FINAL all about emeralds

EMERALDS…

OVERVIEW:

Emeralds are the grass green variety of the mineral beryl. And hence its physical properties are same as those of beryl. But there is something special about its colour; Emeralds have the most beautiful, most intense and most radiant green that can possibly be imagined: Emerald green, that’s what its colour is known as. As far as origin of this colour of Emerald is concerned, it is due to presence of trace amounts of chromium or sometimes vanadium.

The name Emerald comes from the Greek 'smaragdos' via the Old French 'esmeralde', and really just means 'green gemstone'. Emeralds sometimes contain featherlike material, often called “silk,” which causes the gem to have a mossy appearance.

PROPERTIES OF EMERALDS-INCLUSIONS:

Flawless specimens of good color and size are exceedingly rare and command higher prices than diamonds of equal weight. Most of history's most notable Emeralds are laced with inclusions. The inclusions present in the Emeralds result due to its course of formation of which we’ll talk about a bit later.

Fine inclusions, however, do not by any means diminish the high regard in which it is held. Affectionately, and rather poetically, the specialists call the numerous crystal inclusions, cracks or fissures which are typical of this gemstone 'jardin' (gardens). They regard the tender little green plants in the Emerald garden as features of the identity of a gem which has grown naturally!

OTHER PROPERTIES:

1 ALL ABOUT EMERALDS: SAURABH SINGH

Coming to its composition now; as already mentioned Emerald is a

variety of beryl, so its composition and chemical formula remains same with an addition of chromium in trace amounts. The following table gives its chemical composition.

Element Percentage composition by mass

Beryllium 5.0%

Aluminum 10.1%

Silicon 31.3%

Oxygen 53.6%

Now applying our knowledge of crystal systems here; we find that Emeralds possess hexagonal crystal system. All bonds in its crystal are single, an obvious case with any other variety of beryl as well. The composition of its unit is “cyclosilicatic”; a word about this term before we proceed further.

From the formula of beryl we see that it contains the unit Si6O18

12-. This is nothing but a hexagonal ring formed of 6 tetrahedrons forming a cyclosilicate. It is formed when 2 oxygen atoms of


SiO4 are shared. They have the general formula SinO3n

2n-; In case of beryl, n=3.

The figure shows a hexagonal cyclosilicate ring (found in Emerald).

A Cyclosilicate Ring

(Here, each oxygen atom carries 2 units of negative charge)

This is a small silicate subclass, but an important one. The symmetry of the rings usually translates directly to the symmetry of these minerals.


Considering its other properties, Emeralds stand on very poor grounds as far as their brittleness is considered; the reason: well, the inclusions are the sole entities that make its cleavage1 very difficult. At the same time they are quite hard, specifically their hardness varies from 7.5 to 8 on the 10 point Mohs’ scale of mineral hardness. Its good hardness protects the Emerald to a large extent from scratches.

The following table summarizes its various mentioned properties:

Classification Mineral

Category Beryl variety

Chemical Formula Be3Al2(SiO3)6::Cr

Colour Green

Crystal System Hexagonal

Composition Cyclosilicatic

Mohs’ scale hardness 7.5 to 8.0

Luster Vitreous

Specific Gravity 2.7 to 2.78

1 Cleavage is the tendency minerals have to break or split along the planes of their crystal structure.


Refractive Index 1.576 to 1.582

Uses As Gemstone, in jewelry and scientific experiments

Coming back to the topic we discussed before: the cause of inclusions in the Emeralds. When we inspect the surface of Emeralds through Magnifying glass or better through a microscope, we see small or large fissures and sometimes even a mini-crystal or a small bubble. As already mentioned that these widely found inclusions in the Emeralds are the result of its course of formation; also only its story of formation can tell that how on earth do Emeralds get formed when Beryllium and Chromium (or Vanadium) never occur at same place! So it would be worthwhile to glance at its genesis.

FORMATION OF EMERALDS:

It’s known that the tectonic plates (on which the continents are mounted on) have never been fixed but drifting on the mantle. Due to these intensive movements of tectonic plates, these contrasting elements found each other and crystallized out to


make one of our most beautiful gemstones: Emeralds.

Further the tension due to movements of plates produced some minor and major flaws. But while the crystals were still growing, some of the flaws had the chance to heal, and hence the inclusions were formed.

Some cavities got filled with fluid, which often also contain a small bubble of gas and some tiny crystals. Hence the formation of Emeralds explains the observation of its surface under microscope and its cause of existence as a whole.

Keeping in mind of the turbulent past of the gemstone, it’s obvious to say that completely flawless Emerald is extremely rare and it is only seldom that a large Emerald with good colour and good transparency is found.

After going through a rigorous way through its past; let us see the Properties That Determine Its Value.

PROPERTIES DETERMINIG THE VALUE:6 ALL ABOUT EMERALDS: SAURABH SINGH

Emeralds, like all colored gemstones, are graded using four basic parameters, the four Cs: Color, Cut, Clarity and Crystal.

CRYSTAL:

Normally, in the grading of colored gemstones, color is by far the most important criterion. However, in the grading of Emerald, crystal is considered a close second. A fine Emerald must possess not only a pure verdant green hue but also a high degree of transparency to be considered a top gem.

COLOR:

The green of the Emerald is the colour of life and of the springtime. But it has also, for centuries, been the colour of beauty and of constant love. And today, this colour still occupies a special position in many cultures and religions. Green, for example, is the holy colour of Islam. This colour has a high status in the Catholic Church too, where green is regarded as the most natural and the most elemental of the liturgical colours. The magnificent


green of the Emerald is a colour which conveys harmony and love of Nature.

Emeralds occur in hues (shades) ranging from yellowish green to bluish green. The primary hue must, of course, be green. Only gems that are medium to dark in tone are considered Emerald. Some definitions go further, demanding that beryls can only be called Emeralds if they are green and colored primarily by chromium. If they are not green enough, they are referred to as green beryls.

The green gemstone has grown so synonymous with Emerald that some other minerals are also termed Emeralds. For example Brazilian Emerald is a green variety of tourmaline, Lithia Emerald, or hiddenite is the Emerald-green variety of spodumene, Oriental Emerald is the green variety of corundum, Uralian Emerald is the green variety of andradite.

In view of the fact that the green colour always changes somewhat between the bright light of day and the artificial light of a lamp, Emerald green retains its lively vigor in all its nuances.

CLARITY:


Emerald’s refractive and dispersive powers are not high, so cut stones display little brilliancy and clarity. Further since Emerald tends to have numerous inclusions and fissures, its clarity is

graded by observing it with naked eyes without magnification. Thus if an Emerald has no visible inclusions to the eye it is considered flawless, which is exceedingly rare

and valuable.

To enhance the clarity, many Emeralds are treated with colorless oils or resins. This is a general trade practice, but it does have the consequence that these green treasures react very sensitively to inappropriate treatment. For example, they cannot be cleaned in an ultrasonic bath.

Cedar oil, having a similar refractive index, is often used in this generally accepted practice. Other liquids, including synthetic oils and polymers with refractive indexes close to that of Emerald are also used. Based on the level of treatment given to Emerald to enhance its clarity, the laboratory community has recently formulated four grades for


it: none, minor, moderate and highly enhanced. Based on its level of enhancement, an Emerald graded in “none” enhancement is more valued than a similar looking Emerald with say “moderate” enhancement.

CUT:

Cut counts a lot in the final appearance of a gemstone. Cut of gemstone or here Emerald is required for many purposes. It has to be cut to return more light and color to the eye, in way so that all of the facet (any surface of a cut gemstone) junctions meet crisply, and that the overall outline is proportional and pleasing.

Sometimes it’s also required to remove imperfections in the Emeralds and is performed by expert workers known as lapidaries.

Gems are shaped entirely by being ground on abrasive wheels or revolving abrasive disks. For the harder stones, such as Emeralds, synthetic grinding wheels of


cemented Carborundum (silicon carbide) must be employed.

Emerald’s brittleness and its many fissures can make cutting, setting and cleaning rather difficult. Even for a skilled gem cutter, cutting Emeralds presents a special challenge, firstly because of the high value of the raw crystals, and secondly because of the frequent inclusions. In spite of this, a special type of cut has been devised for this special gem: the Emerald cut or step cut.

In this cut, the gem is given a number of symmetrical plane surfaces bringing out the beauty of this valuable gemstone to the full, at the same time protecting it from mechanical strain.

To do so, the top of the gem is ground to a large, flat surface (called a table) which may be a square or rectangle and the sides from it slope outwards (i.e. not perpendicular to table) towards the broadest portion of the gem (called


a girdle). Below the girdle the facets slope inwards and terminate at a small, flat surface (called a culet). In this cut the total number of facets so obtained amount to 58.

Emeralds are also cut in many other, mainly classical shapes, but if the raw material contains a large number of inclusions, it may often be cut into a gently rounded cabochon (i.e. stone is smoothly rounded), or into one of the Emerald beads which are so popular in India.

So the four Cs are well understood now. We all are well acquainted with the significance of the Emeralds; but has it enjoyed the same reputation in the past as well? To know, let us see into Emeralds In History.

EMERALDS IN HISTORY AND CULTURE:


Emerald is regarded as the traditional birthstone for May, as well as the traditional gemstone for the astrological sign of Taurus and symbolizes love and success. In some cultures, the Emerald is also being used as traditional gift for the 55th wedding anniversary. It is also used as a 20th and 35th wedding anniversary stone.

Many virtues and healing properties have been ascribed to Emeralds over the years, when worn as a charm, from preventing epileptic seizures, curing dysentery, and driving away evil spirits to preserving the chastity of the wearer. The gems were even administered internally for their medicinal value.

Emeralds have been cherished for as long as there has been a written history. Archaeologists have traced the origins of the use of Emerald to almost 3000 B.C. in both ancient Egypt and India.

Emeralds of ancient times were mined chiefly in Egypt. As a matter of fact the oldest known finds of Emeralds were once made near the Red Sea in Egypt. Cleopatra prized her Emeralds more than any other gem.

In India too, Emeralds have been held in high esteem since ancient times. The Vedas, the holy scriptures of the Indians,


say of the precious green gems and their healing properties: 'Emeralds promise good luck ...’ and 'The Emerald enhances the well-being ...'. So it was no wonder that the treasure chests of Indian maharajas and maharanis contained wonderful Emeralds. Especially the Moguls of India loved Emeralds so much they inscribed them with sacred text and wore them as talismans.

The Authorized King James Version of the Bible, in Exodus 28:18 and 39:11, lists "Emerald" as one of the precious stones in the breastplate2 of the high priest of the Jews. The Incas and Aztecs of South America, where the best Emeralds are still found today, also regarded the Emerald as a holy gemstone. The Romans also loved Emeralds because, as the ancient scholar Pliny said, "Nothing greens greener." The Turkish sultans also shared great affection towards Emeralds. In Istanbul's Topkapi Palace there are exhibits with items of jewellery, writing-implements and daggers, each lavishly adorned with Emeralds and other gems.

Discussing about some reputed Emeralds of the history; the Gachala Emerald is

2 A garment worn over the breast by Jewish high priests in ancient times, set with 12 precious stones representing the 12 tribes of Israel.


one of the largest gem Emeralds in the world, at 858 carats (172 g).

This stone was found in 1967 at La Vega de San Juan mine in Gachala, Colombia.

One of the world's other magnificent sized Emerald is the so-called 'Mogul Emerald' from India. It dates from 1695, weighs 217.80 carats, and is some 10cm tall. One side of it is inscribed with prayer texts, and engraved on the other there are magnificent floral ornaments.

Similarly Chalk Emerald from Colombia and Bahia Emerald from Brazil are one of the notable Emeralds of the World.

Most of the World famous Emeralds form a part of museums and collections. The New York Museum of Natural History, for example, has an exhibit in which a cup made of pure Emerald which belonged to the Emperor Jahangir is shown next to the 'Patricia', one of the largest Colombian Emerald crystals, which weighs 632 carats. Similarly the Gachala Emerald is housed at the National Museum of Natural History of the Smithsonian Institution in Washington, D.C. The collection of the Bank of Bogota includes five valuable Emerald crystals with weights of between 220 and 1796 carats, and


The Gachala Emerald

splendid Emeralds also form part of the Iranian National Treasury.

So knowing about the skyscraping pedestal on which Emeralds have stood in the past, it’s important to know their presence in today’s world.

GEOGRAPHICAL LOCATIONS OF EMERALDS:

Colombia continues to be at the top of the list in terms of the countries in which fine Emeralds are found. Colombian Emeralds are generally the most prized due to their transparency and fire (shine and sparkle). It has about 150 known deposits, though not all of these are currently being exploited; the best known being Muzo and Chivor. In economic terms, the most important mine is at Coscuez. According to estimates, approximately three quarters of Colombia's Emerald production now comes from the Coscuez Mine. Colombian Emeralds differ from Emeralds from other deposits in that they have an especially fine, shining Emerald green unimpaired by any kind of bluish tint. This fascinatingly beautiful colour is so highly esteemed in the international Emerald trade that even obvious inclusions are regarded as


acceptable. A rare stone, found only in this region, is known as a "Trapiche Emerald", and is characterized by star-shaped rays that emanate from its center in a hexagonal pattern (called an asterism) resembling the spokes of a millwheel! It is caused due to black carbon impurities that happen to form in the same pattern.

Fine Emeralds are also found in other countries, such as Zambia, Brazil, Zimbabwe, Madagascar, Pakistan, India, Afghanistan and Russia. Emeralds have also been found in Australia, the Urals, Norway, Austria, and North Carolina (USA).

Zambia, Zimbabwe and Brazil in particular have a good reputation for fine Emeralds in the international trade. Excellent Emerald crystals in a beautiful, deep Emerald green and with good transparency come from Zambia.

Similarly Brazil's gemstone mine Nova Era also produces Emeralds in beautiful green tones, and if they are less attractive than those of their famous neighbor (Columbia) it is only by a small margin. Brazil also supplies rare Emerald cat's eyes and extremely rare Emeralds with a six-spoked star.


So the world is full of Emeralds after all! But still, we encounter “synthetic Emeralds”.

SYNTHETIC EMERALDS:

The first commercially successful emerald synthesis process was that of Carroll Chatham. The other large producer of flux emeralds was Pierre Gilson Sr., which has been on the market since 1964. Gilson's emeralds are usually grown on natural colorless beryl seeds which become coated on both sides.

Hydrothermal synthetic emeralds have been attributed to IG Farben, Nacken, Tairus, and others. These stones were initially sold under the names "Emerita" and "Symeralds" and were grown as a thin layer of Emerald on top of natural colorless beryl stones.

Although these are synthesized by still-secret method, it’s known that acidic conditions are required in the synthesis to prevent the precipitation

of chromium (used as colorant). Also, it is important that the silicon-containing nutrient


(which gives the material for formation to the seed crystal) be kept away from the other ingredients to prevent nucleation (formation of a crystal around a solid core) and confine growth to the seed crystals. Growth occurs by a diffusion-reaction process, assisted by convection.

The synthetic emeralds can be distinguished from natural Emeralds by their red glow under ultraviolet light, since generally natural Emeralds are inert to UV light. However many synthetic emeralds have also been found inert to UV light.

So know we all well know about the beloved gemstone: The Emeralds. However before closing out this, it shall be worthwhile to discuss the precautions taking when one tries to buy an Emerald.

CONSIDERATIONS WHILE BUYING EMRALDS:

Since there are innumerable synthetics and imitations of Emeralds, one should be very cautious while buying one. Large Emeralds in particular should only be purchased with a report from a reputable gemological institute. Such an


institute will be able, thanks to the most modern examination techniques, to differentiate reliably between natural and synthetic emeralds.

It should also be checked whether the Emerald has been treated or not; since the price of Emerald falls if it acquires a good look after undergoing a considerable degree of enhancement. Hence while if one tries to purchase of an expensive Emerald, he/she is well advised to insist upon a treatment report from a reputable gemological laboratory.

The Emeralds are priced very high if they have the real Emerald green tone and are near to transparent with least inclusions. Apart from cut and clarity, the way Emerald is cut and its size also play a vital role in determining the cost of an Emerald. Emeralds can be very expensive; some even reach the lofty heights of $10,000 or $15,000 per carat while an Emerald with a decent look (perhaps with high degree enhancement and little fire) can cost about few hundred dollars per carat as well.

A THING OF BEAUTY IS JOY FOREVER:

Whatever be the case, Emerald has always been a fascinating gemstone leaving the humankind in


awe by its remarkable beauty and colour and would continue to incite human to know more about it.


FINAL all about emeralds

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