaps the best summary of the gem business in Burma was that of British

officer, Major F.L. Roberts (Chhibber, 1934). Although speaking in reference to the

jade business, he could just as easily have been discussing the ruby trade:

From the time jade is won in the Jade Mines area until it leaves Mogaung in

the rough for cutting there is much that is underhand, tortuous and

complicated, and much unprofitable antagonism. In my opinion the whole

business requires cleansing, straightening and the light of day thrown on it.

Major F.L. Roberts,

former Deputy Commissioner of Myitkyina

Figure 34. British sorters at the Company mines,

at Mogok, Burma. (From O'Connor, 1905)

Judging from the tone of his statement, it sounds like Major Roberts would have

been just the man for the job, too.

Figure 35. When miners do find

something, their market is close at hand.

Here a small trader awaits the results of a

byon washing session at Inn Gaung (`Big

Hole Mine'). (Photo: Thomas Frieden)

Local classification of gems

Through the many generations of trading in Mogok, a local classification system

has evolved as follows (based on the author's interviews with Burmese and Thai

traders; George, 1915; Halford-Watkins, 1932):

Thai names

Gim baw siang: A Thai word describing a Burmese cabochon ruby with

calcite matrix (literally `more than enough to eat', in reference to the

belief that this stone brings prosperity)

Burmese names

Individual stones are termed lon-bauk. Ruby parcels are graded by size and

color.

First-water stones (deep rich crimson)

Anyun: Two ct and over

Lethi: Average 1.75 ct

The-bauk (haibauk): Average 0.75 ct

Saga-the: Average 0.50 ct

Ame-the: Average five stones per carat (0.20 ct each)

Second-water stones (bright crimson)

Ani-gyi: 2–6 ct weight

Third-water stones (bright light crimson)

Ani-te: 2–6 ct weight (also known as Bombaing, because they were

fancied in Bombay, India)

Fourth-water stones ( Ahte-kya )

Ahte-kya (literally `fallen from the top'): Mixed stones of the above

grades but slightly defective in shape or water

Kyauk-me: Very dark stones which were sold mainly in Madras, India

Parcels of lesser-quality stones

Gaungsa or Yawya: Pale inferior stones of mixed sizes (up to 6 ct)

Asa-yo: Dark inferior stones of mixed sizes (up to 6 ct)

Asa-yo kya: Inferior to Asa-yo

Akyan-the: Similar to Asa-yo but smaller

Apya: Flat stones of fine quality

Apya-kya, or Apya-sa: Flat stones of second quality

Apyazone: Third-quality flats

Awa: Large defective stones

Gair: Large, impure, almost opaque stones

Ani-the: Small stones of second water and good quality

Akyaw-the: Small, pale, good

Apyu-the: Small, pale, inferior and rough

Atwe: Rough and impure

Zon-si: Spinels and rejections from other classifications

Mat-sa: Opaque sapphire

Thai: Tiny stones (literally `sand')

Pingoo-cho: First-quality star rubies (literally `spider's thread')

Pingoo or Pingoo-sa: Silky rubies (with or without star)

Gaw-done or Gaw-cho: Star sapphires

Am nyunt: Ordinary mixed waterworn spinels

Am nyunt-nat-thwe: Rose spinel octahedra of perfect luster and

crystallization (literally `spinels polished by the spirits')

Am nyunt-seinche: Tiny spinels of the same type as anyan-nat-thwe

above

Nila: Large sapphires

Nila-sa: Mixed inferior sapphires

Notes

5. Starting as a mule track, it was later widened for carts until its fully-metalled

completion in 1901–2. Before its completion, one convoy of carts took over six

weeks to make the journey (George, 1915). [ return to chapter text ]

6. Heavy rains in 1925 caused a fall, blocking the tunnel, causing the valley to

revert to its former state of a series of large lakes, which is how it remains today.

[ return to chapter text ]

7. This opinion was probably only expressed by Brown because his report was

confidential. In his public writings on the Burma ruby mines, Brown said nothing

about it. [ return to chapter text ]

8. The above has been taken from the accounts of Martin Ehrmann. Readers

should be aware that Mr. Ehrmann was not the most reliable of authorities; while

his articles are rich in detail, they are also riddled with errors and misspellings.

Unfortunately, his are virtually the only non-geological accounts for the period

1930–1960. [ return to chapter text ]

9. To circumvent this ban, Burmese gems were typically traded in cheap, base-

metal settings, both in Burma and at the Thai border (based on the author’s OFE;

post-1970s; number of stones observed: plenty). [ return to chapter text ]

10. Myanmar Gems Corp. was founded by the Ministry of Mines on April 1,

1976. It was renamed Myanma Gems Enterprise in 1989 (Kane & Kammerling,

1992). Beginning in 1996, the military-run Union of Myanmar Economic Holdings,

Ltd. (UMEHL) has taken over much of the role formerly played by MGE. [ return to

chapter text ]

11. This is probably the Dató of de Terra (1943). The name is said to mean

"mercury." De Terra explored several rich cave deposits at Dató. [ return to

chapter text ]

12. I probably shouldn't mention the British meaning of that term. [ return ]

Buy the Book

Continued in Part 3

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Burma Continued from Part 2

Pigeon's blood: Chasing the elusive Burmese bird

The Burmese term for ruby is

padamya (`plenty of mercury').

Other terms for ruby are derived

from the word for the seeds of the

pomegranate fruit.13 Traditionally,

the Burmese have referred to the

finest hue of ruby as "pigeon's

blood" (ko-twe ), a term which may

be of Chinese (Anonymous, 1943) or

Arab origin. Witness the following

from al-Akfani, who described thus

the top variety of ruby:

Rummani has the colour of the fresh seed of pomegranate or of a drop of

blood (drawn from an artery) on a highly polished silver plate.

al-Akfani, ca. 1348 AD (from Sarma, 1984)

Some have compared this color to the center of a live pigeon's eye (Brown &

Day, 1955). Halford-Watkins described it as a rich crimson without trace of blue

overtones (Anonymous, 1943). Others have defined this still further as the color of

the first two drops of blood from the nose of a freshly slain Burmese pigeon. But

the piece de resistance of pigeon's-blood research has to be that of James Nelson

(1985; Nelson discourages use of such fanciful terms):

In an attempt to seek a more quantitative description for this mysterious

red colour known only to hunters and the few fortunate owners of the best

Burmese rubies, the author sought the help of the London Zoo. Their

Research Department were quick to oblige and sent a specimen of fresh,

lysed, aerated, pigeon's blood. A sample was promptly

spectrophotometered…. The Burmese bird can at last be safely removed

from the realms of gemmology and consigned back to ornithology.

Figure 36. A fine 7.01-ct. Mogok ruby. (Stone: Jan

Goodman; photo: Tino Hammid)

James B. Nelson, 1985, Journal of Gemmology

After that, the only question remaining is whether or not "spectrophotometered"

is a genuine English verb.

Color preferences do change with time. The preferred color today is not

necessarily that of a hundred, or even fifty, years ago. In the author's experience,

the color most coveted today is that akin to a red traffic signal or stoplight. It is a

glowing red color, due to the strong red fluorescence of Burmese rubies, and is

unequalled in the world of gemstones. Thai rubies may possess a purer red body

color, but the lack of red fluorescence leaves them dull by comparison. It must be

stressed that the true pigeon's-blood red is extremely rare, more a color of the

mind than the material world. One Burmese trader expressed it best when he said

"…asking to see the pigeon's blood is like asking to see the face of God." (Nordland,

1982)

The second-best color in Burma is termed "rabbit's blood," or yeong-twe. It is a

slightly darker, more bluish red. Third best is a deep hot pink termed bho-

kyaik. This was the favorite color of the famous Mogok gem dealer, A.C.D. Pain. U

Thu Daw, longtime Mogok dealer and a contemporary of Pain's, has stated that

bho-kyaik is not so much a color term, as an overall quality description. To qualify,

a ruby must fulfill six requirements. First, it must be at least one carat. Second, the

color must be of the third quality (exceeded only by ko-twe and yeong-twe ). The

table facet must be perpendicular to the c axis, it must be well cut, of good luster

and eye clean. The literal meaning of bho-kyaik is "preference of the British" (U Hla

Win, pers. comm., 2 May, 22 June, 1994).

Fourth-best is a light pink color termed leh-kow-seet (literally `bracelet-quality'

ruby). At the bottom of the ruby scale is the dark red color termed ka-la-ngoh. This

has an interesting derivation for it means literally either "crying-Indian quality" or

"even an Indian would cry," so termed because it was even darker than an Indian's

skin. Most dark rubies were sold in Bombay or Madras, India. Ka-la-ngoh stones

were said to be so dark that even Indians would cry out in despair when confronted

with this quality.

Figure 37. U Hmat, the "Ruby King," at the town of Mogok, in

Burma. (From O'Connor, 1905) According to O'Connor…

U Hmat was great here in the days before any

Englishman had come within sight of Mogôk. He is not

a foreigner… but a native of the soil. He lives some

distance from the market-place in a rambling wooden

house on piles…. At one end he has built himself a

strong-room of brick, in which lie hidden, according to

popular tradition, rubies of extraordinary value. U

Hmat is seldom seen abroad. He goes, it is said, in

terror of his life; and his courtyard is thronged with

retainers, who make for him a kind of personal

bodyguard. But in bygone days he travelled every year

to Mandalay with a present of rubies, and was received

in audience by the king. He is a builder of many

monasteries and pagodas; but is said to be less lavish

in this respect than most of his compatriots in Burma.

He is believed accordingly by his European neighbours

to have `his head screwed on the right way.' His

character for economy is the topic of very favourable

discussion at the dinnertables of the settlement, and it

is a commonplace of opinion that he is the only

Burman at the mines who is not a fool. Let it be added

that he is the father of a pretty daughter, whose jewels

are the despair of every other woman in Mogôk, and

that he keeps her in strict seclusion, lest some

adventurous youth should steal away her heart, or her

person, or both. He has been good enough, however,

to show me some of her most beautiful jewels.

V.C. Scott O'Connor, 1905, The Silken East

Burmese rubies compared

Until the discoveries in Vietnam in the late 1980s, Burmese rubies were without

peer. Other sources, such as Kenya and Afghanistan, produced the occasional stone

which could stand with Burma's best, but such stones were extremely rare.

Discovery of ruby in Vietnam changed all that. For the first time in hundreds of

years, a viable alternative to Burma presented itself. Only time will tell if the

Vietnamese mines can continue to produce, but, historically speaking, Burmese

rubies are in a class by themselves.

The color of a fine Burmese ruby is due to a combination of two factors. First,

the best stones have high color intensity. This results from a mixture of the slightly

bluish red body color and the purer red fluorescent emission. It is this red

fluorescence which is the key, for it tends to cover up the dark areas of the stone

caused by extinction from cutting. Thai rubies possess a purer red body

color,14 but lack the strong fluorescence. In Thai rubies, where light is properly

reflected off pavilion facets (internal brilliance), the color is good. However, where

facets are cut too steep, light exits through the side instead of returning to the eye,

creating darker areas (extinction). All stones possess this extinction to a certain

degree, but in fine Burmese rubies, the strong crimson fluorescence masks it. The

best Burmese stones actually glow red and appear as though Mother Nature

brushed a broad swath of fluorescent red paint across the face of the stone. This is

the carbuncle of the ancients, a term derived from the glowing embers of a fire.

A second factor is the

presence of silk. Tiny

exsolved inclusions tend to

scatter light onto facets that

would otherwise be extinct.

This gives the color a

softness, as well as spreading

it across a greater part of the

gem's face. Thai/Cambodian

rubies contain no rutile silk,

and thus possess more

extinction.

In actuality, rubies from

most sources possess a

strong red fluorescence and

silk similar to those from Burma, with the Thai rubies being the exception.

Figure 38. A large crystal of calcite in an unheated Mogok

ruby, in polarized light. Calcite is suggested because of the

intersecting twinning planes visible within the included

crystal. Such calcite crystals containing repeated glide

twinning are often seen in Burmese rubies, which were

formed in a calcite (marble) matrix. (Photo by the author)

However, those from Sri Lanka are generally too pale in color, while, with other

sources, such as Kenya, Pakistan and Afghanistan, material clean enough for

faceting is rare. Thus the combination of fine color (body color plus fluorescence)

and facetable material (i.e., internally clean) has put the Burmese ruby squarely

atop the crimson mountain. Some old-timers consider Burma to be not just the

best source, but the only source of stones fit to be called ruby. When one considers

that today probably 90% or more of newly-mined rubies owe a good measure of

their clarity and color to heat treatment, this statement does not seem so

outlandish (unfortunately, most Burmese rubies are today heat treated).

Features of Mogok ruby

Mogok's famous rubies display a distinctive internal picture, often allowing

separation from rubies of other sources. Typical are both euhedral (`well-formed')

and rounded crystal grains, along with dense clouds of rutile silk. Rhombohedral

twinning is common, as is straight/angular color zoning, at times in a swirled

pattern termedtreacle. Generally absent, or in small numbers only, are the fluid-

filled inclusions so common in Thai/Cambodian and Sri Lankan rubies.15

Varieties and occurrence

Mogok rubies range from lightest pink, through bright red, to deep garnet-red.

Most tend to be slightly purplish-red in hue position, and grade into purple and

violet sapphires. Fine star rubies are also found. Twelve-rayed star rubies have

been reported, but are extremely rare.

Mogok rubies are derived from a crystalline limestone (marble) matrix, resulting

from either contact or regional metamorphism.

Solids

Crystalline solids of many types are characteristic of Mogok rubies. They typically

form clusters of rounded and/or euhedral grains of a light color (or colorless), often

concentrating in the center of the crystal. The most common guests are calcite,

spinel, corundum, apatite, rutile and zircon.

Calcite is present as both rounded and angular rhombs, recognizable by its

cleavage and polysynthetic glide-twin lamellae. Twinning striations may also be

found in included corundum crystals, which occur as tabular or rounded individuals

of extremely low relief. These corundums included in corundum typically show

a terraced, or step-like, appearance from multiple development of the basal

pinacoid. Spinel crystals occur as both octahedra or, more often, as rounded

irregular forms of low relief.

In addition to lightly colored or colorless mineral inclusions are guests with

distinctive colors. Primary rutile crystals of deep red color and metallic luster stand

out in high relief. Their square outline and knee-shaped twin or prismatic habit

indicate their identity. Bright to pale yellow, partly resorbed crystals of low relief

may be apatite; Eduard Gübelin (pers. comm., May 5, 1994) has reported that

apatites in Mogok rubies tend to be rounded, while apatites in Sri Lankan stones

often show distinct faces.

Yellow crystals of high relief suggest sphalerite or sphene. Rounded, partly

resorbed grains of olivine are pale green. Deep-green prisms of a vanadium-

bearing amphibole, pargasite [NaCa2 Fe4 (Al,Fe) Al2 Si6 O22 (OH)2 ] have been seen

by the author in one spectacular vanadium-colored Mogok specimen (courtesy of

Valaya Rangsit, ca. 1985). Dark brown to opaque slabs/plates suggest phlogopite

mica. Zircon is also found, with and without stress halos.

Primary cavities

Primary fluid-filled cavities are not particularly common in Mogok rubies. This is

said to result from the metamorphic processes in which they grew, which combine

extremely slow growth rates with a fluid-poor environment (Roedder, 1982).

Negative crystals in Mogok rubies exhibit similar faces and habits as their host.

Typical examples show a terraced appearance made up of numerous steps, the

result of alternating development of pinacoid and pyramid (or rhombohedron)

faces. Some are well-formed, with flat faces, while others are rounded. Negative

crystals can be separated from solids because negative crystals show the same

orientation as their host. In other words, the pinacoid face of each negative crystal

is exactly parallel to the same face of the host and to any other negative crystals

present in the stone.

When seen, negative crystals in Mogok rubies are often two phase. Eppler

(1976) identified the filling as gases containing hydrogen sulfide. This constituent

was recognized by its odor when the gems were crushed, opening the cavities. He

speculated that gas bubbles within the growth solution perched on a face as the

crystal grew. This provided an obstacle to the growth at that point on the face,

while adjacent areas continued to grow. Eventually the surrounding gem engulfed

the bubble completely, trapping it while simultaneously creating the negative

crystal.

Secondary cavities

Untreated Mogok rubies contain far fewer secondary fluid inclusions (healing

fissures or fingerprints ) than rubies from Thailand/Cambodia, Sri Lanka or Kenya.

Heat-treated Burmese rubies may, however, contain many secondary fluid

inclusions formed during the heat treatment process.

When secondary fluid inclusions are found

in untreated Mogok rubies, they tend to be

well healed, with angular negative-crystal

pockets sometimes containing gas bubbles.

Others may be fractures where little healing

has occurred. Generally lacking are the

intermediate-stage, lacy fingerprints with

narrow fluid tubes common to rubies from

Thailand/Cambodia, Sri Lanka and Kenya.

Heat-treated Mogok rubies, however,

contain far more fingerprints and

secondary-fluid inclusions, making the

identification of origin more difficult.

Growth zoning

Straight, angular growth zoning is common in Mogok rubies, as with rubies from

sources other than Thailand/Cambodia. The zoning is always found parallel to

crystal faces. When looking parallel to crystal faces, the bands of color line up into

Figure 39. While strong color zoning is

rare in Mogok sapphires, it is common in

the rubies from this area. A fine example is

shown above, viewed parallel to the caxis.

(Photo: Tony Laughter)

sharp narrow zones; however, in other directions they may appear in irregular

swirls termed treacle, from their resemblance to the swirls in syrup.

Twin development

Rhombohedral twinning is common, and may feature long, white exsolved

boehmite needles at intersecting twin junctions.

Exsolved solids

One of the most diagnostic features of Mogok rubies is the dense white clouds of

exsolved rutile. At high temperatures, when atomic spacing is greater, titanium

enters into solid solution with the host corundum. As the corundum cools, however,

its crystal lattice contracts, literally squeezing the titanium atoms out of solution,

where they join with oxygen atoms to form minute crystals of rutile (TiO2). This

process is known among mineralogists as exsolution-- the unmixing of a solid

solution. Because of constraints on their movement by the solid corundum host,

titanium atoms are unable to travel large distances. Therefore, rather than forming

large crystals, they migrate together to form thousands of tiny slender needles

where space permits. For rutile in corundum, this space is parallel to the faces of

the second-order hexagonal prism, intersecting in three directions at 60/120° in

the basal plane.

At times, only long slender threads are visible, while in other cases knife or dart

shapes appear. Closer examination reveals many of these to be twin crystals with

tiny v-shaped re-entrant angles visible at the broad end. They are flattened so thin

in the basal plane that when illuminated with a fiber optic light guide from above,

bursts of iridescent colors are seen, due to the interference of light from these

microscopically-thin mineral lances.

Rubies from Mogok usually contain at least some rutile silk. It is found in dense

white clouds made up of relatively short individuals, whereas in Sri Lankan

corundums the rutile silk tends to be longer and less densely woven.16

Along with the rutile silk in Mogok rubies are clouds of minute particles of an

unknown nature. These particle clouds, like the silk, also appear to result from

exsolution, and are arranged in an identical pattern. At times, it has been noticed

that heat treatment removes the rutile silk, but not the particles. Thus, in some

cases at least, they may be composed of a mineral other than rutile. Due to their

arrangement, they also influence the star effect of asteriated gems. In asteriated

gems where silk clouds consist mainly of particles, the star is diffuse and lacking in

definition. Conversely, where clouds contain a preponderance of needles, the star

possesses better definition. Both needle- and particle-dominated stars can be found

in Burmese corundums.

Boehmite

Mogok rubies display one additional

type of exsolved needle inclusion:

boehmite. Boehmite needles are

long white inclusions which form at

the junction of intersecting twinning

planes and, as a result, lie parallel to

faces of the rhombohedron {1011}.

Where planes meet, they intersect

at angles of 86.1° and 93.9° (three

directions total, two in the same

plane). If one understands the vast

differences in orientation and

appearance, there is little likelihood

that boehmite needles be confused with rutile silk.

Boehmite results from pressure-induced exsolution. This pressure also is

responsible for the gliding (slipping) of atomic planes, creating polysynthetic twins.

Since pressure also causes stress fractures, low-grade corundum is generally filled

with these twin planes and the accompanying boehmite needles.

Boehmite needles are often long, running completely across the stone. When

intersecting in the above manner, they appear like a sort of lattice framework, or

creation from Mother Nature's erector set. At times, close examination shows the

appearance of narrow fluid fingerprints and frequently one observes narrow stress

fractures extending outwards from the needles at 45° angles in a spiral fringing

Figure 40. Rounded crystal grains are a common

feature of Mogok rubies, such as those seen above,

which are probably apatite. (Photo: Wimon

Manorotkul)

appearance. When twin planes run through secondary fluid inclusions, the boehmite

needles often divide them into parallel sections.

Together, the rhombohedral twinning/boehmite needles combination provide

one of the best methods of separation from the synthetic stone, for they are seen

in a large percentage of natural corundums from all sources. Although

rhombohedral twinning and boehmite needles have on rare occasions been found

by the author in Verneuil synthetic corundum, curved growth lines and gas bubbles

allow separation. Nothing resembling this combination occurs in flux synthetics,

making it important in the battle against sophisticated factory products. Twinning is

sometimes found in flux synthetics, but without the accompanying boehmite

needles.

Within Mogok rubies, rhombohedral twinning with boehmite needles is seen,

although not as often as in Thai/Cambodian rubies.

Properties of Mogok (Burma) ruby

Property Description

Color range/phenomena Colorless to a deep red; the red of Burmese rubies is

generally more purple than Thai/Cambodian rubies; some

stones are of a 'garnet' red color. Most are strongly

fluorescent.

Six-rayed stars are common; 12-rays are known, but rare.

Color-change stones (colored by vanadium) are rarely found.

These have a color change similar to the Verneuil synthetic.

Geologic formation Found in metamorphosed crystalline limestones (marble) and

secondary deposits derived from the same.

Crystal habit Typically stubby crystals consisting of prism/pyramids terminated by

pinacoid faces and modified by the rhombohedron. Crystals often

display a terraced appearance due to oscillation between the pinacoid

and rhombohedron. Triangular depressions may be seen on pinacoid

faces.

RI & birefringence n omega = 1.760–1.766; n epsilon = 1.768–1.774; Bire. = 0.008 to

0.009

Specific Gravity ~4.00

Spectra Visible: Strong Cr spectrum; V spectrum has been seen on rare

occasions.

Fluorescence Strong to very strong red to orangy red (LW stronger than SW). Heat-

treated gems sometimes show chalky fluorescence from colorless

patches.

Other features None reported

Inclusion types Description

Solids

Various, often in dense concentrations, including:

Apatite, hexagonal prisms (Gübelin, 1973)

Calcite, transparent, often with rhombohedral glide twinning

(Gübelin, 1969b)

Dolomite (Gübelin & Koivula, 1986)

Corundum (Gübelin, 1953)

Garnet (Gübelin, 1953)

Graphite flakes, black (Kammerling & Scarratt et al., 1994)

Mica (muscovite) (Gübelin, 1953)

Olivine (Gübelin, 1973)

Pargasite, bright green crystals (Gübelin, 1973)

Pyrite (Gübelin & Koivula, 1986)

Pyrrhotite (Gübelin & Koivula, 1986)

Rutile prisms (not silk), dark red to black (Gübelin, 1953)

Scapolite, well-shaped crystals (Kammerling & Scarratt et al.,

1994)

Sphalerite, brown (Gübelin, 1973)

Sphene, yellow-orange, high dispersion (Gübelin, 1969b)

Spinel group minerals (Gübelin, 1953)

Sulfur (Fritsch & Rossman, 1990)

Zircon (Gübelin, 1953)

Cavities

(liquids/gases/solids)

Primary negative crystals (rare)

Secondary negative crystals (healed fractures) are rare,

except in heated stones. They often lack the lovely `lacy'

appearance of Sri Lankan stones; typically they have fluid-

filled channels which are widely spaced.

Growth zoning Straight, angular growth zoning parallel to the faces along

which it formed; irregular `treacle' like swirls in other

directions

Twin development Growth twins of unknown orientation

Polysynthetic glide twinning on the rhombohedron

Exsolved solids Rutile silk in dense clouds of (often, but not always) short

needles, parallel to the hexagonal prism (3 directions at

60/120° ) in the basal plane

Boehmite, long white needles along intersecting

rhombohedral twin planes (3 directions, 2 in one plane, at

86.1 and 93.9° )

a. This table is based on the author's own extensive experience, along with published reports of

Eppler (1976), Fritsch & Rossman (1990), Gübelin (1973), Gübelin & Koivula (1986) and

Kammerling & Scarratt et al. (1994).

Burmese sapphires

Although rubies are found with much greater frequency at Mogok (rubies form

about 80–90% of the total output), sapphires may reach larger sizes. Cut gems of

over 100 carats are not unknown. Large fine star sapphires are also found at

Mogok, in addition to star rubies. Near Kabaing, at Kin, is located a mine famous

for star sapphires.

The sapphires of Burma occur in intimate association with rubies in virtually all

alluvial deposits throughout the Mogok area, but are found in quantity at only a few

localities, particularly 8 miles (13 km) west of Mogok, near Kathé (Kathe) (Halford-

Watkins, 1935b). At Kyaungdwin, near Kathé, in 1926 a small pocket was

discovered that yielded "many thousand pounds' [sterling] worth of magnificent

sapphires within a few weeks." (Halford-Watkins, 1935b)

Figure 41. Map of the sapphire-producing regions of Burma's Mogok

Stone Tract. (Modified from Halford-Watkins, 1935b)

According to Halford-Watkins (1935b), the majority of fine sapphires were derived

from the area between Ingaung and Gwebin, and the present author (RWH) also

found this to be the case during his 1996 Mogok visits. Today, important mines are

located at Thurein Taung and Yadanar Kaday Kadar.

One magnificent Gwebin gem mined in 1929 was scratched up just below the

grass by miners preparing a site for digging. It was a water-worn, doubly-truncated

pyramid weighing in at an incredible 959 ct, and was named the Gem of the

Jungle. Purchased and cut by Albert Ramsay, it produced nine fine stones, ranging

in size, from 66 to 4 carats (see ).

Sapphires have also been found near Bernardmyo:17

Bernardmyo itself at one time produced large quantities of sapphires, many

of which were of magnificent colour and quality, though a number were of a

peculiar indigo shade, which appeared either very dark or an objectionable

greenish tint by artificial light. During an extensive native mining rush to

Bernardmyo in 1913 a number of these stones were placed on the London

market.

Many of the stones found in this area were coated with a thin skin of almost

opaque indigo colour which, on being ground off, revealed a centre sometimes

of a fine gem quality, but in many cases of greenish shade. The method of

occurrence was different from that anywhere else as the majority of stones

were taken from a hard black iron-cemented conglomerate, which was found

layers a few inches thick, often only a few feet below the surface. This area now

appears to be exhausted, and little mining is carried on there to-day except for

peridots, which are abundant.

Another isolated local deposit which has produced some fine sapphires

occurs at Chaungyi, four miles north of Mogok, and about a thousand feet

higher.

J.F. Halford-Watkins, 1935b

Other than blue, sapphires also occur in violet, purple, colorless and yellow

colors at Mogok. The violet and purple stones may be fine; yellows tend to be on

the light side and are not common. Green sapphires are known, but rare.

Burmese sapphires compared

Although it is rubies for which

Burma is famous, some of the

world's finest blue sapphires

are also mined in the Mogok

area. Today the world gem

trade recognizes the quality of

Burmese sapphires, but this

was not always the case.

Edwin Streeter (1892)

described Burmese sapphires

as being overly dark.

Unfortunately this error was

later repeated by Max Bauer

and others. G. Herbert Smith

wrote…

While the Burma ruby is famed throughout the world as the finest of its kind

the Burma sapphire has been ignominiously, but unjustly, dismissed as of

poor quality. In actual fact nowhere in the world are such superb sapphires

produced as in Burma.

G.F. Herbert Smith, 1972, Gemstones

While this statement must be qualified by adding that the finest Kashmir

sapphires are in a class by themselves, those from Burma are also magnificent. J.

Coggin Brown said this:

It has been stated that Burmese sapphires as a whole are usually too dark

for general approval, but this is quite incorrect; next to the Kashmir

sapphires they are unsurpassed. Speaking generally, Ceylon sapphires are

too light and Siamese sapphires too dark, and it is more than probable that

many of the best `Ceylon' stones first saw the light of day from the

mountainsides of the Mogok Stone Tract.

J. Coggin Brown & A.K. Dey, 1955, India's Mineral Wealth

Figure 42. 21.09 caratsof Burmese midnight-blue mystery.

This stone, an example of Mogok's finest product, was

offered in the late 1980s in Bangkok for $10,000/ct.

wholesale. (Photo: Adisorn Studio, Bangkok)

Not all Burma sapphires are deep in color. The best display a rich, intense,

slightly violetish blue, but some are quite light, similar to those from Sri Lanka. The

key difference between Burma and Ceylon sapphires issaturation, with those from

Burma possessing much more color in the stone. Color banding, so prominent in

Ceylon stones, may be entirely absent in Burma sapphires.

Features of Mogok (Burma)

sapphire

In certain respects, the inclusions in

Mogok sapphires differ from their

red relatives. These differences can

be accounted for by the different

modes of origin for each. Although

mined in close proximity to one

another, the sapphires are believed

to have originated in pegmatites and

nepheline-corundum syenites, while

the rubies formed in a

metamorphosed crystalline

limestone.

Like the rubies, Mogok sapphires contain dense clouds of rutile silk, and a

number of fine star sapphires in various shades of blue have been unearthed.

Included crystals, however, are less common in the blue gems than the red, while

secondary fluid inclusions are far more abundant. Finally, the color of Mogok

sapphires is exceptionally even, and banding is not found in some specimens, even

under immersion. The lack of sharp zoning (and presence of rhombohedral glide

twinning) helps to separate Mogok sapphires from those of Sri Lanka, where it is

less common.

Varieties/phenomena

Near colorless to rich, deep blue almost verging on the violet. Despite the

stereotypical 'intense blue' Burma sapphire, many Burmese sapphires are

Figure 43. An offerring of small sapphires in a

Mogok temple. (Author's photo; April, 1996)

quite light in color, wholly resembling those from Sri Lanka. The blue color of

Burmese sapphires is often just slightly more violet than those of Sri Lanka.

Purple to violet.

Yellow, generally a light, straw yellow.

Green has been reported (U Hla Win, personal comm., 1994), but is

relatively rare.

Six-rayed stars are common in many colors; 12-rayed stars are rare.

Occurence

Burmese sapphires have been found in a variety of environments, including

pegmatites, corundum syenites, gneisses and urtites. Gems are recovered from

both primary and secondary deposits.

Solids

With the exception of exsolved minerals, solid inclusions are somewhat rare in the

sapphires from Mogok. Zircon has been identified as rounded grains, both with and

without halos, as well as magnetite (spinel group) octahedra, large single rutile

prisms and pyrrhotite (magnetic pyrite) crystals. One specimen examined by the

author possessed a highly corroded tabular crystal of low relief with a pale green

color. This might possibly have been olivine. Other crystal inclusions reported are

apatite, monazite, fergusonite and phlogopite mica.

Figure 44. Two views of a secret…

Two different looks at unknown red crystal inclusions in a Burmese

sapphire from the Mogok area. (Photos by the author)

Cavities

Negative crystals are common in sapphires from the Mogok Stone Tract, although

most appear to be of secondary, rather than primary, origin. Healing fissures, in all

their glory, are usually profusely distributed across the stones. These range from

fingerprints with slender, worm-shaped fluid channels, to curving concentrations of

angular negative crystals, some two phase in nature. At times, fluid-filled

fingerprints are superimposed upon these arrangements of negative crystals,

suggesting two separate stages of fracturing and healing. Characteristic are the

fingerprint patterns which appear folded or crumpled like flags in the wind.

Growth zoning

The color distribution of Mogok sapphires is exceptionally even; this is one of the

key differences between Mogok and Sri Lankan blue sapphires. In gems from each

locality the blue hue is equally fine, but one can never get too much of a good thing

and Sri Lankan stones normally contain substantial areas without color. Thus, the

even coloration of Mogok sapphires gives them an intensity lacking in most Sri

Lankan stones. So well dispersed is the color in the former that, in many cases,

even close scrutiny while immersed in di-iodomethane fails to yield evidence of the

zonal banding. In the author's experience, only with the small blue sapphires from

Yogo Gulch, Montana and those from Mogok is the banding often lacking.

Twin development

Polysynthetic twinning along the rhombohedron faces is common in Burma

sapphires. Often accompanying these lamellae are long white boehmite needles.

Such twinning is comparatively rare in Sri Lankan stones.

Exsolved solids

Rutile silk in Mogok sapphires is similar to

that of the Mogok rubies. Compared with

Sri Lankan stones, the silk tends to be

shorter and more densely packed, and can

be recognized by its spike or dart shapes.

These needles lie in the basal plane and run

parallel to the faces of the second-order hexagonal prism, intersecting at

60/120° angles.

The author has observed in certain Mogok sapphires what appears to be a

second type of silk, differing from the rutile silk in several respects. Its color tends

to be more brownish or yellowish than the rutile. Although it is oriented along three

directions at 60/120° angles in the basal plane, these directions are offset 30° from

that of the rutile, running parallel to the faces of the first-order hexagonal prism,

not the second-order. Differences in shape are also apparent, with the new silk

occurring as ultra-thin elongated plates of a distorted hexagonal outline. Possible

identities include hematite, ilmenite, or a hematite/ilmenite intermixture, such as

has been identified in Thai, Australian and Umba sapphires. Rarely, 12-rayed star

sapphires have been found in Mogok. These possibly result from near-equal

presence of both rutile and a second type of silk, as described above.

Again, like Mogok rubies, zoned clouds of minute exsolved particles are common

in Mogok sapphires. While it seems possible that, in some cases, they are merely

smaller versions of rutile silk, in others, differences between the silk and the

particles can be seen. At times, the particles produce a pinkish reflection with

overhead fiber-optic lighting. In others, the reflection is simply white. Apparently,

like the two types of silk, there exist at least two types of exsolved particles in

Mogok sapphires.

Exsolved boehmite needles are common. They differ radically from the

orientation of the exsolved rutile silk, lying not in the basal plane, but instead along

the rhombohedron faces, at the junctions of crossing twin planes. Their angles of

intersection are 86.1/93.9°, as they follow the edges of the rhombohedron faces.

Figure 45. Although Burmese sapphires

share a number of similar features with

their cousins from Sri Lanka, polysynthetic

twinning is generally not one. The

rhombohedral twinning in the Mogok

sapphire above is rather rare in Sri Lankan

sapphires. (Photo by the author).

Figure 46. Rutile silk in a Burmese sapphire from

the Mogok region. (Photo by the author)

Properties of Mogok (Burma) sapphire

Property Description

Color range/

phenomena

Near colorless to rich, deep blue almost verging on the violet. Despite

the stereotypical `intense blue' Burma sapphire, many Burmese

sapphires are quite light in color, wholly resembling those from Sri

Lanka. The blue color of Burmese sapphires is often just slightly more

violet than those of Sri Lanka.

Purple to violet.

Yellow, generally a light, straw yellow.

Green has been reported (U Hla Win, personal comm., 1994), but is

relatively rare.

Six-rayed stars are common in many colors; 12-rayed stars are rare.

Geologic

formation

Burmese sapphires have been found in a variety of environments,

including pegmatites, corundum syenites, gneisses and urtites. Gems

are recovered from both primary and secondary deposits.

Crystal habit Unlike sapphires from most other sources, Burmese blue sapphire

crystals tend to be rather tabular, consisting of short prism/pyramids

with large pinacoid faces. The result is cut stones which are often flat.

RI &

birefringence

n omega = 1.757–1.765; n epsilon = 1.766–1.774 Bire. = 0.008–0.009

Specific gravity ~3.95–4.10 (higher readings in darker stones)

Spectra Visible: Weak to strong Fe spectrum.

Fluorescence Generally inert (LW & SW). Cr-bearing stones may show a weak red under LW.

Other features To the best of the author's knowledge, Burmese blue sapphires are not

typically heat treated. This is not for lack of trying, but because the treatment

secrets of this gem have yet to be unlocked. But give them time…

Inclusion types Description

Solids Apatite (Gübelin, 1973)

Brookite, yellow crystals (Gübelin & Koivula, 1986)

Dolomite (Gübelin & Koivula, 1986)

Fergusonite (Gübelin, 1973)

Monazite (Gübelin, 1973)

Mica (phlogopite) (Gübelin, 1973)

Pyrrhotite (rare) (Gübelin, 1973)

Rutile, dark red prisms (Gübelin, 1953)

Spinel group (magnetite) (Gübelin, 1973)

Unidentified green crystal

Zircon (Gübelin, 1973)

Cavities

(liquids/gases/solids)

Secondary healed fractures are quite common (unlike Mogok ruby);

they take on a variety of patterns and thicknesses.

Fractures may be lined with reddish secondary limonite stains (Gübelin

& Koivula, 1986)

Growth zoning Growth zoning is not so common; occasionally broad areas of zoning

are seen.

Twin development Growth twins

Polysynthetic glide twinning on the rhombohedron

Exsolved solids Rutile in dense clouds of (often, but not always) short needles, parallel

to the hexagonal prism (3 directions at 60/120°) in the basal plane.

Rutile is reportedly rare in yellow and green stones (U Hla Win, pers.

comm., May 2, 1994).

Boehmite, long white needles along intersecting rhombohedral twin

planes (3 directions, 2 in one plane, at 86.1 and 93.9°).

a. The above is based on the author's own extensive experience, along with published reports of

Eppler (1976), Gübelin (1973), Gübelin & Koivula (1986) and Kammerling & Scarratt et al. (1994).

Notes

13. The Thai word for ruby, taubptim, also means pomegranate. [ return to

chapter text ]

14. Purer in the sense that the hue position is closer to the center of the red

(relative to purple and orange). [ return to chapter text ]

15. After heat treatment, Burmese rubies may contain numerous fingerprints

and feathers, a result of stress-induced fracturing and subsequent healing in the

oven. [ return to chapter text ]

16. It has been suggested by some that the length of the rutile needles and

density of its clouds can be useful in separating Mogok and Sri Lankan rubies, but

this is a test the author would not want to rely upon. [ return to chapter text ]

17. The plateau of Bernardmyo was chosen by the first British expedition to

Mogok as a suitable place for a sanitarium for British troops. It was thought the

climate better suited Europeans and hoped that the place would eventually develop

into the Simla of Burma. Bernardmyo was christened after the first British Chief

Commissioner of Upper Burma, Sir Charles Bernard (G.S. Streeter, 1887b, 1889).

It was once home to the local airport, but today consists just of a small village.

[ return to chapter text ]

Continued in Part 4

This page is http://www.ruby-sapphire.com/r-s-bk-burma5.htm v. 1.0

Page updated 7 March, 2013

Burma Continued from Part 4

Namsèka rubies: Salt of the earth?

One Burmese locality that has received scant mention is that of

Namsèka. Located 24 km (15 miles) southwest of Mainglôn (which is

just south of Mogok), in the narrow valley of the Nampai, it was

described by Fritz Noetling in 1891.

At the time of his visit the deposit had apparently not been

worked for some time. The exact occurrence is said to be less than 1

km northwest of the small village of Namsèka. According to Noetling,

the first samples of ruby brought to the attention of the Government

of Burma were of high quality and were provided by Lieutenant Daly,

Superintendent of the Northern Shan States. However, Noetling spent

three full days with twelve coolies working the deposit, and found not

even a single fragment of ruby. Only some dark purple spinels turned

up.

According to a story told to Noetling…

When the Thibaw Sawbwa sent one of his officials to Namsèka

to get samples of good stones from the mines, none could be

procured. The man therefore went over to Mogôk, where he

purchased the stones which were handed over to the Sawbwa

as "Namsèka rubies.

Noetling told the local Sawbwa about his doubts regarding ruby

occurring at Namsèka. The Sawbwa proceeded to produce a plate of

stones which included both rubies and other gems, with the rubies

matching those of Lieutenant Daly perfectly.

In the end, Noetling had to conclude that he just wasn't sure

about rubies at Namsèka. It was possible that the mine was originally

salted in an attempt to sell the mining rights, but it was equally

possible that the rubies occurred in irregular concentrations which

would be uncovered only by sustained work at the site. Since

Noetling's report in 1891, nothing more has been heard of the rubies

of Namsèka..

Other Burma corundum

localities

Gem-quality rubies and

sapphires are found in a

number of other areas, all of

which are in upper Burma.

These include:

1. Sagyin, near

Mandalay, where poor-

quality rubies have

been mined from the

marble quarries.

2. Thabeitkyin, along the

Irrawaddy river, west

of Mogok, for ruby.

3. Yet-Kan-Zin-Taung, 50 miles (80 km) from Mandalay along the Mogok road,

for ruby.

4. Namsèka, south of Mainglôn (Möng Long), for ruby.

5. Naniazeik, Myitkyina district, Kachin State, for ruby.

6. Möng Hsu, Southern Shan States, for ruby.

7. Möng Hkak, Southern Shan States, for sapphire.

8. Nawarat (Pyinlon), Shan State, for ruby.

9. Namhsa, 15 km north of Nawarat (Shan State), for ruby.

Sagyin Hills

In the Sagyin Hills, just 26 km north of Mandalay and 3.2 km from the Irrawaddy

river, rubies were once obtained from the detritus of clay-filled hollows and fissures

in the crystalline limestones. Such hollows were said to yield sapphires, spinels and

amethysts, in addition to rubies (Penzer, 1922). This locality is famed for fine

marble, as well.

Figure 48. Möng Hsu rubies revitalized Burma's moribund

gem industry when they first hit world gem markets in the

early 1990s. The above two stones, weighing 2.59 ct total,

are superb examples of just what all the fuss was about.

(Photo: © 1994 Tino Hammid; stones: Amba Gem Corp.,

New York)

Apparently the mines had been worked for many years. King Mindon Min was

said to have obtained Rs30,000 worth of rubies in one month from an old cave-

working and pit in the adjoining alluvium, which were called the Royal

Loo 18 (Holland, 1898).

About 1870, the mines were under the supervision of a German engineer

named Bredemeyer, who stated that stones were best when the detritus was of a

yellow color. In 1873, Captain G.A. Strover, described the Sagyin rubies in the

Indian Economist as being lighter in color that those from Mogok (Penzer, 1922).

According to Penzer (1922) and Chhibber (1934), a Sir Henry Hayden inspected

the tract in 1895. He found the rocks to be gneisses and schists, with bands of

crystalline limestone in them. The latter were considerably altered, and contained

numerous minerals, including spinel and ruby overlying the crystalline limestone.

Moisture moved through the joints between the limestone and surrounding rocks,

dissolving the limestone and creating fissures and hollows. These open spaces later

trapped the more resistant and insoluble clayey materials, including rubies.

At the time that Penzer described the deposit (1922), little work was being done

and it appears that little work has been done since.

In May of 1996, the author visited Sagyin, which is mainly worked for marble. A

few workers were digging into the marble for gems, but apparently having little

luck.

Figure 49. Sagyin is famous for marble, as evidenced by the large block roughly formed

for a Buddha carving. At the time of the author's visit in May, 1996, a few people were

also digging for rubies. (Author's photos)

Buying at the source

Before the discovery that Burmese rubies

could be heat treated, the presence and

relative abundance of fluid fingerprints

and feathers was useful in determining

whether or not a particular ruby

originated from Burma. The author recalls

examining large numbers of suspected

Burmese rubies brought for examination.

A quick look in the microscope, however,

revealed numerous fingerprints and

feathers. Looks of anticipation turned to

frowns when told that the only thing

"Burmese" about the gems were the

nationality of the sellers.

In the same vein, a story regarding

an acquaintance comes to mind that

speaks volumes about the efficiency of

modern transportation. This gentleman

journeyed all the way from Bangkok to

Peshawar, Pakistan for the purpose of

buying Afghan gemstones. He bought

several lots of rubies from Afghan

refugees who had just crossed the border,

eager to raise cash for purchasing

weapons to drive the Russian infidels out

of their homeland. Back in Bangkok I

examined his purchases and was forced to

relay the information that his journey had

Thabeitkyin (Thabeikkyin)

Burma's Thabeitkyin area has received

little notice.The following is based on the

1938 report of U Khin Maung Gyi (Gyi,

1938).

Thabeitkyin township is located on the Irrawaddy river north of Mandalay. In

former years, access to Mogok was via river steamer to Thabeitkyin.

From there, the road heads east to Mogok, some 60 km away (today a road

heads directly to Mogok from Mandalay).

Rubies at Thabeitkyin were reportedly mined as early as the 1870s, though no

valuable stones were found until the reign of King Thebaw [1878–1885]. U Yauk,

from Ye-nya-u village, is said to have found a ruby the size of a hen's egg.19 Since

all large finds were considered the property of the king, the stone was duly

delivered to the palace. This was how the king came to learn of rubies at

Thabeitkyin, and from that point on a ruby tax was levied on the villagers of the

area.

Old mining sites at Thabeitkyin are west of Wabyudaung, at Twindawgyi,

Kyaukpya, Ohnbaing and Ye-nya-u Pandwin. In the 1930s, ruby was found at Kyet-

saung-taung, Zaneechaung and Nyaungbintha. Kyet-saung-taung lies roughly 5 km

southwest of Wabyudaung.

In addition to rubies, blue and star sapphires have been recovered from

Thabeitkyin.

In recent years, several spots in the Thabeitkyin tract have been worked,

mainly for spinel. Bangkok gemologist, Mark Smith, visited a locality known as

"One Cock Hill" in 1998, where people were digging mainly spinels.

Yet-Kan-Zin-Taung

Corundum is said to occur at Yet-Kan-Zin-Taung village, which lies on the east side

of the Mandalay-Mogok road, some 50 miles (80 km) towards Mogok, near the

village of Let-Pan-Hla (U Hla Win, pers. comm., 27 June, 1994). Good-quality ruby

is said to occur along with red spinels. The locality is also notable for its production

of red star spinels. Mining is said to be difficult due to the rocky nature of the soil.

been for naught. Most of the rubies were

from Thailand.

Naniazeik (Nanyaseik)

In the early 1890s, ruby was found at Naniazeik, Myitkyina district, Kachin State.

Naniazeik lies some 80 km west of Myitkyina and 19 km west of Kamaing.

According to Penzer (1922), Warth examined the deposit, in 1895. "He [Warth]

stated that rubies, sapphires, and spinels were obtained from the detritus afforded

by the disintegration of crystalline limestones surrounded by intrusive masses of

granite."

The most complete description of this occurrence is that of Chhibber (1934),

with Tanatar (1907), Bleeck (1908) and Hertz (1912) also weighing in with reports.

Chhibber (1934) examined the deposit in the early 1890s. He described the major

localities as being in the neighborhood of Mawthit and Marrawmaw. Shan women

would wash for gold, while the males would work for rubies and other gems. In

addition to ruby, spinel is also found. Their color was said to vary from a near-

opaque, dark green to a bright, translucent red, with the latter color being rare.

Metamorphosed limestones were thought to be the source of origin for both the

rubies and spinels.

The author is unaware of anything published on this deposit since Chhibber in

1934. In 1996 and 1997, the author visited the village of Naniazeik. Inquiries were

made about mining in the area, but little work was apparently taking place. In late

1997, gemologists George Bosshart and Thet Oo visited Naniazeik, where they

were shown corundum rough, mostly pink and blue, with some small reds.

Diamonds are also found in the area. A restaurant owner stated to them that the

alluvial deposits north of the village were more productive than those to the south.

(G. Bosshart, pers. comm., 21 July, 1999)

Figure 50. Möng Hsu rubies

In their untreated state, Möng Hsu rubies typically display a bluish core.

Heat treatment removes the bluish

core, leaving white clouds in its

place.

(Photos: Tony Laughter)

Möng Hsu (Shan: Maing Hsu)

In 1991, U Tin Hlaing first reported on the occurrence of ruby at Möng Hsu. The

following is based largely on his reports (Hlaing, 1991, 1993a, 1994).

Rubies at Möng Hsu were said to have been discovered by a local resident who

had worked as a miner at Mogok. While bathing in the Nam Nga stream, which runs

near the town of Möng Hsu, he stumbled across rubies among the pebbles on the

banks. Thus began the most recent of Burma's ruby rushes. Fortune seekers

flocked to the area and the population swelled from 8000, to over 30,000 at the

peak of mining activity. This tapered off, however, as between April and June, 1993

the price for Möng Hsu ruby rough dropped by half (Hlaing, 1994).

Möng Hsu is one day's drive northeast of Taunggyi, (173 km by road; 83 km as

the crow flies). It lies between the Nam Pang and Salween rivers. Typical of many

areas in Burma's Shan States, the population of the Möng Hsu area consists of

Shans in the valleys, with hill tribes (Palaungs at Möng Hsu) living at higher

elevations. These Palaungs were involved in tea cultivation before the discovery of

ruby (Hlaing, 1994).

Mining was initially restricted to valley alluvials, but later moved into the in-situ

marble deposits in the surrounding limestone hills. Minerals associated with the

ruby are flattened quartz, green tourmaline, red-brown garnet, staurolite, pyrite,

and radiating acicular tremolite (Hlaing, 1993a).

In early 1994, the Burmese government was said to be considering joint

ventures with foreign firms for the mining of ruby at Möng Hsu (Ted Themelis, pers.

comm., Feb., 1994). Similar noises were made in 1989–90 about allowing

foreigners to mine at Mogok, but turned out to be nothing but a pipe dream.

Much of the material mined at Möng Hsu makes its way into Thailand,

particularly through Mae Sai. Initially the deposit has shown great promise, so

much so that by the early 1990s, Möng Hsu was supplying the world with as much

as 90% or more of all facet-grade ruby in sizes of 2.0 cts. and under.

But this material is not without its problems. Most of the Möng Hsu ruby is

heavily fractured. Thai burners combat this by heating the stones in the presence

of flux (typically borax), which heals the fractures shut. Unfortunately, the fact that

this treatment was performed on virtually all rubies from this deposit was not

disclosed to buyers by sellers in Thailand, leaving these customers feeling literally

like they had been "burned." The eventual result was a rejection of these goods by

a substantial number of buyers.

Today, this flux-healing treatment is generally known by most buyers, meaning

that Möng Hsu rubies fetch prices far less than their fully natural brethren from

Mogok. For a full description of the problems with Möng Hsu ruby, see the

author's Foreign Affairs: Fracture Healing/Filling of Möng Hsu Ruby.

Characteristics of Möng Hsu (Burma) corundum

Since the discovery of ruby at Möng Hsu, good reports of their characteristics have

been published. These are summarized in the following table on Mong Hsu rubies:

Properties of Möng Hsu (Burma) ruby

Property Description

Color range/

phenomena

Generally medium to deep red. Before heat treatment, crystals display

cores of a blue to violet color. Such blue cores are eliminated during heat

treatment. Star stones have not been reported.

Geologic

formation

Found in primary metamorphosed crystalline limestone (marble), as well as

secondary deposits derived from the same

Crystal habit Well-formed crystals consisting of pyramids/bipyramids terminated by the

basal pinacoid. Development of the hexagonal prism is generally slight.

RI &

birefringence

RI readings may vary depending upon the area of the crystal tested, with

higher RIs found in the crystal center. It has been hypothesized that this is

due to higher Cr concentrations in crystal centers.

n omega = 1.760–1.770; n epsilon = 1.768–1.778 Bire. = 0.008 to

0.009

Specific

gravity

3.97 to 4.01

Spectra Visible: Strong Cr spectrum, identical to other natural and synthetic rubies

Ultraviolet: Differences were found between the UV spectra before and

after heat treatment. Heat-treated specimens showed dramatically

increased transmission from 340-280 nm.

Infrared: Sharp peaks were recorded at 3189, 3233, 3299, 3310,

3368, 3380, and 3393 wavenumbers. Such peaks have not been found in

rubies from other sources.

Fluorescence UV: Moderate to very strong red (LW stronger than SW)

Other features Not reported

Inclusion types Description

Solids Many Möng Hsu rubies possess no solid inclusions. When they are found,

they tend to occur near the surface, making them rare in cut gems. Those

identified to date include the following:

• Apatite (Smith & Surdez, 1994)

• Chlorite: Mg-rich (Peretti & Schmetzer et al., 1995)

• Diaspore: in veins. These were not found in heat-treated specimens and

are easily confused with glass infilling (Smith, 1995).

• Dolomite: colorless, rounded to subhedral grains (Smith & Surdez,

1994)

• Feldspar: plagioclase (Peretti & Mullis et al., 1996)

• Fluorite: euhedral crystals (Peretti & Schmetzer et al., 1995)

• Mica: white (Peretti & Schmetzer et al., 1995); fuchsite & Mg-chlorite

(Peretti & Mullis et al., 1996)

• Rutile: red-brown crystals (J. Koivula, pers. comm., 28 Feb., 1995)

Cavities

(liquids/gases/solids)

• Secondary fluid inclusions (healed fractures) are common, in a variety of

patterns. Many of these result from flux-assisted healing of fractures during

heat treatment. See the author's Foreign Affairs article for more

information on this treatment.

Growth zoning • Straight angular growth zoning parallel to the crystal faces is present in

all specimens. Irregular `treacle'-like swirls in other directions. Zoning can

be extremely sharp (use shadowing illumination).

• Many crystals display zoned blue cores (such areas actually alternate

blue and red) at their center. Such blue zoning may also be found in other

parts of the crystal. Heat treatment eliminates such blue areas.

Twin

development

• Polysynthetic glide twinning on the rhombohedron {1011} is often

present

• Twinning has also been seen on the first-order hexagonal prism {1010}

Exsolved solids • Clouds of tiny exsolved inclusions of unknown identity are common. As

with all exsolved inclusions, these follow the growth structure of the crystal,

and are concentrated relative to the original impurity content of the crystal

at that stage of growth.

• Extremely fine, short rutile needles have been rarely seen

a. Information is based on the published reports of Smith (1995), Smith & Surdez (1994) and

Laughter (1993a-b), along with the author's own observations. See the author's Foreign

Affairs article for more information on this material.

Möng Hkak

Vague reports of a Kengtung Stone Tract have existed for years (Halford-Watkins,

1934). In 1993, U Tin Hlaing (1993b) gave specific information on a sapphire

deposit in that area. Located in the Southern Shan States, 75 km east of Möng Hsu

and just north of Kengtung, sapphires are said to occur in a secondary deposit

associated with surrounding metamorphic (schist, gneiss) and igneous (granite,

basalt) country rocks. The gems were found near the village of Wai Hpa Fai, 5 km

from Möng Hkak, with ethnic Wa mining sapphire from open pits. Möng Hkak

sapphires are said to have an average length of 1.5 cm, with gem-quality material

being "much smaller (about 0.3 mm in size)" (Hlaing, 1993b). This description of

the size of the gem material may be a typographical error, for unless larger

material were forthcoming, the deposit would seem to have little potential. Blue-

green bi-color sapphires are also said to be found at Möng Hkak (Hlaing, 1993b).

Nawarat & Namhsa

Kane & Kammerling (1992) reported on two additional areas where ruby has been

found. Nawarat,20 also known as Pyinlon, lies in the northern Shan State, near the

Chinese border; Namhsa is some 15 km north of Nawarat. Mining in this area has

apparently been ongoing since 1990. Immediately after the 1991 MGE emporium, a

5.25-ct faceted ruby "of exceptional color and clarity" was shown to Kane &

Kammerling. This gem was later christened the Nawarat Tharaphu, and was

reportedly cut from a 9.70-ct piece of rough found on April 23, 1990 at Nawarat.

Pilgrimage to Mogok

Everyone has their own personal Mecca, their own pilgrimage to make. For myself, it has been

Burma's Mogok Stone Tract. I waited patiently for over 15 years for this door to open. In April-May of

1996, it happened.

Mogok was everything I expected, and more. The town itself is no longer a small village of a few

thousand inhabitants, but a bustling city. Today, the entire district probably contains 300,000–

500,000 inhabitants. These consist of Burmese and Shan (Buddhist), Nepalese Gurkhas (Hindu), Lisu

(Christian and Animist), along with a smattering of Muslims, Sikhs and those of Eurasian origin. The

region's population has swelled tremendously in recent years, following the Burmese government's

liberalization of the gem trade.

Today, urban Mogok encompasses everything from Myintada in the southwest, to On Bin, in the

northeast. One valley over, the town of Kyatpyin has merged with Kathé. Many areas, which were

once distinct villages, are now simply urban appendages of either Mogok or Kyatpyin.

During my trips, in addition to Mogok/Kyatpyin, I visited mines at Ah Chauk Taw, Chaunggyi,

Dattaw, Inn Chauk, Inn Gaung, Lay Oo, Lin Yaung Chi, On Bin, Ongaing, Pingu Taung, Pyaung Gaung,

Shwe Pyi Aye, Thurein Taung, and Yadanar Kaday-kadar.

Today, the easily-accessible valley alluvials have been exhausted, and thus mining has largely

moved to hillside and hard-rock deposits. During the author's five days in Mogok, not a single twinlon

was seen, with the only valley mines observed consisting of lebins.

Hard-rock mining takes place at a number of localities, including Dattaw, Thurien Taung, and Lin

Yaung Chi, among others.

Perhaps the most exciting part of my journey was a visit to a loodwyin at Thurien Taung. The

indefatigable Dr. Saw Naung Oo, who resides in nearby Kyauk Pyatthat, guided us through thin cracks

deep inside the mountain. These represented solution cavities and fissures within the marble, and

provide places for gems to concentrate. Small wooden channels have been constructed to carry the

overburden and byon out for washing. While most loos consist of narrow cracks, in places these widen

out into limestone caverns. Dr. Saw Naung Oo told us of one chamber at Yadanar Kaday-kadar which

was nearly as big as a football field.

Another fascinating day was spent traveling to Bernardmyo. Transport was Willy's Jeep, ca. 1950,

but the road was strictly 19th century ox-cart path. Indeed, while it takes 1.5 hours by jeep, one can

walk it in less than six. This gives some idea of the speed of the jeep. Thankfully, while the jeep

sometimes carries as many as 20 passengers, ours had only five.

Halfway to Bernardmyo is the fascinating Inn Chauk mine, where rubies are pried from beneath

towering marble pillars. Due to weathering, such marble outcrops feature a black skin, and are

common throughout the Mogok area.

At Pyaung Gaung, peridot is obtained by blasting in a peridotite. Bernardmyo itself is a small

village inhabited by Chinese and Lisu. Nearby is a cemetery, where tombstones bear mute witness to

early trials of British soldiers in this area. Most graves date from 1888–1892.

My pilgrimage to Mogok was a dream come true. It is a Mogok tradition that one wishes the

owner luck when leaving a mine. Thus, to the people of Mogok I wish them luck. Kyauk gyi, kyauk

gaung, yaba zay. Good luck. May the stones you find bring you as much happiness as my visit to

Mogok brought me.

Mining areas and trading

While a variety of stones are found in most deposits, local inquiries revealed that certain areas are

famous for a particular variety.

Locality Varieties

Ah Nauttaw Good star rubies

Balongyi Top star rubies

Dattaw Good TP rubies

Ho Mine Top TP rubies

Inn Gaung Good star rubies

Kyauk Sin Good fancy spinels

Kyauk Pyatthat Good blue sapphires

Lebin Sin Top TP rubies

Lin Yaung Chi Good TP rubies

Mainglong Tourmaline

On Bin Top red spinels; good fancy spinels

Pyaung Gaung Top peridot

Sakangyi Quartz, topaz

Shwe Pyi Aye Good TP rubies

Sinkwa Good star blue sapphires

Thurein Taung Top TP blue sapphires

Yadanar Kaday Kadar Top star blue sapphires; Good TP blue sapphires

The Mogok area also features several regular gem markets, which have certain specialties and times

of operation.

Market Time Specialty

Kyatpyin town

Cinema-hall area 09:00–11:00;

14:00–17:00

All kinds of gems from the western

part of the Mogok Stone Tract

Inn Gaung 15:00–18:00 (every

5th day)

Various kinds of rough

Mogok town

Lay Oo 07:00–09:00 Small rough of all kinds

Myintada 15:00–18:00 Small rough

Peik Shwe 9:00–12:00; 14:00–

17:00

All kinds of rough and cut stones.

This is the biggest market in the

Mogok area (3 Kyat entrance fee)

Yoke Shin Yone

(Cinema Hall)

15:00–17:00 Fine gems. Also a meeting place for

exchanging information on mining

and trading.

Bernardmyo village Every fifth day Peridot, enstatite, diopside and

other semi-precious stones

Note: The best stones are not offered in the markets at all, but are shown to

customers in private homes.

In the past few years, trading in Burma has undergone a revolution. Just four years ago, private gem

trading was illegal; today, both rough and cut stones can be freely purchased by foreigners with

dollars from licensed traders, with only a 10% export tax to be paid. And most importantly, such

licenses are cheap and easy for locals to obtain. Thus, for the first time in over 30 years, private

trading and export of gems is both simple and legal.

In a land where private business was once the sole province of the tatmadaw(military), these

changes are nothing short of remarkable. Make no mistake, the tatmadaw still has their fingers in

many pies, but, for the first time in decades, they are allowing others to have a taste, too.

Future prospects for

Burma

Production from Burma's mines has

never been great, a fact consistently

overlooked by those seeking to

exploit the deposits.21Although

mining methods have improved over

the past few years, production

remains small. This has pushed

prices for Mogok rubies and

sapphires to record levels. Prospects

for the future appear no better than

the past. While it is likely that

material remains in the ground

waiting to be mined, only a change

in government seems destined to

bring about a total revitalization of Burma's gem and jewelry industry. In the

meantime, other sources, such as Thailand, and recently Vietnam, fill, to a degree,

the world's appetite for ruby. This may push away the pangs of hunger, but it does

not satisfy the heart's longing for the storied stones of history. Thus the world is

forced to wait, with bated breath, for the day when the glowing red stones of

Burma will again take their rightful place as the world's premier ruby.

Figure 51. Foreign buyers examine rough jadeite

at the 1992 gem emporium at Rangoon's Inya Lake

Hotel. Such emporiums were once the only legal

way to do business in Burma, but today trading is

possible via licensed private gem dealers. (Photo by

the author)

Notes

18. The "Royal Loo" was also mentioned by Brown and Judd (1896), but described

it as being at Bobedaung, near Mogok. It seems likely that the name was applied to

any deposit that produced a "Royal" ruby.[ return to chapter text ]

19.Rubies the size of "a hen's egg" have been frequently reported in the

literature. The author is still waiting to see his first fine specimen of such a

size.[ return to chapter text ]

20. Literally "nine gem talisman," which is related to the nine planets of Vedic

astrology. Ruby, the gem of the sun, is traditionally placed at the

center.[ return to chapter text ]

21. Witness Samuel Chappuzeau, who in 1671 wrote of Burma: "Nothing comes

thence but Rubies, and not in so great quantities as is believed, seeing that every

year there comes not out to the value of an hundred thousand Crowns, and

amongst them you'll very rarely find a Stone of four or five Carrats that is fair."

[ return to chapter text ]

Further Reading

Pigeon's Blood: A Journey to Mogok by R.W. Hughes

Foreign Affairs: Fracture Healing/Filling of Möng Hsu Rubies by R.W.

Hughes & O. Galibert

Identifying Sources of Burmese rubies by Han Htun & George E. Harlow

This page is http://www.ruby-sapphire.com/r-s-bk-burma6.htm v. 1.0

Page updated 7 March, 2013

https://www.youtube.com/watc

h?time_continue=7&v=AvSLUptKO04

http://www.gemresearch.ch/monghsu/per1.htm

Rubies from Mong Hsu

Since 1991, the Mong Hsu area in north-eastern Myanmar (Burma) has produced large quantities of superb rubies.

Peretti A. (1993): Foreign substances in Mong Hsu rubies. JewelSiam, Vol. 4, No. 5, p. 42

Peretti A. and Mouawad F. (1994): Fluorite inclusions in Mong Hsu ruby. JewelSiam, Vol. 5, No. 4, pp. 136-137

Peretti A., Schmetzer K., Bernhardt H.J. and Mouawad F. (1995): Rubies from Mong Hsu. Gems and Gemology, Vol. 31, No. 1, pp. 2-26

Peretti A., Mullis J., Mouawad F. (1996): The role of fluorine in the formation of color zoning in rubies from Mong Hsu, Myanmar (Burma). J.Gemm., 25, 1, pp. 3-19

Peretti A. and Mullis J. (1997): Distinction of natural and synthetic rubies by fluid inclusion analyses. XIV Ecrofi, European Current Research on Fluid inclusions, Nancy, France, July, Abtracts, p. 264-

265.

Introduction & History

Geographical Location

Geology & Mining Ruby Market

Market News At Auctions

Mogok and Mong Hsu Rubies

Unique Mong Hsu Ruby

Gemological Properties

Crystal Morphology

Microscopy & Inclusions

Chemical Composition

© Swiss Gemmological Institute SSEF

The beauty of colour

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The quest for "Kashmir" sapphires and "Burma" rubies

Origin determination of gemstones: Possibilities, Challenges and limitations !

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Origin determination:

Combining(classical(approaches(with(advanced(scienti5ic(analytical(methods(

The$origin$of$a$gemstone$on$a$report$is$always$an$opinion$of$experts,$indica9ng$its$most$probable$geographic$origin.$$It$describes$stones$which$originate$from$a$mining$opera9on$in$that$geographic$area.$$It$is$related$to$the$geological$seCng$$characteris9c$for$the$origin$(mining$area).$$The$origin$is$expressed$based$on$wellEestablished$criteria$(e.g.$inclusions,$chemical$composi9on...).$$$Challenges:$$E $New$mining$areas$are$discovered.$

E$The$analy9cal$methods$get$more$and$more$sophis9cated.$

© SSEF Swiss Gemmological Institute

Near$Bawpadan$in$Mogok$

Origin$determina9on$at$SSEF$is$relying$on:$$E $$scien9fically$and$gemmologically$highly$educated$staff$$

E $sophis9cated$analy9cal$instrumenta9on$

E $reference$samples$from$different$mines$

E $con9nuous$research$

E $long$established$experience$

© SSEF Swiss Gemmological Institute Photo © H.A. Hänni, SSEF 2004

© Swiss Gemmological Institute SSEF

$1)$Observa9ons$and$collec9on$of$analy9cal$data$$2)$Interpreta9on$of$observa9ons$and$data$$3)$Weigh9ng$of$evidences$and$consistency$check$$4)$Conclusion(s)$$$$Important:$Independent$assessment$of$a$gemstone$by$second$(third$etc...)$expert$(gemmologist)$and$mutual$discussion$!!$

Four steps of origin determination:

Deposits connected to Pan-African tectonometamorphic events

Distribu9on$of$corundum$deposits$connected$to$PanEAfrican$tectonoEmetamorphic$events$(750E450$ma)$by$the$collision$of$eastern$and$western$Gondwana.$$In$midEJurassic$(about$160$ma),$India$started$to$drig$towards$north.$

Distribu9on$of$marbleEhosted$ruby$deposits$along$the$Himalayan$orogeny$(45E5$ma)$due$to$the$collision$between$the$Indian$plate$and$Eurasia.$$

Dahaw$mine$:$Mogok$East$

marble-hosted deposits

after Jobbins & Berrangé, 1981

Corundum from alkali basalts

Ter9ary$and$quaternary$basalts$and$related$

corundum$deposits$in$SouthEEast$Asia.$

Jobbins & Berrangé, 1981!

Pailin!

Analytical instruments used for origin determination at SSEF

$E  XEray$fluorescence$(EDXRF)$E  Raman$Microspectrometry$E  FTIR$Infrared$Spectrometry$E  UVEVisENIR$Spectrophotometer$E  Photoluminescence$

Eventually:$E  LAEICPEMS$(laser$abla9on$induc9vey$coupled$plasma$mass$spectrometry)$E  LIBS$(laser$induced$breakdown$spectroscopy)$

© Swiss Gemmological Institute SSEF

© Swiss Gemmological Institute SSEF

Raman microspectrometry

UV-Vis Spectrometry

© SSEF Swiss Gemmological Institute"from H.A. Hänni, Journal of Gemmology 1994!

Chemical data versus spectroscopic data

© SSEF Swiss Gemmological Institute!

Basaltic!

Kashmir!

Burma!

Ceylon!

Laser Ablation Inductively Coupled Plasma Mass Spectrometry LA-ICP-MS

© SSEF Swiss Gemmological Institute

With$Dr.$Thomas$Pehke$$at$the$Geochemical$Lab,$$University$of$Berne,$Switzerland$

© Swiss Gemmological Institute SSEF

Laser ablation

© T. Pettke,, University Berne

Local$hea9ng$and$vaporiza9on$

© Swiss Gemmological Institute SSEF

Data processing

LA-ICP-MS Pearls

10

100

1000

10000

100000

1000000

10000000

100000000

30 40 50 60 70 80 90 100 110 120

time (sec.)

co

un

ts

Mn

Ca

I

Ba

Mg

homogeneous(signal(

Setting(of(integrals(for(data(processing(is(easy(

Integration time

Raw data

From:$P.$Halicki,$SSEF$(Masterthesis)$

Surface$contamina9on$!$

Spikes$!$ Spikes$!$Spikes$!$

Surface$contamina9on$!$

Data processing

From:$P.$Halicki,$SSEF$(Masterthesis)$

© Swiss Gemmological Institute SSEF From:$P.$Halicki,$SSEF$(Masterthesis)$

Madagascar!

Kashmir!Sri Lanka!

Burma!

Fe#(ppm

)#

Ti#(ppm)#

Sapphire Results:

From:$P.$Halicki,$SSEF$(Masterthesis)$

Madagascar!

Kashmir!

Sri Lanka!

Fe#(ppm

)#

Ga#(ppm)#From:$P.$Halicki,$SSEF$(Masterthesis)$

Sapphire Results:

Madagascar(

Kashmir(

Burma(

Madagascar!

Kashmir!

Burma!

Ti#(ppm

)#

Mg#(ppm)#From:$P.$Halicki,$SSEF$(Masterthesis)$

Sapphire Results:

20.12.2011 75

© Swiss Gemmological Institute SSEF

24.04.2012

Zentraler Weiterbildungskurs SGG

30

Comparison

Peucat et al (2007) Kashmir this study

Trace(element(concentrations(generally(indicate(origin(„trends“,(but(are(often(not(resulting(in(conclusive(results.(

Possibilities & Limitations:

24.04.2012

Zentraler Weiterbildungskurs SGG

30

Comparison

Peucat et al (2007) Kashmir this study

Peucat(et(al.(2007(20.12.2011 80

Thailand (Bo Phloi) + Cambodia

Peucat et al (2007)

From:$P.$Halicki,$SSEF$(Masterthesis)$

Kashmir sapphire

The(Maharaja(of(Jammu(and(Kashmir,((circa(1900(www.kashmirphotos.org/history.html(

The velvety blue of Kashmir sapphires

Sapphires$from$Kashmir$contain$subEmicroscopic$inclusions$which$scaher$the$transmihed$light.$$$As$a$result,$these$stones$ogen$show$a$$highly$appreciated$velvety$blue$colour.$

Photo © H.A. Hänni, SSEF

© Swiss Gemmological Institute SSEF

Characteristic inclusions in Kashmir sapphires

healed$fissure$with$interrupted$fluid$tubes$

Subtle$„dust“$tracks$

Photos: © H.A. Hänni, SSEF

Zoning$pahern$no$ru9le$needles$in$Kashmir$sapphires$!$

Pargasite$needles$(prisma9c)$

ShortEprisma9c$greenish$dravite$(tourmaline)$ Prisma9c$but$corroded$zircons$

Characteristic inclusions in Kashmir sapphires

Corroded$plagioclase$ Photo © H.A. Hänni, SSEF

Photo © H.A. Hänni, SSEF

The Kashmir - Madagascar challenge !

© Swiss Gemmological Institute SSEF

Origin$determina9on$=$combina9on$of$data$$$

Kashmir- Madagascar-

Blocky$zoning$with$red$VISEfluorescence$ Very$dense$zoning$

„Parquet“Estructure$ Dark-grey-colour-layer-(zone)-

Photo © H.A. Hänni, SSEF

© Swiss Gemmological Institute SSEF

Origin$determina9on$=$combina9on$of$data$$$

Kashmir- Madagascar-

subtle$„dust“$flakes$and$patches$

dense$and$wellEshaped$(rhombic)$„dust“$patches$

Photo © H.A. Hänni, SSEF

© Swiss Gemmological Institute SSEF

Origin$determina9on$=$combina9on$of$data$$$

Kashmir- Madagascar-

Fine$and$partly$curved$„dust“$lines$and$tracks$

Dis9nct$and$straight$„dust“$lines$

Photo © H.A. Hänni, SSEF

© SSEF Swiss Gemmological Institute

Characteris9c$$blocky$zoning$

Kashmir – Sri Lanka – Madagascar - Basaltic

ogen$narrow$zoning$

ogen$narrow$zoning$with$dark$zones$

Very$regular$$narrow$zoning$

Usually$$quite$included$

Ogen$$rather$pure$

Ogen$$rather$pure$

Usually$$included$

Characteris9c$$Inclusions:$E$pargasite$...$

Characteris9c$Inclusions:$

E$apa9te,$diaspore...$

Ogen$only$$few$inclusions$

Characteris9c$$Inclusions:$

E$UEpyrochlore$

Metamorphic$$UVEVis$spectrum$

Metamorphic$$UVEVis$spectrum$

Metamorphic$$UVEVis$spectrum$

Basal9c$UVEVis$spectrum$

Low$Fe$Low$Fe3+$

Low$Fe$Slightly$higher$Fe3+$

Higher$Fe$Slightly$higher$Fe3+$

High$Fe$High$Fe3+$

New source: Fancy sapphires from Batakundi, Kashmir area (Pakistan)

Sleeping$beauty$?$

New source: Fancy sapphires from Batakundi, Kashmir area (Pakistan)

Usually$included$(graphite),$milky$and$with$dis9nct$colour$zoning$(Cr).$

© Swiss Gemmological Institute SSEF

Ruby

Burmese ruby

© Swiss Gemmological Institute SSEF

The$ruby$ring$of$Marie$José,$Queen$of$Italy$

Courtesy of Albion Art collection!

Mogok

Gemmarket$in$Mogok$(January$2014)$

Dahaw$mine$:$East$of$Mogok$

Introduction

Jade,(since(thousand(of(years(a(mythical(stone(appreciated(in(Far(East(and(in(the(high(cultures(of(native(Americans,(is(currently(again(rising(high(and(is(sought(after(at(auctions(in(Hong(Kong(and(elsewhere.((

Ruby-tes<ng-at-SSEF-

The$quest$for$the$perfect$ruby$from$Mogok...$

approx.$14$ct$

Inclusions in Ruby from Mogok

!!!

Ru9le$silk$ Calcite$crystals$

Twin$lamella$ Corroded$calcite$crystals$

Photos © H.A. Hänni, SSEF

Colour$swirls$

© SSEF Swiss Gemmological Institute"

Generally$included$

105$ct$

© SSEF Swiss Gemmological Institute"

Titanite$and$plagioclase$inclusion$in$ruby$from$Mogok$ www.op9cs.rochester.edu$

www.vcbio.science.ru.nl$

www4.nau.edu/microanalysis$

Scanning$Electron$microprobe$

Burmese$Ruby:$approx.$48$cts$

Approx. 48 cts!

„Cut$tongues“$and$geometric$(trigonal)$platelets$

Mong Hsu, Burma important source of rubies since the 90ies!

Many rubies from Mong Hsu have a dark blue core

Mong Hsu, unheated

Dark$blue$to$black$core$zone$(TiEenriched)$

Mong Hsu, unheated

Cross$clouds$ Dust$tracks$„comets“$

Mong Hsu, unheated

Zoning$$$

&$healed$fissures$

Carbonates$

Mong Hsu heated LW$UV$reac9on$

SW$UV$reac9on$

Photos © H.A. Hänni, SSEF

New Ruby Deposit: Montepuez in Mozambique

Photo © H.A. Hänni, SSEF

Mozambique (Montepuez) Rubies$from$Amphibolite$

Photos © H.A. Hänni, SSEF

Inclusions:$$Rounded$crystal$inclusions,$$ru9le$needles,$twinning$planes,$$green$amphibole.$$E$Inclusions$±$similar$to$Mogok,$Burma$E$Trace$elements$±$similar$to$Winza$

Montepuez Ruby

© Swiss Gemmological Institute SSEF

Photos © H.A. Hänni, SSEF

© SSEF Swiss Gemmological Institute

Ruby from Winza (Central Tanzania)

Photo © H.A. Hänni, SSEF

Rubies from Winza

Characteris9c$inclusions:$$

E$curved$hollowEchannel$

E$whi9sh$granular$fluid$inclusions$

E$blue$to$greyish$colour$zones$

© H.A. Hänni, SSEF

Colour zoning in corundum from Winza

© Swiss Gemmological Institute SSEF

Vive la France!

New rubies and sapphires from Madagascar (Didy):

A(ruby(of(25(ct(from(Didy((Madagascar)(showing(an(exceptional(clarity(

The Cinderella job....!

Unheated Burmese rubies mixed with very few heated ones, or even synthetic rubies or ruby imitations (dyed quarzite)!

© Swiss Gemmological Institute SSEF

The colour of ruby

ruby(

pink((sapphire(

purple(

Pigeon$blood$red$$SSEF$defini9on:$Poe9cal$and$historical$colour$term,$describing$a$saturated$and$vivid$crimson$red$colour$of$gemquality$untreated$rubies$from$Burma$(Myanmar).$$The$SSEF$does$not$apply$this$term$to$rubies$from$other$sources,$nor$to$heated$stones.$$At$SSEF$$stones$are$compared$to$colour$charts$and$reference$stones.$

Conclusions:

Origin$of$a$gemstone$should$not$be$misinterpreted$as$a$quality$grade.$$Origin$determina9on$is$always$a$expert$opinion$$It$is$based$on$a$combina9on$of$me9culous$observa9ons$and$analy9cal$data$$New$analy9cal$methods$have$made$and$will$make$important$contribu9ons,$but$due$to$overlapping$proper9es,$these$data$need$careful$interpreta9on$(no$black$box$!)$$S9ll$nowadays,$microscopy$is$a$very$important$and$useful$tool,$as$the$presence,$shape,$and$distribu9on$of$inclusions$and$zoning$features$are$very$sensi9ve$markers$of$specific$local$forma9on$processes.$$New$deposits$may$be$a$challenge$for$gemmologist,$but$are$welcomed$by$the$trade$to$answer$the$high$demand$in$gems.$$$

Thank you for your attention

For$more$informa9on,$check$www.ssef.ch$

The Gem and Jewelry Institute of Thailand (Public Organization)

GIT’s Geologist Team under CLMV Project 19 July 2013

GIT Exploring Ruby and Sapphire Deposits of the Mogok Stone Tract, Myanmar

During the second week of June, 2013, a geological expedition team from GIT, with the inestimable permission of Myanmar government and the mine owners, had a great opportunity to visit a number of gem deposits including ruby, sapphire, peridot and spinel in the Mogok Stone Tract of Myanmar

The GIT’s geologist team was led by Mrs Wilawan Atichat, a former GIT Director, and a senior geologist and gemologist. The team also includes Mr. Tanawut Sirinawain, a senior exploration geologist who has more than 30 years experience in the areas of geology and mineral resources of South East Asia, Mr. Boontawee Sriprarasert, a GIT academic advisor and a senior mineralogist of the Department of Mineral Resources, Dr. Prayat Nantasin, a petrologist and lecturer at the Department of Earth Sciences, Faculty of Science Kasetsart University, The team also had the honor of Dr. Dietmar Schwarz of Gubelin Lab joining the trip as well.

Our team was probably the first group of foreigners who was allowed to visit Mogok after the period of prohibit that lasted over 15 years. Witnessing with our own eyes, the magical Mogok Stone Tract was still appeared as the so-called ‘Ruby Land’ since numerous precious stones especially ruby and sapphire could be virtually found and unearthed everywhere there. Standing at the peak of a mountain on the southern part of Mogok, we could still see thousand of mining activities emanating on the panorama view.

The Gem and Jewelry Institute of Thailand (Public Organization)

GIT’s Geologist Team under CLMV Project 19 July 2013

As an official governmental gemmological laboratory, GIT aims at ourselves to the identification and interpretation of the scientific characteristics of gemstones. We are committed to contributing to and maintaining a high potential and sustainable gemstone industry, and it is our mission to protect our customers by providing the trade with accurate and relevant information on gemstones.

During the exploration trip, we had a chance to visit only a few active mining sites, for instance, Shwe Pyi Aye, Pun Lin, Bar Nus (or Bernard), Pyaung Gaung, Ye Oo Gyi 24, Baw Mar, Kyauk Sar Taung, Inn Gaung, Yadannar Kaday Kadar, Pein Pyit, San Taw Wyn, Kyauk Saung, Kadoktat, and Kin mine. Some of them belong to private enterprises whereas others are owned by either the government or partnership between those two parties, some of which shared with foreign partners.

Geologically, two types of gem deposits could be defined for those mining sites, primary and secondary deposits. Ruby and sapphire in such primary deposits are mainly hosted in white marble intercalated with other meta sediments of the Mogok metamorphic belt. The corundum-bearing marble bed is always in contact with either mica-rich granitic?? gneiss or calc-silicate rocks. Some localities host only either ruby or sapphire but some sites host both ruby and sapphire such as at the Baw Mar mine (personal communication with Mr. Tint Lwin, the mine owner). In fact, there was no evidence of the existence of both ruby and sapphire within the same marble bed. Hence, detailed research work is required to unravel this clue.

Shwe Pyi Aye Mine

The Gem and Jewelry Institute of Thailand (Public Organization)

GIT’s Geologist Team under CLMV Project 19 July 2013

Pan Lin mine

Not like in the old days when the mining was carried out only by primitive method, today modern large scale open pit mining are a more common scene in the vicinity of Mogok, for example, at the Shwe Pyi Aye, San Taw Wyn, Yadannar Kaday Kadar, PeinPyit mining sites by using mechanized equipment such as bull dozer, trucks, heavy equipment, washing plant and jigs to recover all gem materials. Nonetheless hundreds of small scale open pit mining using gravel pumps and jigs are still present throughout the Mogok area. These are very similar to the gem mining in Thailand. Not only those, underground mining, tunnellings and sinking shafts that are very high cost of operation, are also in operation in some primary or hard rock deposits such as at the Kyauk Sa Taung, Kadoktat, and Baw Mar mining sites.

Bernard Mine

The Gem and Jewelry Institute of Thailand (Public Organization)

GIT’s Geologist Team under CLMV Project 19 July 2013

BawMar Mine

The secondary ruby and sapphire deposits was mainly colluvium since most alluvium deposits have been mined out through a long history. Gem re-mining in areas called Inn Gaung and Kin was probably operated in alluvium or secondary deposits. More variety of gemstones could be found in secondary deposit compared to the primary one. It was told that the gem mining operation in Mogok area was unpredictable and the business profitability was rather in doubt due to the high cost of operation.

Pein Pyit Mine

Though the actual reserve of ruby and sapphire at Mogok area is vague and suspected due to the long history of gemstone excavation but the geology of the area had made it unique and facinating.

The Gem and Jewelry Institute of Thailand (Public Organization)

GIT’s Geologist Team under CLMV Project 19 July 2013

Gem Market at the Htar Pwe in Mogok was still active and had a remarkable influence on day-to-day living. The prominence of gem trading in the town led to the establishment in the middle of the 20th century of Htar Pwe Gone, or gem market hill, a place where traders buy and sell gems on small copper trays. This daily open gem market has attracted speculators from throughout the surrounding area, traders showed their gemstones, gave a starting price, haggled and finally got a deal. Our team went to this market to buy samples and observe the purchasing process. The market became more active after one o'clock. This is similar to the market town of Chanthaburi. Cars, bicycles and motorbikes lined up along the crowded compound at the Htar Pwe, where the traders sat under big umbrellas, identified precious stones with unaided eye or loop before negotiating a price.

Opinions differ as to the current state of Htar Pwe, but our team agreed that good quality gems became rare. Most of the stones traded there were semiprecious, ranging in quality, type and size. We did not see the best quality stones in the Htar Pwe anymore. We were told that most of the best stones went directly to Yangon and Mandalay. Although most agreed that business at Htar Pwe was not as strong as before, the market was however still crowded and alived with gem traders where bargaining to get the best price was also a familiar and common scene there.

Htar Pwe Gem Market

With the potential to produce high quality raw gems in Myanmar, the new context of Myanmar to boost trade and investment policy of the country begins to open up. The international business opportunities start to open for

The Gem and Jewelry Institute of Thailand (Public Organization)

GIT’s Geologist Team under CLMV Project 19 July 2013

trade and investment in Myanmar's gem materials. Thailand gems and jewelery entrepreneurs should not overlook this opportunity as Thailand is a country with territorial cohesion together with a good political and economic relationship. Business opportunities in Myanmar will be open when the AEC is completely enforced in 2015 Hence, it is believed that access to Myanmar’s gemstone raw material sources will be easier and more legal. Nonetheless legal barriers and the exchange rate may still be the key issues for operators in Thailand to be careful when stepping into the path of trade and investment in Myanmar.

︱October 201354

GEMSTONES

The Mogok Valley in Myanmar (Burma) is home to some of the world’s most coveted gemstones but only a few outsiders have ever forged a

way into this region. GRS (Gem Research SwissLab), however, has kept a presence in the area for two decades. During this time, GRS has accumulated the most comprehensive gemmological data on spinel, as well as ruby and sapphire found in the region.

Unprecedented access GRS had been monitoring the Mogok Mines since

1994. This has allowed us to collect valuable data during numerous field trips to the region. Only very recently has Mogok opened up to a select few gemmologists. Through a series of complicated permit procedures, GRS gained access to every single important mine in Mogok. These expeditions target the location of the most important source of Pigeon’s Blood ruby, which up until this time had remained off-limits to outsiders.

The mine for this rare ruby deposit is accessed solely by three 100m vertical elevator systems (total 300m vertical depth). A huge marble mountain fitted with sophisticated and complex elevated transportation

By Dr. A. Peretti

GRS expedition to the Mogokruby, sapphire and spinel mines

Anong Kanpraphai-Peretti climbs out from a 40m vertical shaft of the Bawmar sapphire mine in

West Mogok. On her back is a 3D camera system recording the treacherous ascent of Dr. A. Peretti

from his studies underground. She is the first camerawoman in the world to film underground

sapphire mining with a 3D camera. The 3D film was shown in a GRS seminar during the September

Hong Kong Jewellery & Gem Fair (www.gemresearch.ch/news).

Photo credit: ©GRS Gemresearch Swisslab AG

Dr. A. Peretti adjusts a 3D movie camera with a high-watt LED light on a Burmese miner. The lightweight mine worker climbs about 100m vertically down the shaft of the Kadotthat mine to record various tunnels for GRS in a 30-minute project. He was able to capture mining conditions within a marble mountain yielding the world’s most important Pigeon’s Blood rubies of the past two decades.

︱October 201356

GEMSTONES

(commonly seen in South African gold mines) was an unexpected sight at this ruby deposit. The elevator system guides miners to a large number of vertically inclined shafts created for ruby mining.

Distinctive geology of the depositThe mountain itself consists of folded marble rocks

interspersed with compositional layering. Because the ruby is only found in certain layers, mining is both costly and extremely difficult. Just one ruby turned up during GRS’ tunnel exploration, underlining the extreme scarcity of these stones. It appears that this traditional key deposit will soon be mined out. The daily production of rock crushing, washing and sorting at the site seemed forlorn, and mirrored the look on the miners’ faces.

New site confirmedAnticipating that the earlier primary mines were

expiring, a marble mountain further east of Mogok at Dattaw mine has commenced operation. GRS discovered that its team was the only group of foreigners allowed into the mine up until this date; and indeed, inspection confirmed that another huge primary mine will begin ruby production again. As with other such mining efforts, these are risky operations with no guarantee as to the size or quality of ruby that will be produced.

By contrast to mining in the mountainous Mogok region, a chain of large-scale open pit mines could be observed along the entire Mogok Valley, stretching from west to east over a 30km span. The strategic mines positioned at previous sites have been inspected numerous times by the author since 1994. Previously, hundreds of so-called square-foot mines (small narrow vertical shafts descending into the gem-bearing layers) were present. The marble hills have been dug out and washed down to the surface. Debris from those mines has since been obscured by vegetation. Beforehand, labour was conducted with minimal equipment. But today, the entire landscape is awash with heavy machinery. While the quest to locate gemstones has become increasingly costly, the concentration of gems in that terrain has decreased significantly due to past mining activity, which depleted the more accessible deposit layers.

Pricing and supply

Going forward, the expectation for private enterprise and governmental joint ventures will be that less quantity is produced with more expensive rough. A recent visit to a local Mogok auction confirmed this premise. An array of gems was offered, but noticeably absent were extremely large, expensive sapphire

Studying the most productive sapphire mine in the Mogok Valley (Bawmar in West Mogok) revealed that these sapphires are slightly over-dark and were originally formed in moonstone layers. The mining area has been transformed into a desert due to extensive surface and underground mining, but reforestation and mountain slope-stabilisation projects have been spotted to counter this erosion

Deep within a marble mountain at Bawpadan, west of Mogok, Burma (Myanmar), Dr. A. Peretti descends the last 30m down an excavated tunnel to study the origin of Pigeon’s Blood ruby. They are found in distinct layers of grey marble within a complicated geological formation of marble. To reach this mining spot, three elevator systems had to be utilised. The ruby is located 900 feet below the surface

︱October 201358

GEMSTONES

and ruby. A 4.5-carat ruby rough sold for $50,000. The 2.5-carat ruby (not Pigeon’s Blood colour) would yield $20,000 per carat after cutting. Over the years, GRS has kept pace with market values and trending patterns of spiking prices arising from a scarcity of good stones. Similar price hikes are mirrored elsewhere in mining areas around the world. However, the robust Burma-origin provenance has propped up demand for these stones even though they are rarely found nowadays.

Emerging individual mining effortsCurrently, over a thousand small-scale private mine

owners are awaiting their mining licences. This private initiative will hopefully re-energise sustainable small-scale mining efforts as that which occurred in the past. The Mogok Valley boasts a magnificently rich cultural heritage, resplendent with pagodas, mosques and churches. It is a multicultural, multilingual exotic locale fuelled by a single goal for everyone – to find the most beautiful gemstones in the world.

Vigorous efforts should be implemented to guard this Valley of Gems by designating it as a Unesco World Heritage site before it is too late. Ethical and sustainable mining of these deposits would guarantee their existence for more than just another decade. The author and his fellow colleagues in the field of gemmology are strongly pushing for that to happen. Please join us in supporting this.

Dr. A. Peretti is CEO and founder of GRS Laboratories, with labs in Switzerland, Thailand and

Hong Kong. He regularly conducts expeditions to the world’s most important ruby and sapphire mines including the remote Kashmir sapphire mines in the high Himalayas. Peretti holds a PhD in Earth Science (specialisation in Geology and Mineralogy) and is one of the world’s still practicing gemmologists with over 25 years of experience. He is renowned for his adventurous field-gemmology films, books and numerous scientific publications. JNA

The difficulties of finding Pigeon’s Blood ruby are realised when the geology of the primary ruby mine at Bawpadan is studied. Dr. A. Peretti interviews engineers and geologists at the mining site to determine if the ruby-bearing levels are folded within the mountain in multiple steps; totally back-flipped (isoclinal in geological terms) and following large-scale open folds (anti-synforms). The ruby layer is so scarce that only one ruby was spotted upon inspecting the rocks and was extremely difficult to follow and locate within the mountain. This results in extremely expensive and risky mining operations with a complicated network of tunnels

Gemstone production at the During Taung mine in West Mogok revealed the size, quality and colour of currently mined spinel, sapphire and ruby by Dr. A. Peretti and local gemmologist-GRS consultant known in the Mogok valley as ‘Ko Pauk’ (Ngwe Lin Tun). The area is being re-mined after centuries of mining here. The production revealed fine gemstones, but mining efforts involved use of heavy equipment and removal of the entire landscape bordering the marble mountains; transforming a former paradise into a desert

Artisanal Ruby Mining in Myanmar: Environmental and Social Impacts

Sally Dickinson DeLeon, Summer 2007

This report was prepared as part of a master’s thesis on gemstone jewelry supply chains and their relationship to artisanal and small-scale miners. This short overview was created to supplement a project conducted by Dr. Saleem H. Ali on the environmental and social impacts and benefits of gemstone mining funded by a grant from the Tiffany & Co. Foundation. Sally DeLeon was a Tiffany Scholar at the University of Vermont for the 2005-2006 academic year when she was in the beginning stages of planning her master’s thesis. Her full thesis is expected to be available in 2008. Legend has it that the Valley of Rubies was created in ancient times when Naga (a serpent) laid three eggs: out of the first hatched the King of Pagan (the major region in ancient Burma), out of the second hatched the emperor of China, and the third egg was stolen away by a hunter but he accidentally dropped it in a stream. The third egg cracked and released all of the precious rubies that spread throughout the land of Myanmar’s modern day stone tract. Burma has always been strongly associated with high-quality rubies since the earliest European contact. Starting with the ancient kings and dynasties of Burma, and ending with the current military-junta dictators, most of the political leaders of this region have been renowned for the way they have made rubies symbolic of their power. An early Italian explorer wrote of a regional king in Burma who wore so many large red rubies “that seeing the person of the king by a light at night, he shines so much that he appears to be a sun.”1 Fine ruby displays luminescence and its ability to fluoresce and phosphoresce gave a mysterious aura of power to this king and other wearers. Than Shwe, the current military dictator of Myanmar, and his predecessors have regimented tight controls over the country’s mines and until recently declared all gemstones to be the property of the State no matter who unearthed them; stealing rubies from the State was punishable by death or lengthy imprisonment. Aung San Suu Kyi, Myanmar’s first democratically elected leader who won the Nobel Peace Prize in 1991 for her efforts to lead Myanmar’s people to stand up for their freedom, is the notable exception to this formula of rubies, fear and power. She has been kept under house arrest for most of the last 19 years by the power-hungry junta. Just as the Burmese creation legend suggests, the strong ties between rubies, political power, and China may be part of what is allowing the continuation of the human rights violations, environmental degradation, and extreme inequity for which Myanmar has become so notorious; if these ties could somehow be severed, perhaps peace and prosperity could finally take hold. Rubies are not the key to democracy and an end to human-rights violations—the revenue they generate pales in comparison to the junta’s earnings from oil and gas, and more of the official gem revenues are from jade than from rubies—but they are a piece of the puzzle. This report is an attempt to examine how rubies are mined in Myanmar and how their flow relates to the social and environmental well-being of communities therein.

Mining History At the northwest end of the Shan Plateau, in the vicinity of the Irrawaddy River, lies the Mogok stone tract. The mines of Mogok, and sub-mines in the surrounding area have produced many of the finest rubies in the world. In addition to rubies, the land yields sapphires, spinel, peridot, aquamarine and a variety of other semi-precious stones. The L-shaped stone tract is estimated to be 1916 square miles in area.2 Ruby was probably first discovered in this region by stone-age humans during the Middle Pleistocene.3 From

the early centuries up until about 400 years ago, the region was ruled by a succession of princes in the Shan dynasty. In 1597 the Burmese king forced the Momeik sawbwa (prince) to trade Mogok and Kyatpyin for a stoneless area called Tajaungmyo.4 The king held direct control over the ruby mines for a few years before the British East India Company made its first contact with Burma and began to act on an interest in developing the gem trade. During the almost 300 years when Mogok was ruled by Burmese kings, forced slave labor was common in the mines and people were punished severely for attempting to hide valuable stones. In the early nineteenth century the British won the first Anglo-Burmese war, and at the end of 1885 the British took Mandalay, ousting the last king of Burma, Thebaw, from power. From 1889-1925, the Burma Ruby Mines Ltd. operated extensive mechanized mining at Mogok, but the company was eventually forced to go into voluntary liquidation because of declining returns and a slumped market in the face of World War I. From 1926-1947, mining was executed mainly by native artisanal methods and continued that way after Burma achieved independence in 1948. In 1962 General Ne Win seized power in a military coup and in 1969 his Ministry of Mines banned private exploration and gem-mining; ruby and jade mining licenses previously issued to prospectors were revoked and all gems were declared military property. Little information is available to the outside world about how mining proceeded after Burma (now called Myanmar) was roped into the extreme isolation regimented by this long-running military dictatorship.

However, in the mid-1990s Myanmar opened up ajar to admit private interests and tourists from the outside world. Gemstone and jade mining were slightly liberalized and expanded. The major ruby mining areas of today, as shown on the map in figure 1, include the Mogok Stone Tract, and Mong Hsu in Shan State, while jade and the rarer jadeite are primarily mined in Kachin State around Hpakant. Some smaller ruby mining areas also became official sources in the 1990s at Nawarat (also called Pyinlon) and Namhsa in Shan State, Sagyin (near Mandalay), Thabeitkyn and Kathe along the Irrwaddy River west of Mogok, Namya, which is located in Kachin State a few miles from Hpakant near the Chinese border, and others. Mining Methods and Society in Mogok Alluvial deposits, where rubies have been transported from their original parent rock by weathering into streams and rivers along the valley floors of this mountainous region, are the source of most of the gemstones that have been mined in Myanmar. In recent years, new technologies have allowed miners to penetrate primary deposits and as of the end of the millennium, there were about 1000 mines operating in the Mogok Stone Tract, approximately half in byon (deep gravel of ancient alluvial deposits) and half in bedrock5. Four traditional types of mines operate in Mogok (as of the 1990s) and these are detailed in table 1. There are also some open-cast mechanized mines that have replaced the mechanized mining efforts of the British Empire. Table 1: Traditional Mine Methods of Mogok, adapted from Hughes (1997): 324-327. Type Used for Technique Twin-lon or pit

Mining the soft alluvial earth in the valleys

2-3 men work together to sink a small round shaft (3-24 m deep) straight down to the byon (gem-bearing gravel) and a small basket on a long-bamboo pole, with a counterweight or a hand-cranked winch, is used to haul up the earth.

Hmyawdwin or open trench

Excavating hillside surface deposits

A stream of pressurized water is directed to the upper end of an open cutting on a hillside and thus sweeps away the lighter material and mud effectively concentrating the heavier gem-bearing material to be scooped up and carried to a suitable site for washing, usually in a stream or river.

Ludwin or cave system

Extracting gem-bearing earth that fills limestone caves

Using a variety of hand-held tools, tunnels are excavated into hillsides to follow veins of byon to caverns in the limestone that form when impurities in the rock are dissolved by minerals in the groundwater; these caverns are often filled with deep layers of byon which is hauled out to the surface for washing.

Quarrying (tunneling)

Tunneling directly into host rock to extract stones

Dynamite and more modern forms of blasting are used to extract both ruby and sapphire from hard rock deposits.

Flooding by groundwater is a constant challenge especially in the twin-lon method. Hand-powered bamboo pumps as well as diesel-powered pumps are often used to remove the previous night’s water at the start of a work day, and twin mining ceases during the monsoon season (June-October). Since the hmyawdwin method requires an abundant

supply of water, it is carried out mainly during the rainy season. The ludwin and quarrying methods are not as common as twinlons and hmyawdwins, but some of the richest discoveries have been made in the caverns and crevices revealed in the limestone bedrock through tunneling. Mechanized mines opened in the era of the Burma Ruby Mines Ltd. and some have been operating in a number of locations since then. These generally involve large pits with centrifugal pumps planted in the middle to dry out the surrounding earth so that mines can work on the byon adjacent to the hole. Trucks may be used to haul excavated byon to a washing plant, where it is processed by machine through a series of screens and washing pans. However, the washing of byon is most commonly done in the traditional way since most mining in Mogok and the other important ruby mines are not mechanized. Large rocks are used to build a shallow enclosure, with a slight slope at one end, to contain the byon. A stream of water is directed onto the mound of byon while it is stirred and the lighter material flows out of an opening in the rocks at the sloped end of the enclosure. The remaining heavy material is removed for washing on circular bamboo trays, also commonly done in shallow enclosures. Poor people with hereditary rights to gem mine tailings, called the kanase, are given spoils from the mechanized open-pit mines as well as byon left over from the artisanal washing enclosures. The kanase, originally just women, wash this gravel in local streams to search for small spinels and other semi-precious stones. The kanase could be viewed as a symbol of the amazing social-system that has organically emerged in Mogok. The size of the population of the Mogok area is unknown, but it includes Burmese and Shan (Buddhist ethnic groups), Nepalese Ghurkas (Hindu), Lisu (Christian and Animist), as well as smaller numbers of Muslims, Sikhs and people of Eurasian origin. Despite differences in ethnicity, religion, language, politics and history, the people of Mogok compete for a stake of the ruby income while cooperating to ensure that everyone has a role to play and a way to participate. In the face of many risks associated with finding, possessing and selling rubies [elaborated on below in the section on Gemstone Mining Regulation], various groups have settled into niches, parts of a whole network that responds to the official channels for ruby production and drives the unofficial channels as well. The peaceful coexistence of all of these groups, and the system of cooperation that they have developed in the face of their common enemy—poverty—is an inspiring story for other ethnically fractured societies. Ruby Processing Mogok rubies are considered the finest rubies in the world because of their natural deep color, clarity, fluorescence, and lore. Due to recent extensive mining around Mogok since the 1990s, these stones are becoming increasingly rare. It is estimated that as of the early 2000s, 95% of all the faceted rubies on the world market come from Mong Hsu.6 Unlike the Mogok Stone Tract, the geology of Mong Hsu is not such that the rubies are a clear, deep, rich shade of “pigeon-blood” red, but instead often have a cloudy bluish-purple tinge and core. In general Mong Hsu rubies cannot be faceted without first being treated in high-temperature furnaces. They are treated both to improve the color and clarity and to heal deep fractures that are characteristic due the geological nature of Mong Hsu. The natural fractures usually cause untreated Mong Hsu stones to break during faceting, so these cracks must be sealed together by high-temperature heating with flux-

glass in order to improve chances of success during cutting and polishing. Even with heat treatment, buyers’ experiences have shown only a 10-30% range of success with cutting good stones from Mong Hsu rough7. While many stones from the Mogok region are cut and polished in the town of Mogok, or in Mandalay or Yangon, Mong Hsu stones are usually sold to Thai gem dealers in rough form. In Bangkok, where heating technology, heating expertise, education and willingness to take risks far exceeds Burmese levels of these resources, Thai “cookers” or “burners” treat the Mong Hsu rough in their furnaces. The treated rough is then offered for sale and may be cut and polished in Thai lapidary shops or taken abroad by dealers for cutting in China, India, the United States or a number of other places. Gemstone Mining Regulation When Ne Win, the first military ruler of Burma who staged a breakthrough coup in 1962, retired after widespread protests calling for liberalization in 1988, a new military junta took control. Many of Ne Win’s old aides were part of the new State Law and Order Restoration Council (SLORC). Headed by Senior General Saw Maung, the SLORC seized power after violently crushing the peaceful civil society protests of August 1988 by shooting as many as 3000 people. The peaceful movement for political change had emerged around Aung San Suu Kyi, the beloved daughter of 1940’s freedom fighter Aung San and leader of the popular political opposition party, the National League for Democracy (NLD). SLORC declared martial law, renamed the country from Burma to Myanmar, and placed Suu Kyi under house arrest. In a 1990 parliamentary election, the only one ever held in Myanmar, the NLD won a majority of seats but the SLORC annulled the results and refused to give up control of the legislative process. The State-Owned Economic Enterprises Law (SLORC Law No. 9/89) was issued in 1989 when the junta was in the early stages of introducing some market economy policies after 26 years of nationalized socialism. Chapter 2, section 3 of this law clarifies which economic activities will continue to be carried out only by the State including “… Exploration, trading, extraction and export of pearl, jade, ruby and other mineral precious stones.” In 1992 General Saw Maung resigned unexpectedly for health reasons, and was succeeded by one of his cabinet members, Senior General Than Shwe. Under new leadership, economic policies were relaxed somewhat to permit more foreign investment and infrastructure development. The Myanmar Mines Law of 1994 (SLORC Law No. 8/94) reformed the mining codes and made clear that no mining company can be held liable for prosecution or fines. Ironically, this law also contains some provisions about environmental protection at mine sites, but no clear way to enforce them. In 1995 the policy landscape for gemstone mining was modified when the junta issued the Myanmar Gems Law (SLORC Law No. 8/95). This law laid the groundwork for private companies and mining cooperatives to enter into joint ventures with the State to mine for precious stones, allowing foreign companies, or native ethnic groups to hold a minority-stake in a particular gem mine. The law also allows landowners to apply for permits to mine rubies provided that they sell them through government-approved channels and pay associated fees and royalties. In keeping with the 1994 National Environment Policy, Law 8/95 Section 12 (a) requires that all applicants for permits from the Ministry of Mines conduct an Environmental Impact Assessment (EIA) prior to receiving official approval to extract

gems, and that the Myanmar Gems Enterprise (MGE) investigate whether gemstone mining activities under each particular permit will negatively affect the environment, flora and fauna, highways, religious property, and/or cultural heritage items. The MGE is the official overseer of gemstone mining rights and grants permits to business people who wish to legally mine for gemstones or jade in Mogok, Mong Hsu, Namya, Hpakant and other areas. The MGE is also responsible for permits to process gemstones and to manufacture them into final products. Figure 2 shows the organizational structure of the Ministry of Mines, including the role of the MGE. Figure 2: Institutional Structure and Human Capital of the Myanmar Ministry of Mines, adapted from Samuels (2003): 163.

Acronym Department Responsibilities Human Resources

Officers 7 Staff 34

MO

Ministers’ Office

Cabinet of the Minister of Mines

Total 41 Officers 251 Staff 1219

DGSE

Department of Geological Survey & Mineral Exploration

Geological Surveying and Mapping, Mineral Exploration, Metallurgical Research Total 1470

Officers 23 Staff 43

DM

Department of Mines

Mineral Policy and Law Formulation, Safety and Environmental Control, Royalty Collection, Planning Total 66

Officers 201 Staff 6405

ME (1)

Mining Enterprise #1

Lead, Zinc, Silver, and Copper

Total 6606 Officers 201 Staff 4027

ME (2)

Mining Enterprise #2

Gold, Tin, Tungsten

Total 4228 Officers 199 Staff 3132

ME (3)

Mining Enterprise #3

Iron & Steel, Coal, and Industrial Minerals Total 3331

Officers 68 Staff 759

MGE

Myanmar Gems Enterprise

Rubies, Sapphires, Jade, Colored Stones, and Jewelry Manufacturing Total 827

Officers 30 Staff 331

PEARL

Myanmar Pearl Enterprise

Cultured Pearls, and Artificial Breeding of Mother Pearl Oysters Total 361

Officers 22 Staff 367

SALT

Myanmar Salt & Marine Chemical Enterprise

Salts by Production from Brine

Total 389

ORGANIZATION OF THE MINISTRY OF MINES

MINISTER

Deputy Minister Ministers’

Office

Deputy Minister

ME (1) DGSE DM ME (2) ME (3) PEARL SALT MGE

Since it was created in 1988 to replace the old Myanmar Gems Corporation, the MGE has hosted annual gem auctions, which until 2002 were only one of two ways to legally buy rubies and other gemstones from Myanmar. The Union of Myanmar Economic Holdings Limited (UMEHL) began selling rough stones, mainly from Mong Hsu, and jade at its own annual auctions in the mid-90s. Currently, MGE and UMEHL auctions are held several times a year and interested buyers can also purchase gemstones through official channels online, at the Gems Museum and Mart in Yangon, at the Myanmar Joint Venture VES Company store next to the museum, or at licensed hotel shops and outlets in Yangon and Mandalay. In 1997, the junta announced that it was changing its name to the State Peace and Development Council (SPDC) and some members were replaced. The SPDC maintains local strategic command offices all over the country, including in mining areas. The decisions of the MGE office in Mogok are reportedly controlled by the local SPDC office, and independent local mine owners who apply for permits are often delayed for so long that they have no choice but to sell their land to foreign Chinese and Indian investors to avoid further accumulation of debt.8 Land seizures by military personnel are not uncommon when valuable gem-bearing pockets are revealed therein. Due to the risks and economic uncertainties of legal gem entrepreneurship, many independent miners prefer to mine secretly, risking imprisonment and worse, and sell through shadow networks that smuggle rough stones across international borders into Thailand, China, India and elsewhere. Enforcement of environmental regulations is virtually non-existent in legalized mining operations, and certainly non-existent for illicit operations. Citizens have no way to seek recourse for relevant health problems and environmental damage done to land, waterways and wildlife in mining areas. Environmental Impacts of Ruby Mining The Valley of Rubies (the Mogok Stone Tract) is surrounded by three to six thousand foot-high mountains, which form a natural amphitheater and were at one time covered with dense tropical forests, which were home to tigers, leopards, bears, reptiles and other predators. Today, the once-admired teak forests are absent and large cats are now locally extinct, but some remain in other parts of the country. Monkeys, bears, wild-boars, snakes and birds still inhabit the Mogok region.9 The Kyauktaung Reserve, the Hintha Reserve, the Ondok Reserve, and the small Chaungyi Reserve all border on the mining areas. Burmese miners at the turn of the last century used to hunt in these forests and return to camp with slain animals to eat; it is not difficult to imagine that those who mine the valley today still depend on the forest for food as well as for materials necessary to sustain shelter, warmth and other human needs. Forest resources are commonly used to construct mine shafts and other structures. Timber, twigs and leaves are used for shoring up the side tunnels of twin-lon shafts and for alternative types of shafts in areas where the earth is not compact enough for twinlons. Nonetheless, prior to 1995, the effects of gemstone mining on the Burmese environment had been negligible since the days of the Burma Ruby Mines Ltd. Because most mining was done slowly using traditional methods, and most of the gem deposits were not found close enough to major river, lake

or marine ecosystems (with the exception of a few sites along the Irrawaddy River) to cause serious damage from siltation, environmental damage existed on a relatively small scale. With the advent of larger mechanized mines backed by foreign investors who could not easily be held to any liabilities, ruby, sapphire and jade mining became a serious threat to habitat preservation and biodiversity. Dynamite and powerful equipment have allowed the new mines to extract a lot of material in a short period of time, and the resulting environmental damage around Mogok and Mong Hsu is extensive.10 Although little research has been done, international environmental NGOs are extremely concerned about the state of biodiversity in Myanmar. The Salween River, which is the second largest river in Asia after the Mekong, flows close to Mong Hsu and some mines are located along its banks. With headwaters in Tibet, a course through the Yunnan Province of China, the eastern side of Myanmar and the western border of Thailand, the Salween is truly an international eco-region. Inside Myanmar it is commonly known by its’ Burmese name, Thanlwin. Figure 3 shows the watershed basins of all the major rivers in Myanmar, including the Salween shown as basin #7. Downstream from the ruby mining area it flows around 800 km before it enters the Andaman Sea at Moulmein. Approximately 140 species of fish inhabit the Salween, one-third of which are endemic to this river11. The river also contains one of the most diverse turtle communities in the world, including the endangered big-headed turtle (Platysternon megacephalum) and several threatened and vulnerable species. Erosion and siltation of the river is accelerated by gemstone mining activities and can damage habitats, reduce oxygen availability for aquatic species, and affect water temperatures leading to a loss of biodiversity. Since the ecological structure of the river is much of what allows it to provide food and a clean, continuous supply of water for local people and animals, the effects of changing this structure can be disastrous. These concerns have been echoed in the controversy surrounding the junta’s plans to build a series of large dams on the Salween for hydropower generation. The topic of preservation of endangered species, while on the whole less concerning than large-scale deforestation, destruction of biodiversity, and changes to the physical and ecological structures of river systems, is part and parcel with wildlife conservation in Myanmar. In general, hunting, over-fishing, logging, oil and gas exploration and gold-mining are the gargantuan threats to the threatened and endangered plants and animals. However, gemstone mining also plays a role, especially when it is carried out with dynamite, powerful machinery and inattention to soil erosion near waterways. The World Conservation Union (IUCN) estimates the remaining wild population of the critically endangered Irrawaddy River dolphin (Orcaella brevirostris) at 59 individuals.12 IUCN research has shown that a large number of gold mines operate along the Irrawaddy River (watershed basins #2, 3, and 5 in Figure 3) in regions of preferred habitat for this dolphin and the toxic mercury, large boat dredges, hydraulic land blasters and noise of these mechanized gold mines pose a major threat to the survival of the species. Small-scale gemstone mining is much less detrimental to the dolphins than the gold mining, but nonetheless, siltation from gravel blasting and washing could harm the health of one of the few-remaining Irrawaddy River dolphins in the world. The same reasoning holds true for critically-endangered birds that depend on the Irrawaddy and Salween River habitats.

Birdlife International is particularly concerned about changes to wetland habitats that are extremely important for threatened and endangered birds in the Irrawaddy River plains, downstream of ruby mining areas.13 However, the amount of additional silt added to rivers from gemstone mining activities is probably not enough to alter wetland habitat

structures significantly on its own. When combined with silt and soil resulting from agricultural land, logging, large-scale gold mining and hydrological changes caused by dams, silt from gemstone mines alone has a negligible effect on downstream habitats. When shafts (from the twinlon method, caverns from the ludwin method, and tunnels) are abandoned and left open when mining is finished, they can become hazards for wildlife, livestock and unsuspecting people. Abandoned pits are perhaps the longest-lasting environmental legacy of artisanal and small-scale gemstone mining in Myanmar. Particularly in areas where large mammals roam the ground, they may act as traps. They often become filled with water, and if small enough in diameter may appear as harmless, shallow puddles through which it is safe to walk. Standing water collecting in pits constitutes a breeding-ground for disease-carrying insects leading to stronger vector populations for malaria and Japanese encephalitis. Once again, the scale of these disturbances is minor from artisanal mining in Myanmar, particularly because much of it is done secretly so pits may need to be refilled and minimized in proximity to one another to avoid attracting attention from officials. Concern about abandoned pits

Figure 3: Map of River Basins in Myanmar showing the passage of the Thanlwin (Salween) River and the Irrawaddy River. © WEPA (Water Environment Partnership in Asia) retrieved 7 October 2007 from: http://www.wepadb.net/policies/state/myanmar/myanmar.htm

from the international conservation organizations has been aimed mainly at the large-scale gold mining going on in and around the newly created Hukawng Valley Tiger Reserve in Kachin State. Conclusion- Balancing Myanmar’s Ruby Costs and Benefits Rubies are a rich and important part of the culture and story of Myanmar. To argue that they are more of a curse than a blessing would be missing the point that they are inherent in the Burmese way of life, both the wonders and the wickedness. There is no way to measure all the contributions Burma Rubies have made to society. However, without a doubt rubies have brought livelihoods and valued traditions to the people of Mogok. When they are mined in the traditional, artisanal-style ways the harm caused to ecosystems is negligible—after all it has been going on four thousands of years. Ecological damage from artisanal and small-scale mechanized mines could be contained with little technical difficulty and capital, but education and environmental justice pose more daunting challenges. While environmental regulations are vague and out-of-date, it seems unlikely that the majority of miners would comply with stronger regulations due to lack of appropriate institutions for enforcement. Furthermore, many hereditary mining families deeply resent the government for their nationalization policies, ties to Chinese and Indian investors, unfair pricing policies, and general abuse of non-Burman ethnic groups. Because of this deep-seated conflict, smuggling and hiding gem deposits from the junta have evolved into proud creative art forms. For many families involved in the mining and gemstone processing businesses in Myanmar, selling a ruby is their only hope of escaping poverty. Other than illegal teak or heroine trading, there are few alternative livelihoods to gemstones that allow people to earn enough income to survive. In the puzzle of how to build stronger human rights and environmental governance in Myanmar, rubies are still a conundrum but one thing about them is clear: they are not the logical first step for leveraging a brutal regime. Because rubies are deeply integrated in the history, mythology and social systems of the places from which they are mined and traded, any policy effort to eradicate the ruby economy without fully understanding it could have serious unintended consequences for the social and environmental well-being of communities in these places. Jade, gold, oil and gas, all of which are more economically viable to the SPDC than rubies, are not as easy to smuggle as rubies nor are they as mired in religious faith and hope. Furthermore, rubies and other small precious stones are more amenable to artisanal mining than jade or gold because of their geological nature. If human rights for marginalized peoples is the international priority in Myanmar, then rubies may best be left as an avenue of hope for the poorest miners while work is undertaken to cut off streams of power and revenue from the larger natural resource honeypots. Endnotes 1 Ludovico di Varthema of Bologna as quoted from Temple (1928) by R.W. Hughes on page 307 of Ruby & Sapphire (1997)

2 George (1961) as referenced by Samuels (2003) on page 117 of his chapter on the Mogok Stone Tract

3 Hughes (1997)

4

George (1915) as referenced in Hughes (1997)

5 Waltham (1999): 145

6 Hughes (2004)

7 Samuels (2003): 158

8 MacLean (2003)

9 Themelis (2000): 85 10

Gutter (2001)

11 WWF (2006)

12 IUCN (2007)

13 BirdLife International (2003)

References BirdLife International. (2003). Myanmar plains. In Saving asia's threatened birds: A guide for government and civil society (pp. 213-216). Retrieved 13 October, 2007, from http://www.birdlife.org/action/science/species/asia_strategy/pdf_downloads/ wetlandsW16.pdf IUCN, The World Conservation Union. (2007). The IUCN red list of threatened species: Orcaella brevirostris (ayeyarwady river subpopulation)- critically endangered. Retrieved 13 October, 2007, from http://www.iucnredlist.org/search/details.php/ 44556/all WWF, Worldwide Fund for Nature. (2006). Salween river - a global ecoregion. Retrieved 13 October, 2007, from http://www.panda.org/about_wwf/where_we_work/ ecoregions/salween_river.cfm George, E.C.S. (1915). Burma gazetteer: Ruby mines district (Volume A). Rangoon, Burma: Govt. Printing and Stationary Office. George, E.C.S. (1961). Ruby mines district. Rangoon, Burma: Govt. Printing and Stationary Office. Gutter, Peter. (2001). Environment and law in burma. Legal Issues on Burma Journal, 9. Hughes, R.W. (1997). Ruby & sapphire. Boulder, Colorado, USA: RWH Publishing. Hughes, R.W. (2004). Fluxed up: The fracture healing of ruby. Retrieved October 13, 2007, from http://www.ruby- sapphire.com/flux_healing_mong_hsu_ruby.htm MacLean, Ken. (2003). Capitalizing on conflict: How logging and mining contribute to environmental destruction in Burma. Washington DC: EarthRights International with Karen Environmental & Social Action Network. Retrieved 13 October, 2007, from http://www.earthrights.org/files/Reports/capitalizing.pdf Samuels, S.K. (2003). Burma ruby: A history of mogok's rubies from antiquity to the present. Tucson, Arizona, USA: SKS Enterprises, Inc. Temple, R.C. (Ed.). (1928). The itinerary of Ludovico di Varthema of Bologna from 1502 to 1508 (Reprinted 1970 by Argonaut Press, London ed.). New York: N. Israel/Amsterdam & Da Capo Press (NY). Themelis, Ted. (2000). Mogok- Valley of rubies & sapphires. Los Angeles: A & T Publishing. Waltham, Tony. (1999, July-August). The ruby mines of mogok. Geology Today, 143- 149.

1 ︱November 2015

MozambiqueFaced with a dwindling supply of Burmese rubies

in the marketplace, gemstone buyers are paying increased attention to gem-quality rubies from

Mozambique, according to GRS GemResearch Swisslab AG.

Strong auction results at Gemfields’ Singapore sale, held from June 16 to 22, for higher-end rough ruby from Mozambique’s Montepuez deposit underscores Mozambique ruby’s swift ascent. Revenues hit $29.3 million with an average realised price of $617 per carat. A total of 47,451 carats were sold from the 72,208 carats offered. Gemfields said these results opened doors to further educate the market on the rarity and value of Montepuez gems.

In an exclusive interview with JNA, GRS founder and CEO Dr. Adolf Peretti discussed how Mozambique ruby’s distinctive appeal is progressively gathering a vibrant response in the market.

JNA: How would you compare Mozambique ruby from its Burmese counterpart?

Dr. Adolf Peretti: Most Burmese rubies are heat-treated while a majority of Mozambique rubies are free from thermal enhancement. This is an important aspect because many Mozambique rubies show no cracks and

are transparent enough to be facetted into gem-quality goods. Burmese rubies fall into two categories: Rubies from Mogok and Mong Hsu, of which, the latter currently dominates the market. Mong Hsu stones often display blue colour zoning and require heat treatment.

From a geological standpoint, rubies from both Burma and Mozambique may reveal high concentrations of chromium, a major contributor to their vividly saturated red colour. After cutting, both Burmese and Mozambique rubies are presented in similar carat sizes. Their colour and face-up appearance make some Mozambique goods indistinguishable from their Burmese counterparts. We can also divide Mozambique rubies into two distinct groups. One group is highly reactive to ultraviolet light with intense red fluorescence similar to that observed with Burmese gems. The second group shows no strong reaction to UV light. The latter type has a much higher concentration of iron than Burmese rubies. Due to their extreme brilliance and transparency, especially with the fluorescent Mozambique variety, they bear a striking resemblance to Burmese rubies with regards to colour. Only a very sophisticated eye may detect the difference.

JNA: To what do you attribute the intense interest in Mozambique ruby?

Dr. Peretti: Looking at the demand for and quality of both Mogok and Mozambique rubies helps explain the unique niche that Mozambique ruby has carved out for itself. Unheated Mogok rubies seldom appear in the market. Therefore, their origin garners huge public interest with a high premium placed on them. Origin, however, does not automatically guarantee quality. Most Burmese stones in the marketplace are, in fact, heated as a necessary means to enhance their beauty. Unheated

GEMSTONES

in the gemstone worldrubies gaining favour

Dr. Adolf Peretti at a seminar on Pigeon’s Blood rubies from Mozambique and Burma sponsored by GRS GemResearch Swisslab AG at the June Hong Kong Fair

A 3.04-carat Pigeon’s Blood Burmese ruby (left) in comparison with a 3.01-carat Pigeon’s Blood Mozambique ruby. Photo taken by Philip Hahn courtesy of Gerhard Hahn GmbH

2

GEMSTONES

︱November 2015

top-quality Burmese rubies may fetch record-setting prices at auctions. But when individuals attempt to acquire such a stone, chances are high that no one has it, or if it is available, it becomes inaccessible due to the price. Mozambique rubies do not yet reflect an origin premium in their price. As to quality, they can appear remarkably similar to Burmese rubies and yet are available as unheated. Burmese rubies’ rarity has reached a stage where it has become challenging to deal with them in the open market. Most of the action now occurs at international auctions. For example, if a buyer tries to acquire an unheated 10-carat Burmese ruby without cracks at a jewellery show, he will have enormous difficulty finding it. If he should locate one, he’ll face a huge premium on the price just for its origin. Conversely, he may find a dozen of Mozambique rubies that are over 10 carats with equal colour to the Burmese gems, but he should expect to pay five to 10 times higher for Burmese goods of similar size and quality. Facing a scarcity of high-quality ruby alternatives, Mozambique rubies will move fast. Another key reason for Mozambique ruby’s growing popularity is the near- impossibility of acquiring sets of unheated Burmese ruby to make necklaces – normally requiring 20 to 30 graduating rubies plus a centre stone of over 5 carats. Assembling a matching suite of unheated vivid red Mozambique ruby suitable for jewellery sets is likewise not an easy feat, but is still theoretically possible.

JNA: What does the future hold for Mozambique ruby in the gemstone trade?

Dr. Peretti: Thanks to Gemfields’ ongoing mining operations in Mozambique, there is a robust supply of Mozambique ruby. The spectacular appeal of

these rubies makes them ideal for creating elegant necklaces rivalling anything seen at auction. There is now a tremendous opportunity for prestigious brands to create bespoke pieces using Mozambique ruby. Top global houses could market their proprietary designs featuring Mozambique rubies at the centre of their promotional campaigns during jewellery shows. Finally, Mozambique rubies’ innate beauty and colour will be the ultimate allure for customers, surpassing origin as a condition of quality. The responsibility of large-scale miners, however, extends far

beyond production numbers and auction results. The emerging trend of end-users focusing more on ethical products whose mine-to-market journey is verified will become a greater factor for future promotions. It is vital for Mozambique’s gemstone producers to face head-on these ethical issues by ensuring that local residents benefit from their region’s natural resources, participating in the value-added chain and restoring mining sites to their original state once they are fully depleted. These key measures will ensure a bright future for Mozambique rubies. Of course, Burmese ruby miners face the same challenge. Sooner or later, they will have to develop a similar ethical stance. If they are not able or willing to do so, ultimately their appeal and prestige might wane, allowing Mozambique rubies to replace their Burmese counterparts. JNA

Dr. Peretti inspecting a rough gemstone in Mogok, Burma

Source: GRS GemResearch Swisslab AG

*Wholesale values in Hong Kong and Bangkok of unheated Mozambique rubies with ‘Pigeon’s Blood’ colour of two different qualities – very good and excellent (top gem). The values are based on GRS’ internal statistics of indicated insurance values during the testing process. The prices are an approximate indication for the purpose of demonstrating price evolution and may vary.

GEOLOGY OF GEMSTONE DEPOSITS –

EXPLORATION MODELS FOR WYOMING

by

W. Dan Hausel

W. Dan Hausel Geological Consulting LLC

Gilbert, Arizona 85233

danhausel@yahoo.com

„Bureaucracy is a giant mechanism operated by pygmies‟ - Honore de Balzac

ABSTRACT Much of Wyoming is underlain by Archean cratonic basement rocks and cratonized

Proterozoic rocks that provide favorable geological environments for a variety of

gemstones – notably diamond, iolite, ruby, sapphire, garnet, kyanite, andalusite,

sillimanite, labradorite, jewelry grade gold, platinum and palladium nuggets, emerald,

aquamarine, helidor, tourmaline, spinel, clinozoisite, zoisite, apatite, jasper, specularite,

etc. Thick Phanerozoic sedimentary rock successions with lesser Tertiary volcanic rock

cover large portions of the basement terrain. Some of these Phanerozoic rocks provide

favorable hosts for other gemstones including opal, placer diamond, placer gold, placer

platinum, placer ruby, jasper, agate, emerald, varisite, etc.

Using traditional exploration and prospecting methods, dozens of gem and precious

metal deposits were discovered over the past 3 decades including major discoveries and

geological and mineralogical evidence for significant undiscovered deposits. Major

swarms of mantle-derived kimberlite, lamproite and lamprophyre, many of which have

proven to be diamondiferous, also host colored gemstones including pyrope garnet (Cape

Ruby), spessartine garnet, almandine garnet, chromian diopside (Cape Emerald) and

chromian enstatite. One lamproite also yielded peridot.

Favorable conditions for crystallization of metamorphogenic gemstones during regional

amphibolite-grade metamorphism occurred during the Precambrian. In this terrain,

metapelite in the central Laramie Range hosts kyanite, sillimanite and andalusite. These

three minerals provide evidence of favorable pressures and temperatures needed for

crystallization of aluminous gemstones including ruby, sapphire and kyanite. Cordierite

(iolite) another aluminum-rich gemstone, formed during a later thermal event. This later

event was responsible for deposition of world-class iolite (Water Sapphire) gemstone

deposits.

Evidence for undiscovered gemstone deposits is predicted based on mineralogical

anomalies detected during various research projects from 1977 until 2005. These include

ruby, sapphire, gold and aquamarine found in stream sediment samples as well as

favorable geological terrains that remain unexplored. Other anomalies include pyrope

garnet (several with G10 geochemistry), picroilmenite, and some chromian diopside that

provide evidence for hundreds of undiscovered diamond deposits. Elsewhere, detrital

diamonds reported by various prospectors provide direct evidence for undiscovered

diamond deposits. Other geological and mineralogical evidence suggest the presence of

additional undiscovered opal, cordierite (iolite) and kyanite deposits.

Wyoming could potentially become a major source for gemstones including diamond,

gold, platinum, palladium, Cape ruby, Cape emerald, iolite and opal.

I dedicate this paper in memory of a friend and former colleague at the Wyoming State

Geological Survey who greatly advanced the State‟s knowledge in industrial minerals

and decorative stones. Ray E. Harris former Industrial Minerals and Uranium Geologist

prematurely passed away – his passing was so unnecessary.

INTRODUCTION Gemstones are timeless treasures of nature that not only represent objects of beauty and

intrigue, but also represent some of the more valuable commodities on earth. The

extraordinary and satiated colors of many gemstones enhance their aesthetic beauty,

while others may produce extraordinary fire, birefringence or other unusual light display

or interference. When Mankind first picked a stone from the ground for its innate beauty

rather than as a tool or weapon, this symbolized an important event in evolution.

Mankind visualized beauty. And when this stone was given to another as a gesture of

friendship or love - a unique quality of the human soul was manifested in the sharing.

This evolution led Man to search for similar rocks and minerals. The recognition of

certain characteristics in a particular stone and its association with nearby specific rock

types, such as agate or jasper in distinct grey to white rock (limestone), or quartz crystals

in vugs of milky white and pink rocks (pegmatite dike), etc., greatly enhanced the ability

of early prospectors to find additional stones of similar quality. Recognition of such

mineral and rock associations signaled the start of the science of prospecting. As time

passed, these primitive prospectors exchanged ideas and concepts that ultimately led to

the science of economic geology.

Recognizing rock and mineral associations and understanding regional geology is

important in a search for new gemstone deposits. In this search, the successful geologist

and prospector not only focus on the regional geology, but also the surrounding host

rocks, mineral and rock associations, and past geological environments. Gemstones, like

any other mineral grow or crystallize under specific physical and chemical parameters.

Some gems have innate favorable characteristics that allow survival during weathering,

erosion, stream transportation and placer concentration. Gems may be found in igneous,

metamorphic, and/or sedimentary environments and are typically associated with specific

rock types and mineral suites. Unlocking these characteristics and clues can lead

geologist to the discovery of additional deposits.

Gemstones are sought for personal adornment and have become the prized possessions of

men, women, Kings and Queens, worldwide. Some of the more exotic minerals and gems

represent the most valuable commodities on earth based on size. Nothing on earth can

compare a fabulous gemstone. For example, Walton (2004) describes a 62-carat royal

blue rectangular cut sapphire valued at $2.8 million ($45,000/carat) (>9,000 times more

valuable than an equivalent weight in gold). In general, rubies are more valuable. In

1998, a Burmese ruby of 15.97 carats sold at a Sotheby’s auction for US$3.63 million

($227,301/carat). More recently (2005), Christie’s of New York sold a near perfect 8.01-

carat Burmese ruby for US$2.2 million - a record per carat price for a ruby

(US$274,656/carat)! Some jade specimens of unimaginable value have included a 1.4-

inch long jadeite cabochon that sold for US$1.74 million (Ward, 2001)! In 1999, a jadeite

bangle of only 2 inches in length and 0.3 inch wide sold at a Christie’s auction in Hong

Kong for US$2,576,600 (Hughes and others, 2000). Even more incredible was a 27-bead

emerald-green jadeite necklace, known as the Doubly Fortunate that sold in Hong Kong

for US$9.3 million in 1997 (Hughes and others, 2000; Ward, 2001).

Many diamonds have attracted the desire of the affluent. Some of the more valuable are

red and pink diamonds. A small 0.95-carat purplish-red diamond (the Hancock Red) sold

for nearly US$1 million. To put this in perspective, one carat weighs only 0.2 gram

(0.007 ounce). At today’s gold price, this diamond was valued at more than 200,000

times an equivalent weight in gold - a common value for flawless pink diamonds.

Other priceless treasures have been purchased by Royalty or donated to Royal treasuries.

Most notable were those cut from the Cullinun rough, the largest diamond ever found at a

whopping 3,106 carats. The extraordinary gems faceted from this huge rough were

donated to the British royalty and reside in the British crown jewels.

Many gemstones have intrinsic properties that make them visually attractive: others

stimulate our imaginations with unique qualities. The value of others has reached

extraordinary heights due to ingenious marketing strategies such as a group of former

industrial diamonds that are now coveted by the wealthy. These include brown and very

light brown diamonds that were at one time considered to be almost worthless, but today

are marketed as rare cognac and champagne diamonds of great demand. Yellow

diamonds, also once considered low-value stones, are now marketed as Canaries. Others,

such as zoisite, an alteration mineral, were brilliantly marketed as Tanzanite. For the

economic geologist, it is important to note how valuable gems are in comparison to other

commodities. This alone should provide incentive to search for these commodities and

for some government agencies to transcend politics and personal agenda and instead

support the interest of the public.

Tapping into geological knowledge allows geologists and prospectors to predict where

gemstones will be found and what type of host rock they will occur. Such information

can lead to significant discoveries, such as the extremely rich diamond deposits in the

Canadian Shield in the 1990s (Krajick 2002; Hausel, 2006a, b), the discovery of major

poly-gemstone deposits (iolite-ruby-sapphire-kyanite) in Wyoming, discovery of one of

the largest opal deposits in North America in Wyoming (Hausel, 2005) as well as several

other gemstones in the Wyoming Craton over the past 2 to 3 decades (Hausel, 2005a),

predictions of very large iolite, ruby, opal and diamond deposits in Wyoming (Hausel and

Sutherland, 2006) and predictions of new discoveries and new commercial host rocks of

diamonds worldwide (Erlich and Hausel, 2002).

GEOLOGICAL SETTING Rocks that form the Wyoming Craton include Archean (>2.5 Ga) basement rocks of the

Wyoming Province that underlie Montana and much of Wyoming (Hausel and others,

1991). Along the southeastern margin of the province, cratonized basement rocks

(Proterozoic schist and gneiss; <2.5 Ga) of the Green Mountain terrain abut against the

Wyoming Province along the Mullen Creek-Nash Fork shear zone (Houston, 1983,

1993). The craton was fragmented during the Laramide orogeny: the style of deformation

was brittle and non-thermal. The resulting uplift was accompanied by erosion and

episodes of renewed uplift.

The basement complex of the Wyoming Province consists of Archean gneiss and schist

with scattered greenstone belts and supracrustal terrains that have been intruded by

granitic plutons. The supracrustal rocks include thin successions of metapelite mixed with

metagraywacke, metavolcanic rock, amphibolites, schist and gneiss. Metamorphism was

predominantly regional amphibolite-grade with isolated upper greenschist facies. The

regional prograde events proved favorable for genesis of metamorphogenic gemstones.

Notable are metapelites. These include sillimanite-garnet-biotite-muscovite-quartz schist,

kyanite-biotite-corundum-quartz schist, andalusite biotite schist, sillimanite-kyanite-

biotite-muscovite-quartz schist, cordierite gneiss and schist, corundum-kyanite schist, etc.

Corundum- and cordierite-bearing metapelite is interpreted to represent aluminous shale

precursors. One corundum-serpentinite in the Granite Mountains is interpreted as an

aluminous ultramafic magma precursor of komatiitic affinity. Other aluminous

serpentinites have been identified in the South Pass and Seminoe Mountain greenstone

belts, although no corundum is reported in those (Hausel, 1991; 1994).

Estimates for burial depth of metapelite in the central Laramie Range are based on the

alumino-silicate polymorphs (andalusite, kyanite, sillimanite). Along the edge of the

Elmers Rock greenstone belt, Graff and others (1982) identified metapelite with

andalusite and sillimanite. A few miles north at Palmer Canyon, kyanite-sillimanite-

corundum-mica schist is found. The presence of polymorphs within a narrow region

supports that the metamorphic grade increased to the north, with the highest-grade

exceeding the polymorph triple point in the vicinity of Palmer Canyon. The data suggests

these rocks were subjected to lithostatic pressures exceeding 3.8 kb (possibly as much as

5.5 kb) equivalent to a burial depth of 8 to 10.5 miles (12.8-16.8 km) and temperatures

exceeding 500°C.

Reports of gem-quality cordierite, corundum and kyanite were rare until the discovery of

the Palmer Canyon deposit, 5 miles (8 km) north of the Elmers Rock greenstone belt, in

1995 (Hausel, 2002). Since that discovery, other discoveries were made and the

possibility of additional gem material in this region is highly probable. This paper focuses

on some of the recent iolite discoveries.

DISCOVERIES Several gemstone, lapidary, and precious metal deposits were found in Wyoming from

1975 to 2004. Some notable discoveries include diamonds (McCallum and Mabarak,

1976; Hausel, 1998a), labradorite (Norma Beers and Letty Heumier, personal

communication, 2000), opal (Scott Luers, personal communication, 2002; Hausel,

2005a), variscite, minyulite (Bob Bratton, personal communication, 2002), sapphire,

ruby, peridot, aquamarine, helidor, iolite, pyrope garnet (Cape ruby), pyrope-almandine

garnet, chromian diopside (Cape emerald), chromian enstatite, specularite, several

varieties of jasper and agate (Hausel and Sutherland, 2000; Hausel, 2006a) and jewelry

grade gold nuggets (Hausel, 1989). Decorative stone deposits also were found and/or

identified (Harris, 1991, 1994) prior to 2004. Essentially all meaningful research related

to these and related projects ended in 2004 due to bureaucratic failures.

Cratons are notable geological environments for hosting major diamond deposits

associated with kimberlite, lamproite and lamprophyre. Archean greenstone and high-

grade supracrustal terrains within cratons provide excellent targets for a variety of gems

including diamond, ruby, sapphire, emerald, aquamarine, and jewelry grade gold nuggets.

Younger rocks, such as those in the Absaroka Plateau and Yellowstone Caldera are fertile

for opal, agate, jasper, gold and several varieties of cupriferous minerals and gemstones,

and the Wyoming sedimentary basins including the Overthrust belt provide potential

hosts for other gems including diamond, emerald, opal, jasper and agate.

Diamond, Cape Ruby, Cape Emerald, Peridot In its simplest form, isometric diamond is equal-dimensional and produces six-sided

cubes referred to as hexahedrons. However, a more common habit of diamond is that of

a octahedron (Figure 1). Octahedrons form 8-sided bipyramids, although some

octahedrons may develop ridges on the octahedral faces resulting in crystals of

trisoctahedral and hexoctahedral habit. Partial resorption of the octahedron will produce

rounded dodecahedrons (12-sided) with rhombic faces. Many dodecahedrons develop

ridges on the rhombic faces resulting in a 24-sided crystal known as a trishexahedron.

Four-sided tetrahedral diamonds are sometimes encountered, and these are probably

distorted octahedrons. Another relatively common form of diamond is the macle, or

twinned diamond. Many macles form flattened triangular crystals.

Figure 1. This parcel of diamonds from the Kelsey Lake mine, Colorado includes a

flawless 14.2 carat octahedron (photo courtesy of Howard Coopersmith).

The surface of diamond may contain growth trigons, and less commonly pits, which

further distort the habit of the crystal resulting in other habits. Diamonds have brilliant

greasy luster likened to oiled glass. Gem quality diamonds can occur as translucent to

transparent colorless, green, yellow, brown, and rarely blue or pink stones. Opaque and

heavily included diamonds are used for industrial purposes and bort.

Diamond is brittle, extremely hard (H=10), has a specific gravity of 3.5, and perfect

octahedral cleavage. Even though it is heavier than water, it is non-wettable

(hydrophobic) and will float on water under favorable circumstances. Diamonds are

grease attractive. Under ultraviolet light, many will weakly fluoresce pale blue, green

yellow, and rarely red.

Since diamonds are extremely rare, it takes considerable effort and patience to find

diamonds. It has been estimated, that diamond occurs in concentrations considerably <1

part per million in commercial diamondiferous kimberlite and lamproite. Diamonds have

been found or reported at several locations in Wyoming, Montana, and Colorado.

Strongly mineralized lamproites host olivine such that there is a correlation between the

amount of olivine and the presence of diamond. Most olivine in lamproites is typically

serpentinized to produce a rock that is not resistant to erosion. As such, most

diamondiferous lamproites lie hidden within fields of non-diamondiferous and more

resistant leucite lamproites (Figure 2). Less commonly, olivine remains pristine in such

rock. Thus, some lamproites may represent potential hosts for another gemstone in

addition to diamond – peridot.

Figure 2. (a) Ellendale 9 lamproite in Western Australia is located within a field of more

resistant lamproites that are barren of olivine. This commercial deposit, exposed in the

bottom of the trench, was discovered by its magnetic signature as it lay hidden within a

prominent field of lamproites much similar to the Leucite Hills in Wyoming. (b) A parcel

of peridot gems from anthills near the Black Rock lamproite in the Leucite Hills. These

are part of the >13,000 carat group collected from just two anthills. Note the excellent

clarity of the faceted gems.

Kimberlites are essentially potassic-peridotites composed almost entirely of serpentinized

olivine. Olivine is rarely preserved other than as serpentine pseudomorphs in kimberlite.

Typically, kimberlites contain varying amounts of mantle material as cognate nodules,

megacrysts, xenoliths and xenocrysts. Some of the more important are the kimberlitic

indicator minerals – pyrope garnet, chromian diopside, chromite and picroilmenite (and

of course diamond). In some kimberlites (and some lamprophyres), pyropes and

chromian diopsides are such high quality that they are used to produce gemstones

referred to as Cape Ruby and Cape Emerald (Figure 3).

Figure 3. (a) Kimberlite breccia from the Sloan Ranch kimberlite, Colorado, exhibits

large gem-quality pyrope-almandine megacryst. (b) parcel of gemstones from anthills in

the Greater Green River Basin include red, pink, and purplish red pyrope, emerald green

chromian diopside, light green olivine that surround a Cape Ruby faceted from a pyrope

garnet. (c) Faceted Cape Ruby (pyrope garnet) from the Green River Basin shows why

these Wyoming gems are some of the best in the world.

Several intrusive episodes of kimberlite, lamproite and lamprophyre occurred in the

Wyoming Craton (Hausel, 1996f). Such magmas are potential hosts for diamond deposits

(Erlich and Hausel, 2002) and it is significant that the two largest kimberlite districts in

the US, the largest lamproite field in North America, some unconventional

diamondiferous host rocks, scattered detrital diamonds, and hundreds of kimberlitic

indicator mineral (KIM) anomalies have been identified in the Wyoming Craton (Hausel,

1998a; Coopersmith and others, 2003).

At least 50 kimberlites (Late Precambrian and Early Devonian) intrude Proterozoic

basement rock and granite in the Colorado-Wyoming State Line district (Hausel, 1998a).

Essentially all of the intrusives that have been tested yielded some diamonds (Hausel,

2006d). Bulk sample tests ranged from 0.5 carat per 100 tonnes (cpht) to 135 cpht

(Waldman and McCallum, 1991) (commercial ore typically averages from about 15 cpht

to 700 cpht). Diamonds from this district include microdiamonds to very high-quality

gemstones >28 carats in weight (Coopersmith and others, 2003). One octahedral

fragment from an estimated 90-carat diamond was also recovered indicating that larger

stones remain to be found in the kimberlites and adjacent stream placers.

More than 130,000 diamonds were recovered during testing in the district. A commercial

mine was developed on the KL1 and KL2 kimberlites at Kelsey Lake, Colorado in 1996,

but operations terminated due to land issues. The recovered diamonds included >30%

gemstones, many of which were excellent transparent white gemstones. Others included

yellow, gray, light brown, green and even pinkish stones!

At the Iron Mountain district to the north near Chugwater, a large dike-pipe complex was

mapped. Testing of KIMs from essentially all kimberlites (Early Devonian) in the district

indicated that nearly all originated from the diamond stability field at depth. The only

exception was a group of small, faulted, intrusive breccias along the southernmost edge

of the district that have carbonatite affinity. Based on mapping, it was apparent that

hidden kimberlites also lie within the district (Hausel and others, 2003). Only 3 small

bulk samples were collected in the early 1980s by Cominco American and one yielded

some microdiamonds along with a 0.3 carat macrodiamond (Coopersmith and others,

2003). The rest remain untested. Some structurally-controlled depressions lie on trend

with the Iron Mountain kimberlites 6 miles (10 km) west in the Indian Guide area.

Kimberlite being relatively soft typically erodes more rapidly than surrounding country

rock often producing subtle topographic depressions devoid of trees. Such depressions

often exhibit some type of structural control.

Kimberlite is one of two host rocks mined for commercial quantities of diamond. The

other is lamproite (Erlich and Hausel, 2002) and the largest field of lamproites in North

America, the Leucite Hills (3.1 to 0.9 Ma), provides a good exploration target

(Coopersmith and others, 2003; Hausel, 2006e). This field overlies a thick cratonic keel

that is a favorable source for diamonds. Olivine is found in some lamproites in the

northeastern portion of the field. The presence of olivine suggests possibilities for hidden

olivine lamproites. The recovery of diamond stability chromites from two of the

lamproites along with the olivine suggest that this region represents one of the better

unexplored diamond targets in the US. Although no diamonds have been found, there has

been no testing even though there is a strong correlation between diamonds and increased

amounts of olivine in lamproites. With few exceptions, olivine lamproites are diamond-

bearing.

During field reconnaissance and mapping another gemstone was discovered was

discovered in the Leucite Hills in 1998. Olivine in this field has excellent transparency

and color and is a source for gem-quality peridot. More than 13,000 carats of the

gemstone was recovered from two anthills (Hausel, 1998c) (Figure 2b).

Cedar Mountain to the southwest of the Leucite Hills along the Utah-Wyoming border

lies on the margin of a very large KIM anomaly covering a few hundred square miles

(McCandless and others, 1995) (Figure 4). The geochemistry of the KIMs suggests that

the source intrusives are not diamondiferous. Even so, a group of detrital diamonds had

been reported in drainages along the southwestern flank of Cedar Mountain and also in

Butcherknife Draw to the east.

Figure 4. Location of some of

the many anomalies related to

diamonds. The heavy dashed

line is the approximate

boundary of the Wyoming

Archean Province (the core of

the Wyoming Craton).

Cratonized Proterozoic rocks

to the south are also

considered good targets for

diamonds. The geological

setting of the Proterozoic

terrain may also be favorable

for fancy diamonds –

particularly „pinks‟, which are

thought to have color lamellae

related to deformation (see

Hausel 2006d) . The presence

of a Proterozoic Benioff zone

(the Mullen Creek-Nash Fork

shear zone) suggests that the

Proterozoic terrain to the

south could provide excellent hunting grounds for pink diamonds.

The discovery of a group of lamprophyre dikes and breccias along the flank of Cedar

Mountain resulted in Guardian Resources and later Anadarko collecting bulk samples

that yielded diamond (Hausel and others, 1999). This discovery represented a third rock

type shown to be diamondiferous in this craton, and similar possibilities are likely

elsewhere in Wyoming and Montana. The age of the intrusives is Tertiary (Oligocene).

These do not show any distinct magnetic or conductivity anomaly, and were recognized

only by following KIM trails to rounded boulders and cobbles on the side of a hill. The

rounded stones are xenoliths hosted by the lamprophyre and represent partially

assimilated crustal material. The matrix of the host rock is primarily brecciated Bishop

Conglomerate containing mini-eclogite nodules and abundant chromian diopside,

chromian enstatite, pyrope and pyrope-almandine, many of which are excellent gems

with extraordinary color that blend into the surrounding country rock. In addition to the

lamprophryres, hundreds of anthills scattered over hundreds of miles contain very high

quality Cape ruby (pyrope garnet) and Cape emerald (chromian diopside). These

represent some of the higher quality pyrope and chromian diopside gemstones found in

the world (Figure 3c).

A similar KIM anomaly is recognized north of Thermopolis where hundreds of pyrope

garnets (Cape ruby) occur in anthills. The source of these remains unknown. In the

1980s, >300 kimberlitic indicator mineral anomalies (KIMs) were identified in 1600

sample sites in the Laramie and Medicine Bow Mountains (Hausel and others, 1988).

These and other results indicate that Wyoming is underlain by a major diamond province!

Some of the sample concentrates collected in the search for diamonds, also yielded traces

of native gold, aquamarine and corundum, and only a handful of the mineral trails were

ever followed because of budget constraints. Later sampling projects identified dozens of

gold anomalies in southern Wyoming (Hausel and others, 1994).

Detrital diamonds have been found at a number of places in Wyoming and Montana

within the Wyoming Craton, and KIMs are reported in the Laramie, Medicine Bow,

Seminoe, Bighorn and Hartville Mountains, and also in the Green River and Bighorn

basins of Wyoming, and in the Sweetgrass Hills in Montana. KIMs are so common that

during one public field trip in 2003, members of the general public were taught to pan

gold in the Middle Fork of the Little Laramie River. Instead of gold, members panned out

numerous pyrope garnets. KIMs were also recovered from gold placers along Douglas

Creek and in paleoplacers north of the Seminoe Mountains surrounding the Miracle Mile.

One gold miner found two excellent diamonds in Cortez Creek in 1977 and later

exploration of the area by Superior Minerals Company identified a KIM anomaly to the

south near Iron Creek in the Medicine Bow Mountains. This same company recovered

diamonds from a Proterozoic age paleoplacers in this region during gold exploration

(Tom McCandless, personal communication).

Ruby & Sapphire

Corundum (Al2O3) includes two gemstones: sapphire and ruby. These are chemically and

physically the same mineral and only differ in color due to trace impurities. Corundum is

found in rocks enriched in alumina and poor in silica: in particular aluminous schists and

volcanic rocks that are silica-undersaturated. The principal habit of corundum is barrel-

shaped, six-sided (hexagonal) prisms and tabular prisms terminated by pinacoids.

Corundum exhibits good basal and rhombohedral parting: twinning sometimes occurs

parallel to the crystal base (Bauer 1968). Growth twins have been reported in corundum

in Sri Lanka and in the Granite Mountains, Wyoming.

Corundum (H=9) has a hardness second only to diamond. Due to its extreme hardness,

transparent to translucent corundum is highly prized as a gem. The mineral has relatively

high specific gravity (3.94 - 4.08) (Bauer 1968), thus detrital corundum may be found in

placers with other minerals of high specific gravity. But due to well-developed parting, it

tends to disaggregate over short transport distances. Even so, corundum placers are

reported along the Missouri River in Montana, along the edge of the Great Dividing

Range in Australia, and in the Big Sandy opening of the Wind River Mountains of

Wyoming. The author also identified excellent gem sapphire and benitoite in a placer at

Poker Flat, California.

Rubies >5 carats in weight are uncommon and >10 carats are rare. One of the largest

known rubies was recovered from the Dat Taw mine in Mogok, Myanmar: the stone

weighed 1,743 carats (Gubelin and Erni, 2000). Kievlenko (2003) describes the Rajah

Vijaya ruby of India to be 2,470 carats. One large red-corundum found in the Red Dwarf

deposit of the Granite Mountains of central Wyoming by the author was the size of a

hen's egg measuring 2.5 inches in length. However the specimen was stolen before it

could be weighed (Hausel, personal field notes, 1995). Another specimen from the same

locality was nearly 90% replaced by zoisite and fuchsite. The 5-inch pseudomorph

weighed 7,150 carats and contained some preserved translucent ruby of excellent pigeon-

blood red color. Thus the original ruby, prior to replacement, would have represented one

of the largest, if not the largest ruby in the world.

Sapphires are typically small; even so, some very large stones have been discovered

including a 63,000-carat sapphire found near Mogok. Another sapphire discovered in

Madagascar in 1996 weighed 89,500 carats (Johnson and Koivula, 1996)! Sinkankas

(1959) reports that an enormous corundum was found in Macon County, North Carolina

that is believe to be largest found. The stone, which contained zones of transparency,

weighed 707,600 carats (312 lbs)!

Corundum is found as an accessory in quartz-poor, aluminum-rich metamorphic rock

such as mica schist, gneiss, and crystalline limestone. It is also found in silica-poor

igneous rocks such as syenites, nepheline syenites, serpentinites, some lamprophyres, and

alkalic basalts. The luster of corundum is greater than glass but less than diamond and is

vitreous to sub-adamantine. Corundum’s birefringence and dispersion is low compared to

diamond, which is why faceted corundum has less „fire‟ than diamond. Some may exhibit

asterism and produce star rubies and sapphires when cut as cabochons. Asterism is either

6- or 12-rayed and a result of light reflecting off oriented, needle-like rutile inclusions in

planes perpendicular to the c-axis.

Gemology

Trace elements (chromophores) responsible for color in ruby include Cr3+

, V3+

and Fe3+

and the trace elements responsible for color in sapphire are Fe2+

, Fe3+

and Ti4+

. Because

much corundum had been mined in the Orient in the past, the suffix 'oriental' is attached

to various colored sapphire gemstones. Modern descriptive terms are suggested (Table 1).

Red gem-quality corundum is termed ruby; all other colors are sapphire.

Relatively common white gem corundum is referred to as white sapphire. Rare orange

sapphire with a pinkish undertone is known as “padparadsha”, meaning “lotus flower”.

All other sapphires are termed ‘fancy’ with a prefix to denote the color of the stone. The

most desirable color for ruby is dark, purplish-red (pigeon blood red). The most attractive

color for sapphire is velvety cornflower blue (Kashmir blue).

Gemstone Archaic Modern

Color Terminology Terminology

red oriental ruby ruby

blue oriental sapphire blue sapphire

colorless leuco-sapphire white sapphire

light bluish-green oriental aquamarine bluish-green sapphire

green oriental emerald green sapphire

yellowish-green oriental chrysolite yellowish-green sapphire

yellow oriental topaz yellow sapphire

aurora-red oriental hyacinth aurora-red sapphire

violet oriental amethyst violet sapphire

pinkish-orange padparadsha

Table 1. Varieties of gem corundum.

The color of ruby is of primary importance followed by transparency. A ruby may show

different shades of red depending on origin. Even though gemologists refer to ‘Burmese’

ruby as top of the line, it does not necessary follow that the stone is from Myanmar

(formerly Burma): the designation is only an indication of a shade of color similar to the

famous pigeon-blood-red rubies. Kashmir blue sapphires are top of the line and have pure

and intensive blue enhanced by a fine, silky gloss. Myanmar sapphire is also considered

valuable and ranges from rich royal to deep cornflower blue.

A very large percentage of marketed rubies and sapphires are enhanced for clarity and

color (Hausel and Sutherland, 2006) with thermal treatments. Such treatments have been

used for centuries as Sanskrit texts show that such treatment was used as early as 2000

BC. As many as 90 to 95% of all sapphires and rubies are thermally treated (Ward,

1998).

Types of Deposits

Corundum is found in (1) magmatic, (2) marble-hosted, (3) metasomatic, (4) regional

metamorphic and (4) placer deposits. Placer concentrations can be economically

important due to natural beneficiation and ease of mining. Essentially all deposits found

in Wyoming are either metamorphogenic or placer. Corundum found as an accessory in

gneiss and schist is typically hosted by silica-poor rocks that were subjected to high

pressure and temperature during regional metamorphism. At Palmer Canyon, Wyoming,

the presence of alumino-silicates (kyanite and sillimanite) in the adjacent country rock,

and andalusite and kyanite a short distance south, provide constraints indicating pressures

and temperatures necessary to reach the alumino-silicate triple point must have been

about 4 kbars (14 km depth) and 500oC (Hausel, 1996).

Deposits

Corundum is described in Afghanistan, Australia, Cambodia, Burma, Thailand, Sri

Lanka, Tanzania, and the US, Kenya, Madagascar and Vietnam. Less important deposits

occur in Brazil, China, India, Laos, Malawi, Nepal, Nigeria, Pakistan, Switzerland,

Russia, Rwanda, and Zimbabwe (Hausel and Sutherland, 2006).

A number of localities in the US have produced minor ruby and sapphire. The most

productive is the alkalic province within the Wyoming Craton in Montana. Montana has

been the source for considerable gem-quality sapphire from placers and a group of

lamprophyres. Sapphires up to 0.5 inch have intermittently been recovered since 1865

(Voynick, 1987). According to Berg (2004), detrital corundum was traced to nearby

ultramafic lamprophyre dikes, which yielded 18.2 million carats of raw sapphire at Yogo

Gulch, 50 miles southwest of Lewistown on the northeastern flank of Little Belt

Mountains.

Metamorphogenic corundum occurrences hosted in metapelite have been identified in

Wyoming. Corundum was reported at a few localities in the Granite Mountains, central

Wyoming. Some gem material was described in alluvium along the Sweetwater River

both east and west of Jeffrey City. Pinkish red sapphires up to 0.25-inch in diameter were

found in pelitic schist in NE section 31, T31N, R89W of the McIntosh Meadows

Quadrangle in the northeastern Granite Mountains (Sutherland and Hausel, 2002). The

corundum is very limited in extent. Deep- to purplish-red ruby was described near

Sweetwater Divide. Some specimens were cut and produced star-rubies (Curtis 1943).

The Red Dwarf deposit near Jeffrey City has produced several large rubies. Corundum

was also found on the Robinson Claim in the Rattlesnake Hills of the northeastern

Granite Mountains. One specimen of purple-red, opaque to translucent hexagonal

corundum from the deposit was a little more than 1.25 inches (3.2 cm) in diameter.

Sapphires were recovered from the Abernathy deposit, 40 miles east of Lander. The pale-

blue to white sapphires were described in N25°E-trending mica schist enclosed by gray-

brown granite near Sweetwater Station. Abundant 1-inch (2.5 cm) diameter nodular

‘sapphires’ were found that were badly shattered and altered on the edges (Love, 1970).

According to Hagner (1942) these are poor quality gray to dirty blue, cloudy corundum

exposed in a prospect pit. The biotite-corundum schist is about 4 feet wide. Pale to

bright-red rubies were found in mica schist north of the Abernathy deposit at the Marion

prospect: some were cut into gems (Osterwald and others, 1966).

Other rubies were found as float in the Granite Mountains. According to Love (1970),

soft green mica schist boulders with dark red rubies were found near Muskrat Creek in

the Wind River Formation (Eocene) near Beaver Rim, west of the Gas Hills district, 12

miles (19 km) north of the Red Dwarf ruby deposit. These rubies were up to 1 inch (2.5

cm) in diameter and highly fractured.

A nearby placer with abundant, bright red (>1 inch in diameter), fractured rubies was

reported (Osterwald and others, 1966). Chloritic schist float with rubies (similar to the

Red Dwarf schist) was also found in the Crooks Gap Conglomerate (Tertiary), along the

northern flank of Green Mountain, about 15 miles (24 km) to the southeast of the Red

Dwarf (Hausel, 1986).

Red Dwarf. The Red Dwarf lies northwest of Jeffrey City (sections 13 and 24, T30N,

R93W). The host rock is corundum quartzofeldspathic gneiss with a strike length of

5,000 feet (1560 m) and widths of 20 to 50 feet (6.25-15.6 m) (Hausel, 1997). The rock

grades from gray quartzofeldspathic gneiss along its northern end, to chloritic schist

along its southern end. It typically contains 1-10% corundum as porphyroblasts enclosed

in fuchsite-zoisite reaction rims.

Some large specimens include one which measured >2.5 inches (6.4 cm) across. Another

specimen was a large fuchsite-zoisite pseudomorph after corundum with small (0.25 to

0.5 inch) specs of preserved purplish-red ruby (J. David Love, personal communication).

Only part of the original sample remained but measures more than 5 inches (12.7 cm) in

length and 3 inches (7.6 cm) across. The other portion of the ruby was cut and removed

and the original specimen was >7 inches in length (Figure 5a). Other Red Dwarf

specimens were cut into cabochons, but none were faceted primarily due to the

translucent to cloudy nature of the corundum. The fashioned stones are purplish-red. One

yielded a 2.77 carat ruby cabochon that shows parting planes on the stone, but otherwise

is an attractive gem. A few specimens of gem-quality ruby cabochons with excellent

asterism were produced from this deposit in past years (George Devault, personal

communication). Overall, lack of transparency of this material greatly diminishes its

value and research in clarification processes (heat treatment) is needed.

Another corundum deposit identified in Palmer

Canyon west of Wheatland includes pink to white

sapphire in Archean age vermiculite schist

(glimerite). Specimens weighing over 35 carats

have been recovered with some faceted pinkish

red sapphires weighing 3.5 carats. The raw stones

are hexagonal prisms terminated by pinacoids

with well-developed rhombohedral parting

limiting the size of the faceted gems. The

corundum occurs with iolite and kyanite (see

Iolite section below). The percentage of gem-

quality material has not been estimated, but could

be 5 to 15%. Locally, some vermiculite has as

much as 20% corundum, but the tonnage of high-

grade rock exposed at the surface is limited. None

of the corundum has been heat-treated.

Figure 5. (a) Large zoisite-fuchsite replacement of ruby from the Granite Mountains with

preserved masses of excellent, high-quality ruby. Prior to replacement of the ruby, this

may have represented the largest ruby in the world. (b) A 1.1 carat, reddish-pink

sapphire from Palmer Canyon (photo courtesy of Chuck Mabarak), and (c) a large pink

sapphire (>3 carats) from Palmer Canyon showing visible parting (specimen courtesy of

Vic Norris).

The largest prism found by the author is a 1-inch (2.5 cm) prism with 0.3-inch (0.75 cm)

diameter. The largest plate measured 0.4 inch in diameter. Larger specimens were later

found by Eagle-Hawk mining (Vic Norris, personal communication, 2002) some of

which has good translucency and a pleasing pink to red-pink color. The corundum

typically averages 0.2 inch (0.5 cm) in diameter.

Three categories of gem and near-gem corundum were most common: (1) reddish-pink

transparent to translucent sapphire, (2) light-pink translucent sapphire, and (3) white to

light pink translucent to opaque sapphire. Microscopic examination of a limited number

of specimens shows mineral inclusions to be relatively common.

Some corundum fashioned from this property included a brownish-pink opaque, 1.4-carat

cabochon, and a near-perfect reddish-pink transparent, 1.1-carat marquise with few flaws

(Figure 5b). Other faceted sapphires included gemstones of 0.75 to 3 carats in weight

(Vic Norris, personal communication, 2002). Some cabochons yield pleasing, light-pink

sapphires, but most faceted light-pink corundum is less attractive due to common, visible

mineral inclusions and or parting (Figure 5c).

Similar deposits were reported to the north at Elk Park, to the south at Grizzly Creek and

in the Platte River valley south of Encampment. Corundum is also found in the Big

Sandy area of the Wind River Mountains (Hausel and Sutherland, 2000). At Big Sandy,

hundreds of rubies and opaque corundum up to 90 carats were recovered from placers.

The source remains unknown, and the placer lies at the base of outwash material from an

alpine glacier. Some ruby-corundum schist with very nice translucent to transparent ruby

was found north of the Big Sandy placer (B. Ron Frost, personal communication, 2004).

The close association of ruby vermiculite schist suggests that many of the Wyoming

deposits are not only metamorphic, but also metasomatic. As such, the gemstones may be

related to desilication and potassic alteration. Corundum in vermiculite in the Platt River

valley along the edge of the Medicine Bow and Sierra Madre Mountains in southeastern

Wyoming includes Baggot's Rock, where specks of corundum with kyanite and

vermiculite occur in biotite- and hornblende-schist (Osterwald and others, 1966). The

deposit was mined on a small scale for vermiculite from 1937 to 1941 (Hagner, 1944).

A few miles south, an open cut dug for vermiculite in granite-gneiss in Homestead Draw

contains scattered pockets of ruby. Some have reaction rims of green zoisite similar to

those at the Red Dwarf ruby deposit in the Granite Mountains. Rubies were also found in

another vermiculite deposit on the Platte Ranch to the southwest (Ralph Platt, personal

communication, 1998). Corundum was initially reported in Wyoming by Aughey (1886)

who described the mineral near the North Platte River in the Seminoe Mountains of

central Wyoming, and in limestone. Unfortunately, the descriptions of these appear to be

erroneous as there are no known corundum occurrences in the Seminoe Mountains, and

no known ruby deposits in a Wyoming limestone.

Iolite (Cordierite, Dichorite, Water Sapphire)

One of the more exciting gemstone discoveries was that of gem-quality iolite in Palmer

Canyon west of Wheatland. This also led to the discovery of the Grizzly Creek iolite

deposit – considered as a world-class gem deposit, and also to the discovery of the

Ragged Top iolite deposit that could potentially lead to the identification of one of the

largest gemstone deposits in the world (Hausel, 2005b).

Gemologists refer to gem cordierite [(Mg,Fe3+

)2Al4Si5O18] as iolite and geologists and

mineralogists exclusively refer to the mineral as cordierite. The mineral has also been

labeled as dichorite and water sapphire although these are less common terms. Cordierite

is typically found in the vicinity of other alumino-silicates such as andalusite, kyanite and

sillimanite. Host rocks include alumina-rich mica schists (metapelites) that have been

subjected to amphibolite-facies metamorphism. In addition to being metamorphogenic,

cordierite is also found as replacements in alumina-rich syenite-anorthosite complexes

and shales.

Cordierite forms short prismatic pseudohexagonal crystals with rectangular cross sections

as well as compact, granular masses and nodules of various shades of blue, bluish-violet,

gray, or brown. Fresh cordierite has a hardness of 7 and specific gravity of 2.55 to 2.75.

The hardness is favorable for durable gemstones and the specific gravity is unfavorable

for placer concentration. Yet the principal deposits mined for iolite in the world are the

Sri Lanka placers, where it is recovered with other gemstones.

Iolite exhibits strong pleochroism that varies from light gray, dark violet-blue, to light

sapphire blue. Pleochroism is pronounced such that the gem may appear deepest blue

when viewed down the c-axis and light blue to light grey in other orientations (Hurlbut

and Switzer, 1979). These color variations are one of the attractive features of this gem.

The gem is often enclosed by pinite, a reaction rim consisting of muscovite or biotite and

chlorite (Dana and Ford, 1949). Iolite discovered by the author in Palmer Canyon and

Grizzly Creek, often shows alteration to limonite and pinite (Hausel, 2002). Pinite rims

on the Palmer Canyon iolite are light-greenish due to the presence of chlorite, and

typically less than a millimeter thick.

Gemology

Perfectly transparent iolite is suitable for gems. The luster of iolite is vitreous and when

polished will become increasingly lustrous. Iolite of highest demand is deep, bright,

vivid sapphire blue. Hematite inclusions that cause reddish aventurescence produce

„bloodshot iolite‟. Other inclusions may produce rare cat's eyes and stars.

Iolite is a low-priced gem marketed in the range of $30 to $150 for small, 1-carat stones.

It typically costs <$1/carat to facet in cutting centers in Sri Lanka. Larger gems of 5 to 10

carats may be valued at $350 to $1100, and flawless faceted stones in the range of 10 to

12 carats may be valued at $1500 to $1600. Gemstones >12 carats are unheard of on the

world market. Rough material collected by the author at Palmer Canyon and Grizzly

Creek represent the largest iolite gemstones found in the world. The value for iolite gems

is relatively low due to a lack of marketing and a steady supply. The gem is rarely found

in jewelry stores, but a large, steady, controlled supply of high-quality material along

with marketing should lead to significant price increases.

Geology & Genesis

Iolite occurs as a metamorphogenic and magmatic mineral. It may crystallize as a direct

product of magmatism since it is stable over a considerable temperature range. It has

been identified in igneous, contact and regional metamorphic environments and in

vitrified sandstones along contacts with basalt, and in shales altered by burning of coal

seams (Dana and Ford, 1949). It is found in alumina-rich schist formed during regional

metamorphism of shale and may occur with andalusite, sillimanite, kyanite, quartz,

biotite and/or spinel in some granites, pegmatites, metapelites and anorthosites. In low- to

moderate-grade schists, cordierite may exhibit xenoblastic to porphyroblastic habit with a

groundmass of quartz, muscovite, and cordierite. In high-grade metamorphic rocks and

pegmatites, cordierite may show well-developed pseudohexagonal habit.

Cordierite may form as a product of chloritization. In silica deficient rocks, it may be

associated with corundum, spinel and alkali feldspar. However, in high temperature

thermally altered rock, cordierite and corundum are incompatible and replaced by spinel

and sillimanite (Deer and others, 1972; Spry, 1969). Where found, cordierite gneiss

typically lacks garnet since garnet and muscovite are replaced by cordierite, potassium

feldspar and spinel during metamorphism. In Wyoming, cordierite is found in gneiss with

quartz and biotite and as large porphyroblasts with xenoblastic texture (Hausel, personal

field notes, 1995).

Deposits

Iolite is known in Canada, India, Myanmar, Sri Lanka, India, Brazil, Tanzania, Finland,

Germany, Norway and the United States. The highest quality iolite gems in the world are

found as pebbles in Sri Lanka and as porphyroblasts in gneiss in Wyoming.

Large nodular masses of iolite were discovered in two separate deposits in Archean

gneiss in Wyoming, and a giant disseminated deposit is described in the Laramie Range

anorthosite-syenite batholith (Hausel 2002; 2004; 2006a). The Wyoming deposits

represent some of the larger and better quality in the world, but these remain to be

exploited (Sinkankas, 1959; Hausel, 2005b).

Two deposits (Palmer Canyon and Grizzly Creek) are poly-gem occurrences that include

ruby, sapphire, kyanite and iolite in schist, glimerite (vermiculite) and gneiss. The

metapelites represent enclaves of aluminous schist and gneiss. A third deposit lies south

in the vicinity of Sherman and Ragged Top Mountain and is hosted by anorthositic-

syenitic rocks (1.5 Ga). This latter deposit is remains unexplored for gems even though

minor granular gem-quality iolite was recently identified, to date (Hausel, 2006a). Local

enrichment of iolite at Palmer Canyon and Grizzly Creek is promising. It is not

uncommon to find iolite gems of several hundred carats in both deposits with masses

weighing several thousands of carats!

Palmer Canyon. Iolite was discovered in Palmer Canyon west of Wheatland during field

reconnaissance (Hausel, 2002). This deposit lies along the eastern flank of the central

Laramie Range of southeastern Wyoming 16 miles (26 km) west of Wheatland within

Archean quartzofeldspathic gneiss, granite gneiss, pelitic schist, and biotite-chlorite-

vermiculite schist north of the Elmers Rock greenstone belt. A shallow prospect pit was

dug in vermiculite prior to 1944 in what is referred to as the Rolf vermiculite prospect.

The schist also contains chlorite, kyanite and corundum. Hagner (1944) interpreted the

deposit as a replacement of biotite by vermiculite under the influence of pegmatitic

fluids. However, pegmatite is not found in the immediate area. Cordierite was not

mentioned or identified and no descriptions were made of the corundum. In the 1930s

and 1940s, vermiculite was sought for fire-resistant insulation.

Samples of vermiculite-chlorite-biotite-corundum schist collected from a small prospect

pit contained as much as 10-20% corundum (the schist averages about 1-5% corundum).

The cordierite was discovered nearby in quartzofeldspathic gneiss a short distance east of

the Roff pit. Samples of the cordierite gneiss yielded many transparent cordierite grains

including several >50 carats in weight. Gneiss collected from the property contained as

much as 20% transparent cordierite.

The cordierite occurs as rounded to disseminated grains and large nodules: a few are

intergrown with quartz. Foliation in the host rock parallels the margin of nodules and in

some samples appears to terminate against the nodule boundary providing evidence that

the cordierite formed post regional metamorphism. The host rock is dark to light gray

cordierite-biotite-sericite-quartz gneiss. Kyanite and sillimanite may also be present, but

as minor components. Some secondary calcite is found as crusts on some surfaces and

many of the cordierite nodules exhibit a very thin (mm-size) alteration halo of chlorite

and sericite.

The gneiss contains intercalated lenses of quartzofeldspathic gneiss, metapelite and

biotite-chlorite-vermiculite schist with N80°W trending foliation. The quartzofeldspathic

gneiss is a primary host for cordierite and nearby kyanite schist contains 20 to 50%

excellent, light to sky blue with lesser tawny, green and red gem-quality kyanite.

Six types of gems and near-gems were identified at Palmer Canyon: (1) high-quality

violet to blue, transparent iolite, (2) dark-gray transparent iolite, (3) reddish transparent to

translucent ruby, (4) white to light pink translucent to transparent sapphire, (5) white to

pink translucent to opaque sapphire, and (6) sky-blue translucent kyanite. In addition, low

quality, dark gray, translucent to cloudy mylonitized cordierite is present, as is corundum

with prominent rhombohedral parting that tends to crumble. These latter two varieties are

of little use as gems.

Transparent blue iolite occurs as large porphyroblasts, nodules and disseminated grains in

quartzofeldspathic gneiss adjacent to corundum and kyanite schist. The iolite was traced

over a strike length of 500 feet and continues under soil for an unknown distance. A

handful of large nodules were initially found by the author at the time of discovery that

include a raw, high-quality transparent gem known as the „Palmer Canyon Blue Star‟ of

342.8 grams (1,714 carats), which was believed to be the largest iolite gemstone in the

world at the time of its discovery (Figure 6). Several thousand carats of fractured iolite

were later exposed in backhoe cuts, and more than 100,000 carats of gem-quality and

mylonitized material were recovered in about a cubic yard of material. In addition to

clear, transparent, violet blue gem-quality cordierite, some black translucent cordierite

(„Palmer Canyon Black‟) was recovered. The Palmer Canyon Black is not facet grade,

but may produce cabochons.

Figure 6. Large iolite porphyroblasts surround

the first three faceted iolite gemstones from

Wyoming. These three gems (0.5 to 1 carat) sit

right of the Palmer Canyon blue star, a 1,714-

carat, nearly flawless rough gemstone that was

the largest found in the world at the time if its

discovery.

Much of the high quality rough material ranges

from pleasing violet to a very light-blue color with only a hint of cleavage and parting.

Microscopic examination shows few mineral inclusions in these gems, which are for the

most part invisible to the naked eye (Figure 7). Where found, the inclusions include white

acicular grains (possibly sillimanite) and distinct pseudo-hexagonal biotite.

Gray to dark gray cordierite also exhibits good transparency. This variety has well-

developed parting parallel to c{001} and cleavage along b{010}. Many specimens

exhibit rectangular cross sections and a few exhibit pseudo-hexagonal habit. A group of

cabochons weighed 0.27 to 3.02 carats. These are dark-gray to black, translucent to

opaque, near gems with distinct cleavage, parting and some fractures.

Another variety does not appear to be suitable for gem material as it has many flaws.

Even so, two were faceted by Eagle-Hawk mining and yielded a 3.9-carat lozenge-cut

stone, and a 3.4-carat marquise. Both stones were extensively flawed with visible

cleavage, parting, and some visible mineral inclusions. However, after mounting in gold

necklaces, they produced surprisingly attractive jewelry (Chuck Mabarak, personal

communication) (Figure 7). Some bluish gray to gray translucent to cloudy material

represents rehealed myonlite that is poor-quality even though translucent. Due to the

brittle nature of the stone and effects of deformation, portions of some iolite masses have

cleavage and parting.

Figure 7. (a) Group of faceted iolites from Palmer Canyon

ranging from 0.5 carat to about 6 carats (specimens

courtesy of Vic Norris), and (b) a faceted, flawed cordierite

(3.4 carats) that makes a surprisingly attractive gemstone

dressed in a necklace (photo courtesy of Chuck Mabarak).

South of Palmer Canyon, is a world-class deposit. Grizzly

Creek lies 4 miles south-southwest of Palmer Canyon

(Figure 8). Rocks in the immediate area include

quartzofeldspathic gneiss and kyanite schist, lesser

corundum-biotite schist and cordierite schist. The Grizzly

Creek deposit also has significant gem-quality kyanite along

with incredible massive iolite replacements (Hausel, 2004).

Figure 8. Location of Palmer

Canyon gem deposit.

Grizzly Creek. Following

discovery of the Palmer

Canyon iolite (Hausel, 1998b),

it became clear that similar

deposits were likely. The later

thermal metamorphic event

responsible for the large

cordierite porphyroblasts at

Palmer Canyon appears to

have been relatively

widespread in the central

portion of the Laramie Range.

The earlier prograde metamorphic event produced large prophyroblasts of kyanite in the

adjacent rocks. The kyanite represents a good, indicator mineral in search for alumino-

silicate and alumina gemstones in this region. Thus the search for similar metapelites

resulted in another significant gemstone discovery south of Palmer Canyon – one that is

likely a world-class discovery, but will need further exploration and research to fully

appraise.

Grizzly Creek became a primary target for similar gemstones to those at Palmer Canyon

because of its geology (Hausel and Sutherland, 2000). During the initial field

investigation, it became clear that a major gem deposit had been discovered. Very large

masses of gem-quality iolite were found with large quantities of gem-grade kyanite.

Cordierite at Grizzly Creek is surrounded by kyanite and sillimanite schists that contain

minor corundum. The kyanite and sillimanite schist lies in a 300 by 5000 foot (94-1,560

m) belt of metapelite. During mapping by George Snyder of the US Geological Survey, a

collector’s quarry was identified that yielded a couple of nice specimens of ruby (George

Snyder, personal communication) but the cordierite and kyanite was essentially

overlooked as gem material.

Much kyanite appears to be cabochon grade and very pleasing, sky-blue color with some

tawny and pink specimens (Figure 9). Iolite found nearby is massive and forms large

replacements of the schist. This one deposit may represent the largest iolite occurrence in

the world. During reconnaissance, specimens of massive iolite were collected including

one football size transparent gemstone that weighed 24,150 carats – the largest iolite gem

found on earth (Figure 9 b). However, this stone is dwarfed by masses of material that

remain in place in Grizzly Creek. Some of the massive gem material will require

quarrying operations to recover. It is very likely that gem specimens >1 ton (>4.5 million

carats) in weight could be recovered and specimens as large as 2 to 4 tons are probable

(Figure 9c)! In outcrop, the iolite is weakly iron stained and shows excellent light blue

color and transparency on fresh surfaces (Figure 9d). But, it is not known how much if

any of this material has been destroyed by mylonitization. For example, several

specimens collected at Palmer Canyon showed distinct mylonitic to ultramylonitic texture

in thin section that resulted in a cloudy, light-blue and glassy material of poor quality.

Figure 9. (a) Palmer Canyon kyanite with pink

corundum. (b) The largest iolite gemstone in the

world – a 24,150 carat giant. Although highly

fractured, the gem material is high quality and could

produce thousands of carats of gemstones. (c) Wayne

Sutherland sits in front of a gemstone of potential weight of 1 to 4 tons (>4.5 million

carats). The iolite forms much of the outcrop in the photo. (d) The iron stained outcrops

yield excellent gem material on fresh surfaces.

Ragged Top (Sherman) Mountain. The first report of iolite in Wyoming was by

Sinkankas (1959). A brief description indicated that iolite was a widespread constituent

of schist and gneiss. In describing a deposit Sinkankas wrote, “…one estimate has placed

the quantity available at thousands of tons. Specimens at this locality examined by the

author are glassy broken fragments of rather light blue color, verging towards grayish,

small sections are clear and suitable for faceted gems. It is entirely possible that

important amounts of gem quality material will be produced from this locality in the

future.” Unfortunately, Sinkankas did not mention the location of the deposit: its

whereabouts remains unknown. At the time of writing (1959), only one cordierite deposit

had been described in the literature. The deposit, known as the Sherman Mountains

deposit, lies along the north fork of Horse Creek near Ragged Top Mountain northeast of

Laramie 15 miles south of Palmer Canyon. In this region, Proterozoic (1.4 Ga)

metanorite, syenite and syenite-diorite gneiss of the Laramie anorthosite complex intrude

the Cheyenne suture (1.8-1.6 Ga) zone. Newhouse and Hagner (1949) and Osterwald and

others (1966) reported widespread lenticular to tabular layers of cordierite in metanorite

(hypersthene gneiss), gneiss and syenite along the southern margin of the anorthosite

complex (1.5 Ga) in sections 13, 14 and 24, T 17N, R 72W and sections 17, 18, 19 and

20, T17N, R71W.

The host rock is described to locally have 50-80% cordierite (this deposit has not been

investigated for gemstones, although based on its size it is possible that this is the deposit

referred to by Sinkankas, 1959, 1964). The occurrence lies 0.5-mile west of Ragged Top

Mountain in a belt 0.3 to 1.2 miles (0.5-1.9 km) wide and 6 miles (9.6 km) long. The host

gneiss is highly foliated, intensely folded and contorted.

Howard (1952) described the weathered cordierite to have dark brown surfaces that yield

to blue or bluish gray massive material on fresh surfaces. In thin section, the cordierite

was described to form colorless, subhedral to anhedral grains ranging from a fraction of a

millimeter to 1 mm across with a refractive index of 1.542 to 1.550. Well-developed

polysynthetic twinning is common, but some cordierite is untwined.

The author was able to obtain small samples from the disseminated margin of this

deposit. Although the material sampled was small and granular, all was gem-quality in

grains typically <1 carat in weight. The massive portions of this deposit described by

Newhouse and Hagner (1949) remain unevaluated for gems and may represent another

world-class deposit. Cordierite is scattered over a few square miles in lenticular to tabular

masses in metanorite in low ridges 5 miles long and 0.25 to 1 mile wide. Some exposures

are described as having 60 to 80% cordierite. It was estimated that the combined deposits

with strike lengths of 100 feet or more, contained >453,600 tonnes (500,000 tons) of

cordierite (Newhouse and Hagner, 1949). In other words, a potential resource of 2.27

trillion carats! Sinkankas (personal communication, 2000) indicated that much of the

material was gem-quality as suggested in his books (Sinkankas, 1959, 1964), although he

could not remember the location. The cordierite is interpreted to have formed by

replacement of metanorite during emplacement of diorite gneiss (Newhouse and Hagner,

1949). In contrast, Subbarayuda (1975) describes the cordierite in cordierite-hypersthene

gneiss that he interprets as contact metamorphosed sedimentary rocks. The formation

temperature was estimated at 1000°C (Miyashiro, 1957).

Another iolite deposit in the northern Laramie Mountains is referred to as Owen Creek.

Snyder and others (1989) report kyanite, sillimanite, cordierite and relict staurolite in

pelitic schist in this region. Another occurrence was reported further north. Cordierite is

also reported at South Pass (Hausel, 1991), Copper Mountain (Hausel and others, 1985),

in the Sierra Madre, and in the Powder River Basin (Osterwald and others, 1966).

Exploration Model

Exploration for iolite in Wyoming should focus on regional metamorphic terrains with

significant metapelite successions. Such successions were subjected to amphibolite- to

granulite-grade metamorphism. The presence of nearby alumino-silicate polymorphs of

kyanite and sillimanite signal distinctly aluminous rocks that have been subjected to

pressures and temperatures favorable for crystallization of cordierite. Field examination

of metapelites with alumino-silicates such as staurolite, andalusite, kyanite, sillimanite

and/or chrysoberyl may lead to previously unrecognized gem discoveries. Anorthosite-

norite-syenite complexes are also potential targets for magmatic iolite.

Opal

Opal [SiO2·n(H2O)] is reported at a number of localities in Wyoming. Hausel and

Sutherland (2005) suggest the following categories for jewelry-grade opal: (1) precious

black opal, (2) precious white opal, (3) fire opal, (4) common opal, and (5) hyalite.

Precious opal is considered to be the most valuable because the internal color play (fire)

producing a very attractive gem. The precious opal can have a white matrix or a dark

matrix. Another category of opal, known as fire opal, may or may not have a play of

colors. It may be translucent to transparent, red, orange-red, orange and/or yellow-orange.

Common opal typically is translucent and milky white, but may also include specimens

that are light-blue, gray, black, yellow, or tawny. Hyalite, a lower quality stone, is

colorless, transparent opal that occurs as globules that resemble drops of water without

color play. Hyalite often resembles glass or quartz but has a brighter surface and an

almost greasy to waxy appearance due to the presence of water in the structure (Hausel

and Sutherland, 2005).

The hardness of opal varies from 5.5 to 6.5 (Sinkankas 1959) and specific gravity 1.9 to

2.2 (Sinkankas 1959). Low specific gravity along with brittleness prevents opal from

concentrating in placers. Common opal can be found in large deposits tens of feet thick

measured in tons. However, precious opal is more restricted. Precious opal seams rarely

exceed an inch or more in thickness. Schumann (1979) noted that most precious opal

seams are less than 2 mm thick. Only a few of the world’s largest opals exceed 10 cm

thick, even so, some weighed as much as several tens of pounds.

The brilliant color play in precious opal results from light diffraction along

submicroscopic orderly arrays of uniformly-sized amorphous silica spheres. A regular

stacking of these spheres allows the pore spaces between them to diffract light. The pore

spaces typically are filled with water, water vapor, or air (Darragh and others, 1966).

Opal is precipitated from silica-rich aqueous solutions associated with volcanic or

sedimentary rocks. The water content varies between 6% and 10% in precious opal and

the greater content equates to greater translucency, whereas lower water content results in

increased opacity (Sinkankas, 1959). Water is bound loosely within the opal structure and

is easily driven off by exposure to dryness or heat, which may cause the opal to turn

opaque and white. When it loses water, the gem often cracks which is referred to as

crazing. Common opal is generally more durable than precious opal, and will withstand

greater temperature and humidity changes without crazing (Eckert 1997). Opals hosted

by volcanic rocks often contain more water than opals found in sedimentary

environments. Consequently, volcanic hosted opals (with the exception of Mexican fire

opals) are generally less stable than opals mined from sedimentary rocks and have a

greater propensity for crazing (Barnes and others, 1992). Opal is often associated with

chalcedony and agate and the opal may grade into chalcedony in some deposits. Igneous-

hosted opals are most often found felsic lavas. Sedimentary-hosted opals may be found

with kaolinite, montmorillonite, bentonite, and concretionary iron in some areas (Keller,

1990).

Gemology

Opal is brittle, easily scratched, and sensitive to heat. However, it earns its place as a

gemstone from the intense color play in precious opal. Some precious opals, because of

their high water content (such as those from Virgin Valley, Nevada) are not cut, but

instead displayed as specimens submersed in liquid to prevent crazing. It is primarily cut

as cabochons to emphasize the play of color or opalescence in common opal. Some

translucent material, particularly Mexican fire opal, may be faceted.

Doublet’s are often manufactured. These consist of a thin slice of precious opal

cemented to a base of common opal or other material. A triplet is a three layer gem where

precious opal is cemented on a dark base and covered with a transparent top layer (quartz

or glass).

Some of the larger raw pieces of precious opal include a 23,610-carat and a 13,381-carat

stone found in Australia (Eckert 1997). Three large uncut common opals collected in

Wyoming in 2003 and 2004 weighed 25,850 carats (11.4 lbs), 57,100 carats (25.18 lbs)

and 77,100 carats (34 lbs) and represent some of the larger found in the world (Hausel

and Sutherland 2006) (Figure 10).

Figure 10. Common opal from the Cedar Ridge

deposit in Wyoming. Note the very large

specimens adjacent to the opal cabochons.

Geology & Genesis Much of the world’s precious opal is produced

in Australia where hosted by Cretaceous

marine sediments of the Great Artesian Basin

in New South Wales, Queensland, and South Australia (Keller 1990). Opal is also found

in joints in deeply weathered Proterozoic gneiss of the Musgrave-Mann Metamorphics in

the Granite Downs of northwestern South Australia (Barnes and others, 1992). The

Australian opal is generally thought to be a product of intense weathering and

silicification.

Sedimentary-hosted opals are attributed to migration of meteoric silica-rich water but

such waters can also migrate up and laterally. The source rocks must contain an abundant

supply of readily soluble silica possibly from ash beds, digenetic changes associated with

bentonite, or in situ kaolinization of detrital feldspars. Deep chemical weathering of rocks

such as pyroxenite and serpentinite, are also suggested to have resulted in the formation

of precious opal (Eckert 1997).

Sedimentary-hosted opal in Australia is found down to depths of about 130 feet (40 m).

Host rocks vary from conglomerates to sandstones, clay stones, and even bentonite beds.

The opal typically is found in pore spaces, joints, fractures, shrinkage cracks, partings,

bedding planes, and cavities or pore spaces (Barnes and others, 1992).

Darragh and others (1966) suggest that the opal formed in openings in the rock by slow

evaporation of localized pockets of groundwater. Deeply weathered rock, combined with

the arid climate in Australia’s opal fields appear to be essential components for the

formation of precious opal, and development of siliceous cap rocks. Stable tectonic

conditions in a cratonic environment such as in Australia, provide an ideal situation for

precious opal, especially where there is an abundance of silica-rich volcanic ash. These

conditions exist in Wyoming and undoubtedly, some major opal deposits (in addition to

Cedar Ridge) will be found. Exploration in that area may later result in the discovery of

precious opal (Hausel and Sutherland, 2006).

Volcanic-hosted opal deposits appear to be related to post-volcanic hydrothermal activity,

or to silica-rich waters derived from surface weathering processes similar to sedimentary-

hosted deposits.

Deposits

Australia produces 95% of the world’s precious opal. The world’s largest opal fields,

Coober Pedy and Mintabie, are found in South Australia. Precious opal is concentrated at

the base of a deep weathering profile along contacts between porous kaolinized sandstone

and underlying montmorillonitic claystone that lie beneath a silicified cap rock

containing considerable common opal (Kievlenko 2003). Most Mexican opal is volcanic-

hosted and mined from vugs, fractures, and openings in rhyolite, with a minority of

material hosted by basalt. Mexican common fire opal exhibits a red to yellow-orange

base color due to the presence of iron oxides.

Precious opal is found in the Bitterroot Range east of Spencer in northeastern Idaho 70

miles (112 km) west of Yellowstone National Park. This Spencer Opal Mine in this area

contains precious opal in one or more thin (up to ¼ inch thick) layers within common

opal partially filling vugs within rhyolite. White to pink common opal and pink precious

opal are produced at the mine (Eckert, 1997).

Opal was found in the Virgin Valley, Nevada. The opals are hosted by a 1.5 to 11.5 foot

(0.45- to 3.5-m) thick layer of montmorillonite clay within a 1000 foot (305 m) thick

sequence of volcanic sediments capped by basalt (Kievlenko, 2003; Eckert, 1997). Much

of the opal replaces wood. Common opal varies in color from white to gray, yellow,

green, tan, brown and black, and ranges from opaque to transparent. Some of the world’s

largest opals have come from the Virgin Valley. These include the 40 pound (18 kg), 10.4

pound (4.7 kg), and 8 pound (3.6 kg) cobbles (Eckert, 1997).

Precious opal is reported only from an isolated occurrence in the Tertiary Absaroka

Volcanics outside the eastern border of Yellowstone National Park. Common opal is

known at a few localities hosted by Oligocene White River and Wagon Bed Formations

(Hausel and Sutherland 2000).

Cedar Rim Discovery.

Opal was reported at Cedar Rim south of Riverton by Sinclair and Granger (1911) as

replacements of soft tuffaceous limestone at the top of the Oligocene sediments that cap

Beaver Rim as well as on several buttes to the south. In places, the limestone formed a

layer with masses of white chalcedony and opal nodules enclosed in calcareous crusts.

The presence of cylindrical pipes of silica, cutting through some of the limy layers was

noted. The source for both the limestone and silica was from underlying ash beds and the

silica was thought to have been mobilized in percolating water in springs. Some

chalcedony and opaline cement was also described in silicified arkose lower in the

section (Wagon Bed Formation).

Van Houton (1964) described opal with chert and chalcedony in the Wagon Bed

Formation, the volcanic facies of the Beaver Divide conglomerate member of the White

River Formation (now the Wiggins Formation), and the Split Rock Formation. Numerous

chert nodules and silicified zones in both the White River and Split Rock Formations

include opal and yellowish-brown to light olive gray chert, in masses up to 3 feet in

diameter in mudstone in the Wagon Bed Formation in the vicinity of Wagon Bed Spring

and northeastward as far as the Rogers Mountain Anticline. Irregular chert masses up to

15 feet long are also found in the Kirby Draw syncline nearby.

The Wiggins Formation in this area forms a wide channel fill within the basal White

River Formation characterized by debris from the Yellowstone-Absaroka volcanic field.

This ranges from sand-sized material to boulders 8 feet long. Within this unit, sandy

limestone lenses up to 5 feet thick have been partly replaced by irregular fibrous

chalcedonic chert and massive gray opaline silica containing irregular tubes and pores:

many of which are filled with calcareous montmorillonitic clay.

South of the Conant Creek anticline Van Houton (1964) described a prominent 160-foot

high south facing escarpment. In the lower 50 feet of the upper part of the White River

Formation are local layers of light blue to greenish-gray, limonite-stained, brittle opaline

chert containing rounded pellets up to 3 mm in diameter. Farther east, the lower greenish-

gray tuffaceous mudstone of the White River Formation that contains several 2- to 4-inch

thick layers of slightly calcareous opaline chert. It was noted that these mixed chalcedony

and opal layers contained 1- to 2-mm diameter ellipsoidal to subspherical pellets. Both

the opal/chalcedony pellets and the rock matrix contain abundant ooliths and round,

structureless, thick-rimmed particles.

Van Houton (1964) reported irregular domal structures several feet in diameter that were

formed of sand adhering to an opaline skeletal structure resembling tuffa or algal mats in

the Split Rock Formation. These are in well-sorted calcareous sandstones southeast of

Devils Gap. He also noted commonly occurring thin beds of chert, irregular concretions

of opaline silica, and fibrous siliceous aggregates along Beaver Rim in the uppermost part

of the Split Rock Formation, hosted within 2- to 6-inch thick light-gray limestone

interbedded with equally thin calcareous tuffaceous sandstone.

Even with these descriptions, the opal lacked any genuine interest until investigated by

the author. The deposit lies south of Riverton along Beaver Rim and consists primarily of

vast amounts of white to very light-blue translucent to opaque common opal, with

significant amounts of translucent to opaque yellow, yellow-orange to orange fire opal,

and significant amounts of clear, transparent hayalite and agate (Figure 11).

Figure 11. Location map of the Cedar Rim opal

deposit.

The opal was found scattered within portions of

14 square miles. Locally, the opal beds are

anywhere between a few to more than 50 feet

thick and often found capping ridges.

Exploration of this deposit at depth, will most

likely lead to discovery of precious opal seams.

Numerous opal samples were collected during

reconnaissance including three giant opals that

weighed 25,850 carats (11.4 lbs), 57,100 carats

(25.18 lbs) and 77,100 carats (34 lbs)! It is

estimated that a vast field of opal exists in the

Cedar Rim area potentially totaling tens of

thousands of tons of opal. The opals range from

small cobble size nodules to large boulders

encased in caliche. The caliche appears to

replace of opal as it weathers and devitrifies

(Figure 12).

Figure 12. (a) Enormous nodular opal found in the Cedar Rim opal deposit represents

some of the larger specimens from the world. The specimen adjacent to the rock hammer

would be >100 pounds. (b) Fire opal collected south of the opal boulders, and (c) one of

several specimens of precious opal. Where found, the rare precious opal occurs as

fracture fillings and veinlets about 1 mm thick.

The following varieties of opal and chalcedony were found:

(1) Opaque milky white to translucent common opal with localized layers or fracture

fillings with transparent clear opal. Some of this material includes very light blue opal

with minor black dendrite-like inclusions. Some opal is perfectly transparent and much

exhibits a very subtle color play with localized zones of stronger color plays. Many of

fractured but also many form large consolidated, unfractured pieces weighing several

hundreds of carats. (2) Translucent light-blue opal enclosed by milky opaque opal which

in turn is enclosed by a narrow perfectly transparent and banded opal crust that exhibits a

pleasant spectrum of color play (bands of blue-yellow-violet red) when natural light is

reflected from the specimen. These are enclosed in a thin rim of tan to pink quartz. (3)

Opal breccia consisting of milky quartz breccia clasts with some light gray to light blue

translucent to transparent opal clasts and veins in a black opal to black chalcedony

matrix. Some of the translucent to transparent opal and rarely the black opal exhibits

some color play. (4) Gray black to black translucent opal and quartz. Some of these

samples have a distinct appearance similar to the Sweetwater agates mentioned by Love

(1970), and this is likely the original source bed of some of the Sweetwater agates. Very

minor play of colors was observed in a couple of the specimens. Much of the color in

these appeared as a surface sheen with uncommon, tiny distinct rainbow bands within the

opal that may occur along fractures. (5) At one location in the opal field, varicolored opal

is common. This opal includes translucent fire opal as replacements and fracture fillings

in silicified arkose. The opal includes milky white translucent to opaque opal,

considerable opaque to translucent yellow opal, and lesser opaque to translucent orange

opal comparable to the Mexican fire opal (Hausel, 2005a).

Much of this material is jewelry grade and large outcrops of the silicified cap rock

containing zones of opal and agate, are excellent for decorative stone for tile and

countertops.

Exploration Model

In Wyoming, key components in a search for opal would include a source for potentially

soluble silica within, above, or adjacent to potential host rocks. In particular, Tertiary age

volcanic ashes provide good sources. Exploration should focus on a search for distinct

silicified cap rock and cobbles and boulders of opal within the ash beds as well as a

bleaching of host rocks. Within these units, valuable precious opals should occur as

fracture fillings, veinlets and seams. Areas of interest would be above impermeable zones

or zones of reduced permeability (clay beds at depth) and beneath zones containing

gypsum as well as in some bedding planes, fractures, and faults. Typically, the better

deposits are found at depth, possibly as deep as 100 to 150 feet below the surface.

In volcanic rocks, such as those in the Absaroka and Yellowstone volcanic fields,

precious opal may occur in vesicular felsic rocks that exhibit evidence of silica

enrichment.

Other Gemstone Deposits

Several other gemstones have been identified in Wyoming in recent years. Some notable

aquamarine beryl was found in pegmatites at Anderson Ridge at South Pass and also in

the Copper Mountain area. Giant helidor beryl was recovered from the Casper Mountain

pegmatite. Some of these contain patches and zones of transparent facetable material.

Wyoming also hosts some very nice copper deposits that contain colorful cupriferous

minerals. Some specularite found in some old mines in the Hartville uplift and Sierra

Madre is gem quality and will produce excellent cabochons. Jewelry grade gold nuggets

have been recovered for years from some of the State’s gold districts. Most notable are

those in the Lewiston district, the South Pass-Atlantic City district, and in the Crow’s

Nest within the South Pass greenstone belt (Hausel, 1991). Other good sources have

included the Sierra Madre, the Douglas Creek district in the Medicine Bow Mountains

and also Sand Creek at Mineral Hill in the Black Hills (Hausel, 1989, 1995).

Other areas of interest are the Seminoe Mountains along Deweese Creek (Hausel, 1995).

Although unexplored for gold nuggets, some are anticipated in this area, especially due to

the abundance of free gold in mines around Bradley Peak. Another commodity that is

always overlooked is placer diamonds. The Colorado-Wyoming State Line district has

several deeply eroded diamondiferous kimberlites that have released hundreds of

thousands of diamonds downstream. But to date, place diamonds have not been sought

and as a result, only a few have been found. These were recovered near George Creek,

Prairie Divide and in Fish Creek. The largest reported placer diamond (6.2 carats) was

recovered from Fish Creek in Wyoming.

Many other possibilities exist. However, research funding for this and similar projects at

the Wyoming Geological Survey has never been based on the merit of projects. Over the

past 30 years, the success of finding gemstones, gold, and other metals on an

unbelievably small budget (typically < $5000/year) led to some of the more impressive

discoveries by a government agency in the US. Anyone of these could lead to a major

new industry in Wyoming. Support for this type of research essentially ended in 2004.

Wyoming is a gemstone-rich state – something that was unknown prior to research

projects that began 30 years ago. Most notable are the Wyoming diamond deposits that

potentially represent a major resource and potentially could result in a new multibillion-

dollar industry, similar to than in Canada. Iolite deposits represent another discovery of

significant proportions that could also lead to a new mega-industry in Wyoming.

ACKNOWLEDGMENTS

Robert Gregory and Wayne Sutherland of the WGS provided invaluable assistance on

various projects related to gemstones. I would like to acknowledge Vic Norris of Eagle-

Hawk mining for providing specimens of gemstones from Palmer Canyon and thank

Robert Odell for access to his claims on the Red Dwarf ruby deposit. The late J. David

Love provided information on various corundum occurrences in the state.

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The Igneous Rocks of theMogok Stone Tract

Their Distributions, Petrography,Petrochemistry,

Sequence, Geochronology and EconomicGeology

A Ph.D. Dissertation by Kyaw Thu

Department of Geology, University of Yangon,Myanmar

Copyright © Kyaw Thu, 2007

Introduction from Bill Larson, PalaInternationalKyaw Thu is a FGA gemologist with a Ph.D. inGeology. Pala International knows him fromtrips in the mid-1990s as one of the mostinteresting young gem enthusiasts, among somany wonderful students and collectors wemet. Both Will and Bill Larson consider him aspecial and close friend. He has helped answermany questions regarding locality informationfor Brendan Laurs of GIA as well as meeting inperson Dr. George Harlow of the AmericanMuseum of Natural History and correspondingwith him for almost a decade. He has opened agem laboratory and has applied to GIA tofurther his education. I was given a copy of hisPhD thesis last month and Dr. Harlow made itavailable by scan for interested parties. PalaInternational is honored to share this with ourreaders.

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AbstractThe Mogok Stone Tract is very famous not onlyfor the finest rubies and spinels but also for gemquality sapphire, peridot, etc. The study area liesin the northeastern part of Mogok Stone Tractcovering the Mogok–Kyat-pyin, Bernard–Pyaung-gaung and On-dan areas. It is amountainous region with two distinct valleys—Mogok Valley and Kyat-pyin Valley. Both valleyswere formed by structural and lithologiccontrols; they are south-plunging synclinalvalleys separated by an anticlinal ridge (Baw-padan Anticline). These two valleys contain alarger proportion of placer gemstones.

The geology and the rock sequence of thearea, modified from some previous works, andthree new geological maps are presented. Therock sequence of the major rock unitsestablished is (from older to younger): Mogokmetamorphics (metamorphosed Lower Paleozoicrock units—metamorphic age Late Oligocene),ultramafic and mafic rocks (Jurassic?),leucogranite (Early Oligocene), syenitic rocks(Late Oligocene), Kabaing Granite (MiddleMiocene), and pegmatites and aplites (MiddleMiocene).

On the basis of detailed microscopicobservations, modal analyses, and normativecalculations, the various igneous rock types

P a l a M i n e r a l s

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according to IUGS and Williams et al.classifications are dunite, harzburgite, pyroxeneperidotite, and hornblende peridotite forultramafic rocks; quartz syenite, alkali-felsparsyenite, nepheline syenite, alkali-felspar syenitepegmatite, and quartz monzonite for syeniticrocks; urtite, ijolite, and jacupirangite for urtiteseries; augite-biotite granite, leucogranite andbiotite microgranite (Kabaing Granite) forgranitic rocks; pegmatites and aplites. Thepegmatites are complex, belonging to rare-element class, beryl type.

Mogok ruby, 7.5 x 5.0 x 4.5 cm. From thecollection of Bill Larson. (Photo: Mia Dixon)

On the basis of petrogenetic interpretationsthe igneous rocks of the area are mainly calc-alkaline and only partly alkaline. This is alsoevident from the bimodal distributions of thepetrochemical data plots. The value of alkali-limeindex (Peacock index) is 55 for the igneous rocksof the area, indicating the calcic to alkalic-calciccharacter in this area. ACF diagram and somedistinctive chemical properties of the graniticrocks of the area indicate that these graniticrocks are mostly S-type granites.

In K O mol. vs Na O mol. variation diagram,the plots of leucogranite, biotite micrograniteand pegmatite fall in the field of late-kinematicgranite. According to the petrochemical data,the granitic rocks of the area may be regarded ascontinental collision granites.

In the alkaline rocks of the area, the(Na O+K O)/Al O ratio is less than 1; thusaccording to Hyndman classification (1985),these alkaline rocks fall in the miaskitic type, i.e.,not peralkaline. The origin of nepheline syeniteas small irregular bodies in the marginal zones ofMogok marbles near the contact withleucogranite (as in the Thurein Taung area) orwith syenite (as in the area northwest of On-dan)can be explained by the well-known limestonesyntexis model. In a similar way the rocks of theurtite series may have been formed by theassimilation and desilication of the leucograniteor syenite in contact with mafic-rich marbles.

The ultramafic rocks occur as layeredintrusions in garnet-biotite gneiss in Bernard–Pyaung-gaung area. The ultramafic rocks of thearea are considered to be not related to anophiolite suite because of the absence of beddedchert, pillow lavas, basalt-diabase sheeted dykeswarms, and large-scale serpentinization.

Field and petrochemical data suggest that theleucogranite and syenitic bodies intrudedforcefully along a highly deformed zone roughlyextending NE-SW. The depth of emplacement isestimated to range from katazone to mesozone.Kabaing Granite which is a large microgranite

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body intruded later at a shallower depth.Radiometric dates of zircon in four rock

samples by U-Th-Pb method give 129± 8.2 Ma(Early Cretaceous) for augite-biotite granite, 32±1 Ma (Early Oligocene) for leucogranite, 25 Ma(Late Oligocene) for foliated syenite, and 16± 0.5Ma (Middle Miocene) for painite from the contactzone between leucogranite and marble.

It has been observed that the syenitic rocksand pegmatites are especially important for theformation of precious gemstones of the area. Theimportant gemstones with regard to the variousigneous rock types are aquamarine, topaz,danburite, amethyst, moonstone, zircon inpegmatites, sapphire in syenite pegmatites,peridot in peridotite, and painite in leucogranite(contact zone).

AcknowledgementsI acknowledge a special debt to Prof. Dr. U Thein(President, Myanmar Geoscience Society) for hisguidance and suggestions for my research works.

I owe a debt of thanks to Dr. Aye Ko Aung(Professor/Head, Geology Department, DagonUniversity) for reading the manuscript andsuggestions rendered. Thanks are also extendedto U Htay Win (Associate Professor/Head,Department of Geology, Yangon University) forhis care and valuable advice.

This dissertation came to fruition under theguidance of Professor Hla Kyi (Part-timeProfessor, Applied Geology Department) forreading the manuscript, his guidance,discussions and suggestions.

My special thanks are due to Professor TheinWin (Pro Rector, West Yangon University),Professor Maung Ko (Part-time Professor,Geology Department, Yangon University), andDr. Khin Maung Myint (Professor/Head, GeologyDepartment, Mandalay University) for reading ofthe manuscript, discussions and suggestions, forthe improvement of this manuscript.

The author is grateful to Dr. Khin Zaw (Centrefor Ore Deposit Research, University of WesternAustralia) for his generous help and suggestionsfor LA ICP-MS tests, X-RF and LRS tests duringthe research, and to Daw Ohh Mar Win (Lecturer,Universities’ Research Center) and to Dr. MoeMyintzu (X-RD section, D.A.E.) for the X-RF andX-RD results respectively.

Individuals who helped are also numerous;my heartfelt thanks are due to U Zaw Nyunt andU Thant Zin and U Nay Myo for providingfacilities and warm hospitality during the fieldtrips.

I wish to express my gratitude to Daw ThuzarAung (Macle Gem Trade Lab.) for the help giventhroughout the study.

Last, but not least I would like to express mysincere thanks to my parents and all my teacherswho guided me to reach such a position.

Contents

Front Matter

Abstract

Acknowledgements

Table of Contents

List of Figures

List of Tables

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Chapter I Introduction

1.1 Location and Accessibility

1.2 Geomorphology

1.3 Objectives and Scope

1.4 Method of Study

1.5 Previous Works

Chapter II Geology of the Area

2.1 Regional and GeologicalSetting

2.2 Rock Sequence

2.3 Distribution of MajorIgneous Rock Units

2.4 Geological Structures

Chapter III Petrography

3.1 Ultramafic and MaficRocks

3.2 Augite-biotite Granite

3.3 Leucogranite

3.4 Syenitic Rocks

3.5 Urtite Series

3.6 Kabaing Granite

3.7 Pegmatites and Aplites

Chapter IV Petrochemistry

4.1 Analytical Data

4.2 Presentation of theAnalytical Data

4.3 PetrogeneticInterpretations

4.3.1 Nature andChemical Changes inIgneous Differentiation

4.3.2 Conditions of theCrystallization of theIgneous Rocks

Chapter V Petrogenesis

5.1 Origin of the GraniticRocks

5.1.1 Origin of Augite-biotite Granite

5.1.2 Origin ofLeucogranite

5.1.3. Genetic Types ofthe Granitic Rocks of theArea

5.2. Origin of Alkaline Rocks

5.2.1 Origin of NephelineSyenite

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5.2.2 Origin of UrtiteSeries

5.3 Origin of Ultramafic Rocks

5.4 Emplacement and Depthof Intrusions

5.5. Metamorphic andIgneous Rocks History of theArea

Chapter VI Geochronology

6.1 Analytical Methods

6.2 Data Interpretation

6.3 Geochronology of IgneousRocks of Mogok Area

6.4 Age of MogokMetamorphism

Chapter VII Economic Geology

7.1 Classification of MogokGemstone Deposits

7.2 Gemstone Deposits inPegmatite

7.3 Gemstone Deposits inSyenite

7.4 Peridot Deposits

7.5 Gemstones in Skarn

Chapter VIII Summary andConclusions

8.1 Objectives and Scope ofthe Research

8.2 Geological Features

8.3 Petrography

8.4 Petrochemistry andInterpretations

8.5 Petrogenesis

8.6 Geochronology

8.7 Gemstones

References

Appendix

List of Figures in Chapters I and II (imagesfrom Pala International are not listed)

1.1 Satellite image of the Mogok StoneTract (scale: 1:500,000)

1.2Three dimensional view of thegeomorphology of the Mogok StoneTract (TM image; 30 m resolution)

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2.1 Regional geological map of the studyarea modified after Bender (1983)

2.2Map showing MMB relative to blocksand plates in the Myanmar region(modified after Mitchell el aI., 2006)

2.3 Geological map of Mogok–Kyat-pyinarea, geology by Kyaw Thu, 2006

2.4Geological Map of Bernard–Pyaung-gaung area, modified after Thet TinNyunt (2000), Kyaw Thu (2006)

2.5Geological Map of On-Dan area,modified after Thuzar Aung (2003),Kyaw Thu (2006)

2.6(a) Highly weathered pegmatiteexposure, Sakhan-gyi, 22° 54' 1.2" N,96° 20' 56.1" E

(b) Dyke of pegmatite at Pan-taw; 22°57 ' 47 .3" N, 96° 24' 15.6" E

(c) Panoramic view of Kabaing Taung,inset; large block of biotitemicrogranite showing exfoliated natureat the peak, near Kabaing village

(d) Small outcrop of Kabaing Graniteshowing onion skin weathering, 22° 57 '14.9" N, 96° 24' 54.6" E, Kyauk-sin–Pan-taw area

(e) An outcrop of showing exfoliationnature in biotite microgranite, near On-dan village, 22° 57 ' 12.2" N, 96° 14'38.05" E

2.7

(a) Phlogopite-diopside marble andurtite rocks contact in Thurein Taung,22° 54' 12.2" N, 96° 22' 18.8" E; urtiteexposure showing highly brecciatednature due to fault contact nature(inset)

(b) Urtite and white marble contact inYadana-kadae-kadar mine, 22° 54' 34"N, 96° 22' 31" E ; mafic minerals mainlyhornblende and nepheline in surface ofurtite exposure (inset)

(c) Urtite intruded into the marbleshowing scapolite-diopside-graphitecontact zone, 22° 54' 11.3" N, 96° 22'17 .3" E

(d) Pegmatite vein intruded into theurtite body, Thurein Taung, 22° 54'12.4" N, 96° 22' 20.6" E

(e) Xenolith of nepheline syenite inurtite, Thurein Taung, 22° 54' 12.7 " N,96° 22' 20.7 " E

2.8

(a) A distinct syenitic rocks exposureshowing exfoliated nature in syeniteexposure, north of Ohn-gaing village,22° 56' 27 .2" N, 96° 29' 36.8" E

(b) Syenite exposure at Kyauk-wa,north of Mogok

(c) Dyke of urtite in syenite exposure,north of On-dan, 22° 57 ' 16.4" N, 96° 14'39" E

2.9 (a) A distinct exposure of leucogranitein Hin-thar Taung

(b) Photograph showing leucograniteand diopside-phlogopite marblecontact to form the painite deposit inWet-loo mine, 22° 54' 28.5" N, 96° 23'34.9" E

(c) Highly weathered leucograniteexposed in Baw-mar mine

(d) An outcrop showing exfoliatednature in leucogranite, north of Baw-mar

(e) Photograph showing leucograniteintruded into the garnet biotite gneiss

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in Pan-taw, 22° 57 ' 44.6" N, 96° 24'41.7 " E

(f) Syenite vein in leucogranite aboutthree feet in thickness, Wet-loo mine,22° 54' 28" N, 96° 23' 35" E

2.10(a) Panoramic view of the peridotite-dunite bodies, north-east of Bernard-myo

(b) Peridotite exposure showing falsebedded nature, Mya-sein Taung, 23" 00'03.4" N, 96" 27 ' 54.4" E

(c) Photograph showing peridotitepartly altered to serpentinite due to theauto metamorphism, 22" 59' 55" N, 96"27 ' 48.8" E

(d) An outcrop showing jointed naturein dunite, Pyaung-gaung, 23° 00' 40.5"N, 96° 28' 40.0" E

(d) Pegmatite dyke in peridotite andchrysoprase veins in upper part ofphoto, Mya-sein Taung, 23° 00' 10.5" N,96° 27 ' 44.9" E

2.11

(a) Panoramic scenery of Taung-meTaung; augite biotite granite exposureat the peak of Taung-me Taung (inset),22° 58' 18.4" N, 96° 28' 8.5" E

(b) Augite-biotite granite exposureshowing the distinct faulted nature inShwe-u-daung taung; inset: smallquartzo feldspathic vein cross cut infoliated augite-biotite granite, north ofOn-dan village, 23° 01' 12.1" N, 96° 13'19.07 " E

2.12

(a) Photograph showing mullionstructure in calc-silicate rock due tothe thrusting, east of Gwe-bin, 22° 53'44" N, 96° 22' 24" E

(b) Dyke of urtite showing foldednature in marble indicates that effectedby tectonism, Kyauk-saung, 22° 55' 21"N, 96° 25' 53" E

(c) The exposure showing Mogokthrust, north-west directed thrustplane at north of Mogok, 22° 56' 37 .5"N, 96° 31' 22" E

(d) Close-up view of photo

(e) Showing footwall carbonatemylonite along the thrust zone

(f) Well jointed nature in phlogopitemarble at Gwe-bin

Additional figures to be added withnext installment

List of Figures in Chapter III – Part 1(images from Pala International are not listed)XN = crossed Nicols (explained here); PPL =plane polarized light (explained here)

3.1Small exposure of gabbro rock in Htan-saing, north of Bernard-myo, 22° 00'25.6" N, 96° 25' 54.7 " E

3.2 Mineral composition of the gabbrorock, XN, 10 X

3.3 Chrysoprase vein in dunite exposure,Mya-sein Taung UMEHL mine

3.4 Olivine (Ol) altered to serpentine (Sp) indunite, XN, 25 X

3.5(a) Photomicrograph showing mesh-like serpentine in olivine of dunite, XN,10 X

(b) Close-up view of serpentine inphoto (a), XN, 25 X

3.6Photograph showing magnetite veins inperidotite outcrop at Pyaung-gaung,22° 58' 16" N, 96° 33' 11" E

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3.7 Olivine with chrysotile veinlets acrossthe olivine in peridotite, XN, 10 X

3.8 Orthopyroxene (Opx) in peridotite, XN,10 X

3.9

Olivine with chrysotile veins,orthopyroxene (Opx), clinopyroxene(Cpx) and anhedral chromite grain(Cm) in peridotite, XN, 25 X

3.10Olivine with chrysotile veinlets acrossthe olivine and amphibole (Amp)crystal in peridotite, XN, 25 X

3.11 Flaky serpentine (antigorite) inperidotite, XN, 25 X

3.12 Chrysotile occurs as cross fiber veinletsin peridotite, XN, 25 X

3.13 Mica flake in olivine grain, inperidotite, XN, 25 X

3.14 Antigorite crystals in chrysoprase(Chry) vein with magnetite, XN, 25 X

3.15 Radial chalcedony and magnetite grainin chrysoprase, XN, 25 X

3.16Mesh-like serpentine and relic ofolivine grains in serpentinized dunite,XN, 25 X

3.17Mesh-like structure of serpentineminerals in serpentinite at Mya-sein-Taung, XN, 25 X

3.18

Photograph showing highly jointednature in augite-biotite granite at thepeak of Taung-me Taung 22° 58' 18.4"N, 96° 28' 8.5" E

3.19

Twinned plagioclase (Pgl), augite (Aug)and quartz grains in augite-biotitegranite, Taung-me Taung; between XN,10 X

3.20Subhedral zoisite (Zoi) crystal in augite(Aug)-biotite granite, Shwe-u-daungTaung; (a) P.P.L. (b) XN, 25 X

3.21Anhedral garnet (Gar) grain and biotite(Bio) flakes in augite-biotite granite,Pan-yaung, P.P.L., 10 X

3.22Sericitization occurs along the cleavageplanes and fan shape sericite (Seri) inborder of k-feldspar, XN, 25 X

3.23

Photograph showing hillock nature ofmarble unit in leucogranite body, NE ofDattaw Taung, 22° 57 ' 56.2" N, 96° 32'29" E

3.24Painite crystal in k-feldspar, near thecontact of leucogranite and marble,Wet-loo, PPL, 25 X

3.25 K-feldspar with string perthitic texture(pe) in leucogranite, XN, 10 X

3.26

Interstitial calcite (Cc) grains among k-feldspar (Or) and quartz (Q) with augite(Aug), near contact of marble unit, XN,10 X

3.27

K-feldspar with string perthite (pe) withmyrmekitic (m-q) intergrowth ofplagioclase feldspar and quartz, Htin-shu Taung, XN, 25 X

3.28Anhedral garnet (Gar) grain with quartz(Q) inclusions in leucogranite, Hin-tharTaung, P.P.L., 10 X

List of Figures in Chapter III – Part 2(images from Pala International are not listed)XN = crossed Nicols (explained here); PPL =plane polarized light (explained here)

3.29 Anhedral aegirine augite (Aug) grain inquartz syenite, PPL, 10 X

3.30Quartz syenite containing alkalifeldspar (Or), aegirine augite (Aug), andquartz (Q), XN, 10 X

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3.31 Anhedral garnet (Gar) grain, iron oreand biotite (Bio) showing foliation inquartz syenite, PPL, 10 X

3.32Anhedral and basal section of scapolitegrains in quartz syenite from contactzone, XN, 10 X

3.33Myrmekitic intergrowth of quartz andplagioclase feldspar in quartz syenite,XN, 25 X

3.34Myrmekitic (m-q) intergrowth of quartzand feldspar, and biotite (Bio) in alkali-feldspar syenite, XN, 25 X

3.35K-feldspar showing grid twinning withpatch perthite (pe) in alkali-feldsparsyenite XN, 25 X

3.36Subhedral nepheline (ne) crystal infoid-bearing alkali-feldspar syenite, XN,10 X

3.37K-feldspar with perthitic (pe) veinletsand opaque mineral in quartz syenite,XN, 25 X

3.38Euhedral sphene crystals in alkali-feldspar of foid-bearing alkali-feldsparsyenite, PPL, 25 X

3.39

Euhedral plagioclase (Pgl) crystalshowing polysynthetic twinning inalkali syenite pegmatite, On-dan, XN,25 X

3.40K-feldspar with flame perthite (pe)enclosing zircon crystal and corundumgrain, On-dan, XN, 25 X

3.41K-feldspar (Or) with flake perthite (fl-pe) in alkali-syenite pegmatite, XN, 25X

3.42Garnet (Gar) and biotite (Bio) flakes inalkali-syenite pegmatite, Lay-thar, PPL,10 X

3.43Corundum (C) crystal enclosed inspinel (Sp), alkali-syenite pegmatite,Lay-thar, PPL, 10 X

3.44

Corundum showing typical three sets ofshort rutile (Ru) needles and smallzircon (Zr) inclusions in alkali-syenitepegmatite, PPL, 25 X

3.45 Plagioclase (Pgl) showing periclinetwinning in quartz monzonite, XN, 10 X

3.46Complex polysynthetic twinning inplagioclase (Pgl) and augite in quartzmonzonite, XN, 10 X

3.47Hornblende and pyroxene and the restwhite colour is nepheline in urtite, PPL,25 X

3.48 Pyroxene is partly altered tohornblende in urtite rock, PPL, 25 X

3.49 Calcite showing twinning andamphibole in urtite, XN, 25 X

3.50 Euhedral biotite crystal in urtite, XN,25 X

3.51 Amphibole showing simple twin inurtite, XN, 10 X

3.52Rectangular shaped nepheline,hornblende and calcite in urtite, XN, 10X

3.53Anhedral deep yellowish brown,titanium rich melanite garnet andaugite in urtite, PPL, 10 X

3.54

Mineral constituents of the ijolitecontaining hornblende, augite,nepheline, iron ore and plagioclasefeldspar, XN, 10 X

3.55Feldspar showing combination ofCarlsbad and albite twin, hornblendeand nepheline in ijolite, XN, 10 X

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3.56 Euhedral zircon crystal in nepheline,PPL, 25 X

3.57Small corundum grains in ijolite,Thurein Taung, PPL, 25 X

3.58

Mineral constituents of jacupriangiteinclude hornblende, pyroxene, andplagioclase showing pericline twinning,XN, 10 X

3.59 Basal section of hornblende injacupriangite, XN, 25 X

3.60Kabaing granite intruded into thedunite body in Pyaung-gaung, 23° 00'18.4" N, 96° 27 ' 8.5" E

3.61Mineral constituents of biotitemicrogranite includes quartz, feldsparand biotite mica, XN, 10 X

3.62Euhedral alkali-feldspar shows zoningwith some biotite in Kabaing granite,XN, 10 X

3.63 Chlorite, alteration product of biotite inKabaing Granite, PPL, 25 X

3.64 Elongated bioite crystal showing bentnature due to deformation, 52 XN, 25X

3.65 Granophyric quartz (Q) in K-feldspar,XN, 10 X

3.66Graphic quartz (Q) in k-feldspar and thequartz protrudes in the orthoclase (Or)by forming indentations, XN, 10 X

3.67 Graphic quartz (Q) with extinctions intothe k-feldspar, XN, 10 X

3.68

K-feldspar with perthite. Both the highproportion of perthite to k-feldspar andthe irregular shapes rather suggest ametasomatic origin for the plagioclase.K-feldspar in the extinction position,XN, 10 X

3.69 K-feldspar showing rare sector twin andintergrowth with quartz, XN, 25X

3.70 Chalcedonic silica vein in k-feldspar inaplite, XN, 25 X

3.71

Plotted data of the igneous rocks in theMogok Stone Tract, except ultramaficrocks (source; IUGS Classification,2006)

3.72

Modal classification of ultramafic rocksbased on the proportions of olivine(Ol), orthopyroxene (Opx),clinopyroxene (Cpx), pyroxene (Px)and hornblende (Hbl) (source: IUGSClassification, 2006)

List of Figures in Chapter IV (images fromPala International are not listed)

4.1

Sample location map of the MogokStone Tract (source; Landsat TM image,30m resolution, band combination7 54)

4.2Variation diagram of major elements vsSiO in igneous rocks of the study area(cont.)

4.3

Na O/K O vs SiO variation diagram,showing the trend of differentiation(KT-1 to KT-9 are granitic rocks/KT-10to KT-15 are syenitic rocks and KT-16to KT-23 are mafic to ultramafic rocks)

4.4

Percent anorthite in normativeplagioclase plotted against theThornton-Tuttle differentiation index(KT-1 to KT-9 are granitic rocks/KT-10to KT-15 are syenitic rocks and KT-16to KT-23 are mafic to ultramafic rocks)

4.5Alkali-lime index diagram for granitic,syenitic, basic and ultramafic rocks(Peacock index)

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4.6 Alkali-lime index diagram for granitic,basic and ultramafic rocks (Peacockindex)

4.7

Major element discrimination ofigneous rocks supposed to be collision-related, subdivided as alkaline, calc-alkaline and strongly peraluminous,and highly fractionated calc-alkaline(after Sylvester, 1989)

4.8 Al O — CaO — (Na O+K O) diagram

4.9

Normative Ab-Or-An diagram for theigneous rocks of the study area, withdividing lines according to O’Connor(1965)

4.10

Plot of Wright’s (1969) alkalinity indexAl O +CaO+Na O+K O/Al O + CaO-Na O+K O solid line and field namesare after Wright, and the dashed line,separates alkaline from calc-alkaline,after Khin Zaw (1986)

4.11

Diagram showing K O vs SiO wt %ration for granitic rocks and syeniticrocks of the study area Calc-alkaline – Jake and Gill (197 0) Alkaline (1) – Gried and Lefeure (197 2) Alkaline (2) – Lemoitre (1962)

4.12Fe -Na O+K O—MgO (AFM) diagram,in terms of alkalis, total Fe and Mg forthe igneous rocks of the study area

4.13

ACF diagram for the granitoids of thestudy area (after Hyndman, 1985);Molar ratio: A = Al O -Na O-K O, C =CaO, F = Fe O +MgO

4.14 K O-Na O-CaO diagram

4.15

General Ca – Na – K compositionaldifference between the main kinds ofalkaline igneous rocks; rocks becomemore mafic rich towards the Ca cornerof the diagram (after Hyndman, 1985)

4.16 SiO -(Na O+K O) – (FeO +MgO)diagram

4.17 SiO -Na O-K O diagram

4.18

Normative Qt-Ab-Or-H O ratios ofigneous rocks from the study area.Diagram showing H O saturatedliquidus field boundaries and isobarictemperature in the system Qtz-Ab-Or-H O for various water pressures (afterTuttle and Bowen, 1958)

4.19

Temperature – differentiation indexdiagram for the igneous rocks of thestudy area, at 2 kb water pressure (afterPiwinskii and Wyllie, 197 0)

4.20

K O mol. vs Na O mol. variationdiagram of granitic rocks in the area,showing the fields of syn-kinematic andlate-kinematic granites (after Marmo,1956)

4.21 Schematic depth-temperature relationdiagram (after Marmo, 1969)

List of Figures for Chapters V and VI(images from Pala International are not listed)

5.1

K O vs SiO diagram for granitoids ofthe study area; distinction betweenoceanic plagiogranite and othergranitoids from the other environment(after Maniar and Piccoli, 1989)

5.2Al O vs SiO diagram for granitoids ofthe study area (after Maniar andPiccoli, 1989)

5.3MgO vs SiO diagram for granitoids ofthe study area (after Maniar andPiccoli, 1989)Shand’s index diagram for granitic

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5.4 rocks of the area. Distinction betweenCCG and CAG+IAG (after Maniar andPiccoli, 1989)

6.1 (a) LA ICP-MS, (b) BSE image of zirconcrystals, (c) LA ICP-MS technique

6.2(a, b, c) Data interpretation processesof zircon dating in LA ICP-MS andSHRIMP techniques

6.3(a, b) Data interpretation processes ofzircon dating in LA ICP-MS andSHRIMP techniques

6.4The concordia plot diagram ofradiometric dating of augite-biotitegranite (A-2) by LAICP-MS technique

6.5

Location map and Ar/ Ar diagramsof dated samples form high grademetamorphic and intrusive rocks ofMogok area; all the ages from this areaare Early to Middle Miocene (afterBertrand et al., 2001)

List of Figures for Chapter VII (images fromPala International are not listed)

7.1Location map of the pegmatitic gemdeposit mines and other mines ofMogok Stone Tract

7.2Highly weathered phlegmatic dykeexposure in Sakhan-gyi, 22° 54' 1.2" N,96° 20' 56.1" E

7.3Entrance of adit in phlegmatic mine,Sakhan-gyi, 22° 54' 1.2" N, 96° 20' 56.1"E

7.4

Illegal mines (Lay-bin-dwin) inphlegmatic deposit, since 2004,Sakhan-gyi, 22° 54' 02.1" N, 96° 20' 51"E

7.5Searching the gems from phlegmatic,Sakhan-gyi, 22° 54' 02.1" N, 96° 20' 51"E

7.6Lay-bin-dwin in phlegmatic mine,Sakhan-gyi, 22° 54' 02.1" N, 96° 20' 51"E

7.7Phlegmatic with topaz,quartz,clevelandite, cassiterite and feldspar,Sakhan-gyi

7.8

Phlegmatic dyke at pan-taw area,entrance of adit in phlegmatic body anddrilling in Kabaing Granite for blastingprocesses (in-set), 22" 57 ' 47 .3" N, 96"24' 15.6" E

7.9

(a) Large aquamarine crystal (21 ern inlength), Sakhan-gyi; (b) roughaquamarine 134 g; (c) after faceted, 119carats from Pein-pyit

7.10

(a) Topaz crystal in phlegmaticgroundmass; (b) some big terminatedtopaz crystals; (c) topaz crystalpenetrates in quartz with muscovite atthe base; (d) unusual aquamarine cat’seye, 90.80 carats, from Sakhan-gyi; (e)herderite crystal, 23.02 carats; (f)rough (120 g) and faceted (6.202carats) yellow scheelites; (g) largeelongated quartz crystal (10 cm inlength); (h) large goshenite crystal, 8 x6 x 4 cm, shows prism, pyramid andbasal pinacoid

7.11

(a) Aquamarine, quartz andcleavelandite in phlegmatic matrixfrom Pan-taw; (b) phlegmatic withhematite and topaz; (c) phlegmaticwith, cassiterite, c1eavelandite,muscovite and quartz from Pan-taw; (d)faceted sherry coloured topaz; (e)amazonite crystals in phlegmatic

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groundmass from Pan-taw phlegmaticdeposits

7.12

(a) Ilmenorutile crystal and its X-RDspectrum; (b) rhodochrosite crystalsand its X-RD spectrum; (c) colour-change fluorite from Pan-tawphlegmatic deposit

7.13

The miners digging the sapphire fromalkali yemenite phlegmatic dyke inBuga mine, On-dan, 22° 59' 7 " N, 96° 12'51" E

7.14

Close-up view of sapphire bearing alkaliyemenite phlegmatic dyke intrudedinto the phlogopite marble at Bugamine, On-dan

7.15Sapphire-bearing alkali yemenitephlegmatic (highly weathered) dykeintruded to the leucogranite in Buga

7.16Sapphire crystal associated with schorlin feldspar groundmass in alkaliyemenite phlegmatic

7.17Sapphire crystal with “black silk” infeldspar ground mass of nephelineyemenite, On-dan

7.18 (a) Large sapphire crystal; (b) sapphirepackage from UMEHL mine, On-dan

7.19 Panoramic view of Thurein Taung

7.20 Geological sketch model of ThureinTaung

7.21Sapphire is enclosed by purplish spinel(X-RD result) from alkali yemenitephlegmatic, Thurein Taung

7.22(a,b,c) Sapphires in alkali-feldspargroundmass of alkali-feldspar yemenitephlegmatic, Thurein Taung

7.23

Alkali yemenite phlegmatic dykesintruded in calc-silicate rocks and localminers digging sapphires from highlyweathered alkali yemenite phlegmatic,JV mine of Lay-thar, 23° 00' 26.3" N,96° 30' 19.5" E

7.24Sapphires embedded in alkali feldspargroundmass of alkali yemenitephlegmatic, Lay-thar JV mine

7.25Local miners searching the sapphires inLay-thar JV mine, 23° 00' 26.0" N, 96°30' 19.0" E

7.26

Fluid and silicate-melt inclusions ofsapphires form alkali yemenitephlegmatic deposits, Mogok. (25 X,transmitted light and dark field)

7.27

Plotting diagram of Cr O /Ga C (%wt)vs Fe O /TiO (%wt) ratios shows thedifferent populations and overlappingfeatures of basaltic and non-basalticblue sapphires (source: GAAJ)

7.28

Photograph showing the peridot mineand miners digging the dunite inentrance of the adit at Mya-sein Taung,23° 00' 03.4" N, 96° 27 ' 54.4" E

7.29

Entrance of the tunnel and railway(made in local miners) used forcarrying of peridotite-dunite wastages,Mya-sein Taung, 23° 00' 07 .5" N, 96°27 ' 51.0" E

7.30

Photograph showing the pocket natureof peridot deposit in dunite, althoughno gems in pocket locally called “Owe-poke” and filled only talc

7.31Peridot crystal in dunite groundmass offragment of pocket deposit from ZalatTaung

7.32Aragonite with peridot from pocketdeposit of dunite and its X-RD

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spectrum, Mya-sein Taung

7.33

Magnesiohornblende crystals,associate minerals of peridot, and its X-RD spectrum, Mya-sein Taung

7.34

(a, b) Gem quality peridot crystals frompocket type deposits, UMEHL mine,Mya-sein Taung; (c) rough peridot, 68carats; (d) after faceted peridot43 carats

7.35

Gem quality peridot lot from pockettype deposit, UMEHL mine, Mya-seinTaung and display in UMEHLEmporium

7.36Marble and leucogranite contactindicate painite deposit at Wet-loomine, 22° 54' 28.5" N, 96° 23' 34.9" E

7.37 Dealer purchasing painite from localminers, near Wet-loo mine

7.38 Dealer checking the painite by eye-sidefrom local miners, near Wet-loo mine

7.39 Painite and rubies in leucogranitematrix, near Wet-loo mine

7.40 Huge painite aggregate with rubiesfrom Thurein Taung

7.41

(a) Gem quality painite crystals; (b)painite shows prism, pyramid andpinacoid faces; (c) faceted painite (3.5cts.) from Thurein Taung; (d) facetedpainite from Namya, 0.59 cts.; (e)pleochroism effect of painite fromThurein Taung

7.42Anatase crystal, shows blue colour,associated with painite from ThureinTaung

7.43Baddeleyite crystal, associated withpainite and its XRD spectrum fromThurein Taung

7.44

(a) Two-phase inclusion, transmittedlight, 30 X; (b) rectangular shape liquidfilled negative inclusions, transmittedlight, 30 X ; (c) needle-like rutileinclusions, transmitted light, 30 X; (d)baddeleyite crystal inclusion in painite,transmitted light, 30 X ; (e) BSE imageof srilankite inclusion in painite fromNamya; (f) srilankite crystal inclusionin painite from Wet-loo, transmittedlight, 30 X

List of Tables

2.1 Major geological succession of thestudy area

3.1Classification of pegmatites of the rare-element class for Sakhan-gyi and Pan-taw area, after Cerny (1991)

4.1Chemical composition and norms of theigneous rocks from the Mogok are (inwt%)

6.1

LA ICP-MS: U-Pb zircon age data forleucogranite (LG-1) and zirconinclusion in painite, associate with rubyin leucogranite matrix (P-1)

6.2Comparison of rock sequence insouthern part of Mogok Stone Tract andthe study area with radiometric ages

7.1 Genetic classification of gemstonesfrom the Mogok Stone Tract

7.2 Various types of gemstones associatedwith igneous rocks

7.3 Classification of granitic pegmatites(modified after Cerny, 1991)

7.4 Classification of granitic pegmatites ofthe rare-element class (Cerny, 1991)

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7.5 Classification of pegmatites of the rare-element class, beryl type for Sakhangyiand Pan-taw

7.6Physical and optical properties ofgemstones from Sakhan-gyi and Pan-taw pegmatites

7.7Trace elements in sapphires fromselected localities tested using LA- ICP-MS method

Mogok ruby. Gem quality in matrix, 9 x 7 cm.The crystal measures 3.4 cm! From thecollection of Bill Larson. (Photo: Mia Dixon)

C h a p t e r I I n t r o d u c t i o n

Any list of the classic, historically mostimportant gem deposits of the world mustinclude the Mogok Stone Tract. It is very famousnot only for the world’s finest rubies and spinelsbut also for gem quality sapphire, peridot, etc.for many centuries. Sapphires are most abundantin Pan-sho, Kyat-pyin, Kyauk-pyat-that, Baw-mar, Lay-thar, and Ondan areas, peridot islimited to the area of Bernard–Pyaung-gaung, 10km north-northwest of the Mogok Valley. Gemquality apatite, scapolite, moonstone, zircon,garnet, iolite, amethyst, danburite, etc. and somerare gemstones, painite, poudretteite, etc. arealso found in this area.

1.1 Location and AccessibilityThe Mogok Stone Tract lies in the northwest endof the Shan Plateau. The tract is sickle-shaped,with the vertical limb being formed by theIrrawaddy river. Its northern terminus is at thebend of the Shweli river, as it twists and bends,flowing at times from south to north into theIrrawaddy. The vertical limb of the tract extendssouth to north from Latitude 22° 54' 00" N up to23° 01' 00" N, and the horizontal arm of the tractrubs along the Longitude 96° 12' 06" E as far as96° 33' 30" E or approximately 380 km NNE ofNaypyidaw, the capital of Myanmar, and also200 km NE of Mandalay; refer to one-inchtopographic maps no. 93 A/8, B/1, B/5, and B/9.The approximate length of the tract is about 37km in E-W and width is about 13 km in N-S.Generally the study area can be divided intothree different topographic units according togemstone occurrences, viz: Mogok–Kyat-pyinarea, Bernard–Pyaung-gaung area and On-danarea.

The general area of the tract is verymountainous, forming a sort of amphitheater.The high mountains to the north run almost east-west. Most of the mining takes place in the alluviaof floors and flanks of the Mogok and Kyat-pyinvalleys. Mogok Valley is the most important,consisting of a narrow alluvial plain, 5 km long

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running northeast-southwest, and about 1 kmwide.

Today a motor road leads from Mandalaynorth to Sagyin, past several villages and leadseastward, up a ridge about 1220 m, thendescends to the beautiful green valley, namelyMogok Valley.

Fig. 1.1. Three dimensional view of thegeomorphology of the Mogok Stone Tract (TMimage; 30 m resolution).

1.2 GeomorphologyMogok–Kyat-pyin area is a mountainous regionwith two distinct valleys, Mogok Valley andKyat-pyin Valley. The Mogok Valley is located atan elevation of 1158 m above sea level and theKyat-pyin Valley is also located at 1350 m abovesea level. East of the Kin chaung, the hills rise tomassive ridges, which culminate in the TaungmeTaung (2300 m), the highest point in the area;this peak dominates both the Bernard-myo (Ywa-thayar) and the Mogok Valley. It forms apyramidal hill from which several ridges radiatein different directions. One of them, running eastand south-east contains the Kyini Taung (2052m) and Let-nyo Taung (1626 m), an arm of theabove ridge, runs towards Mogok.

Dattaw Taung (1555 m) in the east of Mogok,Shwe-daing, Lin-yaung-chi to Kadoke-tat, Baw-padan, Kyauk-poke, Kyauk-saung, Pingu Taung(1186 m), Kyauk-pyatthat (17 00 m) in the westof Mogok show typical fold pattern (anticline-syncline nature) and famous for primary rubydeposits. The hills north of Kyat-pyin formpicturesque ridges cut by deep valleys, thewestern most ridge being the Baw-lone, Kyauk-pyat-that, Myaing-gyi Taung, running west-south-west towards Kabaing. In this area, Kyauk-sin Taung forms the highest point. The typicalfeature is formed by the arc like or sinuousparallel ridges, which start from the east, run inan east-west direction, turn south in the centre

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and again run westwards.Bernard (Ywa-thaya)–Pyaung-gaung area

forms the highest elevation of the Mogok StoneTract, 1585 m above sea level. Most of the area ismountainous, rugged with steep slopes at thehigher region, whereas moderate slopes tolowland with rounded hills at the lower part. TheInjauk valley runs through this area, wherediverging arms of the Taung-me Taung form highridges and peaks at the Maw-giwa Taung (2043m). However, some isolated hills and ranges,such as Mya-sein Taung, Zalat Taung, HtinshuTaung and Lay-thar Taung are also found asdistinct landmark and famous gem deposits ofthis area.

On-dan area occurs in the rugged and hardaccessible territories of the hill regions, whichare covered with dense forest. The mostdistinctive mountains are Shweu-daung Taung(1900 m), the highest peak in this area andHnamataw-lay range. The Shwe-u-daung Taungtakes a bend to the south, dividing Momeik fromMogok. Due north is Hnamataw-Lay range(approximately 1524 m high); to the south is asmaller hill, just 97 5 m high. Directly to the westare lower mountains that stretch to theIrrawaddy river, falling off as they approach theriver.

Fig. 1.2. Three dimensional view of thegeomorphology of the Mogok Stone Tract (TMimage; 30m resolution).

In the study area drainage falls into twodifferent systems. The first system starts fromthe northern watershed of the rugged, hilly andmountainous terrain and flowing from south tonorth, and then flowing into the Shweli river.Laung-zin chaung, On-dan chaung, Kin chaung,Nanpeit chaung and Nammeik chaung are typicalfor the drainage flowing from south to north, andalso flowing into the Shweli river. Many streamscriss-cross and help to drain the valley. Thesecond drainage system start from the southernwatershed of a rugged, hilly and mountainousregion, flowing generally from northeast tosouthwest and from north to south, and thenflowing into the Nampai chaung to Chaungmagyiriver. Yini chaung, Nannga chaung, Nanatchaung, and Natpan chaung are good examplesfor the second system of drainage. Nampi chaungdivides Mogok subdivision from the Mong-long.

1.3 Objectives and ScopeThe research will attempt to contribute thegeology, mineralogy, petrology andmineralization of the igneous rocks of MogokStone Tract. The main objectives of this researchare as follows:

a. To study the distributions of the igneousrocks in the Mogok Stone Tract.

b. To document the petrography,petrochemistry and petrogenesis(sequence and geochronology) of these

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igneous rocks.

c. To investigate the gemstone deposits fromthese igneous rocks.

1.4 Methods of Study

A. Field Study1. Detailed geological mapping of the

Mogok Stone Tract to investigatethe structural and lithologicalfeatures of igneous rocks.

2. Systematic sampling of variousigneous rock types.

3. Gemstones sampling and to studythe mode of occurrence ofgemstones from igneous rocks ofthis research area.

B. Laboratory TechniquesThe representative samples of theresearch area were studied by means ofthe following techniques:

1. Detailed microscopic examinationof various igneous rocks for betterunderstanding of the petrography ofthe area.

2. Quantitative and qualitativeelements analysis of variousigneous rocks and minerals samplesusing the EDX-RF in URC, YangonUniversity and WDX-RF, LA ICP-MStechniques in University ofTasmania, Australia to contributethe petrochemistry and mineralchemistry.

3. X-ray diffraction analyses ofunknown minerals from theseigneous rocks in X-RD Laboratory,Department of Atomic Energy.

4. The radiometric dating of foursamples of the area was analysed byU-Th-Pb geochronology methodusing LA ICP-MS and SHRIMPtechniques at University ofTasmania, Australia.

5. Some selected gemstone sampleswere identified by LRS (LaserRaman Spectroscopy) at Universityof Tasmania, Australia to contributethe solid/fluid inclusions in thecorundum.

1.5 Previous WorksThe Mogok Stone Tract has attracted manygeologists, mineralogists and gemmologists frommany parts of the world for producing the finestrubies on earth. Though rubies have been minedin Mogok for centuries, it remains unknown whenthese deposits were first discovered.

The earliest historical record is a descriptionof the ruby mines at Mogok by Father Giusepped’Amato as reprinted, unedited, [by] the Journalof The Asiatic Society of Bangal, in 1833 (v. 2,pp. 7 5–7 6).

Brown and Judd (1896) reported mode ofoccurrence of the rocks and origin of gems, andfirstly named the area as Mogok Stone Tract.Also they pointed out that the Mogok limestone,which [was] later named as marble, originatedfrom the basic igneous rocks by means ofcomplicated chemical reaction. They alsoconsidered the source of alumina in the

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corundum and spinel as the limestone itself.La Touche (1913) reported the principal rock

types of the Mogok Stone Tract and its environs;the term “Mogok Gneiss” as Archaen in age wasfirstly given by him, published in Memoirs of theGeological Survey of India, Northern Shan State,1913. The arrangement of the geologicalsuccession is as follows:

Iyer (1953) contributed a valuable account ofthe geology and gemstones of the Mogok StoneTract and mapped Mogok and its surroundingarea, four-inches-to-one-mile; published inMemoirs of the Geological Survey of India,Volume 82, 1953 and arranged the geologicalsuccession of Mogok Stone Tract as follows:

13. Recent Alluvium

12. Pleistocene: Raised Terraces near Mogokand Mong-long

11. Basic and Ultrabasic Intrusives: Dolerite,peridotite, hornblende-pyroxene rock andhornblende rocks. Hornblende andaegirine-scapolite rocks

10. Urtite Series: Hornblende-nepheline rocksand aegirine-nepheline rocks

9. Tourmaline Granite

8. Kabaing Granite: Pegmatites, aplite,leptynite, minor intrusions, etc.

7 . Syenites: Nepheline syenite, etc.

6. Augite and Hornblende Granites

5. Quartzites: Quartz-sillimanite rocks ofNammi

4. Calc-granulites: Scapolite-gneiss andpyroxene granulites

3. Crystalline Limestones and Calciphyres(Rubies and Spinels): also bands of calc-gneiss

2. Khondalites: Feldspathic garnet-sillimanite-gneisses with graphite andhybrid rocks

1. Biotite-gneisses, Garnet-gneisses andBiotite-garnet gneisses: Highly injectedwith acid intrusives as pegmatites,feldspathic veins and quartz veins

He pointed out the origin of sapphire fromMogok as “the presence of sapphire in thepegmatite and granite in the Mogok area alsopresents as a case of supersaturation withalumina; and if this magma was supersaturatedwith alumina, this alumina must have beenconveyed into the limestones by the agents ofpneumatolysis.”

Searle and Ba Than Haq (1964) described therelationship of Mogok Belt to HimalayanOrogeny. They firstly explained themetamorphism of the Mogok Slone Tract tookplace in the Middle Tertiary and also theyreported the rock type into groups. They are:

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Myint Lwin Thein et al. (1990) studied thegeology and stratigraphy of the metamorphosedearly Paleozoic rocks of the Mogok-Thabeikkyin-Singu-Madaya areas. They correlated themetasediments of this area to the LowerPaleozoic carbonate-dominated sediments of theSouthern Shan Slate, based on the macroscopicand megascopic lithologic similarities. Theyarranged the geological succession and the rockunits in the present area as follows:

Also they described

ruby and sapphire regionallyoccurring in the Kyetsaung taungmarble (a unit of WabyudaungMarble) of this Mogok Belt is related tothe fact that the Kyetsaung Taungmarble is the host rock for thecorundum mineral formation. Thismarble formation, like itsunmetamorphic equivalent WunbyeFormation, with clayey or siltylaminations, patches, or burrows wasa carbonate unit rich in alumina. Thisrich alumina source, together withchromium content of the limestoneafter suffering from the high graderegional metamorphism caused by thegranitic emplacement and severaltectonism, was responsible for theformation of ruby. They furtherremarked that the occurrence ofsapphire in syenite-alaskite might beaccounted to the magma rich inalumina.

Thet Tin Nyunt (2000) studied themineralogy and petrology of Bernard–Pyaunggaung area.

Thuzar Aung (2003) studied the petrologyand gemstones of On-dan and its environs.

In addition, the various workers fromuniversities also carried out the geologicalinvestigation, on the basis of their purposes,mainly concentrated on the gemmology,mineralogy, petrology and structural geology for

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their M.Sc., M.Res. and Ph.D. research.

Mogok ruby. From the Pala InternationalCorundum Collection. (Photo: Mia Dixon)

C h a p t e r I I G e o l o g y o f t h e A r e a

2.1 Regional Geological SettingMogok Stone Tract is a segment of the MogokMetamorphic Belt (MMB) of Searle and Ba ThanHaq (1964), and is situated south of the easternHimalayan syntaxis at the western margin of theShan-Thai terrane. This originated in Gondwana(Ridd, 197 1) and collided with Asia either in thelatest Triassic (Mitchell, 197 7 ; Metcalfe, 1988) orearliest Triassic (Metcalfe, 2000). The studyarea, situated in the northern part of MMB haslong been of great interest because of the rubies,sapphires and other gemstones. The geology ofthe Mogok area is very complex, consistingmainly of high-grade metamorphic schists andgneisses, igneous intrusives, including gembearing pegmatites, peridot bearing ultramaficrocks, and most importantly ruby and spinelbearing marble. Generally, metamorphism,migmatization and structural deformation haveinvolved metasediments, which range in agefrom Precambrian or Cambrian to possiblyCretaceous. Acid, intermediate, mafic toultramafic igneous rocks form an integral part ofthe Mesozoic to Tertiary igneous unit.

The area is bounded in the north by east-westtrending Momeik dextral fault (Sein Myint et al.,197 9), Cretaceous Orbitolina bearing limestoneswhich are intruded by gabbro and related rocksand older alluvial deposits are exposed. Theboundary between the Tagaung-Myitkyina beltand the MMB is the high-angle Kyaukphyu fault,locally a southeast-dipping thrust (Mitchell et al.,2004). In the southern part of the area, Mong-long mica schist exposes a gneissic area intrudedby tourmaline granite along the boundary. Westof Mogok, Sagaing fault, major right-lateralstrike-slip fault which is running north-south alsodissecting Singu lava flow, and the westernmargin of the MMB is juxtaposed with lateTertiary sediments in the western portion.

[In] the southern part of the Mogok, Mong-long mica schist striking nearly east occupies a

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broad belt of the gneissic area and is intruded bytourmaline granite along the boundary withgneiss. The Mogok Stone Tract is bounded, aswell as overthrusted, by the Chaung-MagyiGroup in the southeast along the Chaung-Magyistream, and tourmaline granite is emplacedalong the thrust plane (La Touche, 1913). Amongthe imbricated thrust sequence, Mogok Thrust(Searle and Ba Than Haq, 1964) is the mostdistinct principal thrust fault in this area. TheKabaing Granite intruded into the area forminglarge exposure at Kabaing village traceable westtowards the Thabeikkyin area.

Fig. 2.1. Regional geological map 0f the studyarea, modified after Bender (1983). Click toenlarge.

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Fig. 2.2. Regional geological map 0f the studyarea, modified after Bender (1983).

2.2 Rock SequenceOn the basis of primarily field observations andpetrographic data, and secondarilypetrochemical and geochronological data, thegeology and the rock sequence of the area aremodified from some previous works (e.g. Iyer(1953), Myint Lwin Thein et al. (1990), Thet TinNyunt (2000), and Thuzar Aung (2003)). Threenew geological maps were prepared for theMogok–Kyat-pyin, Bernard–Pyaung-gaung andOn-dan areas (Figs. 2.2, 2.3 and 2.4).

According to radiometric dating suggestedthat the age of leucogranite, syenite, KabaingGranite, and pegmatite of the area. [Wordingappears to be omitted from previous sentence. —Editor] However, the age of ultramafic rocks ofthe area are correlated with [the] easternophiolite belt of Myanmar (personalcommunication, Dr. Hla Htay, 2007 ). Fieldobservations indicate that most of the igneousbodies in the area have intrusive contacts withthe surrounding Mogok metamorphics or otherigneous rocks.

Regarding the age of the latest regionalmetamorphism of the Mogok metamorphics,Maung Thein (2000), using some GIAC data,mentioned that the age of regionalmetamorphism along the Mogok MetamorphicBelt occurred in Late Oligocene. On the basis ofsome radiometric dating Bertrand et al. (2001)suggested that the age of metamorphism alongthe Mogok Metamorphic Belt ranged fromOligocene to Middle Miocene. However, it shouldbe pointed out that Kabaing Granite (15–16 Ma)intruded into the Mogok metamorphics. Thus,the metamorphic age of the Mogokmetamorphics would not range up to MiddleMiocene.

The major geological succession of the studyarea is as follows:

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Table 2.1. Major geological succession of thestudy area.

The Mogok Stone Tract, composed [by] avariety of igneous rocks, ranges in compositionfrom granite to peridotite. The probable igneoussequence in the area is contrived from the fieldrelationships of some igneous rocks, andradiometric dating of some igneous rocks. Theseare shown in Table 2.1, and the fieldrelationships are as follows:

Ultramafic rocks are relatively subordinate inthe Bernard–Pyaung-gaung area, which aremostly intruded into the garnet-biotite gneiss(probably older than Mogok metamorphics).However, the biotite microgranite and the latestage of pegmatite are intruded into theperidotite at Pyaung-gaung, so these ultramaficrocks are generally older than biotitemicrogranite and pegmatite. It may be assumedthat they have been emplaced to the garnet-biotite gneiss as early Jurassic?.

Recent field evidences indicate foliated andhighly jointed augite-biotite granite (129.8±8.2Ma). Early Cretaceous is intruded byleucogranite, which are foliated at the margin ofthe intrusion and trending nearly NE-SW atTaung-me Taung and Shwe-udaung Taung, thehighest peak of Mogok area, showing that thefoliated augite-biotite granite is older than theleucogranite (32±1 Ma) Early Oligocene in age.

Leucogranite occurs widespread as smallstocks and dykes, which are intruded intoregionally metamorphic rocks as well as syeniteintruded into these rocks at Thurein taung. Thecontact relationship between leucogranite andbiotite microgranite is absent in the study area.However, U/Pb zircon age of syenite is 25 Ma(Late Oligocene); it is younger than leucogranite.Also, some pegmatite dykes are intruded into theleucogranite at Dattaw and Pein-pyit area,indicating that the leucogranite is older than thepegmatite.

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Fig. 2.3. Geological map of Mogok–Kyat-py in area,geology by Kyaw Thu, 2006. Click to enlarge map.

Fig. 2.4. Geological map of Bernard–Pyaung-gaung area, modified after Thet Tin Nyunt (2000),

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Kyaw Thu (2006). Click to enlarge map.

Fig. 2.5. Geological map of On-dan area, modifiedafter Thuzar Aung (2003), Kyaw Thu (2006).Click to enlarge map.

Syenitic rocks and urtite series have intrudedinto the Mogok metamorphics in this area, aswell as intruded into the leucogranite, i.e.,syenite is younger than the leucogranite. But,biotite microgranite has intruded into thesyenite in On-dan area, indicating that syenite isolder than biotite microgranite (15.8±1.1 Ma)Middle Miocene.

The Kabaing Granite occupies a large tract ofcountry to the NW of Mogok–Kyat-pyin area. Itis intruded into the all Mogok metamorphic rockunits and parts of the syenite, ultramafic andleucogranite. Unlike the augite-biotite granite,leucogranite, and syenite, the Kabaing Graniteshows no signs of diastrophism and itsemplacement post-dates that of the syeniticrocks. In Sakhan-gyi and Pan-taw, the KabaingGranite is intruded by pegmatite dykes (15 Ma)Middle Miocene (Searle and Ba Than Haq, 1964)with trend of NNE-SSW in direction indicat[ing]that these pegmatites are younger than otherigneous rocks.

2.3 Distribution of Major Igneous Rock

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UnitsPegmatites and Alpites

The term pegmatite is a textural definition.The important pegmatite exposures [are]situated at Sakhan-gyi and Pan-taw, which areintruded into the Kabaing Granite. They usuallyoccur as medium to very coarse-grained dykes,highly weathered and mostly kaolinized, whitishon fresh surfaces and brownish on weatheredsurfaces. The important gemstones and somerare gemstones are found in these pegmatites.Other pegmatites are also exposed at west of Pan-lin, Dattaw, Le-u and Pein-pyit area intruding theleucogranite and metamorphic rocks. Southeastof Pyaung-gaung area, the pegmatites areintruded into the peridotite and dunite. Minoraplite dykes and veins are also present in thisarea.Kabaing Granite (biotite microgranite)

Kabaing Granite is one of the major intrusiveigneous rocks in Mogok, and was first noticed byBrown and Judd (1896) near Kabaing on themotor road. This granite is a biotite granite,greyish, hard, compact and massive, medium-grained, homogeneous in texture, and regionallydiscordant to Mogok metamorphics. It occupiesa vast area centered at Kabaing village,extending to Kyauk-pyat-that, turns northeast[to]wards Sawlone-gyi, and also extending toKyauk-sin, Pan-taw and Injauk to Tam-saing andLaythar near Momeik boundary, where it isintruded into the Mogok metamorphic rockunits. This microgranite is found at the southernand western part of On-dan village, which areintruded into the marble and leucogranite. Itssouthern boundary starts from Nam-sita chaungand passes under the quartzite south of Gwe-bin.This granite is also found north of Kathe, Kyauk-sin–Kyat-pyin road, north of Kyat-pyin viewpoint and intruded into the marble north of Ludaon the Mogok–Kyat-pyin road. It is also intrudedinto the garnet-biotite gneiss in Chin-the Taungand Hin-tha Taung slopes. The boundary of theKabaing Granite and the country rocks [is] notvery definite, as there is a thick cover of soil and[it is] heavily forested. Exfoliated or spheroidalweathered exposures are common in this area.

Fig. 2.6. (a) Highly weathered pegmatiteexposure, Sakhan-gyi, 22° 54' 1.2" N, 96° 20'56.1" E; (b) dyke of pegmatite at Pan-taw, 22°57' 47.3" N, 96° 24' 15.6" E; (c) panoramicview of Kabaing Taung; inset: large block ofbiotite microgranite showing exfoliated natureat the peak, near Kabaing village; (d) small

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outcrop of Kabaing Granite showing onion skinweathering, 22° 57' 14.9" N, 96° 24' 54.6" E,Kyauk-sin–Pan-taw area; (e) an outcropshowing exfoliation nature in biotitemicrogranite, near On-dan village, 22° 57' 12.2"N, 96° 14' 38.05" E. Click to enlarge.

Urtite SeriesProf. Adams (1926) was the first to discover

this suite of rocks on the Mogok motor road nearview point to Sin-khwa. These rocks are mainlyfound in Kyauk-pyat-that, Myaing-gyi Taung,Thurein Taung, Sin-khwa and Ye-aye environarea, which are intruded into the marble andleucogranite, forming lenticular bodies, 10 cm to20 cm in exposed width and at least 100 m inexposed length. These rocks show a gneissicbanding nature, or are granulitic and vary in theamount of their salic and femic constituents.Other minor exposures of these rocks occur nearChaung-gyi, Injauk, south-east of Taung-meTaung and north-west of Bernard-myo (Ywa-thayar).Syenitic Rocks

The syenitic rocks were first discovered inthis area by Fermor (1932). These rocks areformed as sills or sheets, dykes and small stocksaround the Mogok area. Syenite exposures arescattered or may cover vast areas and they mayshow foliation. This unit is found well developedin the area between Mogok and Taung-me Taungand around Let-nyo and Lay-thar Taungs. It iswell seen as small stock between Taung-me–Mogok area, which is in contact with the marble.The rock occurs as dykes north of Ohn-gaing, Ye-bu, Dattaw chaung, Pein-pyit, Kyauk-wa,Achauk-taw, and Chaung-gyi chaung. Exfoliatedsyenite boulders are found near the village ofMa-nar and are locally called “ge-sein” (inMyanmar, green rock).

Fig. 2.7. (a) Phlogopite-diopside marble andurtite rocks contact in Thurein Taung, 22° 54'12.2" N, 96° 22' 18.8" E; urtite exposureshowing highly brecciated nature due to faultcontact nature (inset); (b) urtite and whitemarble contact in Yadana-kadae-kadar mine,22° 54' 34" N, 96° 22' 31" E; mafic mineralsmainly hornblende and nepheline in surface ofurtite exposure (inset); (c) urtite intruded intothe marble showing scapolite-diopside-graphitecontact zone, 22° 54' 11.3" N, 96° 22' 17.3" E;(d) pegmatite vein intruded into the urtitebody, Thurein Taung, 22° 54' 12.4" N, 96° 22'20.6" E; (e) xenolith of nepheline syenite inurtite, Thurein Taung, 22° 54' 12.7" N, 96° 22'20.7" E. Click to enlarge.

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Fig. 2.8. (a) A distinct syenitic rocks exposureshowing exfoliated nature in syenite exposure,north of Ohn-gaing village, 22° 56' 27.2" N, 96°29' 36.8" E; (b) syenite exposure at Kyauk-wa,north of Mogok; (c) dyke of urtite in syeniteexposure, north of On-dan, 22° 57' 16.4" N, 96°14' 39" E. Click to enlarge.

Bernard-myo exposure is the next largestone, which is well exposed at the southwest andnorthern part of Bernard-myo. Small exposuresare found at the southern part of Pyaung-gaungvillage and east of Pan-lin village. It extends asthe minor bands on to the Kyauk-thita Taung andnorth-east of Injauk. Other smaller exposures arealso present.

Other exposures are found at the Kyat-pyinenvirons, such as east of Kyauknaga, north-eastand west of Tha-dut-sho and north of Pyaung-pyin, and north-east of Baw-Ion-gyi, Kyauk-sin,and Baw-ma. Exposures of syenitic rocks are alsofound as small stock and dykes around Pin-guTaung, Kyauk-pyat-that, and Thurein Taung,Gegyi Taung, and northwest of On-dan villageassociated with leucogranite. A few smallexposures of the syenitic rocks are also observedin this study area closely associated with theMogok marble as a result of ruby formation bycontact metamorphism.Leucogranite

These rocks were previously described as“Alaskite Suite” by Searle and Haq (1964), laterrenamed by Myint Lwin Thein et al. (1990) as“Pingu Taung Leucogranite.” Leucograniteconstitutes the major part of the igneous rocksfound in the Mogok Stone Tract, which intrudedinto Mogok metamorphic rocks and it appearshighly weathered, showing pronouncedexfoliation with graphic texture and foliation.

Between Mogok and Kyat-pyin, these rocksare found in the west of Pein-pyit, south, south-west and north-east of Dattaw Taung, east andnorth-east of Le-u. This unit crops out as anintrusive mass around the peak of Kyauk-taung-kon, Myo Taung, Chin-the Taung, and as small

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bodies in Ye-aye valley, and also at the base ofwestern and northern spur of Pingu Taung,extended along the foot path between Baw-Ion-gyi and Baw-mar, and at the Gwe-bin chaung nearthe Kyauk-pya village. These leucogranites areclosely related to the syenitic rocks, andprobably important source rocks for radioactiveminerals in Mogok.

In the Bernard-myo area, it is the mostabundant igneous rock and mainly found in thewestern part of Pan-lin and Ye-ne-inn villages,which are intruded into the garnet-biotite gneissand calc-silicate rocks. In the southern part ofHtin-shu Taung, leucogranite intruded into themarble and shows foliated nature.

Leucogranite occurs as the largest intrusivemass in the On-dan area, typically found in Pa-Iaung Tung, Hnama-taw-Iay range, at the base ofTant-khan Taung to [the] western part of On-danvillage. These rocks are closely associated withMogok metamorphic rocks as well as syenite andaugite-biotite granite in this area.

Fig. 2.9. (a) A distinct exposure ofleucogranite in Hin-thar Taung; (b) photographshowing leucogranite and diopside-phlogopitemarble contact to form the painite deposit inWet-loo mine, 22° 54' 28.5" N, 96° 23' 34.9" E;(c) highly weathered leucogranite exposed inSaw-mar mine; (d) an outcrop showingexfoliated nature in leucogranite, north of Saw-mar; (e) photograph showing leucograniteintruded into the garnet-biotite gneiss in Pan-taw, 22° 57' 44.6" N, 96° 24' 41.7" E; (f)syenite vein in leucogranite about three feet inthickness, Wet-loo mine, 22° 54' 28" N, 96° 23'35" E. Click to enlarge.

Augite-biotite GraniteThe main intrusions are along the Shwe-u-

daung Taung range, north of On-dan village andTaung-me Taung peak, north of Mogokrespectively. In On-dan, augite-biotite granite isfound intruded by leucogranite in someoutcrops. It shows strong foliation on weatheredsurfaces, similar to ridge and furrow structure.Other small exposures occur in the area such asKyauk-sin and Saw-mar, which are very similarin weathering effect to the syenitic rocks, [and]represent their more acid phase.Ultramafic and Mafic Rocks

Ultramafic rocks of the Mogok Stone Tractoccur as layered intrusions in garnet-biotitegneiss (probably older than Mogokmetamorphics) in Bernard–Pyaung-gaung area,north-eastern part of the Mogok. These rocks aredistinctly cropped out at the Pyaung-gaung,Zalat Taung, Mya-sein Taung, Thit-ta-pin Taung,and Htin-shu Taung environs. Rarely,

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amphibolite and micaite rocks are alsoencountered in this area. Smaller bodies ofbiotite microgranite, feldspathic veins andveinlets of chrysoprase are also found intrudedin these peridotite-dunite.

The mafic rocks, mainly gabbro, occur assmall bodies in the surrounding area of Kyauk-pyat-that, environs of Ye-aye, Injauk and north-west of Tam-saing, which are not always largeenough to be mapped.

Mogok ruby. From the collection of BillLarson. (Photo: Mia Dixon)

2.4 Geological StructuresAccording to the TM image and photogeologicalinterpretation, the study area is very complex ingeological structure. [The] general trend of therocks of Mogok area is distinctly in ENE-WSWdirection and generally steeply inclined towardssoutheast direction. Numerous folds, faults andjoints are involved. This area lies in a series ofcontinuous and discontinuous anticlinal ridgesand south-plunging synclinal valleys extendinglaterally from Kyini Taung to Kabaing, [and]marble and calc-silicate rocks are widespreadthroughout in this regional fold pattern.

Fig. 2.10. (a) Panoramic view of theperidolite-dunite bodies, north-east of Bernard-myo; (b) peridotite exposure showing falsebedded nature, Mya-sein Taung, 23° 00' 03.4"N, 96° 27' 54.4" E; (c) photograph showingperidotite partly altered to serpentinite due to

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the auto metamorphism, 22° 59' 55" N, 96° 27'46.6" E; (d) an outcrop showing jointed naturein dunite, Pyaung-gaung, 23° 00' 40.5" N, 96°26' 40.0" E; (e) pegmatite dyke in peridotiteand chrysoprase veins in upper part of photo,Mya-sein Taung, 23° 00' 10.5" N, 96° 27' 44.9"E. Click to enlarge.

Fig. 2.11. (a) Panoramic scenery of Taung-meTaung; augite-biotite granite exposure at thepeak of Taung-me Taung (inset), 22° 58' 18.4"N, 96° 28' 8.5" E; (b) augite-biotite graniteexposure showing the distinct faulted nature inShwe-u-daung Taung; inset; small quartzofeldspathic vein cross cut in foliated augite-biotite granite, north of On-dan village, 23° 01'12.1" N, 96° 13' 19.07" E. Click to enlarge.

[An]other distinct feature is the Mogokthrust, generally NE-SW trending and whichfollows a sinuous outcrop from the head ofMogok valley to southwest of Gwebin village;however, the appearance of the thrust betweenMogok and Kyat-pyin is vague by the highaccumulation of faulting, and some forcefulemplacement of leucogranite. Deformation, asbeing the equivalent of local stretching of crustalmaterial around the eastern Indian syntaxis,[was] active between Oligocene and MiddleMiocene (Bertrand et aI., 2001). At the Latitudeof [the] Mogok area, the deformation was sealedat about 16 Ma (Middle Miocene) by intrusion ofthe Kabaing Granite.

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Fig. 2.12. (a) Photograph showing mullionstructure in calc-silicate rock due to thethrusting, east of Gwe-bin, 22° 53' 44" N, 96°22' 24" E; (b) dyke of urtite showing foldednature in marble indicating tectonism effect,Kyauk-saung, 22° 55' 21" N, 96° 25' 53" E; (c)the exposure showing Mogok thrust, north-westdirected thrust plane at north of Mogok, 22° 56'37.5" N, 96° 31' 22" E; (d) close-up view ofphoto (c) showing footwall carbonate mylonitealong the thrust zone; (e) well jointed nature inphlogopite marble at Gwe-bin. Click to enlarge.

Thus conclude Chapters I and II. AccessChapter III here.References follow.

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Thuzar Aung, 2003. Petrology and Gemstones ofOndan and its Environs, Mogok Township,Mandalay Division. Unpublished M.Res.Thesis, University of Yangon, 90 pp.

Tuttle, O. F., and N.L. Bowen, 1958. Origin ofgranite in the light of experimental studies inthe system NaAISip8-KAISiP8-Si02-H20. In:Hyundman, D.W., 1985. Petrology of igneousand metamorphic rocks. New York,McGraw-Hill. 2nd edt., 7 86 pp.

United Nations, 197 8. Geology and explorationgeochemistry of the Shan scarps area, east ofKyaukse, Thazi and Tatkon, central Burma.Technical Report. UN/BUR 7 21002, no. 3,United Nations Development Programme,New York.

Washington, H.S., 1917 ; Chemical analyses ofigneous rocks published from 1884 to 1913,inclusive. U.S. Geol. Survey Prof. Paper, no.99, pp. 9–1201.

Wiebe, R.A., 197 4. Differentiation in layereddiorite intrusions, Ingonish, Nova Scotia.Jour. Geol., v. 82, pp. 7 31–7 50.

Williams. H., F.J. Turner and C.M. Gilbert, 1982.Petrography; an introduction of the study ofrocks in thin section. 2nd ed. W.H. Freemanand Co., San Francisco, 626 pp.

Win Naing, 2001. Tertiary deformation patternsof the northeastern part of Myanmar:structural and microfabric evidences fromthe Mogok-Momeik area. UnpublishedM.Res. Thesis, Dept. of Geol., University ofYangon 198 pp.

Wright, J.B., 1969. A simple alkalinity ratio andits application to questions of non-orogenicgranite gneiss. Geol. Mag., v. 106, pp. 523–548.

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No.2 August 2003

Rare Gemstone: Painite

Report on a Ruby and Spinel Minein Namya (Northern Burma)

Identification of Spineland Ruby from Namya

Beryllium Treatment (Part B)

EXTRAVCD Inside

ABSTRACT

Editor

Dr. A. Peretti, FGG, FGA, EuroGeolGRS Gemresearch Swisslab AG, P.O.Box 4028, 6002 Lucerne, Switzerland

aperetti@gemresearch.ch

Swiss Editorial Review Board

Prof. Dr. B. Grobety, Institute of Mineralogy and Petrography, University of Fribourg, Fribourg, Switzerland(Mineralogy and Special Methods)

PD. Dr. J. Mullis, Institute of Mineralogy and Petrography, University of Basel, Basel, Switzerland(Fluid inclusions)

Prof. Dr. W. Oberholzer, Institute of Mineralogy and Petrology, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland.Former Curator of the Mineralogical Museum (ETH ZH).

Prof. Dr. K. Ramseyer, Institute for Geological Sciences, University of Berne, Switzerland (CL)

Prof. Dr. D. Gunther, Institute of Chemistry, ETH (SFIT), Zurich, Switzerland (LA-ICP-MS)

Publisher

J.C.C. Printing Co., LTD. Bangkok, Thailand

Distributor

GRS (Thailand) Co., LTD. 388 Mahaesak Rd., Bangkok 10500, Thailand.

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Abstract

The "Second Issue of Contributions to Gemology" focuses on the latest news from the world of gemological discoveries.

New mines producing "pigeon's blood" rubies and vibrant colored spinels have been found in a remote part of Northern Burma (Myanmar) called "Namya". An intriguing GRS expedition to Namya in 2001 is documented in a photo album and VCD movie report.

Gemological research and identification of the new rubies and spinels from Namya include the use of latest technology for chemical analyses (LA-ICP-MS).

Two more of the world's rarest collector gemstones - "Painite" - have been found which resulted in scientific research cooperation.

Part B of the contribution to the understanding of a new treatment for corundum is the research on Beryllium-treated pink sapphires and rubies.

CONTENTS

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What's inside?

Expedition to the Ruby and Spinel Mines of Namya(Northern Burma/Myanmar)Namya Expedition Photo Album

Photo Album of the Namya Ruby and Spinel Mines

Namya Rubies

Table of ED-XRF and LA-ICP-MS Analyses of Namya Rubies

Namya Ruby Rough and Inclusion Photo Album

Spinel from Namya (Burma/Myanmar)

Comparison of Mogok and Namya Spinel

New Light Element Test for Spinel Identification using LA-ICP-MS

Namya Spinel Rough and Inclusion Photo Album

New Findings of Rare Collector Gemstone "Painite"from Mogok (Myanmar)

Beryllium Treatment Part B

Inclusions in Beryllium Treated Corundum and Cathodoluminescence

Beryllium Treatment of Synthetic Pink Sapphires

Beryllium Treatment of Synthetic Rubies

Chemical Identification Charts for Beryllium Treated Corundum

Origin of Color in Beryllium Treated Corundum

Tables of LA-ICP-MS Analyses of Beryllium Treated Synthetic Corundum

Tables of LA-ICP-MS Analyses of Beryllium Treated and Conventional Heated Natural Corundum

Tables of LA-ICP-MS Analyses of Natural and Synthetic Spinel

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01

Expedition to the Ruby and Spinel Mines of Namya (Northern Burma/Myanmar)

Namya 100 km

490 km

Mogok

Mong Hsu

315 km

275 km

The Burmese Ruby Triangle

Expedition to the Namya Mines in Northern Burma

Adolf Peretti(*) and Anong Kanpraphai (**)

* GRS Gemresearch Swisslab LTD, Lucerne, Switzerland** GRS (Thailand) Co., LTD, Bangkok, Thailand

02

Namya Expedition Photo Album

Map of the Central and Northern Part of Burma (Myanmar) showing 3 major mining areas of commercial importance: Mong Hsu, Mogok and Namya. The mines are found in a distance of several hundred kilometers (see inserted "Ruby mine triangle"), and the 3 typical rough stones from these mines are shown: A rough ruby with bluish core (as formed in the marble-mother rock) from Mong Hsu; an over 50 ct rough ruby with well-established crystal growth faces from the Dattaw mine in Mogok; and a 2ct rough ruby with its own characteristic growth features from Namya. Both Mogok and Mong Hsu mines are found in the Shan States of

Eastern Burma, which border Thailand, Laos and China (the so-called "Golden Triangle" region). The Namya mines are situated in the Kachin State in the Northern part of Burma, which borders China in the East, and India in the West. The expedition to the mines was separated into 5 different steps:1.) a flight from Bangkok to Yangoon (Capital of Burma, Myanmar);2.) a flight from Yangoon to Mandalay;3.) a flight from Mandalay to Myitkyina;4.) a cross-country car ride from Myitkyina to Namya, and5.) a messy elephant ride (during the rainy season) to the mining area.

Shwedagon Pagoda, Yangoon (Myanmar) Preparation for expedition to the ruby mines inNorthern Burma: From Myitkyina to Namya

The well-known Shwedagon Pagoda in Yangoon, Burma (Myanmar).

A 4 wheel drive pick-up with high-wheels is an absolute necessity for the drive from Myitkyina to the Namya mining area. The expedition material list was extensive and included a digital camera, camera film (for backup) and video, a portable laboratory (including a microscope), GPS for satellite orientation, various Burmese language dictionaries, packing material for collection of reference samples (and labeling ruby samples), a portable kitchen with gasoline stove, a first aid kit, extensive preventive medicine (including anti Malarial, antibiotic and anti diarrhea drugs) and water cleansing chemicals.

Namya Expedition Photo Album

03

Landscape on the way to Namya

The scenery in Myitkyina (Kachin State). Impressions: Buddhist temples, kiosk with local journals, local housing, and some road infrastructure from WWII. Driving on unpaved country roads from Myitkyina to Namy: the landscape is dominated by rice fields, rivers and farming. Notably absent is any modern agricultural machinery.

Rainy season road conditions (July 2001) on the way to the Namya mine. This main road over a hilly pass connects the central part of Kachin state with the Namya ruby and Pagan Jade mines. Heavy traffic often delays public transportation by days, or renders any passage virtually impossible during heavy rain

Myitkyina

On the way from Myitkyina to Namya (25o 18.42N/ 096o 56.31E)

04

Namya Expedition Photo Album

Road conditions on the way to Namya (25o 36.98N/ 096o 34.94E, 773Ft)

We finally entered the village of Namya after days of delay caused by muddy roads and traffic jams. Hotels and good food were scarce in the village in July 2001, thus food quality needed to be constantly monitored. Basic fresh food, including rice, eggs and corn, was cooked in local kitchens.

Namya village (25o 37.73N/ 096o 33.17E, 525 Ft)

05

Namya Expedition Photo Album

By Elephant to Sabow Mining Camp (near Namya)

We switched transportation to elephants for the daily excursions into the jungle mining areas, making sure to prepare a day bag, including a camera, a change of clothing, a first-aid kit, bags for samples and labeling, gemological equipment (a portable laboratory), camera equipment, malaria and other insect bite prevention (long white trousers and spray), boots for working at the mines, extensive sun protection, sunglasses, and enough food and water for two days (2 liters of water per person per-day). All bags were placed in the baskets on either side of the elephants. A secondary elephant also followed carrying a government guide with stamps and permission from the government to enter the mines and wireless communication. The expedition route was monitored by a satellite positioning system (GPS).

Hiring Elephants at Namya

*Hiring an elephant is a must. Along the way we constantly came across foolhardy adventurers who were either too exhausted to continue, were suffering from the effects of the sun, or couldn't cross 1-2 meter deep rivers. Elephants also keep you away from natural predators such as snakes, ants, bugs, and mosquitoes, as well as any difficult vegetation. The terrain is also covered with dangerous mine shafts and tunnels, which should only be negotiated on elephant back.

06

Photo Album of the Namya Ruby and Spinel Mines

Mining at Sabow Mining Camp (near Namya)

Entering the Sabow mining area (which maintains the characteristics of a gold rush town, except here the hunt is for rubies and spinel). Infrastructure - food, a barber's kiosk, entertainment and gambling activities - was in limited supply. Upon arrival we were dramatically received by local law enforcement personnel, who wrongly assumed we had arrived at the restricted area without permission. We soon discovered we were the first foreigners ever to do so.

Our main purpose at the mine was to investigate the scale of mining activity, to study the occurrence of rubies, collect reference samples, and to film and document the mining activities. This would eventually lead to a guide on the commercial importance of the mine, while providing the lab with valuable reference samples. It became evident that the mining activities were relatively well mechanized with diesel motor driven high pressure hoses and several washing places prevalent. The mining was near surface in secondary sedimentary deposits, composed of fine grained clay soils and marble fragment sands. Mining activities were constantly on the move to new areas for near surface mining, gradually covering an increasing larger area and causing rapid deforestation.

Sabow Mining Camp near Namya (25o 30.74N/ 096o 32.87E, 524 Ft)

07

Photo Album of the Namya Ruby and Spinel Mines

Sabow was also home to a makeshift hut incorporating a temporary restaurant, which was in extremely close proximity to the mine. The location gave us an ideal place to set up our laboratory, including a binocular microscope with fiberoptic illumination run on a battery supply. Through one of our local guides, we organized an inspection of currently and previously produced rubies. We bought the samples with characteristic inclusions, and proceeded to journey by elephant to another mining spot, yet were intercepted by a none-informed armed police patrol that placed us - and our elephants - under short arrest. It became evident that entering such areas without accreditation is near impossible, and of very high risk, as even with official papers we still had to enter into tough negotiation before we were allowed to continue our journey.

Our journey continued with visits to different mines in the area, covering around 5km. At Manow mining camp we discovered a completely different scene. This mine had already been active for several years, it extended over a larger area, and mining was individually organized and on a much more primitive basis than the previous camp. Mining involved primarily digging the rubies directly from under the trees, and washing and dumping places were widely unorganized and spread over a large area. Groups of miners constantly circled our group, badgering us to buy their stones until agents appeared, desperately trying control the situation. The mine was multi-ethnic and they appeared to have greater experience in dealing with foreign buyers.

Manow Mining Camp (25o 37.34N/ 096o 32.51E, 560 Ft)

By Elephant to Manow (near Namya)Checking Gemstones at the Sabow Mining Camp

08

Photo Album of the Namya Ruby and Spinel Mines

Expedition to the ruby and spinel minesof Namya (Burma/Myanmar)

c Copyright G

RS

Gem

research Sw

isslab LTD., S

witzerland

The trip concluded with an enjoyable elephant ride back to the Namya village, where we began preparing for the exhausting journey back to Myitkyina. However, there was a cloud hanging over us - we were all well aware that soon we would have to embark on the much-dreaded journey back to Yangoon, where we would no doubt encounter numerous official road blocks, each with an officer demanding to see and collect a set of official documents from our guide, each around 150 pages deep. This is the price gemologists must pay to be the first to visit a new mining area.

Acquisition of Rough Ruby and Spinel Reference Samples at the Manow Camp (Namya)

Mining at the Manow Mining Camp (near Namya)

Reference:

Peretti A. (2003): Expedition to the new ruby and spinel mine in Burma (Namya). Contributions to Gemology, No. 2, EXTRA VCD Movie

How to play this movie on a computer?

This VCD can be played in a PC. A movie player is automatically started when the VCD is put in the CD-drive, unless the auto play feature is disabled. If it is disabled, double click on VIPLAY.EXE.

The VCD can also be played in VCD/DVD players. DVD quality can be ordered by contacting http://www.gemresearch.ch

Warning: Authentic VCDs are marked with a GRS hologram. No hologram identifies an unauthorized copy.

Appendix:A VCD Movie (see cover) is attached to this publication showing the details of the expedition. Included are details on studied inclusions characteristic of Namya rubies and samples of commercially important ruby and spinel. Please note the user instructions below.

Namya Rubies

09

Fig. B2 This unheated 11ct rough Namya ruby yielded an over 5 ct faceted gemstone

Fig. B1 An 11ct rough Namya Ruby appeared at an auction for a reserve price of over US$100 000.

Fig. B3 This preformed unheated vivid red Namya ruby exceeded 6 cts and was faceted to a magnificent ruby of over 3cts.

Fig. B4 Two examples of unheated vivid red "pigeon's blood" rubies from Namya (Burma/Myanmar) which were on the market in 2003. Courtesy C.H. Lapidaries LTD (Bangkok, Thailand)

Fig. B5 Absorption spectra of Namya ruby characteristic of highly fluorescent rubies of low Fe and high Cr- concentrations, similarly known in Mogok rubies (including fluorescent lines produced by multi-channel spectroscopic measurements) .

Namya Rubiesby Adolf Peretti

GRS Gemresearch Swisslab AG, Lucerne, Switzerland

Every time a new mine appears on the market, a new challenge is presented to gemologists in gem testing laboratories all over the world, with regard to the positive identification of the new material against natural and synthetic counterparts. A review of international auctions on gemstones, such as Christie's and Sotheby's, showed that the auction houses state the country of origin in their catalogues, alongside international recognized laboratory reports (Reviewed at www.gemresearch.ch /auctions). This study presents the first results of the identification of Namya rubies collected by the expedition (Peretti and Kanpraphai, 2003, this issue). A total of 1000 samples were tested, and then stored in the permanent GRS reference collection. From the 1000 samples, approx. 30 gem quality faceted gemstones in the range of 3ct to over 10cts were investigated. They were available for testing as rough, and after cutting as finished faceted rubies (e.g. Figs. B3, B4). Other high valuable rough and faceted rubies were also investigated (An example of a high valuable rough is shown in Fig. B1, also published as lot 513 in the Union of Myanmar Sixteenth Gems & Jade Sale (2003) catalogue of the Myanmar Gems & Jade Auction (in the catalogue, "Namya" is written as "Nant Yah") with a reserve price of over US$100, 000 - final

auction price not known at time of printing). Other samples of high valuable gemstones are shown in the VCD Movie in the Appendix.

Provided in this section is a photo album of inclusions in rubies authentically collected from the mines. The rubies are presently stored in the GRS collection for further research by Scanning Electron Microscopy and Raman spectroscopy. This project, however, is currently in preparation and is not the scope of this article. The purpose of the photo album is to help identification of these materials through microscopy. A

comparison is made between rubies from the classical mining area of Mogok (Myanmar) and rubies from Namya (Myanmar) on the basis of chemical and spectroscopic testing using ED-XRF and LA-ICP-MS and absorption spectroscopy.

Gemmological properties

Color

All different color varieties have been found, ranging from light pink to vivid pink (belonging to the group of natural pink sapphires), to deep red. A set of rubies from the expedition material has been sorted in terms of increasing color and subsequently been cut to sizes ranging from 0.3 to 0.6 ct. Most vivid red colors can be found, including those which can be characterized as "Pigeon's blood" (See Photo Album Fig. 1,2)

A large quantity of rough are available from the colors that are graded as pinkish-red, either belonging to pink sapphires or pinkish-red rubies, depending on subtle differences in the number of red reflections emerging from a faceted stone face-up. Lines of pinkish-red to red rubies, sized 2-3 cts, were assembled in a circle according to size, shape and color (similar to a necklace format) for evaluation purposes (see VCD Movie in Appendix). Sets with such excellent clarity and brilliant color reflections are

rare. Faceted rubies are characterized by clarity and brilliancy. For pinkish-red colors, occasionally purple overtones were present, and a small percentage of the tested materials were deep to dark red.

Commercial highly valuable fine red rough stones exceeding 10 ct were occasionally observed (see VCD Movie in Appendix). Large stones clean to the naked eye with fine color and excellent clarity do occur, but must be considered extremely rare (see VCD-Movie in Appendix). Rare single stones of "pigeon's blood" quality faceted in sizes of approx. 3 ct. do occur (see VCD Movie in Appendix), and should be classified as very rare.

The commercial importance of the Namya ruby mines

In general, the absence of cracks in the Namya rubies, the fluid feathers, the relative lack of inclusions, and the array of fine colors, will see the mine provide a new important source of unheated facetable goods of all color varieties. The rubies are of significant commercial size and value.

10

Tab.B1: ED-XRF and LA-ICP-MS Analyses of Natural Rubies

Origin Pyen Pit Pyen Pit Mogok Mogok Mogok Mogok MogokSample 12624-0.910 12625-1.226 12627-1.150 12613-4.932 12602-0.613 12603-0.632 BU-0.864Color pastel pink pastel pink pastel pink pink pink pink vivid redCut faceted faceted faceted faceted faceted faceted facetedTiO2 0.005 0.008 0.011 0.009 0.071 0.005 0.032V2O5 bd bd 0.009 bd 0.11 0.033 0.197Cr2O3 0.013 0.016 0.005 0.007 0.18 0.122 0.916MnO 0.001 bd bd 0.002 bd bd bdFe2O3 0.437 0.409 0.077 0.065 0.017 0.009 0.016Ga2O3 0.014 0.017 0.014 0.017 0.021 0.013 0.008

Namya Namya Namya NAYA-1.92 NAYA-0.77 NAYA-0.69

purple purple-pink vivid redrough rough rough

0.042 0.029 0.0390.058 0.238 0.560.079 0.408 1.8540.001 bd 0.0060.024 0.025 0.080.013 0.011 0.031

Origin Namya Namya Namya Namya Namya Namya Namya Sample NAYA-0.343 NAYA-0.421 NAYA3-0.252NAYA4-0.0343NAYA5-0.256 NAYA6-0.269 NAYA7-0.182Color colorless pink pink pink pinkish-red vivid red deep redCut faceted faceted faceted faceted faceted faceted facetedTiO2 0.028 0.022 bd 0.015 0.034 0.003 0.006V2O5 0.059 0.013 0.076 0.062 0.115 0.156 0.13Cr2O3 0.039 0.119 0.21 0.329 0.353 1.204 1.561MnO bd bd 0.002 bd bd 0.008 0.012Fe2O3 0.028 0.006 0.026 0.018 0.018 0.017 0.009Ga2O3 0.02 0.004 0.013 0.005 0.024 0.014 bd

Li Be B Na Mg Si K Ca Ti V Cr Mn Fe Co Ni Cu Ga Sn7 9 11 23 25 29 39 42 49 51 53 55 57 59 61 65 69 120

ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppmap09b09 Nr. 9 bd bd bd 8.06 152.0 762 12.1 bd 227.1 179.9 935 bd 224.3 bd bd bd 72.7 bdap09b10 Nr. 9 bd bd bd 0.92 168.0 654 bd bd 217.2 173.1 758 bd 38.7 bd bd bd 72.8 2.15ap09b11 Nr. 9 bd bd bd 5.93 165.0 bd 62.3 bd 220.6 238.1 1348 bd 183.5 bd 8.39 bd 79.2 1.13

average bd bd bd (.97) 162.0 (521) (25) bd 221.6 197.1 1014 bd 148.8 bd bd bd 74.9 (1.40)stdev. - - - 3.67 8.0 329 32.4 - 5.04 35.7 303 - 97.5 - - - 3.8 bd

Sc, As, Rb, Sr, Y, Nb, Mo, Sb, Cs, Ba, La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, Th, U, Bi, Pb, Zr

Normalized to Al = 526604 (Detection limit - See Table)

Elements below detection:

Namyapinkish-red

Ruby

Tab.B1 Chemical analyses of rubies by ED-XRF in wt.-% (by Dr. A. Burkhardt, IFZAA, Switzerland) and LA-ICP-MS analyses (in ppm, on the top) by the Laboratory of Inorganic Chemistry, SFIT, Zurich.

Namya Rubiesby Adolf Peretti

GRS Gemresearch Swisslab AG, Lucerne, Switzerland

Every time a new mine appears on the market, a new challenge is presented to gemologists in gem testing laboratories all over the world, with regard to the positive identification of the new material against natural and synthetic counterparts. A review of international auctions on gemstones, such as Christie's and Sotheby's, showed that the auction houses state the country of origin in their catalogues, alongside international recognized laboratory reports (Reviewed at www.gemresearch.ch /auctions). This study presents the first results of the identification of Namya rubies collected by the expedition (Peretti and Kanpraphai, 2003, this issue). A total of 1000 samples were tested, and then stored in the permanent GRS reference collection. From the 1000 samples, approx. 30 gem quality faceted gemstones in the range of 3ct to over 10cts were investigated. They were available for testing as rough, and after cutting as finished faceted rubies (e.g. Figs. B3, B4). Other high valuable rough and faceted rubies were also investigated (An example of a high valuable rough is shown in Fig. B1, also published as lot 513 in the Union of Myanmar Sixteenth Gems & Jade Sale (2003) catalogue of the Myanmar Gems & Jade Auction (in the catalogue, "Namya" is written as "Nant Yah") with a reserve price of over US$100, 000 - final

auction price not known at time of printing). Other samples of high valuable gemstones are shown in the VCD Movie in the Appendix.

Provided in this section is a photo album of inclusions in rubies authentically collected from the mines. The rubies are presently stored in the GRS collection for further research by Scanning Electron Microscopy and Raman spectroscopy. This project, however, is currently in preparation and is not the scope of this article. The purpose of the photo album is to help identification of these materials through microscopy. A

comparison is made between rubies from the classical mining area of Mogok (Myanmar) and rubies from Namya (Myanmar) on the basis of chemical and spectroscopic testing using ED-XRF and LA-ICP-MS and absorption spectroscopy.

Gemmological properties

Color

All different color varieties have been found, ranging from light pink to vivid pink (belonging to the group of natural pink sapphires), to deep red. A set of rubies from the expedition material has been sorted in terms of increasing color and subsequently been cut to sizes ranging from 0.3 to 0.6 ct. Most vivid red colors can be found, including those which can be characterized as "Pigeon's blood" (See Photo Album Fig. 1,2)

A large quantity of rough are available from the colors that are graded as pinkish-red, either belonging to pink sapphires or pinkish-red rubies, depending on subtle differences in the number of red reflections emerging from a faceted stone face-up. Lines of pinkish-red to red rubies, sized 2-3 cts, were assembled in a circle according to size, shape and color (similar to a necklace format) for evaluation purposes (see VCD Movie in Appendix). Sets with such excellent clarity and brilliant color reflections are

rare. Faceted rubies are characterized by clarity and brilliancy. For pinkish-red colors, occasionally purple overtones were present, and a small percentage of the tested materials were deep to dark red.

Commercial highly valuable fine red rough stones exceeding 10 ct were occasionally observed (see VCD Movie in Appendix). Large stones clean to the naked eye with fine color and excellent clarity do occur, but must be considered extremely rare (see VCD-Movie in Appendix). Rare single stones of "pigeon's blood" quality faceted in sizes of approx. 3 ct. do occur (see VCD Movie in Appendix), and should be classified as very rare.

The commercial importance of the Namya ruby mines

In general, the absence of cracks in the Namya rubies, the fluid feathers, the relative lack of inclusions, and the array of fine colors, will see the mine provide a new important source of unheated facetable goods of all color varieties. The rubies are of significant commercial size and value.

3 4 5

6 7 8

9 10 11

12

13 14

2

1

Before cutting:Rough rubies collected by the author at the Namya mines

After cutting:Faceted Namya rubies of pink to vivid red colors (below 1ct in size).

Rough crystals

The typical rough shape of Namya rubies is shown in Figs. 3, 4, 5, 6, 9, 11 and 24. A distorted triangle shape with irregular curved markings on the surface is clearly noticeable. A majority of the rubies tested were not water-worn and also did not exhibit typical pyramidal, rhombohedral, prismatic or pinacoid growth faces. Their formation was obviously related to interstitial growth in metamorphic rocks, such as marbles. Such triangular shapes are often observed in highly metamorphosed rocks.

Inclusion description

3,4,5,6,9,11 = Rough Namya rubies.

7,8,10 = Typical surface markings on rough Namya rubies.

12 = Oriented rutile needle inclusions.

13 = "silk dust" and crystal inclusions in central part of the crystals.

Solid inclusions

- Concentrations of transparent inclusions in the center of the gemstones (Fig. 14).- Irregular shaped crystal inclusions with rounded edges in different colors (Fig. 14, 21, 22, 26, 27, 29 and 36).- Isometric round crystals with one prominent crystal face (Fig. 23).

Fluid feathers

Secondary healing feathers are remarkably rare (Fig. 18).Irregularly shaped large negative crystals (Fig. 19).

LocationCoordinates

25o 39.74N/ 096o 32.87E Namya Mine (Sabow camp)Fig. 3 - 23,37 - 38

25o 37.34N/ 096o 32.51E Namya Mine (Manow camp)Fig. 24 - 26, 28 - 29,32 - 35

Inclusion description

15, 17 = Different arrangements of rutile in nests along internal growth features.

18 = Fluid feathers with isolated negative tubes.

19, 20, 21, 22, 23, 25, 26 = Inclusions of various shapes and arrangements.

24 Namya rough with rutile enrichments in central portions of the rubies.

11

Namya Ruby Rough and Inclusion Photo Album

1715 16

24

25

26

21

2223

18

1920

Before cutting:Rough rubies collected by the author at the Namya mines

After cutting:Faceted Namya rubies of pink to vivid red colors (below 1ct in size).

Rough crystals

The typical rough shape of Namya rubies is shown in Figs. 3, 4, 5, 6, 9, 11 and 24. A distorted triangle shape with irregular curved markings on the surface is clearly noticeable. A majority of the rubies tested were not water-worn and also did not exhibit typical pyramidal, rhombohedral, prismatic or pinacoid growth faces. Their formation was obviously related to interstitial growth in metamorphic rocks, such as marbles. Such triangular shapes are often observed in highly metamorphosed rocks.

Inclusion description

3,4,5,6,9,11 = Rough Namya rubies.

7,8,10 = Typical surface markings on rough Namya rubies.

12 = Oriented rutile needle inclusions.

13 = "silk dust" and crystal inclusions in central part of the crystals.

Solid inclusions

- Concentrations of transparent inclusions in the center of the gemstones (Fig. 14).- Irregular shaped crystal inclusions with rounded edges in different colors (Fig. 14, 21, 22, 26, 27, 29 and 36).- Isometric round crystals with one prominent crystal face (Fig. 23).

Fluid feathers

Secondary healing feathers are remarkably rare (Fig. 18).Irregularly shaped large negative crystals (Fig. 19).

LocationCoordinates

25o 39.74N/ 096o 32.87E Namya Mine (Sabow camp)Fig. 3 - 23,37 - 38

25o 37.34N/ 096o 32.51E Namya Mine (Manow camp)Fig. 24 - 26, 28 - 29,32 - 35

Inclusion description

15, 17 = Different arrangements of rutile in nests along internal growth features.

18 = Fluid feathers with isolated negative tubes.

19, 20, 21, 22, 23, 25, 26 = Inclusions of various shapes and arrangements.

24 Namya rough with rutile enrichments in central portions of the rubies.

12

Namya Ruby Rough and Inclusion Photo Album

13

Namya Ruby Rough and Inclusion Photo Album

27

28

29

30

31

32

33 34 35

37 38

36

Color zoning

Blue color zoning is largely absent. Swirled growth zones are found instead (Fig. 31 and Fig. 32).

Rutile needles

The most prominent type of inclusions are rutile inclusions of various arrangements:

- Short needles in dense networks (Fig. 34, 35, 38)

- Long loose needles of rutile (Fig. 12).

- Short needles concentrated along growth zones (Fig. 17).

- Oriented rutile needles emerging from concentrations of nests of short rutile needles (Fig. 15).

- Rutile needles may be dense and oriented causing a star effect (Fig. 37).

Inclusion Descriptions

27, 28, 29, 36 = solid inclusions of various shape, isolated, or clustered .

30 = Rarely observed non-rutile needles and twinning.

31, 32 = Swirled crystal growth and complicated irregular internal growth patterns.

33, 34, 35, 38 = oriented short rutile needles in arrangements producing star effect.

14

Namya Ruby Rough and Inclusion Photo Album

Gemological Properties

UV fluorescence: Very strong red in long UV, strong red in short UV. Refractive indexes, densities were found in the normal range for corundum.

Chemical testing

ED-XRF analyses were performed on 10 rubies from Namya, and 7 samples from Mogok and Pyen Pit. Seven of the 10 Namya samples correspond to a master set ranging from near colorless, pink, and pinkish-red, to red, vivid red and deep red. Preliminary LA-ICP-MS analyses were performed on a typical pinkish-red Namya Ruby. For the details of the methods, see Peretti and Günther (2002).

Results

As shown in Tab. B1, the rubies from Namya are characterized by Cr-concentrations up to 1.5 wt-% (deep red overtones). The typical vivid red rubies ("pigeon's blood" color) have Cr-concentrations of approx. 1 wt-%.

Iron (Fe) -concentrations are below approx. 0.03 wt-%, titanium are also relatively low, vanadium concentrations show a high variability (up to relatively high values of over 0.2 wt.-%) and Ga - concentrations are relatively high (with some variations). Lighter elements, such as Lithium (Li), Beryllium (Be), and Boron (B) are below the detection limit. The relatively high V, Ga, Cr and low Fe values are typically found in rubies from Mogok and other rubies originating from marble deposits (see Muhlmeister et al. (1998).

Literature:

Muhlmeister S., Fritsch E., Shigley J.E, Devouard B., Laurs B.M. (1998): Separating Natural and Synthetic Rubies on the Basis of Trace-Element Chemistry. Gems & Gemology, Vol. 34, No.2, pp.80-101.

Photo Album Picture No.23 enlarged:Solid inclusions in Namya rubies

Photo Album Picture No.35 enlarged:Rutile needles in Namya rubies

Photo Album Picture No.36 enlarged:Typical solid inclusions in Namya rubies

Spinel from Namya (Burma/Myanmar)

15

LW-UV Fluorescence of pinkish-red spinels from Mogok and Namya

Pink to red spinel from Namya

Fig. C2 Absorption spectra of a series of pinkish-red to vivid red spinels from Namya.

Fig. C3 Two samples of the spinels with high fluorescence intensity are shown. Left side Mogok and right side Namya with subtle differences due to the variation in chemistry (see Tab. C1).

Fig. C1 A series of commercially important faceted spinels are shown in the category of 2-3 carats in size. The first row shows 2 spinel from Mogok, the second and third row shows 4 spinels from Namya.

Spinel from NamyaBy Adolf Peretti (*) and Detlef Günther (**)

(*) GRS Gemresearch Swisslab AG, Lucerne, Switzerland(**) Institute of Chemistry, Swiss Federal Institute of Technology, Zurich, Switzerland.

During gemological testing at the Namya mines in 2001, spinel was discovered mixed in with the ruby lots. Further samples of these Namya spinel materials occurred later-on in the market in Bangkok at the end of 2002 and early 2003. The spinel soon gained market attention due to its unusually vibrant color (Fig. 1) (see VCD Movie in Appendix). Larger sizes over 10 cts were studied later on in the market as valuable specimens could not be acquired at the mining spots. In this report, we present chemical analyses for these spinels by LA-ICP-MS which were carried out in the Laboratory on Inorganic Chemistry of the Swiss Federal Institute of Technology in Zurich (Switzerland). In addition, absorption spectroscopy of different spinel from different origins were acquired. The focus of this analyses was on different spinel from Mogok and Namya, as well as two types of synthetic spinels.

For additional identification criteria, a photo album of spinel inclusions is attached.

Materials and Methods

Approx. 150 spinels were tested, the majority from the expedition to Namya, including a series of gem quality faceted Namya spinel from 1 to over 10cts originating from the market in Bangkok .

A representative set of samples was selected for testing by LA-ICP-MS (Tab. C1). From the synthetic material, approx 50 chemical analyses are presently available and are currently being expanded for further statistics. For details on methods see Guillong and Günther (2001) and Peretti and Günther (2002).

Comparison of Namya and Mogok Spinel

The color of the Burmese spinels (Mogok and Namya) stretches across the entire spectrum as shown in Fig. C4. Three different color groups can be distinguished:

Group A: Purple to green.

Color description: purple, violet, blue and bluish-green colors with variable color saturation from pastel to vivid, strong variation in tone, creating blackish overtones.

Absorption spectra: bands and lines in the range of

630-650 nm, 550 to 565nm, 460nm, 387nm and 373nm. The absorption edge is typically found between 300nm to 350nm. Depending on the color (Fig. C4), the absorption spectra is variable with respect to the intensity of the 458 and 650nm bands, the 386nm and 374nm absorption bands and the 556nm band (Fig. C4). In greenish-colored samples, the 374nm line dominates the 386nm band. The UV absorption edge continuously shifts from 295nm (in purple colors) to 350nm in more greenish colored spinels (Fig. C4). The chemical composition of this group is characterized by trace elements Cr, Fe and Zn concentrations (Fig. C5 and Tab. C1).

Group B: Brown or orange-red colors

Color description: Red or pink color is modified by orange and/or brown.

Absorption spectra: Major bands at 550nm can be correlated with orange color components. The absorption minimum and edge in the UV is variable and can be correlated with the color. High Vanadium (V) concentrations were found in addition to Cr (Fig. C4, and C5).

Group C: Pink to vivid red Colors

Absorption spectra: Major absorption bands centered at 538nm and 391 nm as well as lines in the red region of the spectrum (Fig. C4). The absorption edge in the UV is found at 295 nm. The Namya spinel studied in this report belongs to this group as well as the Mogok spinels. These spinels have the highest UV transparency window (absorption band minimum at 342nm), the lowest total absorption edge towards the UV, and show fluorescent lines in the red region of the spectrum. Chemical composition is characterized by dominantly chromium and low iron concentrations. Additional light elements present were Lithium (Li) and Beryllium (Be), which were of special gemmological interest.

Other Gemological Data

The refractive index is lowest in pastel purple to green and orange to brown colors. It increases with color intensity and tone. The variation is, however, relatively small, covering a range between 1.715 to 1.719. The Namya and Mogok spinels of pinkish-red to vivid red colors are highest ranging from an RI of 1.719 to 1.720. Density of the spinels varies between 3.61 to 3.69.

UV fluorescence is found to be strongest in group C (Fig. C3). The highest level of fluorescence in this group is found in the Namya spinelsUV 254: Strong orangy-redUV 365: Very strong orangy-red.

16

Comparison of Mogok and Namya Spinel

orange

vivid orangy-red

brown-orange

Brown to orange-red spinel from Burma

deep red

vivid red

red

pinkish-red

pink

Pink to deep red spinel from Burma

blue

violet

purple

blackish bluish-green

bluish-green

Purple to green spinel from Burma

Spinel from NamyaBy Adolf Peretti (*) and Detlef Günther (**)

(*) GRS Gemresearch Swisslab AG, Lucerne, Switzerland(**) Institute of Chemistry, Swiss Federal Institute of Technology, Zurich, Switzerland.

During gemological testing at the Namya mines in 2001, spinel was discovered mixed in with the ruby lots. Further samples of these Namya spinel materials occurred later-on in the market in Bangkok at the end of 2002 and early 2003. The spinel soon gained market attention due to its unusually vibrant color (Fig. 1) (see VCD Movie in Appendix). Larger sizes over 10 cts were studied later on in the market as valuable specimens could not be acquired at the mining spots. In this report, we present chemical analyses for these spinels by LA-ICP-MS which were carried out in the Laboratory on Inorganic Chemistry of the Swiss Federal Institute of Technology in Zurich (Switzerland). In addition, absorption spectroscopy of different spinel from different origins were acquired. The focus of this analyses was on different spinel from Mogok and Namya, as well as two types of synthetic spinels.

For additional identification criteria, a photo album of spinel inclusions is attached.

Materials and Methods

Approx. 150 spinels were tested, the majority from the expedition to Namya, including a series of gem quality faceted Namya spinel from 1 to over 10cts originating from the market in Bangkok .

A representative set of samples was selected for testing by LA-ICP-MS (Tab. C1). From the synthetic material, approx 50 chemical analyses are presently available and are currently being expanded for further statistics. For details on methods see Guillong and Günther (2001) and Peretti and Günther (2002).

Comparison of Namya and Mogok Spinel

The color of the Burmese spinels (Mogok and Namya) stretches across the entire spectrum as shown in Fig. C4. Three different color groups can be distinguished:

Group A: Purple to green.

Color description: purple, violet, blue and bluish-green colors with variable color saturation from pastel to vivid, strong variation in tone, creating blackish overtones.

Absorption spectra: bands and lines in the range of

630-650 nm, 550 to 565nm, 460nm, 387nm and 373nm. The absorption edge is typically found between 300nm to 350nm. Depending on the color (Fig. C4), the absorption spectra is variable with respect to the intensity of the 458 and 650nm bands, the 386nm and 374nm absorption bands and the 556nm band (Fig. C4). In greenish-colored samples, the 374nm line dominates the 386nm band. The UV absorption edge continuously shifts from 295nm (in purple colors) to 350nm in more greenish colored spinels (Fig. C4). The chemical composition of this group is characterized by trace elements Cr, Fe and Zn concentrations (Fig. C5 and Tab. C1).

Group B: Brown or orange-red colors

Color description: Red or pink color is modified by orange and/or brown.

Absorption spectra: Major bands at 550nm can be correlated with orange color components. The absorption minimum and edge in the UV is variable and can be correlated with the color. High Vanadium (V) concentrations were found in addition to Cr (Fig. C4, and C5).

Group C: Pink to vivid red Colors

Absorption spectra: Major absorption bands centered at 538nm and 391 nm as well as lines in the red region of the spectrum (Fig. C4). The absorption edge in the UV is found at 295 nm. The Namya spinel studied in this report belongs to this group as well as the Mogok spinels. These spinels have the highest UV transparency window (absorption band minimum at 342nm), the lowest total absorption edge towards the UV, and show fluorescent lines in the red region of the spectrum. Chemical composition is characterized by dominantly chromium and low iron concentrations. Additional light elements present were Lithium (Li) and Beryllium (Be), which were of special gemmological interest.

Other Gemological Data

The refractive index is lowest in pastel purple to green and orange to brown colors. It increases with color intensity and tone. The variation is, however, relatively small, covering a range between 1.715 to 1.719. The Namya and Mogok spinels of pinkish-red to vivid red colors are highest ranging from an RI of 1.719 to 1.720. Density of the spinels varies between 3.61 to 3.69.

UV fluorescence is found to be strongest in group C (Fig. C3). The highest level of fluorescence in this group is found in the Namya spinelsUV 254: Strong orangy-redUV 365: Very strong orangy-red.

Fig. C4 Different spinels from Namya and Mogok almost covering the entire color spectrum are shown (size 2-4 cts). The absorption curves of the different spinel colors were measured by UV-VIS-NIR spectroscopy (including fluorescent lines produced by multi-channel spectroscopic measurements). The origin of color is interpreted in terms of Fe2+, Fe3+, V3+, Cr3+ (Schmetzer et al. (1989)). For chemical compositions see Tab. C1 and Fig. C5

V3+>Cr3+

Cr3+ V3+

Cr3+, V3+, Fe3+, Fe2+

17

New Light Element Test for Spinel Identification using LA-ICP-MS Analyses

Light Element Test for Identification of Spinel by LA-ICP-MS The chemical composition of the spinels is presented in Tab. C1 and graphically in Fig. C5. Different groups of natural and synthetic spinels are shown. From the different elements present in the spinels, our research has been focused on the presence of concentrations of light elements which have not yet been considered in the gemological literature. In natural spinel from different origins, trace elements of Lithium (Li) and Beryllium (Be) were determined in pink to vivid red colors such as spinels from Namya and other natural and synthetic counterparts. Si, Ti, V, Cr, Zn and Ga concentrations are highly variable and were detected in many spinel and in synthetic spinel from Russia with the exception of Zn. However, in more than 50 spot analyses of synthetic spinels none of the elements Be and Li were detected above the limits of detection (Tab. C1). Therefore, we propose that these elements can be used as a new separation test between synthetic and natural counterparts, which can be seen as an additional test using Zn and Ti - concentrations as proposed by Mühlmeister, et al (1993). References: Mühlmeister S., Koivula J.I., Kammerling R.C., Smith, C.P., Fritsch E. and Shigley J.E. (1993): Flux-grown Red and Blue Spinels from Russia, Gems&Gemology, Summer, VolXXIV. Schmetzer K., Haxel C. and Amthauer G. (1989): Color of natural spinels, gahnospinels and gahnites. Neues Jahrbuch Miner. Abh., 160, 2, pp. 159-180.

Field of Natural Spinel

Synthetic Spinel

Fig. C5 Diagrams showing the different compositions for spinel. Chemical differences in Cr, V, and Fe can be correlated with the different color types (see Schmetzer et al. (1989)) but no correlation was found with respect to Cobalt (Co), see Tab. C1. Light element concentrations (Li and Be) provide a new test for identification of natural spinel against synthetic counterparts. Non-averaged values of Tab. C1 used (ppmw transformed into ppma) Legend on the right.

18

Namya Spinel Rough and Inclusion Photo Album

1 2 3

4 5 6

7 8 9

Rough Crystal 1 Octahedral shaped rough spinel as identified and collected at the Namya mines (below 0.5 ct). 2,3 Larger sized Namya Spinel crystals (2-3 ct). Inclusion description Negative crystals of octagonal shape with (7), or without, associated tension cracks (4). Round transparent solid inclusions (5) are rarely seen along with elongated crystal inclusions (6). Geometrically arranged particles or needles (8,9) with whitish clouds and streamers are found. Particle concentrations are found along junctions and steps following the c r y s t a l l o g r a p h i c a l l y determined directions in spinel. 1-3 Namya rough crystals. Perfect octahedral crystal (1), and irregular rounded shapes (3). 8,9 Oriented whitish reflecting particles. 4,7 Octahedral negative crystals with tension cracks (4), or without, and with secondary feathers (4) 5 Solid rounded inclusions (5), and elongated (6) inclusions.

10

19

New Findings of Rare Collector Gemstone "Painite" from Mogok (Myanmar)

MANDALAY

VIEW POINT

MONGLONG

MOMEIN

KinSinkwa

InnPye

Bawlongyi

KaukpokKyauk Saung

Bawpadan

KotanTan Ta Yar

YEBUHa-pha lai

Myaw Pyet

PyenpitHo-wine-showChaung Gyi

Inn Chauk

Dattaw

Padantyer

Thapanbin

Leu

KauksataungMyeme

Pyaung-Pyin

BawlongaleKabaing

KYAUKPHAR

Thurin Taung KYAUKPYATTHAT

MOGOK

Kyauk Kyan

Inn Gaung

Lin Yaung Chi Ho Mine

Ohn Bin

Shwe Pyi Aye

Ohn Gaing

KYATPYIN

Pingukaung

Bawmar

Gwebin

Wetlu

Tidutsho

PANMA Lue Hta

Wun-Bear Inn

Myintada

KTHAE

Miles0 1

Kilometers

KEY

RubySapphirePaved road (tar)Dirt roadRiver stream

New Findings of Painiteby Adolf Peretti (*)

(*) GRS Gemresearch Swisslab AG,Lucerne, Switzerland

Painite was first mentioned by Claringbull-Gordon et al. (1957) after being found in the Mogok Stone Tract and named after Arthur Charles Davy Pain - a well known mineralogist and gemologist of the Mogok area. Painite is so rare that worldwide available specimens are individually numbered. To the best knowledge of the author, crystals No.1 and No.2 are currently deposited in the collection of the Natural History Museum London (a small sample slice from No. 1 is at Caltec University), Crystal, No.3 is in the

Gemological Institute of America collection, while Crystal No. 4 is now in two pieces - both privately owned. Two more samples have recently been discovered by A. Peretti: A 2.54 ct faceted Painite, which was identified through testing in Bangkok (Thailand) and labeled as Painite No.5, Painite No. 6a, a large rough fragment of 54 cts (dimensions: 18.7x14.3x10.8 mm) - indirectly discovered from the miner's production, not directly from the mining spot - during an expedition in May 2002 to Mogok close to the private, government licensed Ohn-Gaing mine, Sagaing, Mogok district, Myanmar (Fig.D5). A small fragment (0.15 ct) of this rough Painite was obtained from 6a, and labeled Painite No. 6b. (Fig.D6), whereas the mother piece remained with its finder in Mogok. A research project on Painite No. 5 and 6b revealed that the crystal structure of Painite as presented by Moore and Araki (1976) needed to be revised. For details on the gemologial and special testing see Armbruster et al. (2003).

Gemmological dataOptical character: Uniaxial, negative, e=1.789 and o=1.815, Pleochroism: very strong brownish-red to orange-yellow, Density: 4.00 +/- 0.01

A scientific study on Painite 5 and 6b will be published elsewhere and is submitted to:Armbruster, Th. (1), Dobelin, N. (1), Peretti A. (2), Günther D. (3), Reusser E. (4) and Grobety, B (5) (2003): The crystal structure of Painite CaZrB[Al9O18], revisited, American Mineralogist, submitted.

(1) Laboratorium für chemische und mineralogische Kristallographie, University of Bern, Berne, Switzerland(2) GRS Gemresearch Swisslab LTD., Hirschmattstr. 6, CH-6003 Luzern, Switzerland(3) Laboratory of Inorganic Chemistry - Elemental and Trace Analysis, Swiss Federal Institute of Technology, Zürich, Switzerland(4) Institute of Mineralogy and Petrography, Swiss Federal Institute of Technology, Zürich, Switzerland(5) Department of Geosciences, University of Fribourg, Fribourg, Switzerland

Further references:Caringbull G.F., Hey M.H., Payne C.J. (1957): Painite, a new mineral from Mogok, Burma. Mineralogical Magazine 31, 420-5.Harlow, G.E. (2000) The Mogok Stone Tract, Myanmar: Minerals with complex parageneses. In: Proceedings of the 4th conference

on "Minerals and Museums", Melbourne, Australia, 75.Iyer, L.A.N. (1953).The geology and gemstones of the Mogok Stone Tract, Burma. Memoirs of the Geological Survey of India, 82, pp. 100.Moore, P.B. and Araki, T. (1976) Painite, CaZrB[Al9O18]: Its crystal structure and relation to jeremejevite, B5[[ ]3Al6(OH)3O15], and fluoborite, B3[Mg9(F,OH)9O9]. American Mineralogist, 61, 88-94.Shigley, J. E., Kampf, A. R., and Rossman, G. R. (1986) New data on Painite. Mineralogical Magazine, 50, 267-270.Webster, R. (1994) Gems, their sources, descriptions and identification, p.1027, Butterworths. Sevenoaks, UK.

Fig. D1 Map of the Mogok and the Ohn-Gaing/ Sagaing mining area (outlined in the Map). Ruby and sapphire mines are indicated. The picture shows the mining area North of Mogok (Myanmar) as seen from the view point (Ohn-Gaing in the foreground and Mogok in the background). Picture taken by the author during the study of the Ohn-Gaing mine and the study of Painite No.6a in Mogok in the year 2002

20

Painite No.5 and No.6 from Mogok (Myanmar)

Painite No. 5

Painite No. 6a

Painite No.6b

Painite was first mentioned by Claringbull-Gordon et al. (1957) after being found in the Mogok Stone Tract and named after Arthur Charles Davy Pain - a well known mineralogist and gemologist of the Mogok area. Painite is so rare that worldwide available specimens are individually numbered. To the best knowledge of the author, crystals No.1 and No.2 are currently deposited in the collection of the Natural History Museum London (a small sample slice from No. 1 is at Caltec University), Crystal, No.3 is in the

Gemological Institute of America collection, while Crystal No. 4 is now in two pieces - both privately owned. Two more samples have recently been discovered by A. Peretti: A 2.54 ct faceted Painite, which was identified through testing in Bangkok (Thailand) and labeled as Painite No.5, Painite No. 6a, a large rough fragment of 54 cts (dimensions: 18.7x14.3x10.8 mm) - indirectly discovered from the miner's production, not directly from the mining spot - during an expedition in May 2002 to Mogok close to the private, government licensed Ohn-Gaing mine, Sagaing, Mogok district, Myanmar (Fig.D5). A small fragment (0.15 ct) of this rough Painite was obtained from 6a, and labeled Painite No. 6b. (Fig.D6), whereas the mother piece remained with its finder in Mogok. A research project on Painite No. 5 and 6b revealed that the crystal structure of Painite as presented by Moore and Araki (1976) needed to be revised. For details on the gemologial and special testing see Armbruster et al. (2003).

Gemmological dataOptical character: Uniaxial, negative, e=1.789 and o=1.815, Pleochroism: very strong brownish-red to orange-yellow, Density: 4.00 +/- 0.01

A scientific study on Painite 5 and 6b will be published elsewhere and is submitted to:Armbruster, Th. (1), Dobelin, N. (1), Peretti A. (2), Günther D. (3), Reusser E. (4) and Grobety, B (5) (2003): The crystal structure of Painite CaZrB[Al9O18], revisited, American Mineralogist, submitted.

(1) Laboratorium für chemische und mineralogische Kristallographie, University of Bern, Berne, Switzerland(2) GRS Gemresearch Swisslab LTD., Hirschmattstr. 6, CH-6003 Luzern, Switzerland(3) Laboratory of Inorganic Chemistry - Elemental and Trace Analysis, Swiss Federal Institute of Technology, Zürich, Switzerland(4) Institute of Mineralogy and Petrography, Swiss Federal Institute of Technology, Zürich, Switzerland(5) Department of Geosciences, University of Fribourg, Fribourg, Switzerland

Further references:Caringbull G.F., Hey M.H., Payne C.J. (1957): Painite, a new mineral from Mogok, Burma. Mineralogical Magazine 31, 420-5.Harlow, G.E. (2000) The Mogok Stone Tract, Myanmar: Minerals with complex parageneses. In: Proceedings of the 4th conference

on "Minerals and Museums", Melbourne, Australia, 75.Iyer, L.A.N. (1953).The geology and gemstones of the Mogok Stone Tract, Burma. Memoirs of the Geological Survey of India, 82, pp. 100.Moore, P.B. and Araki, T. (1976) Painite, CaZrB[Al9O18]: Its crystal structure and relation to jeremejevite, B5[[ ]3Al6(OH)3O15], and fluoborite, B3[Mg9(F,OH)9O9]. American Mineralogist, 61, 88-94.Shigley, J. E., Kampf, A. R., and Rossman, G. R. (1986) New data on Painite. Mineralogical Magazine, 50, 267-270.Webster, R. (1994) Gems, their sources, descriptions and identification, p.1027, Butterworths. Sevenoaks, UK.

Fig.D2 UV short wave fluorescence ofPainite No. 5

Fig.D3 Painite is dichroitic and uniaxial as can be seen using a polariscope (parallel and crossed polarizers) and a projection sphere.

Fig.D4 A faceted Painite of 2.54 ct which was identified in 2001 during testing in Bangkok (labeled as Painite No.5). Painite No.5 was used for detailed chemical analyses (see Armbruster et al., submitted)GRS collection.

Fig.D6 Picture of the Painite No. 6b (Painite "No. 6b"). A 0.15 ct reference sample from Painite No. 6b was used for detailed chemical and structural analyses which guided to a revision of the crystal structure of Painite (Armbruster et.al (2003), submitted).GRS collection.

Fig.D5 Picture of the 54 ct Painite (labeled Painite No.6a) photographed with crystallographic faces present and in a direction where ruby overgrowth has been found. Studied in Mogok. This piece remains in the country of origin.

21

Beryllium Treatment Part B

The Beryllium Treatment of Fancy Sapphires with a New Heat-treatment Technique (Part B).

by Adolf Peretti (*), Detlef Günther(**) and Anne-Liese Graber (**)

(*) GRS Gemresearch Swisslab LTD, Switzerland(**) Institute of Chemistry, Swiss Federal Institute of Technology, Zurich, Switzerland.

IntroductionThe new heat treatment of corundum is a technique that involves extremely high temperatures, oxidation conditions and diffusion of Beryllium into the corundum's surface (Peretti and Günther, 2002, Hanni and Pettke, 2002, Emmet et al., 2003). Part A of this study (Peretti and Günther, 2002) concentrated on the interaction of Beryllium with the parent chemistry of natural fancy sapphires and other gemological aspects. It was noticed that only very minor concentrations of Beryllium were present in the treated sapphires. This data was confirmed later by Hanni and Pettke (2002). As mentioned earlier, the understanding of the direct contribution of Beryllium to the color of these treated natural sapphires needed additional research (see Peretti and Günther, Contributions to Gemology 2002, vol. 1, page 39). As pointed out in a recently published article on this new treatment (Emmett et al., 2003), the understanding of the new treatment needs more precise data on various trace elements that are not yet available in world literature. In part B of the characterization of the new treatment, we provide extended chemical analyses of natural and synthetic materials, including sapphires, and test the models proposed by Emmett et al. (2003).

Materials and MethodsThe studied materials include synthetic materials from various manufacturers. Colorless synthetic sapphires

were from watch glass producers in Switzerland, synthetic pink, orange and yellow Verneuil sapphires were obtained from Djevahirdijan SA (Monthey, Switzerland), and synthetic hydrothermal rubies were from Novosibirk (Russia). Further natural samples are listed in Tab. 6 of Peretti and Günther (2002) and additional samples of rubies and blue sapphires were collected in the market in Bangkok (see Tab. E2 and E3).

Samples were prepared with rough, as well as faceted materials, and cut in half. One piece was kept untreated for reference ("reference samples"), and one half piece sent for commercial Beryllium treatment with the new method to a specialized commercial factory in Chantaburi (Thailand). The heating experiments were reportedly carried out at very high temperature near the melting point of corundum under high oxidation conditions, including Beryllium diffusion. Details of the method remain the intellectual property of the factory. After the Be-treated samples came back from Chantaburi, untreated and treated samples were compared and color changes investigated (E1, E9 and E13). The treated samples were cut in half for further chemical and spectroscopic analyses (e.g. Fig. E5). Further samples of natural blue sapphires, fancy sapphires and rubies have also been Beryllium-treated by the same factory as well as by another factory in Bangkok. For comparison, additional natural orange sapphires were investigated which were heated by conventional methods (Tab. E3). The samples were measured for chemical composition by LA-ICP-MS (see Guillong and Günther (2001)), for origin of color by UV-VIS-NIR-Spectroscopy, and for structural/chemical analyses by Cathodoluminescence .

Cathodoluminescence Analyses (CL)The analyses were carried out by Prof. K. Ramseyer at the University of Berne, Institute of Geological Sciences, Berne (Switzerland). The same methods were applied as described by Ramsayer K. (2002).

Table E1: Synthetic Rubies and synthetic Colored Sapphires before and after Beryllium treatment. Dominant trace elements are in bold. Note: Only Cr-rich samples were reacting to the Beryllium treatment. Be = Beryllium, Na = Sodium, Mg = Magnesium, Si = Silica, K= Potassium, Ti = Titanium, Cr = Chromium, Fe = Iron,Ni = Nickel.

ColorSample Color Doped by Sample Color Doped by Change

GRS 1 (from GRS 2)

GRS 13 (from GRS 12)GRS 5 (from GRS 4)

GRS 9(from GRS 8)

GRS 16(from GRS 15)

GRS 11(from GRS 10)

GRS 18(from GRS 17)

GRS 20(from GRS 19)

GRS 26(from GRS 25)

GRS 28(from GRS 27)

GRS 30(from GRS 29)

(*) color change from pink to pinkish-orange induced by irradiation treatment

After Be -Treatment

Synt

hetic

Cor

undu

mSy

nthe

ticR

uby

Before Be - Treatment

Be, Na, K, (Si, Fe, Ti) (x)GRS 12 light pink Mg, Ca, Cr, Si (Fe, Na, Ti) (x)

GRS 2 colorless Na, Mg, K, (Si, Fe, Ti, Cu) light brown

GRS 4 pink Na, Cr (Mg, Si)

GRS 8 vivid pink Na, Cr (Fe)

GRS 15 vivid pink Mg, Si, Ti, Cr, Fe

GRS 10 light orange (*) K, Cr, Si

GRS 17 orange Ti, Mg, Si, Cr

GRS 19 yellow Mg, Si, Ni

GRS 25 purplish pinkish red Na, Ti, Cr, Fe, Ni

GRS 27 red Mg,Ti, Si, Cr, Fe, Ni

GRS 29 dark red Na, Mg, Si, K, Ti, Cr, Fe, Ni

orangy-pink**

orange

orange

vivid orange

orange

orange

yellow

orange

orange-red

dark orangy-red

Be, Na, Mg, Ca, Cr

Be, Cr (Mg, Si)

Be, Cr, Zr

Be, Ti, Si, Cr, Fe, Ni

xBe, Cr (Si) x

Be, Na, Mg, Si, K, Ti, Cr x

Be, Ti, Mg, Si, Cr

Be, Mg, Si, Ni

xBe, Mg, Si, Ti, Cr, Fe, Ni xBe, Mg, Si, Ti, Cr, Fe, Ni x

(x)

22

Inclusions in Beryllium Treated Corundum and Cathodoluminescence

Fig. E1 Pink sapphires and brownish pink sapphires were subjected to the new Beryllium-treatment.Note: Color change from pink to orangy-pink due to the new treatment.

Fig. E2 Cathodoluminescence microphotograph of a Beryllium-treated natural orangy-pink sapphire (by Prof. K. Ramseyer). The Beryllium treatment produces a zoning of chemical and/or structural defect contrasts showing an outer rim, inner rim and an inner core. Methods see Peretti and Günther (2002). Craters from LA-ICP-MS (80 micrometers in diameter).

Fig. E3 Cathodoluminescence microphotograph of a Beryllium-treated natural orangy-pink sapphire (by Prof. K. Ramseyer). The picture shows the chemical and/or structural defect contrasts of the natural growth in the centre of a faceted gemstone (diagonal growth lines). The Beryllium treatment resets this contrast in a rim perpendicular to the natural growth zones.

Fig. E4 Microphotograph of inclusions in Beryllium-treated natural sapphires. Melted inclusions with feathers characteristic for high temperature treatment. More on http://www.gemresearch.ch/inclusions. Magnification in the microscope 60x-80x. Fibre optic illumination. Pictures by John de Jaegher. Copyright GRS.

23

Beryllium Treatment of Synthetic Pink Sapphires

Fig. E5 Polarized UV-VIS-NIR absorption spectra of synthetic pink sapphires (reference sample) and Beryllium-treated synthetic orange sapphires. Inserted picture shows the untreated reference (pink) and Beryllium-treated samples (orange) (including fluorescent lines produced by multi-channel spectroscopic measurements). Spectra are recorded in the same crystallographic direction. There is a shift in absorption due to a different sampling volume. Increase in absorption towards the blue region of the spectrum is interpreted as Beryllium (Be)-Chromium (Cr)-color centers superimposed to Cr3+ (Emmett et al., 2003).

Results

The results of the CL investigation on two samples are shown in Fig. E2 and E3. More confirmation found that the trace element distribution is completely rearranged by the new treatment, particularly in the zones containing Beryllium. This was evident by extinction of chemical and structural patterns in the treated sapphires (Fig. E3). As shown in Fig. E2, an inner core was detected. This inner core is formed outside the zones enriched in Beryllium.

LA-ICP-MS chemical analyses

The LA-ICP-MS measurements were carried out by the Laboratory of Inorganic Chemistry at the Swiss Federal Institute of Technology, Honggerberg Zurich). The details on the methods, data calculation, normalization procedures and error margins can be found in Peretti and Günther (2002) or on the Internet underwww.gemresearch.ch/journal/E-IM.htm An additional set of more than 40 samples has been analyzed including various categories of synthetic, unheated, conventional heated, as well as Beryllium treated samples (see Tab. E1, E2 and E3). Due to detailed series of spots in various profiles on the samples, a total of approx. 1000 chemical data points were collected. Each spot was analyzed for 40 elements. The data shown in Tab. E2 and E3.

Results:Beryllium-Treated Synthetic Pink and other Synthetic Colored Sapphires

The results of Beryllium-Treated Synthetic Sapphires are shown in Fig. E6 to E25 and in Tab. E1, E2 and E47a. The group of synthetic Pink Sapphires can be subdivided into two different categories depending on the reaction to the Beryllium treatment. One group of

synthetic sapphires did not color-change after Beryllium treatment. The non color-changing category includes synthetic orange and yellow sapphires that contain various elements including Na, Mg, Ni, Sn and Zr (see Tab. E1 and E2). The second group of color-changing samples include synthetic pink sapphires that became more orange with Beryllium-treatment (Tab. E1 and E2). These samples were dominated by Cr traces. Another sample which was doped by Cr and Mg was only partially color-changed. All the Beryllium-treated samples contain traces of Beryllium, with enriched concentrations at the rim (e.g. Fig. E12). Increasing Cr and Beryllium concentrations are correlated with increasing intensity in orange color. Trace element concentrations of many of the elements were heterogeneous (Fig. E8, E12, E16, E22, E19, E25): This is interpreted as chemical zoning in the stones, which is not uncommon in the Verneuil materials.

Be-Treated Hydrothermal Synthetic Rubies (TAIRUS, Novosibirsk)

After Beryllium-treatment, synthetic rubies changed to more orange or less dark colors (Tab. E1). The results of the chemical analyses are shown in Fig. E26 to E45). This color change can be correlated with increasing Be-concentrations, independently of the concentrations of Fe (Fig. E47b). A series of other trace elements are present in these synthetic hydrothermal rubies, including Mg, Ti, Si, Cr, Mn, Fe, Ni and minor Sn. They did not prevent the treatment success (Fig. E29. E33, E37, E40 and E46).

Be-Treated Synthetic Colorless Sapphire

White corundum (without Cr-concentrations) slightly color-changed to light brown after the Beryllium treatment. Additional traces of Beryllium were detected in the samples (Tab. E1)

24

Beryllium Treatment of Synthetic Corundum

0

100

200

300

400

500

600

700

0 10 20 30 40 50 60

Pit N°

Cr (

ppm

)

0

10

20

30

40

50

60

Mg,

Ti,

Fe (p

pm)

CrMgTiFe

0

100

200

300

400

500

600

0 2 4 6 8 10 12

Pit N°

Cr (

ppm

)

0

2

4

6

8

10

12

14

16

18

20

Be,

Ti (

ppm

)

CrBeTi

Mg, Ti, Cr and Fe concentrations in GRS 8 Be, Ti and Cr concentrations in GRS 9

Before Beryllium Treatment After Beryllium Treatment

Fig. E8 The chemical variations in a profile across a synthetic pink sapphire (GRS 8) are shown (in ppm). Complete data see Tab. E2

Fig. E9 Polarized UV-VIS-NIR absorption spectra of synthetic pink sapphires (GRS 8) parallel and perpendicular to the c-axis. Absorption characteristics (including fluorescent lines produced by multi-channel spectroscopic measurements) due to Cr3+.

Fig. E13 Polarized UV-VIS-NIR absorption spectra of Beryllium-treated synthetic orange sapphires parallel and perpendicular to the c-axis. Absorption characteristics (including fluorescent lines produced by multi-channel spectroscopic measurements) due to Cr3+ and Cr-Beryllium color centers. The untreated reference sample is GRS 8.

Fig. E12 The chemical variations in a profile across a Beryllium-treated synthetic orange sapphire (GRS 9) are shown (in ppm). Untreated reference sample is GRS 8). For complete data, see Tab. E2.

Fig. E6 Microphotograph of GRS 8 (Synthetic light pink sapphire)Fig. E7 Drawing of GRS 8. Analysis was performedwith 61 spots along the broken line (crater diameter :80 µm)

Fig. E10 Microphotograph of GRS 9 (synthetic orange sapphire)Fig. E11 Drawing of GRS 9. Analysis was performedwith 12 spots along the broken line (crater diameter :80 µm)

25

Beryllium Treatment of Synthetic Corundum

0

2000

4000

6000

8000

10000

12000

14000

0 5 10 15 20 25 30 35 40

Pit N°

Mg,

Si (

ppm

)

0

20

40

60

80

100

120

140

160C

r, Ti

, Zr (

ppm

)

MgSiTiCrZr

0

200

400

600

800

1000

1200

1400

1600

1800

0 5 10 15 20 25 30 35

Pit N°

Cr,

Si (p

pm)

0

10

20

30

40

50

60

Be,

Ti (

ppm

)

CrSiBeTi

0

500

1000

1500

2000

2500

3000

0 10 20 30 40 50 60 70 80 90

Pit N°

Cr,S

i,Ti (

ppm

)

0

10

20

30

40

50

60

70

80

90

Mg,

Ga,

Sn

(ppm

) TiCrSiMgGaSn

0

200

400

600

800

1000

1200

1400

1600

1800

0 5 10 15 20 25 30 35

Pit N°

Cr,

Mo,

Si (

ppm

)

0

5

10

15

20

25

30

Be,

Ti (

ppm

) CrMoSiBeTi

Mg, Ti, Cr, Si and Zr concentrations in GRS 12 Be, Ti, Si and Cr concentrations in GRS 13

Mg, Ti, Si, Cr, Ga and Zn concentrations in GRS 17 Be, Ti, Si, Cr and Mo concentrations in GRS 18

Before Beryllium Treatment After Beryllium Treatment

Fig. E16 The chemical variations in a profile across a synthetic pink sapphire are shown (in ppm). Complete data see Tab. E2.

Fig. E22 The chemical variations in a profile across a Beryllium-treated synthetic orange-pink sapphire (GRS 13) are shown (in ppm). The untreated corresponding sample is GRS 12. complete data see Tab. E2.

Fig. E19 The chemical variations in a profile across a synthetic deep orange sapphire (GRS 17) are shown (in ppm). Complete data see Tab. E2

Fig. E25 The chemical variations in a profile across a Beryllium-treated synthetic deep orange sapphire (GRS 18) (in ppm). Corresponding untreated sample is GRS 18. For complete data, see Tab. E2

Fig. E14 Microphotograph of GRS 12 (synthetic pink sapphire) Fig. E 15 Drawing of GRS 12. Analysis was performed with 40 spots along the broken line (crater diameter: 80 µm)

Fig. E20 Microphotograph of GRS 13 (synthetic pink sapphire) Fig. E21 Drawing of GRS 13. Analysis was performed with 33 spots along the broken line (crater diameter: 80 µm)

Fig. E17 Microphotograph of GRS 17 (synthetic deep orange sapphire)Fig. E18 Drawing of GRS 17. Analysis was performed with 80 spots along the broken line (crater diameter: 80 µm)

Fig. E23 Microphotograph of GRS 18 (synthetic deep orange sapphire)Fig. E24 Drawing of GRS 18. Analysis was performed with 35 spots along the broken line (crater diameter: 80 µm)

26

Beryllium Treatment of Synthetic and Natural Corundum

Fig. E26 Polarized UV-VIS-NIR absorption spectra of synthetic hydrothermal rubies (reference sample) and Beryllium-treated synthetic deep orange sapphires (including fluorescent lines produced by multi-channel spectroscopic measurements). Inserted picture shows the untreated reference (red) and Beryllium-treated samples (orange). Spectra are recorded in the same crystallographic direction. A shift in absorption is due to a different sampling volume. Increase in absorption towards the blue region of the spectrum is interpreted as color centers involving Beryllium and other trace elements superimposed to Cr3+-absorptions (see Emmett et al., 2003).

Be-Treated Natural Rubies and Sapphires

The measured samples of natural rubies and sapphires are listed in Tab E3 and shown in Fig. E47c and Fig. E48. Reviewing the data of Tab. E3, it is evident that concentrations of Silica (Si) were found in all samples. Comparing the values with those presented by Emmett et al. (2003), it was found that much higher Si concentrations were measured in our investigation. They are approx 10 to 20 times higher than the values published by Emmett et al. (2003) on similar samples. The distribution of Si in the samples, however, was found to be heterogeneous, e.g. areas that had Si below the detection limit were found in a distance of 50 to 100 microns next to areas of significant Si concentrations. Only minor concentrations of Sn, Ni, Mn, Ca and Li were occasionally also detected in addition to the elements Mg, Ti, V, Cr, and Fe, both in samples before and after Beryllium-Treatment (Tab. E3). Beryllium was found in all Beryllium-treated samples. The concentration of Beryllium increased towards the rim as previously reported (Peretti and Günther, 2002).

Chemical Identification Charts for Beryllium-Treated Corundum

For further interpretation of the data, we selected 660 spot analyses from our data bank, which included various samples unheated, enhanced and Beryllium-treated sapphires. A further selection was made for the group of Beryllium-treated samples, from which we did not take into account the data that were obtained from measurements at or near the surface. In such a way, we eliminated contamination resulting from the treatment experiments which were found at the surface of the samples (high Be, Mg, Cr, Fe, Zr). The data were transformed from ppmw (w = weight) to

ppma (a = atomic) and are graphically presented in Fig. E48 and E49.

UV-VIS-NIR Spectroscopic Origin of Color Analyses

UV-VIS-NIR Spectra was measured with a 1024 diode array multi-channel spectrometer (for further details see Peretti and Günther (2002)). Polarized spectra were measured on synthetic corundum, both for untreated and for Beryllium treated samples. The results are shown in Figs. E5, E9, E13, E26, E30 and E34. In comparison to the untreated reference samples, it was found that the absorption curves increased towards the blue region of the spectrum. These broad bands in the UV region of the spectrum can be interpreted as proof of the presence of color centers involving Beryllium and other elements (see Emmett et al., 2003).

Identification by Inclusions

In Part A of our study we elaborated on the melting of zircon and transformation into Zr-Oxide and glass using Scanning Electron Microscope analyses. This melting of minerals other than corundum has been related to the high temperature used for Beryllium treatment (Peretti and Gunther, 2002). This findings have been recently confirmed by the studies of Emmett et al. (2003) on studies on zircons included in sapphires, where they found that the Zr-Oxides can be identified as badelleyite. This mineral melting phenomena has become a help in identifying this new treatment (see Fig. E4). Further valid identification criteria in orange to orange-red sapphires from Songea (Tanzania) turned out to be the blue halos around mineral inclusions. For further information on inclusions we have provided extensive inclusion website under www.gemresearch.ch/inclusions.

27

Beryllium Treatment of Synthetic Rubies

1

10

100

1000

10000

100000

0 2 4 6 8 10 12 14 16 18

Pit N°

ppm

MgTiCrMnFeNiSi

0

1000

2000

3000

4000

5000

6000

7000

8000

0 2 4 6 8 10 12 14 16

Pit N°

Cr,

Fe, S

i (pp

m)

0

20

40

60

80

100

120

140

160

Be,

Mg,

Ti,

V, N

i (pp

m) Cr

FeSiBeMgTiVNi

Chemical variations in GRS 25 Chemical variations in GRS 26

Fig. E31 Microphotograph of GRS 26 (syntheticorange-red sapphire)Fig. E32 Drawing of GRS 26. Analysis was performedwith 16 spots along the broken line(crater diameter: 80 µm)

Fig. E27 Microphotograph of GRS 25 (synthetic ruby)Fig. E28 Drawing of GRS 25. Analysis was performedwith 18 spots along the broken line(Crater diameter: 80 µm

Before Beryllium Treatment After Beryllium Treatment

Fig. E29 The chemical variations in a profile across a synthetic hydrothermal ruby are shown (in ppm). Sample No. GRS 25. complete data see Tab. E2.

Fig. E30 Polarized UV-VIS-NIR absorption spectra of a synthetic hydrothermal ruby in a direction parallel and perpendicular to the c-axis. Absorption characteristics (inclusive fluorescence lines) due to Cr3+(including fluorescent lines produced by multi-channel spectroscopic measurements).

Fig. E34 Polarized UV-VIS-NIR absorption spectra of a Beryllium-treated synthetic orange-red sapphire (GRS 26) in a direction parallel and perpendicular to the c-axis. Absorption characteristics (including fluorescent lines produced by multi-channel spectroscopic measurements) due to Cr3+ and color centers involving Beryllium and other trace elements (General increase in absorption in the blue region of the spectrum). Untreated reference sample is GRS 25.

Fig. E33 The chemical variations in a profile across a Beryllium-treated synthetic orange-red sapphire are shown (in ppm). Sample No. GRS 26 (untreated reference sample is GRS 25). Silica concentrations out of scale.

28

Beryllium Treatment of Synthetic Rubies

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

0 2 4 6 8 10 12 14

Pit N°

Be,

Cr,

Fe, S

i (pp

m)

0

50

100

150

200

250

300

350

Mg,

Ti,

Ni,

Sn (p

pm) Be

CrFeSnSiMgTiNi

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

0 5 10 15 20 25

Pit N°

Cr,

Fe, S

i (pp

m)

0

50

100

150

200

250

300

350

400

450

Mg,

Ti,

Ni (

ppm

) CrFeSiMgTiNi

0

500

1000

1500

2000

2500

3000

0 5 10 15 20

Pit N°

Cr,

Fe, S

i (pp

m)

0

20

40

60

80

100

120

140

B, M

g, T

i, M

n, N

i (pp

m) Cr

FeSiBMgTiMnNi

0

500

1000

1500

2000

2500

0 2 4 6 8 10 12 14 16 18 20

Pit N°

Cr,

Fe, S

i (pp

m)

0

20

40

60

80

100

120

140

Be,

Mg,

Ti,

Ni,

Nb

(ppm

) CrFeSiBeMgTiNiNb

Chemical variations in GRS 27 Chemical variations in GRS 28

Chemical variations in GRS 29 Chemical variations in GRS 30

Before Beryllium Treatment After Beryllium Treatment

Fig. E37 The chemical variations in a profile across a synthetic hydrothermal ruby (GRS 27) are shown (in ppm). Complete data see Tab. E2.

Fig. E43 The chemical variations in a profile across a Beryllium-treated synthetic orange sapphire (GRS 28) are shown (in ppm). Untreated reference sample is GRS 27. complete data see Tab. E2.

Fig. E40 The chemical variations in a profile across a synthetic hydrothermal ruby (GRS 29) are shown (in ppm). Complete data see Tab. E2.

Fig. E46 The chemical variations in a profile across a Beryllium-treated synthetic orange sapphire (GRS 30) are shown (in ppm). Untreated reference sample is GRS 29. complete data see Tab. E2.

Fig. E35 Microphotograph of GRS 27 (synthetic ruby)Fig. E36 Drawing of GRS 27. Analysis was performed with 16 spots along the broken line(crater diameter: 80 µm)

Fig. E41 Microphotograph of GRS 28 (synthetic orange sapphire, Beryllium-treated sample GRS 27)Fig. E42 Drawing of GRS 28. Analysis was performedalong the two broken lines (crater diameter: 80 µm) Side 1: 23 pits; Side 2: 15 pits

Fig. E38 Microphotograph of GRS 29 (synthetic ruby)Fig. E39 Drawing of GRS 29. Analysis was performed with 21 spots along the broken line(crater diameter: 80 µm)

Fig. E44 Microphotograph of GRS 30 (synthetic orange sapphire, Beryllium-treated sample GRS 29)Fig. E45 Drawing of GRS 30. Analysis was performed with 20 spots along the broken line (crater diameter: 80 µm)

29

Chemical Identification Charts for Beryllium Treated Corundum

Be+Mg Cr

Ti/Fe

14

14

17

16

1 8

8

12 4

11

5

9

Be/Mg Cr*10

Fe*2

13

10

11

9

12

15

Be*5 Cr

Fe

2526

24

Be*20 Cr

Fe

23

2221

20

19

18

Legend 1. Natural Padparadscha (N) 2. Natural Violet Sapphire (N) 3. Natural Purple Sapphire (N) 4. Natural Purple to Violet Sapphire (N) 5. Natural Yellow Sapphire (E) 6. Natural Orange Sapphire (E) 7. Natural Padparadscha (E) 8. Natural Pink Sapphire (E) 9. Natural Colorless Sapphire (Be-treated)10. Natural White Sapphire (Be-treated)11. Natural Yellow Sapphire (Be-treated)12. Natural Orange Sapphire (Be-treated)13. Natural Padparadscha Pinkish-orange (Be-treated)14. Natural Padparadscha (Be-treated)15. Natural Padparadscha (Orangy-pink) (Be-treated)16. Natural Orangy-red Sapphire (Be-treated)17. Natural Sapphire (Be-treated)18. Synthetic hydrothermal Ruby GRS 2919. Synthetic hydrothermal Ruby GRS 2720. Synthetic hydrothermal Ruby GRS 2521. Synthetic hydrothermal Ruby (Be-treated) GRS 2822. Synthetic hydrothermal Ruby (Be-treated) GRS 2623. Synthetic hydrothermal Ruby (Be-treated) GRS 3024. Light cream Colorless Synthetic Sapphire (Be-treated)25. Synthetic Pink Sapphire26. Synthetic Orangy-Pink Sapphire (Be-treated)

Discussion

The new treatment is characterized by the formation of an additional yellow to orange color in Corundum. Chemical and spectroscopic measurements show that the color change can be explained by color centers involving various trace elements including Beryllium (Peretti and Günther (2002), Emmett et al. (2003) and references therein). From detailed LA-ICP-MS chemical analyses, it is evident that a large variety of trace elements are present in the Beryllium treated samples (Fig. E12, E22, E25, E33, E43 and E46). As shown by our experiments with synthetic pink sapphires, Cr and Be alone, at the absence of other trace elements, are sufficient for the formation of orange color centers. From the Beryllium treatment of synthetic materials, it is concluded that corundum without Ti and Cr is not changing the color. Other trace element combinations without the presence of Ti, Mg and Be can also form yellow to orange coloration (e.g. Ni see Tab. E1). Synthetic materials, lacking V but with Cr, Ti, Mg, Fe did color change after treatment with Beryllium. This indicates that V does not have to be present for a color

change. In more chemically complex natural corundum, increasing relatively lower Ti-concentrations in the presence of other trace elements (such as Beryllium) are favorable for the formation of the orange color. Special attention, however, needs to be paid to the additional presence of detectable concentrations of Si in the treated samples. A model for the explanation of the formation of orange color centers was proposed by Emmett et al. (2003) based on the (Ti+Si/Mg+Be)-ratio. As shown by our investigation (Fig. E48a and Fig.E48b), a better correlation is found using the Ti/(Mg+Be)-ratio, without taking into account the Si concentrations. The orange color is formed by the new treatment in samples with Ti/(Mg+Be)<1 (Fig. E48b). From the distribution of Si in our samples, it seems that Si is hetrogeneously distributed in the Be-treated corundum and may not take part in the reaction with Beryllium. For other trace elements that can theoretically be important to the origin of color in corundum, we found that the concentrations of Co, Cu, Zr, Ba and Pb were present at, or below, the detection limits. Therefore, their role in the treatment is limited as well as unlikely (Tab. E3). Other areas of additional research are necessary to understand the complex re-crystallization process that occurs in connection with this new treatment (see Fig. E2 and E3). Furthermore, it seems to us that modern multi-element cluster analyses (see Moon A.R. and Philips M.R. (1994) are unavoidable in understanding the new treatment.

Literature

Emmett J.L., Scarratt K., McClure S.F, Moses Th., Douthit T.R., Hughes R., Novak S., Shigley J.E., Wang W., Bordelon O. and Kane B. (2003): Beryllium Diffusion of Ruby and Sapphire, Gems&Gemology, Vol. XXXIX, Summer Issue, p. 84-135 (see further references therein).

Guillong M. and Günther D. (2001): Quasi 'non-destrutive' laser ablation-inductively coupled plasma-mass spectrometry fingerprinting of sapphires. Sepctrochmica Acta, Part B, 56, p. 1219-1231.

Hanni H. A. and Pettke T. (2002): Eine neue Diffusionsbehandlung liefert orangefarbene und gelbe Saphire. Zeitschrift der Deutschen Gemmologischen Gesellschaft, Vol. 51, No. 3, pp. 137-152.

Moon A.R. and Philips M.R. (1994): Defect clustering and color in Fe, Ti:a-Al2O3. Journal of the American Ceramic Society, Vol. 60., No.1, pp. 86-357.

Peretti A. and Günther D. (2002): The Color Enhancement of Fancy Sapphires with a New Heat-treatment Technique (Part A). Contributions to Gemology, No. 1, May, p. 1-48. Online-version at: www.gemresearch.ch/journal/E-IM.htm

Ramseyer K. (2002): Cathodoluminescence and EDS Characterization of Corundum Crystal 1, Internal Report No. 0202, University of Berne, Institute of Geological Sciences, Switzerland.

Fig. E47 Chemical comparison of Beryllium-treated and untreated samples (see Legend below). Data from Peretti and Günther (2002), Tab. E2 and E3 (non-averaged complete data set used, see text).Fig. E47a Beryllium treatment produces orange in synthetic pink sapphires caused by an increase in Beryllium (Be) in presence of Chromium (Cr). Fig. E47b Beryllium treatment of synthetic rubies shifts the color to orange, due to an increase in Beryllium in presence of Cr, independent of Iron (Fe)-concentrations.Fig. E47c Beryllium treatment of natural fancy sapphires produces orange with increasing (Mg+Be)-concentration at variable Ti/Fe-ratios and variable Cr-concentrations (Mg = Magnesium, Ti = Titanium)Fig. E47d Padparadscha color is produced at variable Be/Mg-concentrations with increasing concentrations of Cr

Fig. E47a Fig. E47b

Fig. E47c Fig. E47d

30

Origin of Color in Beryllium Treated Corundum

(Si + Ti) / (Be + Mg) < 1

(Si + Ti) / (Be + Mg) > 1

Si +

Ti

Be + Mg

Ti / (Be + Mg) > 1

Ti / (Be + Mg) < 1

Ti

Be + Mg

Discussion

The new treatment is characterized by the formation of an additional yellow to orange color in Corundum. Chemical and spectroscopic measurements show that the color change can be explained by color centers involving various trace elements including Beryllium (Peretti and Günther (2002), Emmett et al. (2003) and references therein). From detailed LA-ICP-MS chemical analyses, it is evident that a large variety of trace elements are present in the Beryllium treated samples (Fig. E12, E22, E25, E33, E43 and E46). As shown by our experiments with synthetic pink sapphires, Cr and Be alone, at the absence of other trace elements, are sufficient for the formation of orange color centers. From the Beryllium treatment of synthetic materials, it is concluded that corundum without Ti and Cr is not changing the color. Other trace element combinations without the presence of Ti, Mg and Be can also form yellow to orange coloration (e.g. Ni see Tab. E1). Synthetic materials, lacking V but with Cr, Ti, Mg, Fe did color change after treatment with Beryllium. This indicates that V does not have to be present for a color

change. In more chemically complex natural corundum, increasing relatively lower Ti-concentrations in the presence of other trace elements (such as Beryllium) are favorable for the formation of the orange color. Special attention, however, needs to be paid to the additional presence of detectable concentrations of Si in the treated samples. A model for the explanation of the formation of orange color centers was proposed by Emmett et al. (2003) based on the (Ti+Si/Mg+Be)-ratio. As shown by our investigation (Fig. E48a and Fig.E48b), a better correlation is found using the Ti/(Mg+Be)-ratio, without taking into account the Si concentrations. The orange color is formed by the new treatment in samples with Ti/(Mg+Be)<1 (Fig. E48b). From the distribution of Si in our samples, it seems that Si is hetrogeneously distributed in the Be-treated corundum and may not take part in the reaction with Beryllium. For other trace elements that can theoretically be important to the origin of color in corundum, we found that the concentrations of Co, Cu, Zr, Ba and Pb were present at, or below, the detection limits. Therefore, their role in the treatment is limited as well as unlikely (Tab. E3). Other areas of additional research are necessary to understand the complex re-crystallization process that occurs in connection with this new treatment (see Fig. E2 and E3). Furthermore, it seems to us that modern multi-element cluster analyses (see Moon A.R. and Philips M.R. (1994) are unavoidable in understanding the new treatment.

Literature

Emmett J.L., Scarratt K., McClure S.F, Moses Th., Douthit T.R., Hughes R., Novak S., Shigley J.E., Wang W., Bordelon O. and Kane B. (2003): Beryllium Diffusion of Ruby and Sapphire, Gems&Gemology, Vol. XXXIX, Summer Issue, p. 84-135 (see further references therein).

Guillong M. and Günther D. (2001): Quasi 'non-destrutive' laser ablation-inductively coupled plasma-mass spectrometry fingerprinting of sapphires. Sepctrochmica Acta, Part B, 56, p. 1219-1231.

Hanni H. A. and Pettke T. (2002): Eine neue Diffusionsbehandlung liefert orangefarbene und gelbe Saphire. Zeitschrift der Deutschen Gemmologischen Gesellschaft, Vol. 51, No. 3, pp. 137-152.

Moon A.R. and Philips M.R. (1994): Defect clustering and color in Fe, Ti:a-Al2O3. Journal of the American Ceramic Society, Vol. 60., No.1, pp. 86-357.

Peretti A. and Günther D. (2002): The Color Enhancement of Fancy Sapphires with a New Heat-treatment Technique (Part A). Contributions to Gemology, No. 1, May, p. 1-48. Online-version at: www.gemresearch.ch/journal/E-IM.htm

Ramseyer K. (2002): Cathodoluminescence and EDS Characterization of Corundum Crystal 1, Internal Report No. 0202, University of Berne, Institute of Geological Sciences, Switzerland.

Fig. E48 Chemical composition of Si, Ti, Be and Mg in natural corundum heat-treated with conventional methods, and with Beryllium treatment. The additional orange color is formed in the field of Ti/(Be + Mg) <1 (Fig. E48b and Legend) and not in the field (Ti + Si)/(Be + Mg) <1. See Emmett et al. (2003) for further discussion on Si in corundum. Symbols, see Legend below.

Fig. E48a

Fig. E48b

LegendOrange Sapphire, MadagascarConventional heatingOrange Sapphire, MadagascarConventional heatingPadparadscha, MadagascarConventional heatingSlightly orangy-pink SapphireMadagascar, New TreatmentPadparadscha, MadagascarNew TreatmentPadparadscha, MadagascarNew Treatment (zoned)Padparadscha, MadagascarNew Treatment (zoned)Ruby, vivid red, MadagascarNew TreatmentNatural Sapphire, blueConventional heatingNatural Sapphire, dark blueConventional heatingNatural Sapphire, dark blueConventional heatingNatural Sapphire, vivid blueNew TreatmentNatural Sapphire, deep blueNew Treatment

GRS 34

12916

12916 S2

Rot 10.69

GRS 35 S1

GRS 35 S2

Rosa 3.59

GRS 33

12132

12344 S1

5.019ct S1

12133

12134

Tab. E2 (continued) LA-ICP-MS Analyses (in ppm)of Beryllium Treated Synthetic and Natural Corundum

31

LiB

eB

Na

Mg

SiK

Ca

TiV

Cr

Mn

FeC

oN

iC

uG

aY

ZrN

bM

oSn

Pb7

911

2325

2939

4249

5153

5557

5961

6569

8990

9395

120208

ppmppm

ppmppm

ppmppm

ppmppm

ppmppm

ppmppm

ppmppm

ppmppm

ppmppm

ppmppm

ppmppm

ppmG

RS 25

min.

bdbd

bdbd

bd6.1

bd65.3

bd5664

bd1152

bdbd

bdbd

bdbd

bd0.93

0.10Synthetic R

ubym

ax.0.39

7.5121

40.4986

30.1474

1271.4

233536.3

19510.35

1931.7

0.460.11

0.950.51

3.30.88

redA

verage(0.39)

bd(6.7)

(15.6)(17.4)

(628)14.2

(253)101

(0.67)11782

(3.2)1642

(0.20)(107)

(1.2)(0.41)

(0.08)(0.30)

(0.23)bd

1.80.50

GR

S 26m

in.-

bd-

bd2.2

bdbd

-47.9

0.304615

bd1031

bdbd

bdbd

0.091.1

bdSynthetic R

ubym

ax.-

35.0-

4.513.5

5384.2

-109

1.47587

4.61892

0.26142

0.420.27

0.502.5

0.16red B

e-treatedProfileG

RS 27

min.

-bd

bd6.0

bdbd

bd81.5

bd5998

bd1477

bd131

bdbd

bdbd

bdbd

bdSynthetic R

ubym

ax.-

5.616.5

71.4717

14.5494

2290.70

172493.3

34290.30

3963.5

0.680.16

0.800.53

7.318.4

dark redA

veragebd

-(5.5)

(9.8)18.2

(525)(9.3)

(354)138

(0.55)12559

(2.3)2497

(0.25)204

(1.6)(0.51)

(0.11)(0.42)

(0.31)bd

(3.0)(1.4)

GR

S 28m

in.bd

bdbd

bd5.3

bdbd

-86.0

bd7087

1740bd

112bd

bdbd

bd1.4

bdSynthetic R

ubym

ax.0.64

35.69.4

5.2273

6088.3

-183

0.8318300

32920.25

4740.62

0.271.0

0.417.3

0.41dark red B

e-treatedProfileG

RS 29

min.

--

bd2.4

17.9406

3.1bd

34.7bd

1161bd

1508bd

bdbd

bdbd

bd2.4

1.1bd

Synthetic Ruby

max.

--

14.055.6

1061216

55.5224

62.02.7

25658.4

21771.6

1321.9

0.610.35

0.1912.4

3.11.1

pinkish-redA

verage-

-(10.3)

22.470.0

54421.7

(172)45.8

(1.3)2036

(5.9)1773

(1.0)(91.5)

(1.3)(0.45)

(0.20)(0.09)

5.4bd

1.9(0.45)

GR

S 30m

in.11.9

bd-

18.7bd

bd-

37.0bd

1147bd

1393bd

47.8bd

bdbd

bd2.0

bd1.2

bdSynthetic R

ubym

ax.61.2

14.1-

86.0686

7.4-

55.33.4

229818.3

20511.6

1195.9

0.760.31

0.1511.1

1.72.9

0.15pinkish-redB

e-treated ProfileG

RS 35

min.

bd40.1

bd-

32.39.2

217-

5207bd

63.1bd

-1.2

bdN

atural orange Sapphire m

ax.6.1

59.1622

-45.6

10.9308

-5659

0.9571.5

0.14-

1.80.22

heated (no Be treatm

ent) Surface analysisG

RS 35.2

min.

bd35.6

bd-

-32.0

8.8256

bd5635

-64.3

bdbd

bdN

atural orange Sapphirem

ax.5.8

57.4491

--

50.311.3

3123.3

6697-

75.60.08

1.80.15

heated (no Be treatm

ent)Surface analysisG

RS 35.3

min.

bd35.6

bd-

-32.0

8.8256

bd5635

-64.3

bdbd

bdN

atural orange Sapphirem

ax.5.8

57.4491

--

50.311.3

3123.3

6697-

75.60.08

1.80.15

heated (no Be treatm

ent)Surface analysisG

RS 21

min.

-bd

bdbd

bdbd

bd-

72.523.6

bd201

--

bdbd

bdbd

bdbd

Natural blue Sapphire

max.

-3.7

5.423.9

3.51290

18.9-

28146.6

14.5635

--

28.40.60

1.40.04

2.10.18

Be-Treated

ProfileG

RS 23

min.

bdbd

bdbd

bdbd

bd70.4

24.5bd

-510

bdbd

0.95-

-bd

bdbd

Natural blue Sapphire

max.

11.27.1

1153.2

27137.6

8137128

45.414.8

-910

5.81.3

2.2-

-1.6

2.50.26

Be-Treated

ProfileG

RS 24

min.

bd32.6

bdbd

6.2bd

bdbd

80.916.9

bdbd

396bd

bdbd

3.73.3

bdbd

bdbd

Natural blue Sapphire

max.

0.3851.0

6.57.5

51.95608

15.9800

15829.4

24.32.1

7910.32

35.13.8

19.15.9

0.160.95

3.60.71

Be-Treated

Surface analysis0.35

2.33.5

2.32.1

3343.7

1244.8

0.3710

1.617

0.2228

0.860.24

0.080.12

0.721.3

0.1

11.8bd

4.9(0.08)

(0.42)(1.5)

(0.36)568

(0.16)(17.1)

(1.2)103

22.3(14.6)

(1.8)22.3

(701)(7.1)

(331)(0.38)

41.4(4.7)

(2.6)

(1.2)(1.7)

(0.22)1.4

-bd

-712

(2.2)bd

(0.91)93.1

35.9(11.0)

-(2.0)

(760)(5.9)

(8137)bd

(6.55)(6.4)

(20.8)

bd(1.5)

(0.15)(0.44)

bd(0.58)

(0.04)401

--

(9.5)137

33.3(9.2)

bd(2.3)

(620)(13.3)

--

(2.1)(4.3)

(11.2)

bd(1.4)

(0.11)70.0

bdbd

(0.04)6191

bd-

b d39.6

10.0279

(3.3)47.7

(375)-

-bd

bd(5.3)

bd

bd(1.4)

(0.11)70.0

bdbd

(0.04)6191

bd-

bd39.6

10.0279

(3.3)A

veragebd

bd(5.3)

bd47.7

(375)-

-

-bd

1.5(0.14)

(0.95)66.7

bd(0.07)

-5429

bdbd

-38.8

9.9280

bd48.4

(370)bd

bdA

veragebd

(5.9)

(0.67)2.0

(0.10)(0.46)

(0.20)(0.11)

5.61669

(0.93)76.7

(3.3)44.6

(1.6)1878

(6.5)53.7

(475)(4.0)

-bd

32.0(10.3)

-

bd2.5

(0.15)(0.39)

(0.12)(0.47)

(0.25)2322

(0.17)243

bd134

(0.61)14174

bd20.3

(503)(4.7)

-(0.38)

(17.95)(6.8)

( 3.5)

bd1.7

(0.11)(0.32)

bd(0.19)

0.241477

(0.20)(93.7)

bd80.9

0.706461

(2.2)7.4

(397)(2.4)

--

(22.96)-

(3.8)

LOD

Be (ppm

)

Pit N

°S

ample N

°

Average

Average

Average

Average

Average

Average

Average

Tab. E2 (continued) LA-ICP-MS Analyses (in ppm)of Beryllium Treated Synthetic Corundum

32

LiB

eB

Na

Mg

SiK

Ca

TiV

Cr

Mn

FeC

oN

iC

uG

aY

ZrM

oSn

PbG

RS 2

min.

-bd

bdbd

bdbd

-bd

bdbd

bdbd

bdbd

bdbd

bdbd

Synthetic White

max.

-4.0

39.922.7

126831.7

-54.8

0.5213.7

537101

4.997.7

63.60.78

2.30.61

SapphireA

verage-

bd(4.0)

(16.7)(8.3)

(489)(15.4)

-(9.8)

(0.45)(13.7)

(537)(41.6)

(1.7)(60.1)

(12.1)(0.33)

bdbd

bd(1.6)

(0.28)G

RS 1

min.

bdbd

bd17.5

bd370

9.81.0

bdbd

bdbd

bd-

0.030.09

White Synthetic

max.

0.496.3

3.5174

128851

41.985.8

0.52143

42.30.91

8.1-

3.10.65

Sapphire Be-treated

ProfileG

RS 10

min.

bdbd

bdbd

bdbd

bd-

bdbd

68.0-

bdbd

bdbd

bdbd

bdbd

Irradiated Orange

max.

0.373.1

4.216.2

14.2717

62.1-

41.11.6

150-

17.20.30

24.11.6

0.200.22

2.50.58

Synthetic sapph.A

verage(0.37)

(2.3)(3.9)

(5.1)(6.9)

(676)(10.0)

-(13.7)

(1.6)90.5

-(17.3)

(0.22)bd

(5.4)(0.93)

(0.05)(0.08)

bd(1.5)

(0.26)G

RS 11

min.

-8.6

-bd

bdbd

bdbd

bdbd

76.9bd

bd-

bdbd

bdbd

bdbd

bdSynthetic O

range Sapphire irradiatedand B

e-treatedG

RS 12

min.

bdbd

bdbd

bdbd

bdbd

bd-

48.9bd

bdbd

bdbd

bdbd

bdbd

bdSynthetic

max.

0.903.3

6.2678.8

125361134

13.74719

90.4-

1402.8

77.83.2

6.40.72

0.1210.6

1.24.6

3.97pink Sapphire

Average

(0.77)(3.3)

(4.9)(33.2)

(5732)(818)

(8.1)(1515)

(31.8)-

92.5(2.6)

(38.8)(0.85)

bd(2.5)

(0.48)(0.06)

(2.1)(0.71)

(2.4)(0.54)

GR

S 13m

in.bd

bdbd

bd2065

bdbd

bdbd

-88.0

-bd

bd-

bdbd

0.37bd

bdbd

Synthetic Pink Sapphirem

ax.1.4

15.530.6

36435158

1529385

802451.4

-161

-28.7

17.1-

3.11.6

5.41.5

3.32.0

Be-treated Profile

Average

(1.4)(8.8)

(9.6)(27.4)

14485(778)

(42.6)(1944)

(15.2)-

112-

(21.9)(7.4)

-(1.5)

(0.99)bd

2.3(0.47)

(2.0)(0.39)

GR

S 4m

in.bd

bdbd

bdbd

bdbd

-bd

bdbd

bdbd

bdbd

bdbd

bdbd

bdbd

Syntheticm

ax.0.49

3.618.8

71.2159

134161.4

-73.8

0.38335

3.5117

0.4041.5

1.20.12

0.690.80

2.90.90

Pink SapphireA

verage(0.42)

(3.3)(10.9)

(13.5)(14.6)

(605)(15.5)

-(13.4)

(0.32)(261)

(2.6)(31.8)

(0.24)bd

(4.5)(0.68)

(0.08)(0.22)

(0.39)(2.0)

(0.29)G

RS 5

min.

-bd

bdbd

bdbd

bd-

bd238

-bd

-bd

-bd

bdSynthetic Pink

max.

-12.4

7.314.6

15.81000

159-

9.9336

-18.1

-0.36

-2.3

0.45Sapphire B

e-treatedA

verage-

(7.8)(4.8)

(5.7)(6.8)

(529)(23.0)

-(6.6)

bd282

-(17.2)

bd-

bd(0.27)

bd-

bd(1.9)

(0.17)G

RS 8

min.

bdbd

bdbd

bdbd

bdbd

427bd

bdbd

bd1.2

bdbd

bdbd

Syntheticm

ax.2.1

4.5143

23.5749

18.227.3

0.44597

3.355.8

0.294.2

2.31.1

1.02.7

2.0Pink Sapphire

Average

bd(1.7)

(4.5)(11.4)

(6.41)(489)

(6.4)bd

(16.9)(0.35)

491(3.3)

(34.4)(0.26)

bd(2.1)

1.6(0.16)

(0.26)bd

(2.1)(0.61)

GR

S 9m

in.-

bd-

bd-

bdbd

-8.7

430-

--

0.30bd

-Synthetic

max.

-13.0

-4.1

-512

6.3-

18.1528

--

-0.79

2.0-

Pink SapphireB

e-treated ProfileG

RS 15

min.

-bd

bdbd

bdbd

bd-

8.8-

459-

bd-

bdbd

bdbd

bdSynthetic

max.

-3.0

5.563.2

50.2542

153-

148-

740-

48.7-

5.30.96

0.123.1

4.2pink Sapphire

Average

-(2.4)

(5.5)(19.4)

(9.1)(504)

(29.2)-

30.3-

565-

(27.2)bd

-(2.2)

(0.59)bd

(0.06)bd

(1.8)(0.50)

GR

S 16m

in.bd

0.65bd

2.6bd

165bd

bd7.3

bd273

bdbd

0.08-

bd0.37

bdSynthetic O

rangem

ax.0.38

150297.7

81.161.9

112728.7

237260

2.4805

3.51881

142-

1701.7

0.30Sapphire B

e-treatedA

verage-

2949-

22.5-

479-

-87.7

-508

--

bdbd

bd24.9

-24.9

bd1.1

-G

RS 17

min.

bdbd

bdbd

bdbd

bd-

bdbd

207bd

bdbd

bdbd

bdbd

bdbd

bdbd

Syntheticm

ax.0.48

3.24.9

63.483.2

264121.5

-87.6

0.88347

2.3216

0.4545.9

6.02.1

0.090.16

0.863.4

2.8O

range SapphireA

verage(0.38)

(1.4)(4.4)

(9.5)(8.9)

(700)(9.5)

-(13.6)

(0.88)250

(2.2)(49.7)

(0.27)(37.1)

(2.0)(0.92)

(0.03)(0.08)

(0.55)(2.1)

(0.39)G

RS 18

min.

bdbd

bdbd

bdbd

bdbd

bdbd

217-

bdbd

bdbd

bdbd

bdSynthetic O

rangem

ax.0.44

24.65.0

28.610.7

16646.2

55910.3

1.5343

-104

0.770.10

2.21413

3.30.14

Sapphire Be-treated

Average

(0.44)(10.2)

(5.0)(8.2)

(3.5)(641)

(4.2)(371)

(7.8)(1.0)

276-

(38.5)bd

bdbd

(0.48)(0.08)

(1.2)(196)

(1.8)(0.09)

GR

S 19m

in.-

bdbd

bdbd

bdbd

-bd

bd-

bdbd

bdbd

bdbd

bdbd

bdbd

Synthetic Yellowm

ax.-

2.75.8

6.057.5

11739.8

-9.1

1.9-

46.9193

62.42.0

1.50.10

0.190.96

3.10.88

SapphireA

verage-

(1.1)(3.9)

(4.2)(7.6)

(681)(6.0)

-(9.1)

(1.9)-

(46.9)(105)

bd(39.4)

(1.5)(0.95)

(0.03)(0.08)

(0.39)(1.7)

(0.34)G

RS 20

min.

bdbd

-bd

bdbd

bd-

-bd

bdbd

bdbd

bdbd

bdSynthetic Yellow

max.

0.7123.1

-7.1

14.5694

7.8-

-60.8

55.80.75

0.120.29

0.732.6

0.25Sapphire B

e-treatedA

verage(0.54)

(11.1)-

(3.9)(5.3)

(476)(7.8)

--

bdbd

bd(29.4)

bd(36.3)

bd(0.48)

(0.06)(0.19)

(0.70)(1.9)

(0.14)0.35

2.33.5

2.32.1

3343.7

1244.8

0.3710

1.617

0.2228

0.860.24

0.080.12

0.721.3

0.1

bdbd

(1.8)-

-bd

0.55bd

476-

-bd

(5.5)-

13.4bd

bdbd

0.25

Average

-(9.7)

-(3.2)

-(411)

(0.34)(1.8)

-0.98

bd(9.5)

bdbd

bd22.3

(0.20)(45.1)

75.6(29.3)

60925.1

Average

(0.21)(2.7)

(1.8)

Average

-

max.

-1.6

1220-

38.30.45

9800.87

2.511.5

2572-

2261145

-bd

(1.5)

568149

1441100

0.61173

5.0

(0.61)97.5

(5.8)(0.18)

(0.62)(1.7)

(5.0)(1220)

(11.5)(245)

LOD

(ppm)

212-

(124)(34.7)

(595)(62.4)

(1145)(18.4)

33

Tab. E3 LA-ICP-MS Analyses (in ppm) of Beryllium Treated and Conventional Heated Natural Corundum

Table D2: Sample texts

Li B

e B

N

a M

g Si

K

Ca

Ti V

Cr

Mn

Fe C

o N

i C

u G

a Zr

Sn B

a Pb

7 9

11 23

25 29

39 42

49 51

53 55

57 59

61 65

69 90

120 138

208 ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

O

range Sapphire, M

adagascar A

verage bd

bd bd

bd 48.45

370.4 bd

bd 38.76

9.94 279.8

bd 5429

bd bd

bd 66.74

bd bd

bd bd

Conventional heating

St. D

ev. 5.6

122.2 4.0

0.4 23.7

149.5 2.6

Orange S

apphire, Madagascar

Average

bd bd

bd bd

47.67 374.7

bd bd

39.63 10.00

279.0 3.32

6191 bd

bd bd

70.04 bd

bd bd

bd C

onventional heating S

t. Dev.

6.5 63.1

4.5 0.7

15.0 324.6

2.9 P

adparadscha, Madagascar

Average

bd bd

bd bd

73.09 (847)

bd bd

69.41 10.96

47.91 bd

145.3 bd

bd bd

104.7 bd

bd bd

bd C

onventional heating S

t. Dev.

9.4 799.8

18.0 1.5

15.1 29.0

6.8 S

lightly orangy-pink Sapphire

Average

bd 6.40

bd bd

96.89 448.6

bd bd

105.4 28.36

656 bd

1031 bd

bd bd

95.89 (1.38)

bd bd

bd M

adagascar, New

Treatment

St. D

ev. 1.6

21.1 104.3

11.3 2.3

51.9 62.9

5.3 2.8

Pink S

apphire, Madagascar

Average

3.95 bd

10.92 (78.44)

(403.0) (1272)

(73.60) 321.9

(225.3) 45.64

384.5 5.04

(116.3) 0.83

bd (50.97)

107.5 bd

bd (4.86)

(3.36) B

eryllium Treatm

ent S

t. Dev.

3.5 128.8

1005.2 1143.0

133.4 211.2

4.5 81.0

236.2 86.9

4.6 6.5

4.2 P

adparadscha, Madagascar

Average

bd 12.67

bd (8.66)

98.78 (543)

(9.48) bd

123.6 25.70

331.2 bd

333.3 bd

bd bd

98.79 (2.21)

bd bd

bd B

eryllium Treatm

ent (zoned) S

t. Dev.

3.4 15.3

20.1 286.4

9.7 16.7

2.2 23.4

46.2 6.0

3.1 P

adparadscha, Madagascar

Average

bd (21.01)

bd bd

96.56 538

(16.74) bd

122.1 22.22

289.2 bd

515 bd

bd bd

101.9 (22.44)

2.29 bd

bd B

eryllium Treatm

ent (zoned) S

t. Dev.

12.3 17.4

232.0 20.0

23.3 2.9

19.7 157.2

5.6 15.2

1.0 R

uby, vivid red, Madagascar

Average

bd (26.78)

bd bd

46.49 (484.1)

bd 214.2

(50.12) 53.99

2059 bd

716 bd

(51.95) bd

132.96 (1.03)

bd bd

bd B

eryllium Treatm

ent S

t. Dev.

19.9 22.5

539.0 243.5

47.9 5.6

98.2 84.1

51.6 3.1

1.3 N

atural Sapphire, blue

Average

bd bd

bd (5.28)

87.89 759

bd bd

183.8 8.35

bd bd

947 bd

bd bd

74.80 bd

(7.61) bd

bd C

onventional heating S

t. Dev.

6.1 12.8

8.4 43.1

0.9 30.5

1.5 4.6

Natural S

apphire, dark blue A

verage bd

bd bd

bd 22.34

914 bd

bd 176.7

4.20 bd

bd 8187

bd bd

bd 238.4

bd bd

bd bd

Conventional heating

St. D

ev. 1.3

112.5 7.4

0.2 79.1

1.7 N

atural Sapphire, dark blue

Average

bd bd

bd bd

bd 451.1

bd bd

98.16 2.89

bd bd

6559 bd

bd bd

242.6 bd

5.68 bd

bd C

onventional heating S

t. Dev.

58.9 24.6

0.2 44.6

4.0 1.6

Natural S

apphire, vivid blue A

verage bd

3.42 bd

bd 48.63

871 bd

bd 177.8

17.91 bd

bd 499.0

bd bd

bd 66.34

bd 3.22

bd 0.55

Beryllium

Treatment

St. D

ev. 1.5

17.2 202.0

15.4 0.3

33.0 1.2

0.1 N

atural Sapphire, deep blue

Average

bd bd

bd bd

188.3 417.3

bd bd

293.8 17.57

(17.47) bd

916 bd

bd bd

44.93 bd

bd bd

0.28 B

eryllium Treatm

ent S

t. Dev.

73.1 32.2

87.0 1.1

22.6 36.1

0.1 0.3

0.85 2.6

10.7 4.5

5.8 290

9.3 174

8.5 0.51

14 2.73

29 0.44

40 1.99

0.61 0.4

2.21 0.26

0.24 LO

D (ppm

)

12132

12344 S1

Al norm

alized to 526600

12134

5.019ct S1

12133

GR

S 35 S1

GR

S 35 S2

12916 S2

Rot 10.69

Rosa 3.59

GR

S 33

GR

S 34

12916

34

Tab. C1 LA-ICP-MS Analyses (in ppm) of Natural and Synthetic Spinel

Table D3: Sample texts Li Be B Na Si K Ca Ti V Cr Mn Fe Co Ni Cu Zn Ga ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm

average 59.0 19.3 bd 3.39 538 7.98 (360) 29.1 271 7329 157 68.3 bd bd 1.14 762 79.2 stdev. 0.1 4 0.6 14 1.1 555 4 2 649 3 23 0.3 13 2 average 225 46.7 bd bd 673 bd bd 15.5 208.0 2196 61.4 1021 0.90 4.25 bd 7408 315 stdev. 9 7 196 0.6 0.1 8 1 34 0.1 0.4 61 3 average 10.2 53.4 bd bd 597 bd bd bd 393 2216 10.93 560 1.51 8.09 bd 5302 836 stdev. 2.3 11 218 1.8 30 0.5 6 0.03 1.5 263 15 average bd 27.5 bd bd 571 bd bd 222 101 3203 154 868 0.21 bd bd 1038 280 stdev. 8 105 13 9 696 7 111 0.1 68 13 average 83.0 24.3 bd 2.41 469 bd bd 47 255 7129 121 78.1 bd bd 1.19 761 64 stdev. 21 2 0.5 126 3 19 207 1 1 0.3 111 1 average bd 19.4 bd 1.45 593 bd bd 567 788 4930 57.4 34.2 bd bd bd 305 47.6 stdev. 8 204 3 3 176 5 13 8 1 average 33.1 9.09 bd 2.13 663 bd bd 138 336 4823 169 55.0 bd bd 1.42 824 51.4 stdev. 6.2 2 0.4 42 2 12 42 3 11 0.8 33 4 average bd bd bd (4.54) 570 bd bd 169 1124 17182 6.96 1613 1.00 17.7 (1.65) 1988 133 stdev. 5.7 65 5 25 1732 0.7 128 0.2 1.3 1.1 12 2 average bd 11.4 bd (15.6) 1095 (24.4) bd 1800 1142 8042 67.8 177 bd bd (14.5) 296 82.6 stdev. 1.6 17 357 26 87 9 122 1 55 13.3 11 3 average 159 (14.0) bd bd 631 bd bd 45.0 1211 6645 20.3 1621 4.11 102 1.04 4372 264 stdev. 33 9 82 3.9 6 316 0.6 94.0 0.2 13 0.5 164 11 average 22.0 bd bd bd 650 bd bd 47.5 969 12569 21.7 1470 4.29 104 bd 3649 293 stdev. 6 154 2 12 69 0.6 81 0.2 1 71 8 average 213 10.5 bd bd 616 bd bd 64.6 1760 18538 16.2 1088 4.52 112 0.85 3784 299 stdev. 63 4 19 12 183 534 0.6 3 0.6 5 0.2 411 27 average bd bd bd bd 595 bd bd 386 611 5858 31.9 906 1.06 7.09 0.70 3739 101 stdev. 240 23 13 238 1.0 40 0.2 0.5 0.3 39 6 average bd 5.16 bd bd 554 bd bd 369 765 7368 48.2 463 0.71 23.7 bd 474 64.8 stdev. 0.3 87 5 4 97 0.5 14 0.01 5 12 0.1 average 185 12.1 bd bd 702 bd bd 246 1215 9321 9.7 3289 0.78 bd 0.74 6194 216 stdev. 11 2 47 5 26 430 0.7 103 0.03 0.2 130 17 average 189 32.2 bd (1.73) 520 bd bd 170 1923 7175 19.8 1744 6.40 112 (3.58) 4191 303 stdev. 14 1.3 1.9 172 4 93 211 2 11 0.2 9.6 3.8 71 7 average 91.2 52.7 bd (2.40) 667 bd bd 589 423 6153 53.3 217 bd bd (0.74) 159 1 stdev. 0.05 5 2.4 291 8 3 78 1.5 15 0.6 10 0.2 average bd (15.4) bd 8.75 474 14.4 bd 59.2 2558 67.7 9.0 680 bd bd 1.17 2620 242 stdev. 12 0.0 96 0.3 21 115 5 0.1 12 0.3 19 10 average bd bd bd 20.1 553 36.4 (175) 155 6198 126 9.21 466 bd 8.18 4.85 1023 154 stdev. 3 9 14.5 234 25 149 31 0.1 19 2.4 0.9 53 6 average 221 bd bd (33.8) 469 8.91 bd 57.3 75.2 317 378 10005 3.47 (3.72) bd 956 171 stdev. 8 28 49 3.1 3 1 13.4 4 413 0.3 3.4 17 0.1 average 37.9 8.50 bd 7.67 644 5.43 bd 8.20 29.1 24 268 7677 2.38 bd 1.16 3239 126 stdev. 10 2.7 1.3 101 0.1 2.0 0.5 2 6 326 0.1 0.4 152 6 average 18.7 bd bd 6.22 681 (13.3) bd 30.6 35.5 95 176 9999 0.42 5.48 (0.94) 1865 62.4 stdev. 0.9 2.5 9 12 6 0.4 3 3 147 0.1 1.3 0.7 1 0.2 average 30.4 bd bd bd 557 bd bd 40.0 26.2 bd 199 16985 10.11 40.4 0.84 1548 134 stdev. 1.8 3 0.2 0.8 3 0.1 0.2 0.7 0.3 11 3 average 73.8 55.6 bd bd 582 bd bd 549 374 3693 35.8 114 bd bd (0.73) 60.8 1.02 stdev. 1.4 5.4 95 23 18 38 2 11 0.7 7 0.1 average 578 11.5 bd bd 548 bd bd 68.3 263 6182 65.5 14331 32.4 86.9 1.26 726 129 stdev. 58 4.8 145 1 2 482 1.4 410 1 13 0.4 53 0.9 average bd bd bd bd 534 bd bd bd 200 3421 185.8 723 0.76 124 1.20 41 58.7 stdev. 9.9 7 46 6.1 21 0.03 25 0.2 1 0.8 average bd bd bd bd 605 bd bd (18.0) 172 3295 183 735 0.87 165 bd 42.6 54.9 stdev. 76 22 4 44 1 9 0.1 9 1 0.2

7.4 4.6 18.2 1.2 314 4.3 167 4.1 0.49 6.6 0.97 14.8 0.14 3.2 0.62 1.3 0.23 LOD (ppm)

Nr. 4_1

Nr. 10_2

Nr. 2_1

Nr.10_1

Nr. 17_2

Nr. 13_2

Nr.11_2

Nr. 12_2

Nr. 14_2

Nr. 3_2

Nr. 4_2

Nr. 5_2

Nr. 9_2

Nr. 6_2

Nr. 7_2

Nr. 8_2

Nr. 1_2

Nr. 3_1

Nr. 1_1

Nr. 5_1

Nr. 18_2

Synthetic Russia pinkish-red

Synthetic, Russia pinkish-red

pink Madagascar

Vietnam pink

Mogok bluish-green

Madagascar blue

Mogok purple

Mogok green

Mogok orange Nr. 16_2

Nr. 15_2 orange-red Mogok

Nr. 8_1

Nr. 19_2

Nr. 7_1

Nr. 6_1

Mogok, Chaung Gyi pinkish-red

Mogok, Shwe Phy Aye red

Mogok, Ohn Gaing red

Mogok, In Gaung red

Mogok, Pyen Pit red

Mogok, Ohn Gaing red

Mogok, Pyen Pit red

Mogok, Pyen Pit red

Namya red

Namya red

Namya pinkish-red

pinkish-red Namya

Namya

Namya

pink

pink

Sample No Origin Color

Namya vivid pink

pinkish-red Namya

pinkish-red Namya

Normalized to Al+Mg = 100 wt.-% by difference

35

Important Internet References

Further Information on the InternetNo.01 : http://www.gemresearch.ch/news/journal/e-im.htm (Contributions to Gemology (2002), No.1 On-line)

No.02 : http://www.gemresearch.ch/news/journal/Pioneer-Issue-No2.htm (Contributions to Gemology (2003), No.2 On-line)

No.03 : http://www.gemresearch.ch/news/journal/ordering.htm (Internet ordering of Contribution to Gemology)

No.04 : http://www.gemresearch.ch/corrigenda.htm (Corrigenda Contributions to Gemology, 2002, No.1)

No.05 : http://www.gemresearch.ch/news/RFC.htm (Reaction to first Contributions to Gemology, 2002, No.1)

No.06 : http://www.gemresearch.ch/news/NewTreatQA/NewTreatQA-E.htm (Historical events on appearance of new treatment, view of GRS, in 5 languages)

No.07 : http://www.gemresearch.ch/news/reply.htm (Correction of wrong citations about GRS in the literature)

No.08 : http://www.gemresearch.ch/news/RepNewTreat/RepNewTreat-E.htm (Disclosure Policy of GRS on new treatment in 5 languages)

No.09 : http://www.gemresearch.ch/inclusions.index.htm (Photo Album of inclusions, e.g. inclusions in Beryllium treated gemstones)

No.10 : http://www.gemresearch.ch/application-IMA.index.htm (GRS discoveries of new minerals and application details)

No.11 : http://www.gemresearch.ch/ordering-ISBN.index.htm (ISBN ordering numbers of Contributions to Gemology)

36

Acknowledgements

Important InformationBy accepting this publication, the client enters into a contract with Gemresearch Swisslab AG, Lucerne, Switzerland (GRS). It is understood that the contract is accepted if the client does not explicitly disagree. The contract is based on the information and limitations of GRS, as published under the website www.gemresearch.ch. It is subject to Swiss law, particularly with regard to regulations concerning contract completion, fulfillment, and examination conditions. This report is not valid without the original GRS hologram. The EXTRA Video inside this report is identified with a GRS hologram. Without a hologram, the Video is identified as a non-authorized copy. The report is the copyright of GRS and cannot be duplicated without GRS giving prior written authorization. Any disputes in connection with the contract will be subject to the jurisdiction of the courts of Lucerne, Switzerland. The parties waive the jurisdiction guarantee of places of their private residence

AcknowledgementsWe would like to thank all the persons and institutions who helped for this report.Dr. A. Burkhardt for ED-XRF analysis, Prof. K. Ramseyer (University of Berne) and Dr. J. Mullis for cathodoluminescene analysis, Mrs Kathrin Hametner and Mr. B. Hattendorf (co-worker in the group of trace elements and micro analytic of LAC laboratory at ETH, Zurich. Mrs Anong Kanpraphai, GRS (Thailand) Co. LTD for digital artwork, Anong Imaging (Bangkok) for picture artwork, IMAGIMAX Animation & Design Studio (Bangkok, Thailand) for graphic and artwork, Mr. Sumet Tanthadilok for designing, Mr. Saleem Michael for scientific graphics and preparing this report for the Internet, Mr. John deJaegher (G.G.) for assistance and Marcus Brogden for English corrections and Lewis Allen for some editorial work. Without the support of the trade including various wholesale companies in Bangkok and mining companies world-wide, it would not have been possible to receive enough reference materials. Thanks also to the companies in Bangkok and Chantaburi (Thailand) for heat treating our reference samples with the new method in their factories. Thanks to all people of Burma(Myanmar) for support during the expedition in 2001. This issue was supported by C.H. Lapidaries LTD. (Bangkok, Thailand), Crown Color, Geneva (Siwtzerland), GRS (Thailand) Co., LTD., Bangkok and by GRS Gemresearch Swisslab AG (Switzerland) and the family of Adolf Peretti.

GRS Gemresearch Swisslab AG, P.O.Box 4028, 6002 Lucerne, Switzerlandwww.gemresearch.ch

Ore Geology Reviews 34 (2008) 169–191

Contents lists available at ScienceDirect

Ore Geology Reviews

j ourna l homepage: www.e lsev ie r.com/ locate /oregeorev

Marble-hosted ruby deposits from Central and Southeast Asia: Towards a newgenetic model

Virginie Garnier a, Gaston Giuliani a,b,⁎, Daniel Ohnenstetter a, Anthony E. Fallick c, Jean Dubessy d,David Banks e, Hoàng Quang Vinh f, Thérèse Lhomme d, Henri Maluski g, Arnaud Pêcher h,Kausar Allah Bakhsh i, Pham Van Long j, Phan Trong Trinh f, Dietmar Schwarz k

a CRPG/CNRS, BP 20, 15 rue Notre-Dame des Pauvres, 54501 Vandœuvre-lès-Nancy cedex, Franceb IRD, UR154 LMTG, 14 avenue Edouard Belin, 34100 Toulouse, Francec Scottish Universities Environmental Research Centre, East Kilbride, Rankine Avenue, Glasgow G75 0QF, Scotland, United Kingdomd UMR 7566 G2R/CNRS, Université Henri-Poincaré, BP 239, 54506 Vandœuvre, Francee School of Earth Sciences, University of Leeds, Leeds LS2 9JT, United Kingdomf Institute of Geological Sciences, CNST, Nghia Dô, Câu Giây, Hanoi, Vietnamg Laboratoire de Géochronologie, Université de Montpellier 2, Place Eugène Bataillon, 34095 Montpellier, Franceh Maison des Géosciences, Laboratoire de géodynamique des Chaînes alpines, 181 rue de la piscine, 38400 — St Martin d'Hères, Francei GSP, Geoscience Laboratory, P.O. Box 1461, Shahzad Town, Islamabad, Pakistanj Vietnam National Gem and Gold Corporation, 91 Dinh Tien Hoang street, Hanoi, Vietnamk Gübelin Gemmological Laboratory, Maihofstrasse, 102, CH-6000 Lucerne 9, Switzerland

⁎ Corresponding author. Present address: CRPG/CNRSE-mail address: giuliani@crpg.cnrs-nancy.fr (G. Giuli

0169-1368/$ – see front matter © 2008 Elsevier B.V. Aldoi:10.1016/j.oregeorev.2008.03.003

A B S T R A C T

A R T I C L E I N F O

Article history:

Marble-hosted ruby deposi Received 11 December 2006Accepted 6 March 2008Available online 24 April 2008

Keywords:AsiaRubyMarbleEvaporiteMetamorphismGeochemistryStable isotopesGenetic model

ts represent the most important source of colored gemstones from Central andSouth East Asia. These deposits are located in the Himalayan mountain belt which developed during Tertiarycollision of the Indian plate northward into the Eurasian plate. They are spatially related to granitoidintrusions and are contained in platform carbonates series that underwent high-grade metamorphism. Alloccurrences are located close to major tectonic features formed during Himalayan orogenesis, directly insuture zones in the Himalayas, or in shear zones that guided extrusion of the Indochina block after thecollision in South East Asia. Ar–Ar dating of micas syngenetic with ruby and U–Pb dating of zircon included inruby gives evidence that these deposits formed during Himalayan orogenesis, and the ages document theextensional tectonics that were active, from Afghanistan to Vietnam, between the Oligocene and thePliocene.The petrography shows that ruby-bearing marbles formed in the amphibolite facies (T=610 to 790 °C andP~6 kbar). A fluid inclusion study defines the conditions of gem ruby formation during the retrogrademetamorphic path (620bTb670 °C and 2.6bPb3.3 kbar) for the deposits of Jegdalek, Hunza and northernVietnam.Whole rock analyses of non-ruby-bearing marbles indicate that they contain enough aluminum andchromiferous elements to produce all the ruby crystals that they contain. In addition, (C, O)-isotopic analysesof carbonates from the marbles lead to the conclusion that the marbles acted as a metamorphic closed fluidsystem that were not infiltrated by externally-derived fluids. The carbon isotopic composition of graphite inmarbles reveals that it is of organic origin and that it exchanged C-isotopes with the carbonates duringmetamorphism. Moreover, the O-isotopic composition of ruby was buffered by metamorphic CO2 releasedduring devolatilisation of marble and the H-isotopic composition of mica is consistent with a metamorphicorigin for water in equilibrium with the micas. The (C, O, H)-isotopic compositions of minerals associatedwith marble-hosted ruby are all in agreement with the hypothesis, drawn from the unusual chemistry ofCO2–H2S–COS–S8–AlO(OH)-bearing fluids contained in fluid inclusions, that gem ruby formed at P~3 kbarand 620bTb670 °C, during thermal reduction of evaporite by organic matter, at high temperature-mediumpressure metamorphism of platform carbonates during the Tertiary India–Asia collision. The carbonates wereenriched in Al- and chromiferous-bearing detrital minerals, such as clay minerals that were deposited on theplatform with the carbonates, and in organic matter. Ruby formed during the retrograde metamorphic path,mainly by destabilization of muscovite or spinel. The metamorphic fluid system was rich in CO2 releasedfrom devolatilisation of carbonates, and in fluorine, chlorine and boron released by molten salts (NaCl, KCl,

, BP 20, 15 rue Notre-Dame des Pauvres, 54501 Vandœuvre-lès-Nancy cedex, France.ani).

l rights reserved.

Fig.1. Location of marble-hosted ruby deposits from AsiaKush, K = Kohistan, P = Pamir (modified from Mattauer

170 V. Garnier et al. / Ore Geology Reviews 34 (2008) 169–191

CaSO4). Evaporites are key to explaining the formation of these deposits. Molten salts mobilized in situ Al andmetal transition elements contained in marbles, leading to crystallization of ruby.

© 2008 Elsevier B.V. All rights reserved.

1. Introduction

Ruby is the red- and chromiferous-variety of corundum. The mainsource for excellent-quality ruby with intense color and high trans-parency is marble-hosted ruby deposits from Central and SouthEast Asia. The deposits occur in Afghanistan, Pakistan, Azad-Kashmir,Tajikistan, Nepal, Myanmar, northern Vietnam and southern China(Hughes, 1997; Fig. 1). The mines in Afghanistan are among the oldestin the world and were already exploited seven hundred years ago(Rossovskiy, 1980; Hughes, 1994; Bowersox and Chamberlin, 1995;Bowersox et al., 2000). Ruby deposits from the Hunza Valley, Pakistan,were discovered in the late 1980's during the construction of theKarakorum Highway which links Pakistan with China (Piat, 1974;Okrusch et al., 1976; Gübelin, 1982; Garnier, 2003). The deposit fromNangimali in Azad-Kashmir was discovered in 1979 by the AzadKashmir Mineral and Industrial Development Corporation (Malik, inpress), and the geology and geochemistry of the deposit is detailed byPêcher et al. (2002). The Tajikistan ruby deposits remain poorly knownand were first described by Henn and Bank (1990). Smith (1998)detailed the standard gemological properties and internal features ofthe Tajik rubies. The first report of marble-hosted ruby deposits fromNepal was published by Bassett (in press), followed by Harding andScaratt (1986); mineralogy was studied by Smith et al. (1997). Rubydeposits from Mogok, Myanmar, have been exploited since the 6thCentury (Chhibber, 1934; Gübelin, 1965; Keller, 1983; Kane andKammerling, 1992; Kammerling et al., 1994), in contrast to thosefrom Mong Hsu, which were only reported in 1991 (Hlaing, 1991;Peretti et al., 1995). In northern Vietnam, a peasant discovered the firstruby in 1983 and exploitation of the occurrences began in 1988 (Kaneet al., 1991; Garnier, 2003; PhamVan et al., 2004). Galibert and Hughes(1995) reported that ruby-bearing marbles were discovered in theYunnan province of China at the beginning of the 1980's. Detailed

. Main structures: CF = Chaman Faultet al., 1999). Ar–Ar dates on phlogo

characteristics of gems in the Ailaoshan structural belt were given byZhang et al. (2003).

The gemological studies predominate over the geological inves-tigations of the ruby deposits and several hypotheses for theirformation are proposed: the rubies formed (1) during the regionalmetamorphism of calcareous rocks enriched in aluminum relative tosilica, chromium and titanium (Okrusch et al., 1976; Rossovskiy, 1980;Rossovskiy et al., 1982). This uncommon bulk rock chemistry wasexplained by a lateritic weathering of an impure limestone, such as ina karst environment; (2) during intrusion of granitoids and pegmatitesin marble: a) ruby has an indirect relation with granite and its for-mation is due contact metamorphism near the intrusion as proposedby Iyer (1953) for the Mogok deposits; b) a direct genetic relationwithmagma during emplacement of alkaline intrusions into marbles forthe Tajikistan deposits (Terekhov et al., 1999), and the magmaticsolutions carrying aluminium interacted with marbles; (3) duringhigh pressure metamorphism of originally impure limestones inevaporitic series (Spiridonov, 1998); and (4) during the metamorph-ism of evaporite lenses intercalated in marbles which resulted in theformation of molten salts that reacted with marble and its impurities(graphite and phengite; Garnier, 2003) to produce CO2–H2S–COS–S8–AlO(OH)-bearing fluids trapped by Vietnamese rubies (Giuliani et al.,2003a,b).

The presence of corundum (Al2O3) in a marble opens the debateinto the source of aluminium and the source versus trap role played bythe marble. The Al may come from Al-bearing minerals in the marble,Al directly linked to a magmatic source or Al and chromiferous ele-ments (Cr, V, Fe) picked up by fluids circulating through the schist andmafic units generally associated with marble, during regional meta-morphismwhich then percolated through the carbonates. Marbles areSi-poor and thus might represent a good chemical environment forthe formation of ruby.

, GF = Gaoligong Fault, SF = Sagaing Fault, RRF = Red River Fault; main blocks: HK = Hindupite syngenetic with ruby from Garnier et al. (2006).

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The aim of this work is to decipher the conditions (pressure,temperature, chemistry andmechanisms) of ruby formation in marbleand to propose a model of genesis. A sub-aim is to test the differentmodels proposed for the formation of these deposits and to decipherthe role of evaporite in its genesis as proposed for Vietnamese de-posits (Giuliani et al., 2003b). This study is based on petrographic andmineralogical observations, whole-rock geochemistry and (O, H, C,S, B)-isotope geochemistry of minerals associated with ruby in themarbles. The data permits us to propose a new genetic model for thistype of ruby deposit.

2. Geologic setting

Marble-hosted ruby deposits in Jegdalek (Afghanistan), Nangimali(Azad-Kashmir), the Hunza Valley (Pakistan), Chumar and Ruyil(Nepal), Mogok (Myanmar) and Luc Yen-Yen Bai (Vietnam) sharemany common structural, mineralogical and radiometric features:

(1) They occur in metamorphic blocks that were affected by majortectonic events during the Cenozoic Indo-Asian collision (Fig. 1;Mattauer et al., 1999). The Jegdalek ruby deposit in Afghanistanis located in the Western Nuristan Block, in the Indus suturezone. The ruby area is underlain by a metamorphic basement ofassumed Precambrian age (Rossovskiy et al., 1982) intruded byOligocene (34 to 26 Ma) plutonic units that define the southernpart of an axial batholith (Debon et al., 1986). The deposit fromNangimali in Azad-Kashmir lies in the High CrystallineHimalaya, in the Southern part of Nanga Parbat (Fig. 2A). TheNangimali deposit is locatedwithin a syncline formed during an

Fig. 2. (A) Nangimali Top deposit (Azad-Kashmir ruby deposits). The mountain is formed by acontained in level c. (B) Ruby-bearing veinlet in a microshear zone from Lower Khorat de(Nangimali). (D) Ruby and phlogopite in a marble from the Foruhar district in the Hunza Va

upper Cretaceous to Miocene Himalayan tectono-metamorphicevent (Pêcher et al., 2002). The deposits from Chumar and Ruyilin Nepal are located on the southeastern flank of the GaneshHimal, in the Nawakot series, just below the Main CentralThrust. These ruby deposits occur within boudinaged marblelenses, 60 to 150mwide andup to1 km long, oriented parallel tothe Main Central Thrust. Deposits from the Hunza Valley inPakistan (Okrusch et al.,1976) are located in the Baltit formationof the Karakorum metamorphic complex, north to the NangaParbat Massif, between the Main Karakorum Thrust and theKarakorum batholith. The famousMogok ruby deposits occur inthe Mogok Metamorphic Belt. This belt accommodated a largepart of the Indo-Asian collision (Bertrand et al., 2001) and ismarked by high temperature ductile Oligocene stretching andpost-Miocene brittle right-lateral faults such as the Shan scarpfault zone and the Sagaing fault (Bertrand and Rangin, 2003).Ruby deposits from northern Vietnam are located in the RedRiver shear zone that was active during Cenozoic times (Schäreret al., 1990; Tapponnier et al., 1990; Schärer et al., 1994; Garnieret al., 2005). The deposits from the Tan Huong mine in the YenBai district are contained within marble units alternating withhigh-grade metamorphic gneisses in the Day Nui Con Voimetamorphic belt. The deposits from Luc Yen (An Phu, Bai DaLan-Mong Son, KhoanThong, Luc Yen,Minh Tien andNuocNgapmines) occur inweakly deformedmarble units from the Lo Gamtectonic zone, located on the eastern flank of the Day Nui ConVoi belt within the Red River shear zone (Leloup et al., 2001).

(2) The marble-hosted ruby deposits have been found in meta-morphosed platform carbonates associated generally with

succession of marbles (a, c, e) and garnet- and sillimanite-bearing schists (b, d). Ruby isposit (Nangimali). (C) Gash vein bearing ruby, phlogopite and pyrite in Lower Khoratlley, Pakistan. Photographs: G. Giuliani.

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garnet–biotite–sillimanite- or biotite–kyanite-bearing gneissesand granites (Fig. 3). The marble units consist of discontinuoushorizons up to 300 m in thickness, now oriented parallel to themain regional foliations, thrusts or shear zones related to theCenozoic Himalayan orogenesis. Dykes of granite and/orpegmatites intrude these metamorphosed sediments. Rubymineralization is generally stratiform and distributed withinmarble layers. In Luc Yen (Vietnam), Nangimali (Azad-Kashmir)andHunza (Pakistan), amphibolite bodies alternatewith calciticand/or dolomiticmarbles. Marble parageneses consist of calcite,dolomite, spinel, phlogopite, margarite, amphibole, chlorite,forsterite, and titanite±graphite±garnet±pyrite. The surround-ing gneisses or schists show assemblages with biotite–garnet–sillimanite±scapolite±kyanite±amphibole±clinopyroxene. InJegdalek (Afghanistan), Nangimali (Azad Kashmir) and Ruyil–Chumar (Nepal), pegmatites are absent (Smith et al., 1997;Pêcher et al., 2002) and ruby occurs in marble lenses parallel tothe main foliation and/or within thin fractures (up to 3 to 4 cmwide) in marble horizons (Pêcher et al., 2002).Ruby crystals occur: (1) disseminated within marbles andassociated with phlogopite, muscovite, scapolite, margarite,spinel, titanite, pyrite and graphite, as in Jegdalek, Afghanistan;Chumar and Ruyil, Nepal; Hunza, Pakistan (Fig. 2D); Mogok andMong Hsu, Myanmar; and Luc Yen, Vietnam; (2) in veinlets orgash veins, as in some occurrences in northern Vietnam, andassociated with phlogopite, margarite, titanite, graphite andpyrite, and sometimes related to micro-shear zones, as inNangimali, Azad-Kashmir (Fig. 2B, C); (3) in pockets associatedwith orthoclase, phlogopite, margarite, graphite and pyrite insome occurrences of northern Vietnam.

(3) Ruby hosted in marble was indirectly dated by 40Ar–39Arstepwise heating experiments performed on single grains of

Fig. 3. The Nangimali Formation showing the location of the ruby-bearing marbles inthe metamorphic pile (modified from Malik, in press; Pêcher et al., 2000).

phlogopite syngenetic with ruby (Garnier et al., 2002, 2006),and zircon inclusions in ruby dated with the U–Pb method byion-probe (Garnier et al., 2005). Ar–Ar ages of phlogopitesassociated with ruby are Oligocene (24.7±0.3Ma) at Jegdalek inAfghanistan, Miocene at Mogok in Myanmar (18.7±0.2 to 17.1±0.2 Ma), at Hunza in Pakistan (10.8±0.3 to 5.4±0.3 Ma) andChumar in Nepal (5.6±0.4 Ma), and Pliocene (4.6±0.1 Ma) atRuyil in Nepal (Fig. 1). In Vietnam, a zircon grain included in aruby from Luc Yen yielded a 206U–238Pb age of 38.1±0.5 Ma,indicating that ruby formed when ductile deformation wasactive under peak metamorphic conditions in the Red Rivershear zone. All these ages are consistent with extensionaltectonics and coeval magmatism that were active fromAfghanistan to Vietnam, in the ruby-bearing metamorphicbelts, between the Oligocene and the Pliocene (Jolivet et al.,1999; Leloup et al., 2001; Barley et al., 2003).

3. Analytical procedures and samples

A study of the major and trace elements was carried out on thevarious lithologies from the sampled deposits, with special emphasison the marble units. Major- and trace-element contents were de-termined by Induction Coupled Plasma-Mass Spectroscopy (ICP-MS)on representative samples of marbles, schists and amphibolites(Laboratory SARM, CRPG/CNRS, Vandœuvre-lès-Nancy): 26 samplesfrom Nangimali, 17 from Luc Yen-Yen Bai, 21 from Hunza, 2 fromMogok, 5 from Nepal and 3 from Jegdalek. In marbles from Nangimali,Al2O3 was analyzed by absorption spectrometry (1 g of powder/analysis) and TiO2 by colorimetry after complete calcination and dis-solution (1 g of powder/analysis).

Thin sections were observed under a scanning electronmicroscopeHitachi 2500 (University H. Poincaré, Vandœuvre-lès-Nancy, France).Mineral analyses were done with Cameca SX50 and SX100 electronmicroprobes (University H. Poincaré, Vandœuvre-lès-Nancy, France)with acceleration voltage of 15 kV, beam current of 10 nA, collectiontimes of 10, 20 and 30 s respectively for major, trace and halogenelements. Natural and synthetic standards were used and the PAPprogram (Pouchou and Pichoir, 1991) was applied for data correction.

The (C, O, H)-isotopic analyses were done at CRPG/CNRS(Vandœuvre-lès-Nancy). Carbon dioxide was extracted from pow-dered calcite for dolomite-free marbles by reaction with H3PO4 at25 °C over 3 hours, and from powdered calcite-dolomite mixtures fordolomitic marbles by reaction at 50 °C for at least 3 days (McCrea,1950). Graphite was prepared for carbon isotope measurement byseparating 1–2 mg of crystals from the marble and subsequent com-bustion with excess CuO and Cu2O at 900 °C over 3 hours. Carbondioxide was extracted by cold traps. The structural water of micas wasextracted in vacuo by heating at ~1500 °C using a methane–oxygentorch. Water contained in mica crystals (about 40 mg) was reduced inhydrogen over uranium at 800 °C in a vacuum line, following themethod of Bigeleisen et al. (1952). The extracted CO2 and H2 wereanalyzed by mass spectrometry on a VG 602Dmass spectrometer. Thereproducibility is ±0.1‰ for C- and O-isotopic analyses and ±1.0‰ forH-isotopic analyses.

Ruby crystals recovered frommarble have colors varying from light(pink sapphire) to very dark pink or red (ruby sensu strictu). Crystalshave idiomorphic bipyramidal shapes with lengths up to 2.5 cm in thestudied samples. In the following text, the term ‘ruby’ will be used todesignate colorless to light pink to deep red Cr-bearing corundum. O-isotopic composition of ruby (samples of about 1 to 2 mg) was ana-lyzed by a laser-fluorination under vacuum (method modified fromSharp, 1990) at the SUERC (Glasgow, U.K.). The O-isotopic compositionwas analyzed in a VG PRISM 3 dual inlet isotope-ratio mass-spec-trometer, with a precision and accuracy of ±0.1‰.

The isotopic composition of sulfur in anhydrite and boron in tour-maline was determined in-situ in thin sections with a Cameca IMS3f

Table 1Chemical compositions of marbles and gneiss, schists and amphibolite with which they are intercalated in ruby occurrences of Central and South-east Asia

Country Afghanistan Azad-Kashmir Pakistan Vietnam Myanmar

Deposit Jegdalek Nangimali Hunza Luc Yen Quy Chau Mogok

Sample JD-4 JD-3 LK2g MKT2 LK1a LK4 HU-25aC1 HU-25aB1 BDL1a2 An Phu4b MC5 MOA

Color Grey Grey Greyish White Grey Yellow Grey White White White White Grey

SiO2 0.73 0.28 0.77 1.22 6.1 bmdl 0.47 bmdl 0.54 1.29 0.27 1.25Al2O3 1.43 0.74 0.44 0.32 3.6 0.072⁎ 0.18 bmdl 1.02 1.73 0.09 bmdlFe2O3 bmdl bmdl bmdl bmdl 1.21 bmdl bmdl bmdl bmdl bmdl 0.02 bmdlMnO bmdl bmdl bmdl bmdl 0.03 bmdl bmdl bmdl bmdl bmdl bmdl bmdlMgO 1.8 1.5 6.46 0.83 12.7 21.31 2.7 1.31 0.28 5.36 3.72 9.58CaO 52.55 53.15 47.14 53.66 34.4 31.88 51.25 54.47 54.77 48.93 54.44 44.19Na2O 0.09 0.05 0.0193⁎ bmdl bmdl bmdl bmdl bmdl bmdl 0.05 0.02 bmdlK2O 0.07 0.06 0.08 0.13 0.81 bmdl 0.09 bmdl bmdl bmdl 0.02 bmdlTiO2 0.1 bmdl 0.0193⁎ 0.0241⁎ 0.18 0.0025⁎ bmdl bmdl 0.04 bmdl bmdl bmdlP2O5 bmdl bmdl bmdl bmdl bmdl bmdl bmdl bmdl bmdl bmdl bmdl bmdlI.L. 43.06 43.04 43.93 42.81 38.87 44.86 44.09 43.5 42.47 41.72 40.86 42.63Total 99.83 98.82 98.82 98.97 97.9 98.05 98.78 99.28 99.05 99.08 99.37 97.65Cr 24 16.8 6.9 10.0 29.9 5.8 27 34 17.2 197 bmdl 15Sr 170 150 188 354 222 127 2000 115 90 121 170 107V 10 7.8 6 5.8 45 3.2 33 3 9 20 bmdl 17

Major and trace element concentrations obtained by ICP-MS, respectively, inwt% and in ppm. ⁎ = analysis obtained bywet chemistry; bmdl=concentration below the detection limitsfor the elements by ICP-MS analysis: SiO2=0.05%; Al2O3=0.015%; Fe2O3=0.04%; MnO=0.001%; MgO=0.01%; CaO=0.02%; Na2O=0.07%; K2O=0.05%.TiO2=0.005%; P2O5=0.015%; Cr=5 ppm; Sr=1.5 ppm; V=1.5 ppm.

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ion probe at CRPG/CNRS (Vandœuvre-lès-Nancy, France) followingthe procedures described by Chaussidon (1988) and Rose (1999), re-spectively. Analytical errors for S-isotopic analyses are small (a few‰).The reproducibility of B-isotopic analyses is ±0.35‰.

The analytical procedure for fluid inclusions characterization wasdetailed in Giuliani et al. (2003a).

4. Major and trace elements analyses

Marbles from ruby-bearing units were analyzed for major and traceelements (Table 1), in order to determine possible sources of theelements in ruby (Al, Cr and V). Ruby-bearing marbles from all thedeposits are dolomite-poor and calcite-rich (MgO between 0.3 and19.2 wt.%; Table 1). The dolomite-richest marbles are those fromNangimali and Hunza. Most of the alumina contents of these marblesrange between 0.5 and 2.5 wt.%. Mass-balance calculations applied tothe Nangimali ruby-bearing formations (Pêcher et al., 2002), shows that

Fig. 4. Al–Mg–Ca diagram showing the distribution of marbles (open symbols) andintercalated schists, amphibolites and gneisses (full symbols) from Nangimali (square),Hunza (triangle up), Jegdalek (circle), Mogok (triangle down) and Luc Yen-Yen Bai(diamond). The domains of evaporites andmeta-evaporites, and of platformal marls andshales are from Moine et al. (1981).

ruby reserves, estimated from the volume of the mineralized unit andthemean grade (11 g/m3) deduced from a 3 year pilot study, correspondto only 0.4% of the reserves calculated when considering the mobiliza-tion of all the Al contained in the marbles (mean content of 1000 ppm).There is thus enough aluminum in the marbles to produce all the rubycontained in the deposits. In addition, marbles from Nangimali, Hunza,Jegdalek, Mogok and Vietnam contain Cr (6 to 94 ppm) and V (3 to34 ppm) in quantities that are sufficient to give ruby its color.

The mafic rocks (especially amphibolites, gneiss and schists) arerich in aluminum and contain significant Cr (up to 390 ppm) and V (upto 800 ppm). These rocks exhibit the same chemical composition asshale and marls from common platform sediments (Fig. 4), and plotwithin the geochemical domain defined by Moine et al. (1981). It maybe hypothesized that Al and chromiferous elements were collected byfluids, circulating through mafic units, and then released as theypercolated through the marbles. Marbles are Si-poor and thus rep-resent a potential trap for the formation of ruby. Petrographic and

Table 2Parageneses observed in ruby-bearing marbles from Jegdalek (Afghanistan), Nangimali(Azad Kashmir), Hunza (Pakistan), Chumar (Nepal) and Luc Yen (Vietnam)

Deposit ParagenesisJegdalek, Afghanistan Two parageneses:

• ruby+mica (phlogopite, muscovite andmargarite)+ feldspar (plagioclase or orthoclase)±graphite±tourmaline±titanite±pyrite• ruby+spinel±chlorite±phlogopite±graphite±titanite±pyrite

Nangimali, Azad-Kashmir • ruby+phlogopite (and aspidolite)+chlorite±pyrite±titanite±tourmaline±amphibole

Hunza, Pakistan Two paragenesis:• ruby+spinel±sapphirine±chlorite±phlogopite±margarite±amphibole±zoisite±graphite±apatite±titanite±pyrite• ruby+phlogopite+muscovite±paragonite±chlorite±margarite±plagioclase±titanite±apatite

Chumar, Nepal ruby+muscovite±margarite±apatite±titaniteLuc Yen district, Vietnam Two parageneses:

• ruby+spinel±chlorite±amphibole±olivine ±humite±graphite±pyrite• ruby+phlogopite+feldspar (plagioclase ororthoclase)±muscovite±paragonite±amphibole±graphite±tourmaline±apatite±titanite±pyrite±pyrrhotite

Table 3Chemical analysis of spinel associated with ruby in marble

Analysis Jegdalek Hunza Vietnam

JD6/7 JD6/7–9 HU4b1/1–7 HU16a2/1–3 HU18a/4–2 HU18a/4–3 V41a/9–6 AP4/10–4

SiO2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.05TiO2 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.00Al2O3 69.15 61.83 58.40 69.63 66.21 46.93 71.89 70.68Cr2O3 0.26 2.08 0.37 0.04 3.27 19.05 0.10 0.93Fe2O3 calc. 0.00 0.00 2.53 0.08 0.00 0.15 0.00 0.45V2O3 0.00 0.00 0.00 0.02 0.00 0.00 0.00 0.00FeO calc. 1.84 1.26 33.42 4.79 5.27 9.97 0.78 0.15MnO 0.00 0.00 0.00 0.00 0.00 0.09 0.02 0.05MgO 22.95 12.14 5.04 24.75 23.54 12.95 26.56 28.20ZnO 6.17 22.63 0.00 0.19 0.91 10.12 0.17 0.04NiO 0.00 0.02 0.05 0.06 0.08 0.07 0.00 0.06CoO 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00Total 100.37 99.96 99.81 99.56 99.27 99.32 99.54 100.57Si 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001Ti 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000Al 2.002 1.974 1.938 1.997 1.937 1.570 2.022 1.972Cr 0.005 0.045 0.008 0.001 0.064 0.427 0.002 0.017Fe3+ 0.000 0.000 0.054 0.001 0.000 0.003 0.000 0.008V 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000Fe2+ 0.038 0.029 0.787 0.098 0.109 0.237 0.016 0.003Mn 0.000 0.000 0.000 0.000 0.000 0.002 0.000 0.001Mg 0.840 0.490 0.212 0.898 0.871 0.548 0.945 0.995Zn 0.112 0.453 0.000 0.003 0.017 0.212 0.003 0.001Ni 0.000 0.000 0.001 0.001 0.002 0.002 0.000 0.001Co 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000Total 2.997 2.991 3.000 3.000 3.000 3.000 2.988 3.000

Samples from Jegdalek, Afghanistan (JD), Hunza, Pakistan (HU), Luc Yen, northern Vietnam (V and AP).

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stable-isotopes studies were conducted in order to determine whichof the open versus closed system hypotheses explains the formation ofruby.

5. Petrography and fluid inclusions

5.1. Mineral parageneses

Minerals associated with ruby in marbles vary from one deposit toanother. The parageneses encountered in each deposit are summar-ized in Table 2. Ruby is commonly associated with micas (phlogopite,muscovite and margarite but also sometimes paragonite and aspi-dolite; Garnier et al., 2004), chlorite, feldspar, graphite and pyrite, and

Fig. 5. All SEM photographs are back-scattered electron (BSE) mode. (A) Ruby (Cor), dolomite(Anh) and spinel (Sp) inclusions in this ruby.

in some cases with spinel, tourmaline and amphibole. Furthermore,relics of anhydrite are found as solid inclusions in ruby crystals as wellas in the carbonates, in samples from the Hunza Valley, Pakistan andfrom the Lo Gam zone, Vietnam; and salt crystals (CaCl2 and NaCl) arefound as solid inclusions in most of ruby crystals observed with theSEM, excepted in Mogok and Mong Hsu deposits.

5.2. Mineral chemistry

Calcite commonly contains small amounts of magnesite (MgCO3

between 0.7 and 4.1 wt.%) and traces of Fe, Al, Zn, Pb, Mn and Sr (Fe2+

between0.001 to 0.008 atoms per formula unit, apfu; Al3+b0.002 apfu;Zn, Pb and Srb0.001 apfu; Mnb0.003 apfu).

(Dol) and calcite (Cc) in a sample from Hunza, Pakistan (HU-18a). (B) Detail of anhydrite

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Most spinels commonly have a composition of spinel sensu strictu(Table 3). Spinel has octahedral shape and pink to light purple color.Spinel associated with ruby in marble has low to medium Cr contents(Crb0.045 apfu). In few samples, the chemical composition of spinelvaries: (1) in the Ting Ten Har occurrence (Hunza Valley), a dark greenoctahedral spinel (sample HU-4b1) has a composition between spinelsensu strictu and hercynite (Fe2+b0.7 apfu; Table 3). Ruby associatedwith this spinel is also Fe-rich (Fe3+ between 1700 and 3100 ppm);(2) at Jegdalek, spinel has a composition between spinel sensu strictuand gahnite and occurs as inclusions in ruby which is also enriched inZn and Mg (Znb2,400 ppm and Mgb1900 ppm). Zn substitutes formagnesium and chromium for aluminium. The high content of Zn forsome of these spinels is up to 22.63 wt.% (sample JD6, Table 3).

At Furandar mine in the Hunza valley, spinel and anhydrite in-clusions are found in ruby (Fig. 5). Ruby in equilibrium with dolomiteforms from the reaction of spinel with calcite: spinel is a pre-rubyphase and its mineral chemistry (sample H18a, Table 3) shows high Cr(up to 19.05 wt.%) and Zn contents (up to 10.12 wt.%); the source ofchromium for ruby in that case is most likely spinel.

Five types of mica are encountered in ruby-bearing marbles(Table 4). Fluorine-rich aspidolite (sodium phlogopite) forms inter-growths with paragonite and phlogopite in ruby-bearing marblesfrom Nangimali (see sample N1 in Table 4; Garnier et al., 2004).Aspidolite is also found in deposits from Luc Yen in Vietnam. In the

Table 4Chemical analyses of micas associated with ruby in marble. Samples from: 1: Nangimali, Azanorthern Vietnam (V and AP)

Aspidolite Phlogopite

Analysis 1 4 1 2 2 3 4

N1-mica/2 AP2/7-12 LKT13/3-2 HU18a/6-4 HU5a2/2-1 Ruyil/4-7 V49/3-

SiO2 42.83 40.29 40.55 41.92 35.43 40.57 37.00TiO2 0.47 0.29 0.35 0.43 1.32 0.56 1.45Al2O3 18.92 24.40 18.53 16.59 21.97 19.19 25.10Cr2O3 0.26 0.13 0.20 0.08 0.35 0.12 0.07FeO 0.19 0.27 0.43 0.66 12.00 1.66 1.49MnO 0.00 0.02 0.04 0.05 0.00 0.01 0.08MgO 25.82 24.16 25.56 25.95 14.13 23.88 19.00CaO 0.00 0.13 0.04 0.01 0.00 0.00 0.00BaO 0.00 0.00 0.00 0.00 0.00 0.00 0.00Na2O 6.49 6.48 1.58 1.55 0.16 0.57 0.22K2O 0.43 0.51 8.37 8.12 9.99 8.99 10.49ZnO 0.00 0.00 0.02 0.00 0.00 0.00 0.05NiO 0.01 0.03 0.00 0.00 0.11 0.01 0.00F 2.78 1.42 3.58 1.69 0.34 1.26 0.00Cl 0.00 0.00 0.00 0.00 0.02 0.00 0.01H2O calc. 3.19 3.89 2.66 3.56 3.92 3.74 4.28.–OfF −1.17 −0.60 −1.51 −0.71 0.00 −0.53 0.00.–OfCl 0.00 0.00 0.00 0.00 0.00 0.00 0.00Total 100.22 101.41 100.41 99.89 99.74 100.01 99.23Si 5.698 5.297 5.574 5.768 5.203 5.602 5.178Aliv 2.302 2.703 2.426 2.232 2.797 2.398 2.822Alvi 0.665 1.079 0.576 0.459 1.005 0.726 1.318Ti 0.047 0.029 0.036 0.044 0.146 0.058 0.152Cr 0.028 0.013 0.022 0.009 0.041 0.013 0.008Fe2+ 0.021 0.030 0.049 0.076 1.474 0.191 0.174Mn 0.000 0.002 0.005 0.006 0.000 0.002 0.009Mg 5.122 4.736 5.238 5.323 3.093 4.915 3.964Zn 0.000 0.000 0.002 0.000 0.000 0.000 0.005Ni 0.001 0.003 0.000 0.000 0.013 0.001 0.000Oct 5.884 5.891 5.928 5.917 5.771 5.904 5.630Ca 0.000 0.018 0.006 0.001 0.000 0.000 0.000Ba 0.000 0.000 0.000 0.000 0.000 0.000 0.000Na 1.675 1.651 0.421 0.414 0.046 0.152 0.059K 0.074 0.085 1.468 1.425 1.871 1.583 1.874Int 1.748 1.754 1.895 1.840 1.917 1.735 1.933F 1.170 0.589 1.556 0.735 0.158 0.551 0.000Cl 0.000 0.000 0.000 0.000 0.005 0.001 0.001OH 2.830 3.411 2.444 3.265 3.837 3.448 3.998Total 19.632 19.646 19.822 19.757 19.688 19.639 19.563

other deposits, the most common micas are phlogopite, muscoviteand margarite. In Nangimali and in the Ting Ten Har district in theHunza Valley, potassium is replaced by sodium in muscovite, leadingto the formation of paragonite (sample HU-4e2 in Table 4). Margariteis less common than phlogopite but it is present in the samples fromall the deposits. The chemical composition in Table 4 shows the sub-stitution of Ca by Na (0.07bNa apfub1.01), and notable Cr and Fcontents (b0.272 apfu and b0.09 apfu, respectively).

Chlorite associated with ruby in marbles is Al- and Mg-rich andbelongs to the chemical groups of sheridanite, clinochlore and penninite(Fig. 6). Mg-chlorite appears either as a retrograde metamorphic phasesurrounding micas or as intergrowths with mica. Inmarble units free ofruby, chlorite is Si-richer and Al- and Mg-poorer than when associatedwith ruby.

Feldspar is not common in ruby-bearing marbles but it is presentin some samples from Afghanistan, Pakistan, Nepal and Vietnam.Two types of feldspar are present: plagioclase (bytownite–anorthite,An87–99) and orthoclase containing up to 1 wt.% Na2O (Table 5).

Calcic amphiboles are associated with ruby in deposits from Azad-Kashmir, Pakistan and Vietnam. They have compositions typical ofedenite, pargasite, sadanagaite and tremolite (Table 6). They are Na-and F-rich (up to 0.800 and 0.450 apfu, respectively) and also con-tain small amounts of Cr (b0.040 apfu), Ti (b0.230 apfu) and Cl(b0.030 apfu).

d-Kashmir (N1 and LKT), 2: Hunza, Pakistan (HU), 3: Nepal (Chumar, Ruyil), 4: Luc Yen,

Muscovite Margarite

1 2 2 3 3 4 1

5 N1/1-7 HU4e2/2-4 HU5a2/1-1 chumar/5-2 chumar/6-1 V33/8-9 LKT2g

49.40 48.90 46.02 45.84 31.70 49.90 45.840.29 0.00 0.88 0.18 0.00 0.05 0.00

33.56 40.55 37.28 36.43 49.66 36.97 28.520.14 0.02 0.19 0.05 0.02 0.00 0.000.00 0.09 0.81 0.14 0.14 0.01 0.000.00 0.07 0.00 0.00 0.00 0.00 0.002.36 0.07 0.80 2.15 2.72 0.37 0.000.06 0.96 0.10 0.00 0.00 0.08 18.660.06 0.00 0.00 0.64 0.60 0.00 0.000.87 4.84 0.46 0.49 0.47 1.61 3.049.52 1.37 9.95 10.11 10.21 6.93 0.230.00 0.02 0.00 0.07 0.15 0.00 0.050.11 0.01 0.00 0.00 0.00 0.00 0.000.48 0.04 0.00 0.05 0.07 0.00 0.000.00 0.00 0.00 0.00 0.00 0.00 0.184.39 4.79 4.59 4.53 4.40 4.68 4.46

−0.20 −0.02 0.00 −0.02 −0.03 0.00 0.000.00 0.00 0.00 0.00 0.00 0.00 60.04

101.02 101.71 101.08 100.66 100.09 100.60 100.946.418 6.100 6.017 6.040 4.287 6.388 6.1041.582 1.900 1.983 1.960 3.713 1.612 1.8963.557 4.061 3.762 3.697 4.201 3.965 2.5790.028 0.000 0.087 0.018 0.000 0.005 0.0000.014 0.002 0.020 0.005 0.002 0.000 0.0000.000 0.009 0.089 0.016 0.015 0.001 0.0000.000 0.007 0.000 0.000 0.000 0.000 0.0000.456 0.013 0.156 0.422 0.547 0.071 0.0000.000 0.002 0.000 0.007 0.015 0.000 0.0050.012 0.001 0.000 0.000 0.000 0.000 0.0004.067 4.096 4.112 4.165 4.781 4.042 2.5840.008 0.128 0.014 0.000 0.001 0.011 2.6620.003 0.000 0.000 0.033 0.032 0.000 0.0000.220 1.171 0.117 0.126 0.122 0.400 0.7851.577 0.218 1.660 1.700 1.761 1.132 0.0391.809 1.517 1.790 1.858 1.915 1.542 3.4860.196 0.016 0.000 0.020 0.031 0.000 0.0000.000 0.000 0.000 0.000 0.000 0.000 0.0413.804 3.984 4.000 3.980 3.969 4.000 3.95917.876 17.613 17.903 18.024 18.696 17.584 18.070

Table 5Chemical analyses of feldspars associated with ruby in marble. Samples from: 1:Jegdalek, Afghanistan (JD), 2: Hunza, Pakistan (HU), 3: Luc Yen, northern Vietnam (V)

Plagioclase Orthoclase

Analysis JD2/3-4 JD2/3-5 HU19b/10-2 JD3/4-2 V22/5-3 V16/1-10

1 1 2 1 3 3

SiO2 45.10 46.37 45.44 66.85 64.82 64.83TiO2 0.00 0.00 0.00 0.00 0.05 0.05Al2O3 35.63 34.39 34.94 18.45 19.17 19.38Fe2O3 0.00 0.04 0.00 0.02 0.03 0.00MnO 0.00 0.00 0.12 0.00 0.00 0.00MgO 0.00 0.02 0.01 0.06 0.09 0.01CaO 18.03 16.87 18.77 0.01 0.08 0.04SrO 0.00 0.00 0.00 0.00 0.00 0.00BaO 0.00 0.00 0.00 0.00 0.00 0.00Na2O 0.70 1.17 0.84 0.70 0.64 1.07K2O 0.02 0.02 0.01 15.21 15.67 15.07Rb2O 0.00 0.00 0.00 0.00 0.00 0.00Total 99.48 98.88 100.13 101.31 100.54 100.44Si 2.08 2.15 2.09 3.024 2.972 2.969Ti 0.000 0.000 0.000 0.000 0.002 0.002Al 1.940 1.88 1.9 0.984 1.036 1.046Fe3+ 0.000 0 0.000 0.001 0.001 0.000Mn 0.000 0.000 0.01 0.000 0.000 0.000Mg 0.000 0 0 0.004 0.006 0.001Ca 0.89 0.84 0.93 0.000 0.004 0.002Sr 0.000 0.000 0.000 0.000 0.000 0.000Ba 0.000 0.000 0.000 0.000 0.000 0.000Na 0.06 0.11 0.08 0.062 0.056 0.095K 0 0 0 0.878 0.917 0.880Rb 0.000 0.000 0.000 0.000 0.000 0.000Total 4.98 4.97 5 4.953 4.994 4.995Ab 6.56 11.14 7.49 6.57 5.78 9.75An 93.32 88.74 92.45 0.04 0.41 0.20Or 0.12 0.13 0.06 93.39 93.81 90.05

Fig. 6. Diagram Si (apfu) vs. XMg of chlorites with XMg=Mg2+/(Mg2++Fe2+);nomenclature after Deer et al. (1963). Open symbol corresponds to ruby-bearingparageneses and full symbol to ruby-free parageneses; circle = Hunza; triangle =Nangimali; diamond = Luc Yen.

176 V. Garnier et al. / Ore Geology Reviews 34 (2008) 169–191

Sapphirine is present only in one sample from the Furandar minein Hunza Valley, associated with ruby and spinel; its chemical for-mulae is Mg6.40–6.62Fe0.12–0.18Al18.54–18.90Si2.49–2.66O40.

Ruby-bearing marbles from Afghanistan, Pakistan and VietnamcontainMg- and Al-rich tourmalinewith composition between draviteand uvite (Table 7).

The mineralized marbles commonly contain rutile and titanite; theseminerals show enrichment in Cr (up to 1.8 and 0.33 wt.% Cr2O3, respec-tively) and Al (up to 0.12 and 4.76 wt.% Al2O3). Humite and forsteriteare found in the Laling Tolian mine, Hunza Valley and An Phu mine,Vietnam. The chemical formula for humite are Mg0.20–0.70Fe0.15–0.25Ti0.00–0.17(OH1.20–2.00F0.00–0.80).3Mg2[SiO4] and Mg0.50–0.02Fe0.15–0.25Ti0.23Ni0.40(OH1.60F0.40).3Mg2[SiO4]. One unique sample of marble from Ting TenHar, in Hunza Valley, contains two grains of zoisite [Ca1.98–2.01Fe0.08–0.09Al2.93–2.94–Si2.98–2.99O12(OH)].

5.3. Petrographic associations

Petrographic relations between minerals coexisting with rubywere observed in the marbles from Jegdalek in Afghanistan, Hunzain Pakistan and Luc Yen in Vietnam. The best preserved phaserelations are those formed during the metamorphic retrograde path,as prograde metamorphic assemblages are modified or destroyed atthis stage. The phase equilibria P–T diagram (Fig. 7) shows thatmargarite and diaspore can respectively form by destabilization ofanorthite and corundum in the presence of water, at temperatures ofabout 450 to 500 °C and 350 to 400 °C, respectively. They are formedduring the retrograde metamorphic path, following reactions (1)and (2).

anorthiteþ corundum þ water↔margarite ð1Þ

CaAl2Si2O8 þ Al2O3 þ H2O↔CaAl2½Si2Al2O10�ðOHÞ2

corundum þ water↔2diaspore ð2Þ

Al2O3 þ H2O↔2AlOðOHÞ

The difference in temperature of formation may explain the abun-dance of margarite compared to diaspore, as margarite formed athigher temperature before diaspore during retrograde metamorphicreactions.

Several reactions are involved in the formation of ruby in marbles.The principal reaction is destabilization of spinel in contact withcalcite (reaction 3) during the retrograde metamorphic path (Fig. 7).

This reaction is observed in marbles from Jegdalek in Afghanistan,Hunza in Pakistan and in Luc Yen in Vietnam (Fig. 8).

spinel þ calcite þ CO2↔corundum þ dolomite ð3ÞMgAl2O4 þ CaCO3 þ CO2↔Al2O3 þ CaMgðCO3Þ2

In a sample from Hunza (HU-18a), spinel occurs as solid inclusionsin ruby crystals associated with anhydrite (Fig. 5A). In some places,anhydrite included in ruby encloses relics of spinel (Fig. 5B). In LucYen, anhydrite crystals of 100 to 350 µm in size are observed by SEM inthe marbles. This mineral texture and association in the marblesupport the hypothesis that anhydrite and perhaps other evaporites,may have played a key role in the ruby mineralization as suggested byfluid inclusion studies in Vietnamese rubies (Giuliani et al., 2003b).

The second reaction is formation of ruby by destabilization ofmuscovite following reaction (4). This reaction is also observed in thesame deposits as the spinel breakdown reaction.

muscovite↔K � feldspar þ corundum þ water ð4ÞKAl2ðSi3AlÞO10ðOHÞ2↔KAlSi3O8 þ Al2O3 þ H2O

Anorthite contains small amounts of Na. This may reflect theformation of ruby during the destabilization of paragonite leading tothe formation of corundum and oligoclase (An11–17), in the samplesfrom Nangimali and Hunza, in which paragonite is present. In thesample fromFurundar, Hunza containing together sapphirine+spinel+corundum+Mg-chlorite, reaction (5) is inferred:

2spinel þ 6corundumþMg� chlorite↔sapphirineþ 4water ð5Þ2MgAl2O4 þ 6Al2O3 þMg5Al½Si3AlO10�ðOHÞ8↔Mg7Al18Si3O40 þ 4H2O

5.4. Fluid inclusions

Fluid inclusions (FI) have been previously studied in rubies frommarble-hosted deposits in Luc Yen and Quy Chau deposits, North

Table 6Chemical analyses of amphibole associated with ruby in marble (nomenclature after Leake et al., 1997, 2004)

Tremolite Mg-hornblende Pargasite Sadanagaite Edenite

Analysis LKT2g'/4-6 LKT2g'/4-4 LKT2g'/1-6 LKT2g'/2-1 HU19b/1-8 HU19b/r-9 HU4B1/4-11 HU4B1/4-13 V41a/65 AP4/10-2

1 1 1 1 2 2 2 2 3 3

SiO2 57.20 55.13 54.53 55.42 39.43 42.29 32.56 34.97 50.04 48.03TiO2 0.10 0.18 0.20 0.20 1.96 1.09 2.17 1.36 0.43 0.09Al2O3 2.03 5.00 5.49 5.33 21.69 19.10 23.66 23.84 10.90 12.28Cr2O3 0.00 0.00 0.00 0.02 0.11 0.34 0.00 0.00 0.00 0.21Fe2O3 calc. 0.00 0.00 0.00 0.00 0.00 0.00 1.91 0.00 0.00 0.16FeO calc. 0.31 0.29 0.32 0.28 0.20 0.37 14.37 15.58 0.61 0.00MnO 0.00 0.08 0.00 0.00 0.03 0.06 0.00 0.03 0.00 0.07MgO 23.73 22.53 22.56 22.96 16.97 17.80 6.38 6.85 20.91 21.27CaO 13.54 13.58 13.61 13.52 13.32 13.38 11.68 11.95 13.48 13.53Na2O 0.17 0.50 0.60 0.42 2.75 2.80 2.15 2.77 1.89 1.77K2O 0.18 0.33 0.29 0.20 0.93 0.75 1.79 0.99 0.16 0.21ZrO 0.00 0.19 0.00 0.10 0.00 0.11 0.00 0.30 0.00 0.06NiO 0.05 0.00 0.00 0.00 0.00 0.00 0.12 0.00 0.00 0.00F 0.00 0.00 0.00 0.38 0.89 0.94 0.00 0.00 0.38 1.04Cl 0.00 0.00 0.00 0.00 0.01 0.01 0.05 0.04 0.02 0.05H2O calc. 2.20 2.20 2.19 2.04 1.70 1.70 1.94 1.99 2.00 1.66–OfF 0.00 0.00 0.00 −0.16 −0.37 −0.40 0.000 0.000 −0.16 −0.44–OfCl 0.00 0.00 0.00 0.00 0.00 0.00 −0.011 −0.010 0.00 −0.01Total 99.50 100.01 99.80 100.71 99.62 100.34 98.749 100.668 100.66 99.98Si 7.804 7.516 7.451 7.491 5.55 5.90 5.002 5.230 6.848 6.635Aliv 0.196 0.484 0.549 0.509 2.45 2.10 2.998 2.770 1.152 1.365Alvi 0.129 0.319 0.335 0.340 1.15 1.04 1.286 1.431 0.607 0.634Ti 0.010 0.019 0.021 0.020 0.21 0.11 0.251 0.152 0.044 0.009Cr 0.000 0.000 0.000 0.002 0.012 0.037 0.000 0.000 0.000 0.023Fe3+ 0.000 0.000 0.000 0.000 0.00 0.00 0.220 0.000 0.000 0.016Fe2+ 0.035 0.033 0.036 0.032 0.02 0.04 1.847 1.949 0.070 0.000Mn 0.001 0.009 0.000 0.000 0.00 0.01 0.000 0.003 0.000 0.008Mg 4.826 4.580 4.596 4.626 3.56 3.70 1.460 1.526 4.266 4.380Ca 1.979 1.984 1.993 1.958 2.01 2.00 1.922 1.915 1.977 2.002Na 0.044 0.132 0.160 0.110 0.75 0.76 0.640 0.804 0.502 0.474K 0.031 0.057 0.051 0.034 0.17 0.13 0.351 0.189 0.028 0.037Zr 0.000 0.013 0.000 0.007 0.00 0.01 0.000 0.022 0.000 0.004Ni 0.006 0.000 0.000 0.000 0.00 0.00 0.014 0.000 0.000 0.000F 0.000 0.000 0.000 0.162 0.40 0.41 0.000 0.000 0.164 0.454Cl 0.000 0.000 0.000 0.000 0.00 0.00 0.012 0.011 0.005 0.012OH 2.000 2.000 2.000 1.838 1.60 1.58 1.988 1.989 1.83 1.534Total 17.062 17.145 17.192 17.129 17.893 17.837 17.991 17.991 17.493 17.588XMg 0.99 0.99 0.99 0.99 0.99 0.99 0.442 0.439 0.98 1.00(Ca)B 1.98 1.98 1.99 1.96 2.00 2.00 1.922 1.915 1.98 1.93(Na)B 0.02 0.02 0.01 0.02 0.00 0.00 0.014 0.023 0.02 0.00(Ca+Na)B 2.00 2.00 2.00 1.98 2.00 2.00 1.936 1.938 2.00 1.93(Na+K)A 0.06 0.17 0.20 0.12 0.92 0.89 0.976 0.969 0.51 0.51

Samples from: 1: Nangimali, Azad-Kashmir (LKT), 2: Hunza, Pakistan (HU), Luc Yen, northern Vietnam (V and AP).

177V. Garnier et al. / Ore Geology Reviews 34 (2008) 169–191

Vietnam (Giuliani et al., 2003a,b). Raman and infrared spectrometrycombined with microthermometry investigations on primary andsecondary fluid inclusions provided evidence of CO2–H2S–COS–S8–Al(OH)-bearing fluids with native sulfur and diaspore daughter min-erals, without visible water (Fig. 9D, K).

Fluid inclusions investigations were performed on rubies from thedifferent mines from Central and South East Asia. The microthermo-metric and Raman data on FI from Mogok are preliminary. Primary,pseudo-secondary and secondary fluid inclusions were recognized onthe basis of their respective chronology. There are commonly two-phase FI (liquid and vapour carbonic phases) but sometimes only havea single phase carbonic-rich inclusions (Fig. 9F). Type-A inclusions areprimary and occur as isolated or oriented FI throughout the growthzones of the crystals especially in Mong Hsu and Luc Yen. Type-Binclusions are pseudo-secondary and are found mainly in intragra-nular fractures between distinct growth zones. Type-C inclusionsoccur along healed fracture planes which are secant to several crystallimits or growth zones.

Microthermometry and Raman spectrometry of the three types ofFI enable the recognition of the same fluid composition as found innorthern Vietnam (Table 8). Diaspore appeared as either as a 2 to 3 µmfilm coating the walls of fluid inclusion cavities as observed in FI

cavities from Luc Yen and Quy Chau in Vietnam, and Ruyil in Nepal(Fig. 9G) or as crystals of 2 to 10 µm wide trapped in the cavities,especially in Mong Hsu and Pamir rubies (Fig. 9B, C). Native sulfur isgenerally nucleated during Raman irradiation but it was observed atroom temperature in Luc Yen, Quy Chau, Mong Hsu and Jegdalek FIcavities (Fig. 9A). The presence of diaspore and COS in the fluidinclusions indicates that a small amount of water was present in thepaleofluid. COS complexes that are uncommon in natural fluids wereidentified in all the deposits except in Tajikistan and Nepal (Table 8).Mole fractions of H2O and CO2 are around 10−2 and the calculatedconcentrations of water in the fluid inclusions is in the 1 to 10 mol.%range. The presence of H2S and S8 in fluid inclusions attests to thelow redox state of the system. H2S, identified by its Raman peak at2603 cm−1 (Fig.10),was found in variable amounts from1 to 43.7mol.%(Table 8); the highest concentrations were found in rubies fromTajikistan and Hunza Valley (Fig. 11). Several minute solid inclusionswere identified in the cavities of FI as diaspore, rutile, dolomite, calcite,feldspar, boehmite, fluorite, phlogopite, apatite, pyrite, arsenopyrite,zircon and margarite; diaspore, rutile and dolomite inclusions arecommon for all rubies.

Crush-leach analyses identified sulfates and chlorides that are dueto the presence of anhydrite and Na–Ca–Cl salts identified by SEM in

Table 7Chemical analyses of tourmaline associated with ruby in marbles

Analysis JD2/1-11 HU18a/6-3 HU19b/6-7 V52a/1-11

1 2 2 3

SiO2 38.53 37.38 36.80 33.96TiO2 0.04 0.45 0.77 0.74Al2O3 36.61 32.10 32.27 39.22Cr2O3 0.01 0.41 0.41 0.03Fe2O3 0.00 0.00 0.00 0.00V2O3 0.00 0.00 0.00 0.00B2O3 (calculated) 11.04 10.94 10.93 10.96FeO 0.00 0.41 0.00 0.41MnO 0.00 0.00 0.00 0.02MgO 7.62 11.73 11.63 7.98CaO 0.29 1.51 2.83 1.77ZnO 0.00 0.00 0.00 0.00SrO 0.00 0.00 0.00 0.00BaO 0.00 0.00 0.00 0.00CuO 0.00 0.00 0.00 0.00Na2O 2.14 2.22 1.40 1.94K2O 0.00 0.00 0.01 0.12Rb2O 0.00 0.00 0.00 0.00F 0.04 0.59 0.01 0.07H2O (calculated) 3.79 3.50 3.77 3.75.–OfF 0.02 0.25 0.00 0.03Total 100.09 100.99 100.81 100.94B3+ 3.000 3.000 3.000 3.000Si4+ 6.067 5.936 5.853 5.385AlIV 0.000 0.064 0.147 0.615AlZ 6.000 5.945 5.903 6.000AlY 0.794 0.000 0.000 0.713Ti4+ 0.005 0.054 0.092 0.089Cr3+ 0.001 0.051 0.052 0.004Fe3+ 0.000 0.000 0.000 0.000V3+ 0.000 0.000 0.000 0.000Fe2+ 0.000 0.054 0.000 0.054Mn2+ 0.000 0.000 0.000 0.003Mg2+ 1.789 2.777 2.757 1.887Zn2+ 0.000 0.000 0.000 0.000Sr2+ 0.000 0.000 0.000 0.000Ba2+ 0.000 0.000 0.000 0.000Cu2+ 0.000 0.000 0.000 0.000Total Y 2.588 2.937 2.901 2.750Ca2+ 0.049 0.257 0.483 0.300Na+ 0.653 0.684 0.433 0.597K+ 0.000 0.000 0.001 0.023Rb+ 0.000 0.000 0.000 0.000Total X 0.702 0.941 0.917 0.920F– 0.020 0.296 0.004 0.035OH– 3.980 3.704 3.996 3.965

Samples from: 1: Jegdalek, Afghanistan (JD), 2: Hunza, Pakistan (HU), 3: and Luc Yen,northern Vietnam (V).

178 V. Garnier et al. / Ore Geology Reviews 34 (2008) 169–191

the crystals of ruby from all the deposits. Anhydrite was identified inrubies from Nangimali (Fig. 9E, H) and Hunza, and fromMogok (Smithand Dunaigre, 2001). It was found also in ruby-bearing marbles fromLuc Yen and Hunza. Salt inclusions were identified by SEM in rubiesfrom Luc Yen (Fig. 9I), Hunza and Jegdalek (Fig. 9J). Crush-leach anal-ysis in rubies indicate that chloride is generally the dominant anion(360bClb3,560 ppb) but sulfate (56bSO4b1,420 ppb) and nitrate(42bNO3b1,066 ppb) are present at only slightly lower concentra-tions, and in some instances either may be the dominant species as inthe Furohar deposit in the Hunza Valley.

5.5. P–T conditions of ruby formation

The thermobarometric conditions of mineral equilibria involved inruby formation were modeled with TWEEQU (Berman, 1991) usingthermodynamic data of Berman (1988) and Holland and Powell (1988)for sapphirine and using equations of state from Kerrick and Jacobs(1981) and Haar et al. (1984). Chemical formulae are based on 12, 18and 20 O atoms, respectively for mica, chlorite and sapphirine, andonly pure end-members were considered. Equilibriumwas calculated

considering that, locally and at the time the reactions occurred, thefluids involved were either pure CO2 or H2O. Sapphirine shouldappeared at low temperature (500 to 600 °C) if the fluid was saturatedin CO2, but it was observed only in one deposit of the Hunza Valley. Forthis reason, the fluid of the prograde metamorphism was necessarilyH2O-saturated and originating from the breaking of phengite andmuscovite in the protolith. H2Owas then incorporated in the hydratedminerals (tourmaline, amphibole, Mg-chlorite) associated with cor-undum. The CO2-fluids were released by devolatilization of the car-bonates and were trapped in fluid inclusion cavities from gem rubyduring retrograde metamorphism. Isochores of CO2-bearing fluidstrapped in inclusions in ruby were added to the P–T diagram (Fig. 7).The densities and relative isochores of the primary CO2-rich fluidswere calculated using the computer program Macflincor version 0.92(Brown and Hagemann, 1995); the densities are in the range 0.84 to0.86 g/cm3 for Jegdalek in Afghanistan, 0.80 and 0.83 g/cm3 for Hunzain Pakistan, and 0.80 to 0.84 g/cm3 for Luc Yen in Vietnam. Fig. 7 showsthat corundum could have formed during the prograde path bydestabilization of diaspore or margarite, or during the retrogrademetamorphic path by destabilization of spinel, muscovite or sap-phirine (reactions 3, 4 and 5, respectively). However, there is noevidence of a protolith enriched in diaspore. Furthermore, these equi-libria release water and this is not consistent with the chemistry of thefluids trapped in the fluid inclusions. In addition, this would cor-respond to a high geothermal gradient (about 500 °C for 2.7 kbar).Even if some ruby formed this way, it is probable that rubywould havebeen involved in retrograde metamorphic reactions, as these marbleswere subject to upper-amphibolite to lower-granulite conditions(Okrusch et al., 1976; Hauzenberger et al., 2001; see section on stableisotopes for more details), and evidence for prograde reactions are notpreserved in the rocks. It appears that gem ruby formed from de-stabilization of spinel or muscovite in Afghanistan and Vietnam, andpossibly from sapphirine in one deposit in Pakistan. The isochorescrosscut the corresponding curves at the following P–T conditions: forformation of ruby from muscovite, at ca. 670 °C and between 2.9 and3.3 kbar for Jegdalek, at about 660 °C and between 2.7 and 3.0 kbar inVietnam; for formation of ruby from spinel, at about 630 °C andbetween 2.9 and 3.1 kbar in Jegdalek, at about 620 °C and between 2.6and 2.9 kbar in Vietnam, and at about 620 °C and between 2.6 and2.8 kbar in Hunza; at about 690 °C and between 2.8 and 3.0 kbar forformation of ruby from sapphirine in Hunza (Fig. 7A, B). Ruby is thusformed during retrograde metamorphism, with the result that it iswell preserved in marbles. In addition, the chemistry of the fluidstrapped in gem ruby indicate that most of the gemstones crystallizedfrom spinel as this reaction uses up CO2 and that only minor rubyformed from destabilisation of muscovite or sapphirine, which israrely observed.

In the Ailao-Shan-Red River metamorphic belt in northernVietnam, the geothermobarometric study of the complex revealedthat peak metamorphism took place at amphibolite-facies conditions,i.e., at ~4.5±1.5 kbar and 710±70 °C (Leloup and Kienast, 1993; Leloupet al., 2001). Nam et al. (1998) estimated the P–T metamorphicconditions for the Day Nui Con Voi belt at ~6.5±1.5 kbar and ~690±30 °C. These temperatures are in agreement with the maxima tem-peratures obtained for ruby-bearing marbles, by isotopic thermo-meters calculated with the isotopic δ13C calcite–graphite pairs(Fig. 12), between 625 and 750±40 °C. It appears that formation ofruby-deposits in marbles may be restricted to a maximum of ~6 kbarand ~700 °C. Gem ruby formed at about 620 to 650 °C and between 2.6and 2.9 kbar during the retrograde P–T metamorphic path.

On the diagram concerning Hunza (Fig. 7B), the isochores crosscutthe curve of muscovite destabilization at about 650 °C and between2.7 and 2.9 kbar. Two hypotheses can be proposed:

(1) Looking at the metamorphic P–T path followed by the rocks,it is impossible that ruby formed from destabilization of

Fig. 7. P–Tconditions of stability for mineral associations from ruby-bearing marbles. Abbreviations: An = anorthite; And = andalusite; Cc = calcite; Clin = clinochlore; Co = corundum;Do = dolomite; Dsp = diaspore; Ksp = K-feldspar; Ky = kyanite; Ma =margarite; Mu =muscovite; Sill = sillimanite; spr7 = sapphirine; Sp = spinel; Zo = zoisite. (A) Jegdalek and Luc Yen,(B) Hunza. The dotted P–T path is supposed for the Furandar occurrences only, because of the presence of sapphirine in one sample from this occurrence. 1=destabilization point ofmuscovite to form corundum. Diagrams calculated with TWEEQU (Berman, 1991).

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muscovite at such P–T conditions. It seems more probable thatit formed at higher pressure conditions (P~4.2 kbar; point 1 onFig. 7B) and thus, that the fluids trapped in the inclusions werenot released by the metamorphic reaction:

Muscovite↔Corundumþ K � feldspar þ H2O ð6Þ(2) As only one sample from Furandar in Hunza contains sap-

phirine, and as all the studied samples from this district do notcontain muscovite, it may be assumed that the dotted P–T path(on Fig. 7B) corresponds to rocks from this district, and thatrocks from the other districts may have followed a P–T pathsimilar (T~650 °C, 2.7bP kbarb2.9) to the path proposed forVietnam and Afghanistan. As water activity in the systemshould have been low, ruby formed at high temperature by thedestabilization of sapphirine and with muscovite preserved inthe rocks. In addition, it is possible that water released by thedestabilization of muscovite participates to the formation ofchlorite and other hydrated minerals (as amphiboles that arealso present in some samples).

6. Stable isotope geochemistry

6.1. Carbonates and graphite

The (C, O)-isotopic compositions of carbonates and the C-isotopiccompositions of graphite, as well as the calculated temperatures ofpeak metamorphism, are presented in Table 9 and in Fig. 13. Theisotopic compositions of all the districts and occurrences of marble-hosted ruby deposits from Asia are consistent with marine carbonates(δ13C between −2 and 4‰ and δ18O between 20 and 28‰; Ohmoto,1986, Valley,1986; Fig.13A). The (C, O)-isotopic compositions of calciteand dolomite vary from one district to another, but are homogeneousin each district. Calcite–dolomite pairs are close to high temperatureequilibriumvalues (Fig.13B. C). Variations observed among the studieddistricts may be explained by variations in the (C, O)-isotopic com-

positions of the protoliths. The variations observed between marblesamples from the same district are in agreement with the processof Rayleigh devolatilization (Valley, 1986). Fluids that circulated inmarbles were released by devolatilization of the carbonates. Rayleighdevolatilization is an end-member casewhere fluids leaves the systemcontinuously as it is formed but in the ruby-bearing marbles noexternally-derived fluids penetrated and thewholemarble unit can beassimilated to a closed system. In Hunza, δ13C above 4.0‰ can beexplainedby sedimentation in restricted, anoxic and/or hyper-saline orshallow water basin (Schidlowski et al., 1976).

Graphite is present as flakes disseminated in carbonates or inveinlets. Two groups of values can be distinguished for the δ13C ofgraphite. Gneisses in Vietnam yield δ13Cgraphite (samples TH2b andVan Yen gneiss) values between −26.1 and −20.2‰. These valuesindicate that graphite in the gneisses formed by metamorphism oforganic matter. In marbles, δ13Cgraphite values are between −5.5 and1.0‰ (Table 8). Considering the isotopic signatures of the carbonates,mantle carbon sources can be discounted (Valley, 1986), and it appearsthat δ13Cgraphite values reflect an organic source of graphite withcarbonate–graphite isotopic exchange during metamorphism. Thefractionation of carbon isotopes between graphite and carbonates isdirectly linked to the temperature of peak metamorphism. Meantemperatures calculated with the isotopic thermometers of Valley andO'Neil (1981), Wada and Suzuki (1983), Dunn and Valley (1992) andKitchen and Valley (1995) are reported in Table 9 with standarddeviations. Considering the accuracy of the thermometers, a precisionof ±40 °C for the mean temperature is estimated. Most of the tem-peratures range between 610 and 790 °C (Fig. 12) and indicate meta-morphism in the amphibolite facies.

6.2. Oxygen in ruby

The oxygen isotopic compositions of ruby from marbles arepresented in Table 10. They fall between 16.9 and 23.0‰. The valuesof δ18O of water that was in equilibrium with ruby (δ18OH2O) was

Fig. 8. SEM photographs in back-scattered electron (BSE) mode. (A) Calcite (Cc)+dolomite (Dol)+ruby (Cor)+spinel (Sp)+Mg-chlorite (Clin)+rutile (Ru) in a marble from Jegdalek,Afghanistan (JD-6). (B) Spinel (Sp) surrounded by a fine-grained intergrowth of ruby (Cor) and dolomite (Dol) in a marble from An Phu in Vietnam (V41a; Cc = calcite). (C) and(D) Spinel (Sp) surrounded by a rim of ruby (Cor) and iron oxides (FeO) in a marble from Hunza in Pakistan (HU-6d; Parg = pargasite; Clin = Mg-chlorite; Dol = dolomite; Py = pyrite).

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calculated following the equation of Zheng (1991) and minimum andmaximum temperatures of peak metamorphism obtained in therelevant district. The calculated δ18OH2O range between 24.2±0.5 and30.4±0.6‰ (Table 10). These values are above those defined formetamorphic waters (between 3 and 20‰; Sheppard, 1986). In addi-tion, the devolatilization of carbonates duringmetamorphism releases18O-enriched CO2 (Valley, 1986). Thus, it appears that the isotopiccomposition of water was buffered by isotopic exchange with thecarbonates and CO2 released during carbonate devolatilization. Theseresults confirm that the marbles were not infiltrated by large volumesof externally-derived fluids. The O-isotopic signatures of rubies fromall the deposits overlap, and it is not possible to distinguish one fromthe other. This homogeneity is consistent with common processescontrolling the formation of ruby in all the deposits (Giuliani et al.,2005).

6.3. Hydrogen in micas

H-isotopic compositions of micas associated with ruby in marblesare presented in Table 11. The isotopic composition of water in equi-librium with mica was calculated following the equation of Suzuoki

and Epstein (1976), using mica chemical compositions indicated inTable 11 and the minimum and maximum peak metamorphic tem-peratures determined by the C-isotopic thermometry relevant foreach deposit. The δD values of mica associated with ruby in marblesare between −100 and −38‰; those calculated for water range from−88±3 to −37±7‰. Metamorphic waters have δD values between 0and −70‰ whereas those from magmatic waters range from −40 to−80‰ (Sheppard, 1986). Thus, the δDH2O values obtained for depositsfrom Jegdalek in Afghanistan, Nangimali and Batakundi in Azad-Kashmir, Luc Yen in Vietnam, Mogok in Myanmar, and Chumar inNepal are typical of metamorphic waters. In the cases of the HunzaValley in Pakistan, Batakundi in Azad-Kashmir, Ruyil in Nepal and TanHuong in Northern Vietnam, a D-impoverished source has partici-pated besides metamorphic waters.

The O-isotopic composition calculated for waters indicates thatmeteoric waters did not circulate in the marbles. The (C, O)-isotopiccompositions of carbonates indicate that no magmatic fluids wereinvolved in the formation of ruby mineralization. The chemistry offluids trapped as inclusions in rubies is explained by the thermo-chemical reduction of sulfates, particularly anhydrite (Giuliani et al.,2003a). Such reactions release H2O (called organic waters) and H2S. It

Fig. 9. Photomicrographs of fluid inclusions (FI) in ruby from different marble deposits in Asia. (A) Jegdalek (Afghanistan). Primary FI (JSD1b) in ruby (Ru) containing a vapour (v), anda liquid phases (l) composed of CO2, H2S and COS, and with a globule of native sulfur (S8) and diaspore (Di). (B) Tajikistan. Primary FI (T1a) containing a liquid phase (l) composed ofCO2 and H2S, and native sulfur (S8). Solid inclusions of diaspore (Di) and rutile (Rt) were identified in the cavity. (C) Mong Hsu (Myanmar). Two pseudosecondary biphased FI (MG6)containing a carbonic liquid (l) and vapor phases (v). The biggest FI contains diaspore crystals (Di) and one globule of native sulfur (S8). (D) Quy Chau (Vietnam). Several sections oftwo-phase primary FI (QCRLT01–12) with a carbonic liquid (l) and a vapour phases (v). Globules of native sulfur (S8) present at room temperature before laser irradiation are a mainfeature. Ru = ruby crystal; As = arsenopyrite identified by Raman spectrometry; Di = diaspore. (E) Nangimali (Azad Kashmir). SEM photograph of a ruby crystal (Ru) showing prisms ofanhydrite (An) capped by phengites (Phg). (F) Luc Yen (Vietnam). Primary FI trapped on a growing zone of ruby (Rugz). The cavity is monophase and formed by a liquid composed ofCO2, H2S and COS. Euhedral crystals of rutile (Rt) are located on a growth zone of ruby and their c axis is perpendicular to thewalls of FI cavity. Calcite crystals (Ca) identified by Ramanare trapped as solid inclusions in ruby and on the edge of the FI cavity. (G) Ruyil (Nepal). Two-phase primary FI (R7-4c) containing a carbonic liquid (l) and vapour (v) phases. Theconstituents of the fluid are CO2, H2S and COS. Diaspore is found either as prismatic crystals in ruby at the bottom of the cavity (Dis) or as a nonvisible film (Dil), 2–3 µm thick, withinthe cavity and coating a part of the inclusion. (H) Nangimali (Azad Kashmir). SEM photograph showing crystals of anhydrite (An) included in a ruby (Ru). (I) Luc Yen (Vietnam). SEMphotograph showingmixtures of salts (Ca–Na–K–[Cl] and KCl) found in ruby (Ru). (J) Jegdalek (Afghanistan). SEM photograph showing a halite crystal (NaCl) in ruby (Ru). (K) Luc Yen(Vietnam). Multiphase primary FI (LY399B-10) with dolomite (Dol), diaspore (Di) and native sulfur (S8). The carbonic phase is composed of CO2, H2S and COS. The two small globulesof native sulfur located around the vapor phase (v) were nucleated during Raman laser irradiation. (l)= liquid. SEM photographs by A. Kholer, University Nancy I; fluid inclusionphotographs by V. Hoàng Quang.

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is possible that hydrogen from these gases may have been incorpo-rated in the hydroxyl sites of mica. Organic waters have δD varyingbetween −250 and −90‰ (Sheppard, 1986). Fractionation of hydrogenbetween H2O and H2S varies with temperatures (Taylor, 1986) and at

temperatures between 600 and 800 °C, the isotopic compositionof H2S in equilibrium with calculated δD in micas (Table 11) will bebetween −300 and −200‰. Thus, if noticeable quantities of the hy-drogen in micas came from H2S, δD values of these minerals would be

Table 8Microthermometric and Raman data of representative fluid inclusions trapped by ruby in marble deposits from Asia

Ruby Inclusion Samples Microthermometry Raman data

Mines Types Flc TmCO2 ThCO2 CO2 H2S COS S8 Diaspore Rutile Feldspar Dolomite Calcite

Jegdalek A JSD1b 70 −58.1 30.1 L 94.7 5.3 + + +A JSD1c 100 −58.2 27.3 V 95.1 4.9 + +B JSD2 65 −62.5 33.4 L 89.2 10.8 + + +C 10-JD06.3 70 −58.0 15.6 L 98.3 1.7 +

Tajikistan A T1a 100 −61.5 11.8 L 56.3 43.7 + + + +C T8a 100 −59.6 10.8 L 93.0 7.0 +

Hunza A R5-1 100 −64.0 31.5 L 95.8 4.2 +A R5-2 100 −62.6 12.3 L 79.0 21.0 + + +A R2-1 50 −59.0 30.0 L 71.2 28.8 + + +

Nangimali A N4-1 40 −64.0 34.0 L 98.4 1.6 + + +A N4-2 30 −63.0 33.7 L 82.7 17.3 + + +

Ruyil A R7-2 60 −57.0 26.7 L 97.0 3.0 + +Mogok M1b 100 −58.3 23.4 L 87.6 12.4 +

M1a 80 −58.0 24.9 L 93.7 6.3 +Mong Hsu A MG2-1 45 −62.8 33.2 L 99.0 1.0 + + +

B MG2-2a 40 −61.1 33.1 L 94.5 5.5 + +A MG2-5a 45 −61.6 33.1 L 90.2 9.8 + + + + +

Luc Yen A LY399B-10 40 −63.4 36.4 L 76.8 23.2 + + + +A LY399A-2 80 −63.7 26.7 L 84.7 15.3 + + +

Quy Chau A QCRA-16a 70 −64.7 30.5 L 88.5 11.5 + + +A QCRA-11a 100 −65.2 20.8 L 85.5 14.5 + + + +A QCRB-2.1 100 −66.7 34.9 L 90.8 9.2 + + +

Flc: volumetric fraction of the carbonic-rich liquid in the carbonic-rich phase; TmCO2: melting temperature of CO2; ThCO2: homogenisation temperature of CO2, vapour (V) and liquid(L) states. All temperatures in °C. Composition of CO2 and H2S in mol. %. + : detected element; S8 : native sulphur.

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considerably lighter than those measured. Calculated δD values below−70‰, obtained for water in equilibrium with mica, are thus con-sistent with participation of small quantities of organic waters re-leased by the thermo-chemical reduction of sulfates.

6.4. Sulfur in anhydrite and boron in tourmaline

The S-isotopic composition of anhydrite in marbles from Hunza inPakistan and Vietnam were analyzed in-situ. Two groups of δ34Svalues were obtained (Table 12). The sample from Hunza and onecrystal in the sample from Vietnam have δ34S values of 1.6±2.2 and4.8±2.0‰, respectively. Two other crystals from the Vietnam sampleyield values of 27.4±2.3 and 23.3±3.4‰. The latter heavy values are inagreement with precipitation of anhydrite from marine sulfates. TheS-isotopic composition of marine evaporites is close to the composi-tion of the marine sulfates fromwhich it precipitated, if the evaporitesdid not suffer post-depositional alteration (Ohmoto, 1986). The lowδ34S recorded in the other Vietnam crystal and in the Hunza samplecan be explained by (1) precipitation of evaporites in a restricted basinin the presence of organic matter (McKibben and Eldridge, 1989;Utrilla et al., 1992); and/or (2) supply of sulfates of continental originto the restricted basin that would enrich the basin in light S-isotopes(Holster and Kaplan, 1966).

Tourmaline in ruby-bearing marbles from Nangimali in Azad-Kashmir and Hunza in Pakistan yielded δ11B values between −1.9±1.9and −0.4±1.8‰, and between −5.3±0.8 and −1.8±1.2‰ respectively,and a value of −10.5±1.1‰ for Vietnam (Table 13 and Fig. 14). Palmerand Slack (1989) show that the B-isotopic signature of tourmalinereflects the isotopic composition of the boron source and that it isinsensitive to metamorphism when fluid activity is low or whenmetamorphism is isochemical. In ruby-bearing marbles, most of thefluids are released by devolatilization of carbonates. Ancient marinecarbonaceous units have δ11B values between 1.5 and 5.3‰ (Ishikawaand Nakamura, 1993) and secular variations of B-isotopic composi-tions were not noticeable during the last billion years (Chaussidon andAlbarède, 1992). 11B is preferentially incorporated in the fluid phase(Palmer and Slack, 1989), therefore the metamorphic fluids releasedby devolatilization of carbonates should have δ11B values above 1.5‰.Non-marine evaporites have δ11B values between −30 and 7‰ andmarine evaporites between 18 and 32‰ (Palmer and Slack, 1989). It

appears from the tourmaline data that continental crust and/or non-marine evaporites were involved in formation of the ruby-bearingmarbles. The non-marine evaporite source is in agreement with thesulfur isotopic composition of anhydrite.

7. Discussion

7.1. Genetic models: a review

Only a few detailed geological studies have been devoted to theruby deposits of South-East Asia but several hypotheses on theirgenesis were proposed:

(1) Ruby formation is a consequence of regional metamorphism inthe amphibolite facies grade of calcareous rocks enriched inaluminum relative to silica, chromium and titanium (Okruschet al., 1976). Such original bulk rock chemistry may result fromlateritic weathering of an impure limestone, formed in a karstenvironment, before metamorphism. This model proposed byOkrusch et al. (1976) for deposits from the Hunza Valley inPakistan was used also by Rossovskiy et al. (1982), Keller (1990)and Bowersox et al. (2000) for the genesis of deposits of Jegdalek,Pamirs in Tajikistan and Mogok in Myanmar. Hunstiger (1990)explained that corundum formed from diaspore as a result ofintensification of pressure and metamorphism of an initialimpure protolith following the prograde transformation fromhydrargillite, to boehmite and diaspore and finally corundum.Dmitriev (1982) and Kissin (1994) proposed a variantmodel withmetasomatic transformations of terrigenous layers inmarbles bymetamorphic fluids. Rossovskiy et al. (1982) studied the Pamirsand Jegdalek ruby deposits and showed that there was norelationship between granitic rocks and ruby in marbles. Rubyformed from spinel and themetamorphism of clays in limestoneis the source of aluminium for ruby. The intrusive granites aresurrounded by contact metamorphism aureoles characterized byspinel-bearing garnet-pyroxene skarn occurring at the contact ofgranite and marble. The Mg-skarns contain spinel, and fancysapphires occurred in desilicified pegmatites that crosscut thoseskarns. The ruby-bearingmarble interlayers are concordant to theregional foliation, and "nopegmatites, neither young, nor old, and

Fig. 12. δ13Ccalcite (‰, PDB) vs. δ13Cgraphite (‰, PDB) for calcite–graphite pairs coexistingin marbles. Isotherms of Valley and O'Neil (1981) and Dunn and Valley (1992) arereported.

Fig. 11. CO2 (mol%) vs. H2S (mol%) for FI in the different ruby hosted in marbles.

Fig. 10. Raman spectra of the main phases analysed in fluid inclusion cavities fromrubies in marbles. Inclusion QCRA-16A (Quy Chau, Vietnam). (A) Diaspore and glassysulfur identified respectively as a nonvisible film coating the wall of the inclusion, and agobule of sulfur nucleated during Raman irradiation of the liquid phase. (B) Spectra ofCO2 and H2S in the same fluid inclusion. (C) Inclusions N4-1 and -2 (Nangimali, AzadKashmir): Raman spectra of respectively native sulfur present at room temperature inthe cavity before irradiation (inclusion N4-1) and native sulfur nucleated during theirradiation. A shift of 10 cm−1 is observed for the main peak at 472 cm−1 between thetwo types of sulfur.

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no amphibolites have been found within the ruby-bearing units"(Rossovskiy et al., 1982).

(2) Ruby formation is linked to the presence of granite and/orpegmatites.a. Ruby has an indirect relation with granite and its formation

is due to contact metamorphism developed around graniticintrusions as proposed by Iyer (1953) for theMogok deposits.Granite is the source of the heat and part of the chemicalelements necessary for ruby formation. The hypothesis ofalkaline metasomatism of marble by the circulation ofmagmatic and/or pegmatitic fluids is retained by NguyTuyet et al. (1994) and Pham Van (1996) for the genesis of

LucYendeposits inVietnam.NguyTuyet (1998) advanced thatmagmatic fluids were channeled by fault zones associatedwith the Red River shear zone in the Cenozoic.

b. Ruby has a direct genetic relation with magma and formedduring the emplacement of alkaline magmatism in marblesfor the Tajikistan deposits (Terekhov et al., 1999). Themagmatic solutions carrying aluminium interacted withmarbles and ruby formed. The deep seated source isreinforced by the numerical modeling of fluid–rock interac-tion betweenmarble and an alkaline fluid, realized by Kolstov(2002). Stability of the corundum-bearing assemblages usedfor the modeling was the following equilibria:

2pargasite þ corundum þ 9CO2↔3anorthite þ 2albiteþ calcite þ dolomite þ 2H2O ð7Þ

The author considered the high concentration of CO2 unusualfor most fluids in amphibolite facies metamorphism and for

Table 9(C, O) isotopic compositions of carbonates and coexisting graphite in marbles

Sample Calcite Dolomite Graphite

% δ13C (0/00)1 δ18O (0/00)2 % δ13C (0/00)1 δ18O (0/00)2 δ13C (0/00)1 T °C (mean)3 σ

AfghanistanJEGDALEKJD_1 77 0.4 26.4 23 0.5 25.4 −3.3 687 21JD_3 72 0.0 25.9 28 0.0 25.0 −3.8 676 18JD_4 66 0.0 26.1 34 0.1 25.1 −3.5 710 23

Azad-KashmirNANGIMALIN1 72 −1.6 25.0 28 −1.3 24.9N3 6.9 1.7 26.7 93 2.2 27.0N6 10 1.0 21.2 90 1.7 24.7N4 68 −1.9 24.5 32 −1.6 24.2LKT2a' 63 0.8 24.3 37 1.0 23.6 −3.2 656 20LKT2c' 66 0.8 24.3 34 1.0 23.7LKT2f'1 100 0.3 25.6LKT2f'2 71 0.0 26.2 29 0.1 25.5LKT3 16 2.0 25.7 84 2.4 25.4LKT2i' 79 2.0 27.3 21 2.2 26.6LKT2h' 100 1.7 27.2LKT2g' 89 2.4 27.7 11 2.6 27.2LK4 12 1.9 26.5 88 2.4 26.7LKT4-a 72 1.5 25.5 28 1.8 25.3LKT4-b 76 1.3 24.0 24 1.8 24.8LKT13 16 1.7 25.8 84 2.0 25.1LKT1bb 1.9 24.8 2.2 25.0LKT1Cg 100 1.7 25.9LKT1Cb 100 1.9 24.8LKT2b 100 1.5 26.0LK2g 100 1.6 26.3MKT1a 100 1.8 25.7MKT2 79 1.7 25.5 21 1.7 24.3 −2.7 636 2

PakistanHUNZADony Das district

HU-2a-g 80 6.0 23.9 20 6.3 23.6HU-2a-b 77 5.4 22.6 23 5.5 21.8HU-3c 63 5.4 24.2 37 5.6 23.5

Ting Ten HarHU-4d 100 0.8 26.1

Laling Tolian districtHU-6g-1 73 4.2 25.5 27 4.5 24.9HU-6g-2 60 4.3 25.6 40 4.4 24.4HU-9b 100 1.2 25.8

Dor Khane occurrenceHU-13d 85 4.0 23.5 15 4.1 22.9 0.5 710 23

Foruhar occurrenceHU-14a 79 2.6 24.2 21 3.1 24.1 −4.3 512 11

Furandar districtHU-17b 73 4.1 20.2 27 4.5 19.6 1.0 760 34HU-19a 84 4.7 24.1 16 4.7 23.9 0.8 676 18HU-19b 69 4.6 20.8 31 4.7 21.1 0.6 656 20HU-18a-1 82 5.3 24.3 18 5.2 23.1HU-18a-2 82 5.3 24.2 18 5.5 23.8

Saeed Kuch Bull occurrenceHU-20b 73 4.4 24.8 27 4.6 24.0 0.2 643 2

Pasu Baltit roadHU-22b 78 3.3 26.8 22 3.7 26.6 −0.2 710 23

Daghan Das occurrenceHU-25a-AA'1 74 3.1 26.8 26 3.5 26.8HU-25a-B2 28 4.3 27.2 72 5.0 27.4HU-25a-C1 69 3.4 26.6 31 3.4 26.0 −0.1 710 23HU-25a-D1 81 5.4 28.2 19 5.5 27.4

NepalRUYILRU-1 66 2.8 24.4 34 3.0 23.8 −2.2 612 23RU-2 −2.4

CHUMARChumar 2.8 22.7 3.1 23.3SuppleB13-SU11-12 100 3.1 23.5

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Table 9 (continued)

Sample Calcite Dolomite Graphite

% δ13C (0/00)1 δ18O (0/00)2 % δ13C (0/00)1 δ18O (0/00)2 δ13C (0/00)1 T °C (mean)3 σ

MyanmarMOGOKMO-1 71 1.1 27.8 29 1.1 26.4 −1.6 775 16MO-2 60 0.6 25.6 40 0.7 24.7A 64 2.2 23.0 36 2.4 22.4F1 76 −0.2 20.8 24 −0.2 19.7F2 80 −0.3 20.6 20 −0.2 19.7R 81 −0.3 20.7 19 −0.2 19.6 −2.8 783V 79 0.5 23.8 21 0.5 22.6 −2.8 734 27

MONG HSUMH/GU1 2 2.7 24.8 98 5.3 27.1MH/GU2 18 4.4 26.2 82 4.9 26.4MH/SC1 47 4.3 25.5 53 4.9 25.4MH/SC2 1.5 4.5 27.2 98 5.3 27.1

VietnamNUOC NGAPNN1b 100 1.0 27.1NN1j 20 −0.3 26.1 80 1.3 26.8 −3.3 750 56

KHOAN THONGKT1 64 1.2 21.5 36 1.2 20.3KT2 82 4.6 26.7 18 4.6 25.8KT3g 79 1.3 27.2 21 1.4 26.3KT3b 25 2.2 27.9 75 2.8 28.0 −1.4 698 21KT3gf −1.6KT3bfKT3j 22 4.6 25.1 78 1.9 27.5KT4b 77 1.8 24.1 23 2.0 23.8 −2.3 642 25

AN PHUAP1g 100 −1.8 25.9 −5.5 687 21VIET7bb 100 0.0 26.0VIET7bg 100 −0.3 26.0 −4.8 623 2VIET7 4 3.9 28.9 96 4.4 29.3

LUC YENLY1b0 100 1.8 26.5LY1b1 100 1.8 26.5LY2b 87 −0.9 24.0 13 −1.0 23.5

MIN THIENMTH1 88 0.7 24.6 12 0.6 23.6MTH3b 100 1.2 24.2MTH3g 100 1.1 24.3VIET7a 88 1.4 24.7 12 1.3 23.9

BAI DA LANGBDL1bg 70 2.0 26.3 30 1.9 25.3 −1.9 666 19BDL1bb 61 1.6 26.5 39 1.5 25.6BDL2b 69 0.3 26.6 31 0.3 25.6BDL2g 91 0.6 26.7 9 0.7 25.9 −2.9 710 23BDL3b 100 3.2 25.6BDL3d

TAN HUONGTH2b −26.1TH1-1 69 2.1 25.0 31 2.2 24.0TH3a 8 1.6 25.9 92 1.9 25.0 −3.0 635 21

Van YenGneiss (Gr) −20.8

1: vs.PDB; 2: vs. V-SMOW; 3: Peak metamorphic temperatures, means obtained with the following thermometers, applied when relevant: Valley and O'Neil (1981), Wada and Suzuki(1983), Dunn and Valley (1992) and Kitchen and Valley (1995).

185V. Garnier et al. / Ore Geology Reviews 34 (2008) 169–191

fluids degassing in magmatic chambers. Thus a deep-seatedsource which interacted with an initial rock package made ofmarble and kyanite–garnet–biotite schist was preferred. Themetasomatic interaction of the fluid with the compositeprotolith resulted in the formation of metasomatic columnswhere corundum formed in Mg or Ca-rich marble zones.

(3) Ruby formed during high pressure metamorphism (PN6 kbar)of originally impure limestones in evaporitic series. Spiridonov(1998) proposed this hypothesis for the ruby deposits of thePamirs (Turakuloma) and the Uralian folded areas. Ruby occurswithin a sequence of dolomite, calcite and magnesite marblescontaining an intercalation of schist. Ruby is associated withcarbonates, scapolite and fuchsite. The model is based on ex-

periments and petrological observations which show thatspinel breaks down into corundum at a high CO2 fugacity ac-cording to the reaction:

MgAl2O4 þ CO2→Al2O3 þMgCO3 ð8Þ

spinelþ CO2→corundum þ dolomite

Spiridonov (1998) thought that meta-evaporites and meta-ultrabasites are both favorable environments for ruby neocrys-tallization because silica, potassium and sodium activities arelow and above 400 °C alumina migrates within aqueous fluids.The model necessitates the presence of chromium and also afluid-saturated environment.

Fig. 13. Carbon and oxygen isotopic signatures of marbles from ruby deposits. (A) δ13Ccalcite (‰, PDB) vs. δ18Ocalcite (‰, SMOW) diagram. (B) and (C) Carbon and oxygen (respectively)isotopic compositions of coexisting calcite and dolomite in the marbles.

186 V. Garnier et al. / Ore Geology Reviews 34 (2008) 169–191

Kissin (1991, 1994) observed the formation of ruby in the Uralsmarbles, from the destabilization of spinel, at a temperaturebetween 620 to 660 °C and pressure around 2.5 kbar, accordingto the reaction:

corundumþ dolomite↔spinel þ calcite þ CO2 ð9Þ(4) during the metamorphism of evaporite lenses which reacted as

molten salts with the limestone and its impurities (organicmatter and phengites; Garnier, 2003) to produce CO2–H2S–COS–S8–AlO(OH)-bearing fluids trapped by Vietnamese rubies(Giuliani et al., 2003a,b). Pêcher et al. (2002) have shown thatthe formation of Nangimali ruby in Azad Kashmir was a goodexample of fluid transfer during metamorphic processes.Parental fluids of ruby are of metamorphic origin and CO2 isderived from the decarbonation of dolomitic marbles. Inmarbles, the presence of aspidolite and anhydrite (Garnier etal., 2004), together with anhydrite and salts in ruby, implies thepresence of evaporites for the genetic formation of ruby. Suchsulfates and salts in ruby were described also at Mogok (Smithand Dunaigre, 2001) and at Luc Yen and Quy Chau (Giuliani etal., 2003a). However, Raman and infrared spectroscopy com-bined with microthermometry investigations on primary andsecondary fluid inclusions in gem ruby from the Luc Yen districtin north Vietnam provided evidence for CO2–H2S–COS–S8–AlO(OH)-bearing fluids with native sulfur and diaspore daughterminerals, without visible water (Giuliani et al., 2003a). Crush-leached analyses identified sulfates and chlorides that areassigned to the presence of anhydrite and Na–Ca–Cl salts foundby SEM in the ruby crystal. The thermoreduction of evaporiticsulfates explains the fluid chemistry.

7.2. A new genetic model

The lack of detailed geological and geochemical information aboutthe Mogok and Mong Hsu ruby-bearing deposits in the literature does

not permit to ensure a genetic model for these two Burmese deposits.The others marble-hosted ruby deposits from Central and South-EastAsia share common features: (i) they are hosted by metamorphosedmarine carbonates; (ii) they formed during amphibolite to lowergranulite grade metamorphism; (iii) ruby has no relationship withdykes of pegmatites; (iv) the ruby-bearing marbles contain scatteredruby mineralization which is concordant with the surrounding strati-form units; (v) they are characterized by similar mineral assemblagesand minerals associated with ruby are enriched in Mg, Al, F andsometimes Cl; (vi) salts and sulfates are found as solid inclusions inmost of the ruby samples; and (vii) rubies have trapped CO2–H2S–COS–S8–AlO(OH)-bearing fluids with native sulfur and diasporedaughter minerals.

The high temperature conditions for ruby formation implies athermal source i.e., metamorphic or magmatic; contact and regionalmetamorphism are both suitable alternatives. Control of the miner-alization is lithologic (Rossovskiy et al., 1982), with ruby formed inmarble intercalated with meta-evaporite lenses as in Nangimali, Hunzaand Luc Yen (Pêcher et al., 2002; Garnier, 2003). (C–O–H)-isotopicstudies have shown that ruby-bearing marbles were not infiltrated byexternally-derived fluids. CO2-rich fluids are metamorphic and derivedfrom devolatilisation of marble. The deposits are metamorphic and arein agreement with the previous genetic models (1), (3) and (4). Thegenetic model (2a), based on a possible circulation of magmatic and/orpegmatitic fluids, and model (2b), based on a direct genetic relation ofrubywithmagma or a deep-seated source as proposed for the Tajikistandeposits (Terekhov et al., 1999), are not suitable.

The presence of a high CO2 fugacity for ruby formation is inagreement with the five proposed genetic models and also experi-ments (Kolstov, 2002). Such thermodynamic conditions are favorablefor spinel breakdown according to the main reaction:

spinel þ calcite þ CO2↔corundum þ dolomite ð10ÞThis reaction occurred during the retrograde metamorphic path

as it is commonly observed in marbles from Jegdalek, Afghanistan,

Table 12S-isotopic composition of anhydrite associated with ruby in marbles from Furandar inPakistan and Nuoc Ngap in Vietnam

Sample δ34S1 (0/00) σ

PakistanFurandar HU-18a 1.6 2.2

VietnamNuoc Ngap V41a

crystal 1 4.8 2.0crystal 2 27.4 2.3crystal 2 23.3 3.4

1: ‰, vs. CDT.

Table 11H-isotopic composition of mica associated with ruby in marble

δΔ1 mica XFe XMg XAl δΔ2 water (mean) σ

AfghanistanJD3 −68 0.006 0.870 0.124 −67 3JD6 −63 0.012 0.865 0.123 −63 4JD1 −75 0.009 0.868 0.124 −75 3

Azad-KashmirBatakundi −76 0.002 0.998 0.069 −74 4LK 1a −69 0.007 0.888 0.105 −67 4LKT 1d −67 0.007 0.888 0.105 −65 4LKT 3 −56 0.007 0.888 0.105 −54 4LKT 10 −68 0.007 0.888 0.105 −66 4

PakistanHU-6d −73 0.029 0.921 0.049 −72 3HU-6f −82 0.074 0.846 0.080 −79 3HU-13a −79 0.025 0.840 0.135 −79 3HU-20b −84 0.011 0.841 0.148 −82 4

NepalChumar −50 0.020 0.822 0.158 −46 4Ruyil −94 0.038 0.839 0.123 −88 3SuppleB13-SU11-12 −72 0.020 0.870 0.110 −67 3

MyanmarMO-H −54 0.017 0.924 0.059 −56 4MO-1 −53 0.019 0.952 0.029 −56 2MO-R −58 0.095 0.844 0.061 −57 2

VietnamKhoan ThongKT3 bm −56An PhuVIET8-1 −69 0.005 0.857 0.139 −64 6

Minh ThienMTH-1 −38 0.030 0.709 0.261 −37 7MTH-3 −41 0.030 0.709 0.261 −40 7

Tan HuongTH1-1a −100

Bai Da LanBDL-4 −61 0.071 0.702 0.227 −58 4

1: ‰, vs. V-SMOW.The isotopic composition of water in equilibrium with the mica was calculatedfollowing the equation of Suzuoki and Epstein (1976) depending on the chemicalcomposition of the mica (XFe=Fe/ (Fe+Al+Mg), XAl=Al / (Fe+Al+Mg), XMg=Mg/(Fe+Al+Mg) and with the range of temperatures corresponding to the district of eachsample.

Table 10O-isotopic composition of corundum from marble deposits

Mine Sample Colour δ18O1

rubyδ18O2

calc.minδ18O2

calc.maxδ18O3 H2O(mean)

σ

AfghanistanJegdalek RNAFG1 Dark

pink21.2 25.9 26.4 28.7 0.8

RNAFG2 Darkpink

18.6 25.9 26.4 26.1 0.8

RNAFG3 Darkpink

18.8 25.9 26.4 26.3 0.8

Azad-KashmirNangimali NAN-12 Dark

pink21.5 21.2 27.2 29.5 0.7

NAN-23 Darkpink

18.2 21.2 27.2 26.2 0.7

Batakundi Batakundi Red 22.0 30.0 0.7

PakistanHunzaFurandar HU-19a Pink 22.7 24.1 30.4 0.6Ahmadabad R4 Pink 21.1 20.2 24.3 28.5 1.2Grechar GRE-1 Dark

pink21.3 20.2 24.3 28.7 1.2

Daghan Das R5 Pink 22.0 26.6 28.2 29.4 0.5Foruhar R1 Pink 20.4 24.2 30.0 0.7Hassanarabad HU-20c Pink 20.1 26.8 28.1 0.6Laling Tolian HU-12b Pink 16.9 25.5 25.8 24.2 0.5Ting Ten Har HU-5a Pink 20.2 26.1 28.5 2.5Dony Das HU-1e Pink 21.6 22.6 24.2 29.9 2.5

NepalRuyil Ruyil Dark

pink20.0 24.4 28.4 0.6

Chumar Chumar Lightpink

19.5 27.9 0.6

CHU-1 Lightpink

17.4 25.8 0.6

CHU-2 Lightpurple

17.0 25.4 0.6

MyanmarMogok Mogok

KY-SARed 20.1 20.6 27.8 27.0 0.8

325 Red 21.1 20.6 27.8 28.0 0.8MO-2 Light

pink22.0 20.6 27.8 28.9 0.8

333 Red 21.2 20.6 27.8 28.1 0.8Mong Hsu MHNID Dark

pink23.0 24.8 27.2

MH GUB. Darkpink

23.0 24.8 27.2

MH “neu”K sui

Darkred

22.3 24.8 27.2

MOHS Darkred

22.5 24.8 27.2

VietnamBai Da Lan BDL Red 22.4 25.6 26.7 30.0 0.9An Phu An Phu 2 Pink 20.4 18.0 28.9 28.3 1.1

An Phu 3 Pink 20.7 18.0 28.9 28.6 1.1

1: ‰, vs. V-SMOW; 2: The range O-isotopic compositions of calcite from the sample orwithin the district fromwhere it originates; 3: The composition of water in equilibriumwith corundumwas calculated following the equation of Zheng (1991) with the relevanttemperatures.

187V. Garnier et al. / Ore Geology Reviews 34 (2008) 169–191

Hunza and Luc Yen in Vietnam and also described in the Urals (Kissin,1994). In dolomitic marbles, the presence of aspidolite and anhydritetogether with hypersaline fluids (salts) in rubies implies the presenceof evaporites for the generation of ruby in marble. Such petrographicaland geochemical evidence is reinforced by the (S–B)-isotopic studieson anhydrite and tourmaline respectively that are consistent with theparticipation of non-marine andmarine evaporites in the formation ofruby. In Hunza, the presence of inclusions of anhydrite and spinel inruby, and inclusions of spinel in anhydrite, and restites of anhydrite in

marble, suggest that limestone of the platform sediments deposited inan environment propitious to the deposition of evaporites. Thisdifferent element supports the models (3) and (4) proposed for theformation of these ruby deposits.

An important result of thefluid inclusions study is the identificationof CO2–H2S–COS–S8–AlO(OH) fluids for all rubies hosted in marbles asswell as in Mogok and Mong Hsu rubies. Elemental sulfur, hydrogensulfide and COS in the CO2-inclusions originated from the partialdissolution and reduction of anhydrite by organic carbon (Giuliani

Fig. 14. Boron isotopic compositions of tourmaline associated with ruby in marbles.Characteristic compositions of boron sources are also indicated (from Slack et al., 1989).

188 V. Garnier et al. / Ore Geology Reviews 34 (2008) 169–191

et al., 2003b). Such chemical association and especially with thepresence of COS in geological fluids, was only described by Grishinaet al. (1992) in the Siberian platform where dolerites intrudedcarbonate-anhydrite and halite beds. In addition, nitrates as NO3

−

were identified in the crush leach of Luc Yen rubies and Giuliani et al.(2003b) proposed a non-marine evaporite origin (evaporitic lakes). Asno externally derived fluids circulated through the marble, the sourceof Al and Crmust have been deposited coevally with the carbonates onthe platform. Aluminum was probably contained in clay mineralswhich are produced in great quantities by weathering of continentalrocks and transported by rivers to the sedimentary basins. Acontribution of organic matter for Cr and Al is a possibility as alreadyevidenced in bitumen associated with Colombian emeralds in a blackshale environment (3bCrb87 ppm, 700bAlb2200 ppm; Giuliani et al.,2000), but also detrital minerals enriched in chromium, and possiblytitanium. Thus, ruby is present only in marble units that preferentiallycontained these Cr–Al-bearing minerals, such as proposed by the pre-vious genetic model (1).

The following new model is proposed for formation of Indo-Asianruby deposits (Fig.15): (1) Deposition of sedimentary protoliths on thePaleotethys platform with local formation of restricted (endoheric)basins. The ages of sedimentation vary from Precambrian (Jegdalek,Afghanistan; Terekhov et al., 1999) to Permo-Triassic [(Nangimali,Azad-Kashmir; Malik, in press), and Mogok in the Mogok meta-morphic belt, Myanmar (Barley et al., 2003)]. (2) During the Indo-Asian collision, the sediments were metamorphosed in the amphibo-lite facies, transforming carbonates into marbles.

Magnesium, Al and Na enrichment of the minerals associated withruby in marble, the presence of Mg-tourmaline, and the replacementof some of the hydroxyl groups by F and Cl are strong evidence for theparticipation of evaporites in the formation of ruby. Molten salts(NaCl, KCl, CaSO4 and Na2CO3) mobilized Al and metal transition ele-ments contained in themarble. Organicmatter played a key role in themineralization process. Thermal reduction of evaporitic sulfates,based on an initial assemblage of anhydrite, calcite and graphite, is aconvenient explanation for the fluid chemistry found in fluid in-clusions but also for the main paragenesis associated with ruby i.e.,carbonate and pyrite, with a reduction of sulfate and oxidation oforganic matter.

Gem ruby formed during the retrograde metamorphic path, attemperatures of ca. 620 to 670 °C and pressures of ca. 2.6 to 3.3 kbar.Evaporites appear to be a key-factor for formation of ruby deposits:(a) Cl and F acted as activators of the mobilization of aluminum inmarble, which normally is poorly mobile. F and Cl allowed the mobi-lization of Al from micas, formed by the metamorphism of clayminerals and organic matter to spinels, leading finally to the for-

Table 13B-isotopic composition of tourmaline associated with ruby in marbles from Nangimali,Azad-Kashmir; Hunza, Pakistan and Minh Thien, Vietnam

Sample δ11B1 (0/00) σ

Azad-Kashmir MKT2Nangimali crystal 1 −1.9 1.9

crystal 2 −1.3 1.4crystal 3 −1.4 1.6crystal 4 −8 1.3crystal 5 −0.4 1.8crystal 6 −1.3 1.6

Pakistan HU-18bHunza crystal 1 −3.7 0.9

crystal 2 −3.3 1.2crystal 3 −5.3 0.8crystal 4 −2.1 1.0crystal 5 −2.8 1.0crystal 6 −1.8 1.2

VietnamMinh Thien MTH3 −10.5 1.1

1: ‰, vs. NBS SRM 915.

mation of ruby; (b) thermoreduction of sulfates produced S8, COS andH2S. Hydrogen sulfide combined with iron to produce pyrite; (c) thepresence of lenses of evaporites in some peculiar horizons explainswhy ruby is sporadic in a single homogenous marble level even if Al isavailable across the entire horizon.

Guidelines for prospecting for new deposits that must be takeninto account are: (1) the lithologic control of mineralization: theprotolith deposited in a carbonate platform, in a lagoonal to lacustrineenvironment, isolated from open sea, and promoting the deposition ofmarine and non-marine evaporites; and (2) the presence of indexminerals such as sodium-rich phlogopite (aspidolite) or pargasite andedenite, Mg-tourmaline, chromium-rich titanite (more abundant thanruby itself), spinel and anhydrite in marbles or in alluvials, indicatespossibilities for marble-hosted ruby mineralization in an area.

The lack of detailed geological and geochemical information sinceIyer (1953) about the famous Mogok mining districts and the MongHsu deposit does not permit us to apply the new genetic model tothose deposits. Future work will probably clarify the relationshipbetween ruby in marble, blue sapphire, spinel and all the gem-minerals found in skarns. The question remains about the timing andthe mode of formation of these different mineral associations whichillustrate polyphased metamorphic and magmatic-hydrothermalmineralizations.

Acknowledgments

This work, part of the senior authors Ph.D. thesis, was supported byInstitut de Recherche pour le Développement (IRD, UR154 LMTG) andCNRS (CRPG), the Programme International de Coopération Scientifi-que between CNRS (INSU) and CNST (Hanoi, Vietnam), the FrenchForeign Office, the French Embassy in Pakistan and the cooperativeprogram DSUR-PAK-4C5-013 entitled ‘Echanges et Recherches dans leDomaine de la Géologie de Haute-Montagne’ between the University J.Fourier (Laboratoire de Géodynamique des Chaînes Alpines, Greno-ble), CRPG/CNRS, IRD and the Geological Survey of Pakistan (Islama-bad). Phan Trong Trinh and Hoang Quang Vinh are grateful to thenational Vietnamese programme of basic research.We thank A. Kholerfor assistancewith SEM imaging, and S. Barda and F. Diot for their helpwith EPMA analyses at the Electronic Microscopy Department of theUniversity Henri Poincaré in Vandœuvre-lès-Nancy, France.Wewouldlike to thank Ch. France-Lanord and C. Guilmette from the StableIsotope Laboratory of CRPG/CNRS in Vandœuvre-lès-Nancy, France, forassistance with stable isotopes analyses of mica, graphite and car-bonates. We thank M. Champenois, M. Chaussidon, D. Mangin, C.Rollion-Bard, E. Deloule from the ion probe service of CRPG/CNRS fortheir help with U–Pb and sulfur and boron isotopic analyses. This workis part of the scientific co-operative program between the Instituteof Geology from Hanoi (NCNST) and the UR154 from IRD (France),and entitled "Genesis of ruby deposits in North Vietnam"; we thank

Fig. 15. Synthesis presenting the proposal model for genesis of ruby deposits in marbles. Structural map of Himalaya modified fromMattauer et al. (1999). The different stages of theformation of these deposits from the sedimentation (from Precambrian to Permo-Triassic) to the Himalayan metamorphism are: Stage I, sedimentation of the protoliths in acontinental platformwith a detrital supply, and deposition of carbonates, dolomitic carbonates, organic matter-bearing shale, andmarine and non-marine evaporites (lagoon, sebkhapaleogeography) as found in the representative lithostratigraphic section of Nangimali in Azad Kashmir; Stage II, Cenozoic Himalayan metamorphism a consequence of the Indo-Asian collision with the metamorphism of the ruby protoliths as shown on the metamorphic unit cross-section of Nangimali. Corundum formed during the progrademetamorphic P–T path and then during the retrograde stage from the destabilization of different mineral assemblages as drawn in the P–T sketch: 1 — from margarite, then 2 —

from micas, and 3 — from spinel. At this stage, corundum is destabilized at lower temperature and pressure in margarite and then diaspore. Gem ruby formed at a pressurebetween 2.6 and 3.3 kbar and temperature between 620 and 670 °C (red rectangles). Abbreviations : An = anorthite ; And = andalusite ; Cc = calcite ; Co = corundum ; Do =dolomite ; Dsp = diaspore ; Kfs = K-feldspar; Ky = kyanite ; Mrg = margarite ; Ms = muscovite ; Si = sillimanite ; Sp = spinel ; W = water.

189V. Garnier et al. / Ore Geology Reviews 34 (2008) 169–191

190 V. Garnier et al. / Ore Geology Reviews 34 (2008) 169–191

J. Berger from IRD Vietnam for its technical assistance for this project.We are grateful to B. Goffé from ENS Paris (France) for access to hissamples from the Mogok district. A first draft of the paper wasimproved by Dr. T. LeCheminant from Ontario in Canada. The presentpaper was reviewed carefully by Dr. N. Daczko, Macquarie University,and Dr. R. Berry, University of Tasmania, Australia, who seriouslyimproved the manuscript by their constructive comments. A specialthank to Dr. Khin Zaw from CODES ARC Centre of Excellence in OreDeposits, University of Tasmania who reviewed the chapter of fluidinclusions and who carefully handled the paper.

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