Summer 2001 Gems Gemology - GIA with trigons • “Burmite” • Cat’s-eye amethyst Brownish...

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Transcript of Summer 2001 Gems Gemology - GIA with trigons • “Burmite” • Cat’s-eye amethyst Brownish...

  • pg. 149

    EDITORIAL

    REGULAR FEATURES

    pg. 115

    96

    FEATURE ARTICLES

    Based on recent visits to the pearl farms of Hanzhou Province, the authorsreport on the latest techniques being used to produce Chinese freshwatercultured pearls.

    Shigeru Akamatsu, Li Tajima Zansheng, Thomas M. Moses, and Kenneth ScarrattThe Current Status of Chinese Freshwater Cultured Pearls

    95Alice S. KellerThe G&G Twenty Year Index: Two Decades of Evolution

    124

    A new polishing process is being used to create the appearance of aster-ism in gems that have seldom if ever shown this phenomenon previously.

    Shane F. McClure and John I. KoivulaA New Method for Imitating Asterism

    114

    UV-Vis reflectance spectra and fluorescence characteristics are useful indistinguishing undrilled natural- and treated-color yellow cultured pearlsproduced from the Pinctada maxima mollusk.

    Shane Elen

    Spectral Reflectance and Fluorescence Characteristics of Natural-Color and Heat-Treated Golden South Sea Cultured Pearls

    130 Banded twinned diamond crystal Diamonds with unusual inclu-sions Feldspar with chrome diopside inclusions Gibbsite dyed to imitate nephrite Devitrified glass resembling jade Early Japaneseassembled cultured blister pearls Dyed black faceted cultured pearls New imitation: Shell pearls with a calcite bead

    Gem Trade Lab Notes

    163 Gemological Abstracts171 Guidelines for Authors

    160 Book Reviews

    137 Thank You, Donors138

    Royal Asscher cut Canadian diamonds PDAC conference A diamondtable with trigons Burmite Cats-eye amethyst Brownish red to orange gems from Afghanistan/Pakistan Clinohumite from Tanzania An engraved emerald Unusual rutilated quartz Rubies and ruby deposits of eastern Madagascar Ruby crystal with a mobile bubble Green sapphire with pyrochlore inclusions Vortex (Yogo Gulch) sap-phire mine update Canary tourmaline from Malawi Bismuth-bearingliddicoatite from Nigeria Jurassic Bugs amber imitation Assembled diamond imitations from Brazil Enamel-backed quartz as a star sapphireimitation Goldschmidt conference Moscow gemological conference Harvard tourmaline exhibit

    Gem News International

    pg. 108

    pg. 133

    VOLUME 37, NO. 2Summer 2001

    NOTES AND NEW TECHNIQUES

  • t has been just over 20 years since Gems & Gemologywas redesigned and the new format introduced.

    Looking at the dozens of covers of these issues, whichdominate the walls of my office, I think of the incredibleeffort that went into each onethe thousands of hoursthat our authors and staff invested in every issue to dothe research, write and refine the articles, and acquire thebest illustrations. I also think of Harold and Erica VanPelt, who photographed the vast majority of the coverimages, as well as the many individuals who loaned valu-able gemstones and jewelry for them to capture on film.

    What am I proudest of? The quality of the informationand the depth of knowledge each issuerepresents. Today, 20 years after thefirst issue of the redesigned G&Gappeared, the articles in that issueonperidot from Zabargad, cubic zirconia,and the detection of diamond simu-lantsare just as solid and useful asthey were in April 1981. Certainly,since then there have been new peridotlocalities, changes in CZ, and morediamond simulants, but these articlescontinue to serve as a solid base forongoing research on those topics.

    In the past two decades, we havepublished over 5,500 pages of timelyand timelessarticles, Lab Notes,Gem News entries, Book Reviews, andGemological Abstracts. This is truly a treasure chest ofinformation. But how do you access it? How do you findwhat you need?

    We are pleased to provide a solution: our TwentyYear Index (19812000). We have revised and updatedthe subject and author listings from our first 15 years,and added the annual indexes for the last five.

    In the course of preparing this Index, we were allstruck by the changes that were necessary since ourfirst index was published in Winter 1981changes notonly in gemology, but also in geography and technolo-gy, many of them interrelated.

    For example, the most significant change to the geopo-litical landscape since the Spring 1981 issue has been thebreakup of the Soviet Union. For our industry, however,this change has been more profound than the simplereplacement of names on a map. With the new socioeco-nomic climate in this region has come an influx of natu-ral gem materials onto the world marketmost notablyfrom the release of diamonds that were in the governmentstockpile, but also from renewed mining activity for suchclassic gems as demantoid garnets. There also has been anunprecedented impact on the availability of syntheticgem materialsnew synthetic rubies, sapphires, emer-alds, and quartz varieties, to name but a few. Russian high

    pressure/high temperature (HPHT) presses are now syn-thesizing diamonds in virtually every color.

    In other regions, names that were unknown to most ofus only five years ago are now part of the gemological par-lanceTunduru in Tanzania, Ilakaka in Madagascar,Ekati in Canada. The availability of these significant newdeposits of sapphires, rubies, and diamonds has shiftedthe balance of supply and demand. At the same time, ithas presented greater challenges to gemologists in identi-fying sources and treatments.

    Scientific advances in the U.S. and elsewhere alsohave brought us synthetic moissanite, the first diamond

    simulant to match the thermal proper-ties of diamond. Whereas there wasalmost nothing written on diamondtreatments in the 1980s, articles ondiamonds that have been fracturefilled or HPHT processed are promi-nent in the current index. Our firstindex simply referred to spec-troscopy. Today, there are entries formore than 10 different types of spec-troscopy. Laser Raman microspec-trometrywhich we first reported ononly three years agois now used rou-tinely in major gem labs around theworld to identify inclusions and gemmaterials, as well as to recognizeHPHT annealing in diamonds.

    For this veteran of two decades of G&G, the AuthorIndex offered a distinct pleasure as I was reminded ofthose who have contributed so much to the journal.Godfathers of gemological research such as RobertCrowningshield, Edward Gbelin, Richard T. Liddicoat,and Kurt Nassau were joined by an impressive group ofnew researchers such as Emmanuel Fritsch, Henry Hnni,Bob Kammerling, Bob Kane, John Koivula, ShaneMcClure, Tom Moses, Ken Scarratt, Karl Schmetzer, andJames Shigley, among many others.

    We hope that you too will enjoy using the index andfind it a valuable reference tool. Explore the thousandsof entries to learn what you need to know to stayabreast of the rapidly evolving world of gemology.

    Alice S. KellerEditor

    akeller@gia.edu

    Note: See the ad on page 159 of this issue to purchase a printedcopy of the Gems & Gemology Twenty Year Index, or access itfree of charge by visiting us online at www.gia.edu/gandg.

    EDITORIAL GEMS & GEMOLOGY SUMMER 2001 95

    The GG&&GG TTwweennttyy YYeeaarr IInnddeexx:

    Two Decades of Evolution

    I

  • THE CURRENT STATUS OF CHINESEFRESHWATER CULTURED PEARLS

    96 CHINESE FRESHWATER CULTURED PEARLS GEMS & GEMOLOGY SUMMER 2001

    demand for information, two of the authors (SAand LTZ) visited six FWCP farms and one nucleusmanufacturer in Chinas Zhejiang district; theyalso examined hundreds of Chinese FWCPs. Thetrip was made from July 25 to 29, 2000; informa-tion in this article has been confirmed and updat-ed since then based on the second authorsmonthly trips to the pearl-farming areas to visithis pearl factory in Zhuji City, as well as to pur-chase freshwater cultured pearls for export. Inaddition, the first author has visited Chinesefreshwater pearl-culturing areas several times dur-ing the past two years. This article reports on thecurrent status of the Chinese freshwater culturedpearl, both the various culturing techniques usedand the cultured pearls themselves, updating (andsuperseding) the pearl-culturing information inScarratt et al. (2000).

    By Shigeru Akamatsu, Li Tajima Zansheng,Thomas M. Moses, and Kenneth Scarratt

    See end of article for About the Authors information and Acknowledgments.GEMS & GEMOLOGY, Vol. 37, No. 2, pp. 96113 2001 Gemological Institute of America

    Chinese freshwater cultured pearls (FWCPs) are assuming a growing role at major gem and jewelry fairs, andin the market at large. Yet, it is difficult to obtain hard information on such topics as quantities produced, inwhat qualities, and the culturing techniques used because pearl culturing in China covers such a broad area,with thousands of individual farms, and a variety of culturing techniques are used. This article reports onrecent visits by two of the authors (SA and LTZ) to Chinese pearl farms in Hanzhou Province to investigatethe latest pearl-culturing techniques being used there, both in tissue nucleation and, much less commonly,bead (typically shell but also wax) nucleation. With improved techniques, using younger Hyriopsis Cumingimussels, pearl culturers are producing freshwater cultured pearls in a variety of attractive colors that are larg-er, rounder, and with better luster. Tissue-nucleated FWCPs can be separated from natural and bead-nucle-ated cultured pearls with X-radiography.

    he popularity of Chinese freshwater cul-tured pearls (FWCPs) has risen dramaticallyin the worlds markets. The unique charac-

    teristics of the Chinese FWCPin terms of size,shape, and colorhave been key to this popularity(figure 1). Chinese FWCPs are available in sizesranging from 2 mm to over 10 mm; in an interest-ing variety of shapes such as round, oval, drop,button, and baroque; and in rich colors such asorange and purple, often with a metallic luster