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| are the possiblesourcerock for many of the Ratnapura-type gem depositsin this area. The cordierite gneissesand...termed by Cooray (1962, p. 257) the "Southwest GEM CEYLON rocksalso belongto this paragenesis, but...sillimanite+ corundum q- sapphirine Fro. 1. The Ratnapura gem area (outlined) in relation to the occurrences...comparablerocksof Ceylon,althoughit is foundin the gem gravels. Most of the mineralassemblages listedabovewere...SiO2-A12Oa-MgOtriangle (Fig. 2). Ratnapura-type Gem Deposits Most of the gem fields are situatedin the southwest |
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| THE ORIGIN OF GEMSTONES TISSA MUNASINGHE OF SRI LANKA AND C. B. DISSANAYAKE Department of Geology...Geology, University of Peradeniya,Peradeniya,Sri Lanka Sri Lanka is well known throughout the world for its...topaz, and zircon. Largescale gem mining is confined mainly to the Ratnapura and Elahera areas (Fig. 1)...1). In most local- ities gem minerals are recovered from residual, alluvial, and eluvial depositsthough...common (Dahanayake et al., 1980). The gem-bearing beds in the Ratnapura area are mostly alluvial in origin |
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| 2 TABLE OF CONTENTS FEATURE ARTICLES 62 Sri Lanka: The Gem Island Peter C. Zwnan The Identification...Illumination: A Controllable System of Lighting for Gem Microscopy John I. Koivula 8 7 Radioactive Irradiated...Greenland Aage Jensen and Ole V. Petersen Carving Gem-Quality Opal Theodore Grussing Two Notable Color-Change...REGULAR FEATURES Gem Trade Lab Notes Editorial Forum Gemological Abstracts Book Reviews Gem News , A B O...a n y fine gemstones found on the island o f Sri Lanka, the subject of Peter Zwaan's article i n this |
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| inclusions or these cannot be seen because the host gem is too opaque. The brownish opal termed hyalite,...KennethScarratt, Kenneth Scarratt, F.G.A. F.G.A. The Gem Gem Testing Testing Laboratory Laboratory of of Great...Laboratory's name that has changed, firstly from 'The Gem Testing Laboratory of the London Chamber of of Commerce...Commerce and Industry' and then to 'The British Gem Testing Laboratory of the London Chamber ofCommerce...The The Laboratory Laboratory is now known as 'The Gem Testing Laboratory of of Great Britain'.. Britain' |
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| Australia: Canadian Gemmological Association: Rhodesian Gem and Mineral Society. F.G.A. F.G.A. F.G.A. F.G.A...time came, the 'American Gem Society'. Very broadly speaking, the American Gem Society corresponds to the...had become attracted to the scientific study of gem materials. In some cases these 'outside' attachments...known as authors of the standard textbook Gems and Gem Materials. Other valuable long-term appointments...laboratory gemmologist as Director of the New York Gem Trade Laboratory. In 1952, at the age of 65, and |
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| Branch: M. P. Gayton, F.G.A. South Yorkshire & District Branch: 1. R. M. Lewis, F.G.A. Examiners: B. W...many others, I owe all such knowledge of gems and gem materials as I possess—apart, in my case, from such...matters more complicated the actual weights used by gem merchants with their balances were numbered 1000...appeared in the early years of the century are The Gem Cutter's Craft by L. Claremont (London, 1906), which...was my standby when I first started work in the Gem Testing Laboratory, but one had to wait until 1940 |
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| invite you to be our guest at Hong Kong Jewellery & Gem Fair September 16th-20th 2019 AWE - Booth 8E03 German...Spinel Pink and Red Gem Spinels in Marble and Placers Spinel from Tajikistan – The Gem That Made Famous...Spinels of Mogok – A Brief Overview Spinels from Sri Lanka 54 The Spinels of Mahenge, Tanzania In Search...Responsibility 94 Book Review Discovering the Gems of Sri Lanka 98 100 108 113 Members 14 Saurabh Bansal Damien...Shirley Xue Li Zhang, Hong Kong E. Gamini Zoysa, Sri Lanka Advisors Jean Claude Michelou, Colombia Ruben |
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| Tribute to Robert M. Shipley, Jr. The Chanthaburi-Trat Gem Field, Thailand Peter C. Keller 197 Gemstones with...Alexandrite Effect E. Giibelin and K. Schmetzer 204 Gem-Quality Grossular Garnets D. Vincent Manson and Carol...Crystal: The Van Pelt Collection John Sinkankcis 221 Gem-Quality Friedelite from the Kalahari Manganese Field...REGULAR FEATURES Gem Trade Lab Notes Editorial Forum Gemological Abstracts Book Reviews Gem News Index to...Liddicoat, Jr. Associate Editor Peter C. Keller Editor, Gem Trade Lab Notes Chuck Fryer Editor, Gemological Abstracts |
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| the authors 4 Iolite (cordierite) 55 Is it a gem? 5 Andalusite, Fibrolite (sillimanite) Finding... 65 Opal 42 Lapis lazuli 66 Amethyst and Citrine 44 Moonstone and Labradorite 68 Garnet 46...Further reading and credits 73 Tanzanite 54 Gem deposits of the world 74 Taaffeite 54 Index ...qualities of beauty, rarity and about the individual gem species. The main durability, which are determined...are described, together with identifying gems. Gem mineral formation is notes on items of particular |
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| provides a comprehensive examination of gems and gem materials including discussion of their properties...and popularity in different cultures. The Museum's gem collection, itself the stuff of legends, is described...factors important in determining the quality of each gem and spells out the possible confusions in gemstone...TO THOSE WHO HAVE HELPED CREATE THE MINERAL AND GEM COLLECTIONS. Those whose donations are featured...Tourmaline PAGE 88 18 Zircon& What1a Rridot Gem? PAGE PAGE 22 Corundum Diamond PAGE PAGE 44 |
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| fibrolite of 19.85 Gold box set with a large, fine citrine and other Superb tanzanite crystal and cut gemstone...carats from Burma. gemstones. Tanzania. Rare Sri Lankan orange sapphire of 57.26 carats. Emerald...illustrated. The section ends with a brief account of gem cutting. The most popular gemstones are described...final section of the book is concerned with how gem minerals form, where they are found and how they...are identified, and a selected index to the main gem species, technical terms and important topics such |
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| E. Post, Geologist, Curator-in-Charge, National Gem and Mineral Collection, National Museum of Natural...at www.dk.com CONTENTS INTRODUCTION What is a Gem? 8 How Gems Form 10 Crystals 12 Classifying...Cutting Gems 28 Polishing and Engraving Gems 30 Gem Enhancement 32 Synthetic Gems 34 History and... 214 Index 218 Acknowledgments 223 HOW THE GEM PROFILES WORK main section ; profile information...viene INTRODUCTION ‘ag yet Gay x 2 WHAT IS A GEM? Gems are generally defined as precious or semiprecious |
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| Cover illustration: A ruby, sapphire, emerald, citrine and diamond clip, mounted by Cartier, Paris, 1940...Properties of crystals Gem crystals 18 19 19 20 20 21 22 32 33 3 3.1 3.2 3.3 Gem testing Hardness Gemstones...56 4 4.1 4.2 4.3 4.4 4.5 Recent developments in gem testing 59 59 60 61 64 65 Thermal conductivity...understandably and rightly, with the science of gem testing and have covered that area very well. Details...entirely new gem mineral species have been found in the last few years; tanzanite, appearing on the gem market |
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| Dimensions in the captions refer to the entire gem or mineral; however, in some cases only a portion...A CHANGING PLANET 11 Vanadinite, San Carlos district, Chihuahua, Mexico * 8 x 4 x 2 cm Mineral Species...can be as valuable as the richly colored stones. Gem cutters bring out the inner beauty of gems by creating...trick with light. Facets allow light to enter the gem; once inside, the light bounces off its other angled...Africa and Canada « 2.00 ct and 3.06 ct leaves the gem, similar to what happens when you pass light through |
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| structure Properties of crystals Gem crystals 19 19 20 20 21 22 32 33 3 Gem testing Hardness Gemstones and...Specific gravity 36 37 56 4 Recent developments in gem testing Thermal conductivity Measurement of refractive...understandably and rightly, with the science of gem testing and have covered that area very well. Details...entirely new gem mineral species have been found in the last few years; tanzanite, appearing on the gem market...with no gem potential whatever. It is not likely that many entirely new mineral species with gem application |
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| Ian Ballour) Contents INTRODUCTION GEM IDENTIFIER Main gem groups Other gemstones Natural glasses...have tried to recognize these fakes. Synthetic gem- and optical properties by which they may be identified...on the scale grains that make them the toughest gem¬ but was in turn scratched by those beneath stones...be un¬ (9) and talc (1). For use in jewellery, gem¬ even, hackly (jagged) or conchoidal (shell - stones...hardness less than 7 are therefore likely common, gem-quality material may be to become scratched with |
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| Manager Telephone: [800! 4 2 1-7250 x 2 0 1 Editor, Gem Trade Lab Notes C. W. Frver Editor, Gemological Abstracts...Misiorowslzi Contributing Editor, John I. Koivula Editors, Gem News John I. Koivula Robcrt C. Kammerling SUBSCRIPTIONS...Robert E. Kane 47 54 Gem Trade Lab Notes Gems & Gemology Challenge 60 Gem News Book Reviews 62 ...only did the first Sumitomo gem-quality synthetic diamonds appear on the gem marlzet, but De Beers released...information revealing just how far their experiments with gem-quality synthetic diamonds had progressed; one such |
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| TREASURES The IN THE SMITHSONIAN Gem Collection Paul E. Desautels ;".'*" - • * « . ^- - ...: »•• * . The Gem Collection TREASURES The IN THE SMITHSONIAN Gem Collection Paul E. Desautels...Paul E Treasures in the Smithsonian: the Gems. gem collection. Smithsonian Institution. Smithsonian...One of the more important gifts to the Smithsonian gem collection in recent years is the 68-carat Victoria-Transvaal...champagne-colored gem was discovered in Africa in 1951. CONTENTS I. II. THE NATIONAL GEM COLLECTION THE |
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| NOTES FROM THE LABORATORY By A. E. FARN, F.G.A. The Gem Testing Laboratory, London Chamber of Commerce and...Apricot Province ___________ Teita Province Morgans Mine Mine Kenya Kenya Teita Province Bridges Mine...stone's absorption of light. But the colour of a gem is due to the light it transmits a n d only in a...California, has been allowed to examine the electronic gem-tes ter called the Jeweler's Eye. This instrument...SPINEL—-V -RUTILE QUARTZ-*' \ QUARTZ Amethyst Citrine Smokey BERYL Emerald Morganite Aquamarine F I |
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| Journal of Gemmology THE GEMMOLOGICAL ASSOCIATION AND GEM TESTING LABORATORY OF GREAT BRITAIN OFFICERS AND... R. Cavey, FGA The Gemmological Association and Gem Testing Laboratory of Great Britain 27 Greville Street...ISSN: 0022-1252 J. Gemm., 1991,22,8 458 THE GEM DIAMOND DIPLOMA GAGTL have brought together the finest...world of diamonds to produce the most comprehensive Gem Diamond home study course available. The course acknowledges...international diamond market and includes every aspect of gem diamond you will ever need to know. Following an |
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| EDITION AREM, PH.D., FG.A. gem gemologists, 1977, jewelers, and gem collectors, dealers have relied...INTRODUCTION What / Gem? a / Scope of This Book / Is The Nature Gems of GEM SECTION 1 2 GEMSTONES...Rock Classification Gem Scarcity Intrusive Crystal 6 Growth Synthetic Gem 9 / Gemstones SOURCES...dealers are aware of the growing value of exotic gem species; the list of known taaffeites has thus grown...greater monetary reward than are the tists who gem scien- build detection equipment. Inevitably, a |
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| E YE WI TNES S HA N D B O O KS GEM STONES The visual guide to more than 130 gemstone varieties...org/details/gemstoneseyewitnOOcall EYEWITNESS HANDBOOKS GEM STONES E YE WI TNESS HANDBOOKS GEMSTONES Cally...varieties are found and fashions change. Over 130 gem species, including some exceptionally rare stones...why the species entries in this its book show the gem rough, natural state, perhaps embedded in still...they can be appreciated by anyone, from the amateur gem-spotter to the enthusiast who enjoys their beauty |
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| Sapphires from Sri Lanka Kcirl Scl~metzerand Olaf Medenbach REGULAR FEATURES 112 120 124 131 Gem Trade Lab...Lab Notes Gem News Gemological Abstracts Book Reviews ABOUT THE COVER: The extraordinary play-of-color...Diffraction, one of the less common causes of color in gem materials, is described in this issue in the third...extensive listing of the known origins o f color in gem materials. The opal, from the Ditto 3 Harold &> Collection...pit. Virtually all o f the diamonds recovered are gem quality, although most are relatively small, averaging |
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| © Tere crree! THE CLEVER GEM BUYER Sclaolalemcveliareln GAVIN LINSELL “She is more precious than...the main reason invariably is that a particular gem means something special to us: they represent a story...perceptions. Now in its second edition, The Clever Gem Buyer brings the reader not only the ‘gemmological’...in an absorbing and entertaining way, The Clever Gem Buyer’s second edition includes even more gemstone...mountain of gemstone rings’ in Thailand's Chanthaburi Province, an international centre for coloured gemstones |
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| CVD synthetic diamond | Updated CIBJO Blue Books | Gem laboratory newsletters | New JVC Essential Guides...Photomicrography using a smartphone camera 24 Gem Notes Colourless cat’s-eye apatite | Prismatic Ethiopian...Excursions 69 From the Archives 73 Conferences 78 Gem-A Notices 80 New Media 84 Literature of Interest...Brendan M. Laurs brendan.laurs@gem-a.com Mary A. Burland mary.burland@gem-a.com Executive Editor Editor...Harding Marketing Consultant Ya’akov Almor bizdev@gem-a.com Assistant Editor Michael J. O’Donoghue Associate |
