Winter 2009 Gems & Gemology
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G EMS & G VOLUME XLV WINTER 2009 EMOLOGY W INTER 2009 P AGES 235–312 Ruby-Sapphire Review V Nanocut Plasma-Etched Diamonds OLUME Chrysoprase from Tanzania 45 N Demantoid from Italy O. 4 THE QUARTERLY JOURNAL OF THE GEMOLOGICAL INSTITUTE OF AMERICA EXPERTISE THAT SPREADS CONFIDENCE. Because Public Education AROUND THE WORLD AND AROUND THE CLOCK. Happens at the Counter. ISRAEL 5:00 PM GIA launches Retailer Support Kit and website Cutter checks parameters online with GIA Facetware® Cut Estimator. NEW YORK 10:00 AM GIA Master Color Comparison Diamonds confirm color quality of a fancy yellow. CARLSBAD 7:00 AM MUMBAI 7:30 PM Laboratory technicians calibrate Staff gemologist submits new findings on measurement devices before coated diamonds to GIA global database. the day’s production begins. HONG KONG 10:00 PM Wholesaler views grading results and requests additional services online at My Laboratory. JOHANNESBURG 5:00 PM Diamond graders inscribe a diamond and issue a GIA Diamond Dossier® A $97.00 value, shipping and handling extra. All across the planet, GIA labs and gemological reports are creating a common language for accurate, unbiased gemstone GIA’s Retailer Support Kit has been developed to help evaluation. From convenient locations in major gem centers, to frontline detection of emerging treatments and synthetics, to online services that include ordering, tracking, and report previews — GIA is pioneering the technology, tools and talent sales associates educate the public about diamonds, that not only ensure expert service, but also advance the public trust in gems and jewelry worldwide. the 4Cs, and thoroughly explain a GIA grading report. Take full advantage of all that GIA has to offer by visiting WWW.GIA.EDU www.retailer.gia.edu To order your FREE kit, log on to www.retailer.gia.edu CARLSBAD NEW YORK LONDON ANTWERP FLORENCE GABORONE JOHANNESBURG DUBAI MOSCOW MUMBAI BANGKOK HONG KONG TAIPEI SEOUL OSAKA TOKYO RTGG09 Winter 2009 Volume 45, No. 4 ® 235 LETTERS _________________ FEATURE ARTICLES __________________ 236 Ruby and Sapphire Production and Distribution: A Quarter Century of Change Carat Points Russell Shor and Robert Weldon A review of the sources, treatments, and global developments that have transformed the corundum market since the early 1980s. 260 Cutting Diffraction Gratings to Improve Dispersion (“Fire”) in Diamonds Al Gilbertson, Benjamin Gudlewski, Mary Johnson, George Maltezos, Axel Scherer, and James Shigley A new process of plasma-etching diffraction grating patterns on diamond facets produces a more fiery appearance. pg. 251 NOTES & NEW TECHNIQUES ___________ 271 Chrysoprase and Prase Opal from Haneti, Central Tanzania James E. Shigley, Brendan M. Laurs, and Nathan D. Renfro The geology, mining, and gemological characteristics of Tanzanian chrysoprase and green prase opal are revealed. 280 Demantoid from Val Malenco, Italy: Review and Update Ilaria Adamo, Rosangela Bocchio, Valeria Diella, Alessandro Pavese, Pietro Vignola, Loredana Prosperi, and Valentina Palanza pg. 267 New gemological, chemical, and spectroscopic data characterize demantoid from this notable locality in northern Italy. REGULAR FEATURES __________________________ 288 Lab Notes A new chalcedony treatment • DiamondView indicates treatment in irradiated brown-orange diamond • Diamond with flower-shaped cloud • Unusual trigon- shaped clouds in two diamonds cut from the same rough • Fancy Intense blue type IIb synthetic diamond • Colorless cat’s-eye phenakite • Blue sapphires diffusion treated with titanium and beryllium • Interesting inclusion aggregate in tsavorite • Uranium mineral as inclusions in turquoise 296 Gem News International Update on benitoite • Large cat’s-eye beryl from India • Emerald mining tech- niques at the Kagem mine, Zambia • Yellow grossular from Tanzania • An unusual blister pearl • Myanmar report • Phenakite from Nigeria • Update on rubies and Cu-bearing tourmaline from Mozambique • Sodalite from Afghanistan • Pseudo-chatoyancy and -asterism in sphalerite from Spain • New find of pink-to-red tourmaline in Nigeria • Rough emerald imitation pg. 308 • Silicon inclusions in black synthetic moissanite • Dyed sillimanite as an emerald imitation • High-RI Ba-Zr glass • Dyed pink alabaster S1 Letters, continued S2 Book Reviews S5 Gemological Abstracts S13 2009 Subject and Author Index www.gia.edu/gandg ® EDITORIAL Editor-in-Chief Editor Editors, Lab Notes STAFF Alice S. Keller Brendan M. Laurs Thomas M. Moses [email protected] Gemological Institute of America Shane F. McClure The Robert Mouawad Campus Managing Editor 5345 Armada Drive Editor, Gem News International Thomas W. Overton Carlsbad, CA 92008 Brendan M. Laurs [email protected] (760) 603-4503 Associate Editor [email protected] Editors, Book Reviews Stuart D. Overlin Susan B. Johnson Circulation Coordinator [email protected] Jana E. Miyahira-Smith Martha Rivera Thomas W. Overton Consulting Editor (760) 603-4000, ext. 7142 Carol M. Stockton [email protected] Editors, Gemological Abstracts Contributing Editor Brendan M. Laurs James E. Shigley Thomas W. Overton PRODUCTION Art Director Image Specialist G&G Online: STAFF Nanette Newbry, Studio 2055 Kevin Schumacher gia.metapress.com EDITORIAL Shigeru Akamatsu Emmanuel Fritsch Robert E. Kane Kenneth Scarratt Tokyo, Japan Nantes, France Helena, Montana Bangkok, REVIEW BOARD Thailand Edward W. Boehm Jaroslav Hyr`´sl Lore Kiefert Chattanooga, Prague, Czech Republic Lucerne, Switzerland James E. Shigley Tennessee A. J. A. (Bram) Janse Michael S. Krzemnicki Carlsbad, California James E. Butler Perth, Australia Basel, Switzerland Washington, DC E. Alan Jobbins Thomas M. Moses Christopher P. Smith New York, New York Alan T. Collins Caterham, UK New York, New York London, UK Mary L. Johnson Mark Newton Wuyi Wang San Diego, California Coventry, UK New York, New York John L. Emmett Brush Prairie, Anthony R. Kampf George R. Rossman Christopher M. Welbourn Washington Los Angeles, California Pasadena, California Reading, UK SUBSCRIPTIONS Copies of the current issue may be purchased for $35 in the U.S., $50 elsewhere. Online subscriptions are $74.95 for one year (4 issues), $194.95 for three years (12 issues). Combination print/online subscriptions are $139.95 in the U.S. and $160 elsewhere for one year, and $399.95 in the U.S. and $465 elsewhere for three years. Canadian subscribers should add GST. Discounts are available for group subscriptions, renewals, GIA alumni, and current GIA students. Subscriptions include G&G’s monthly gemological e-newsletter, the G&G eBrief. To purchase subscriptions and single print issues, visit www.gia.edu/gandg or contact the Circulation Coordinator. Electronic (PDF) versions of individual articles and sections from Spring 1981 forward can be purchased at gia.metapress.com for $12 each. Full issue access can be purchased for $25. To obtain a Japanese translation of Gems & Gemology, contact GIA Japan at [email protected]. Our Canadian goods and service registration number is 126142892RT. Gems & Gemology’s impact factor is 1.172 (ranking 12th out of the 26 journals in the Mineralogy category), according to the DATABASE Thomson Reuters 2008 Journal Citation Reports (issued July 2009). Gems & Gemology is abstracted in Thomson Reuters COVERAGE products (Current Contents: Physical, Chemical & Earth Sciences and Science Citation Index—Expanded, including the Web of Knowledge) and other databases. For a complete list of sources abstracting G&G, see www.gia.edu/gandg. Gems & Gemology welcomes the submission of articles on all aspects of the field. Please see the Guidelines for Authors on MANUSCRIPT our Website, or contact the Managing Editor. Letters on articles published in Gems & Gemology are also welcome. SUBMISSIONS Abstracting is permitted with credit to the source. Libraries are permitted to photocopy beyond the limits of U.S. copyright law for private use of patrons. Instructors are permitted to photocopy isolated articles for noncommercial classroom use without fee. Copying of the photographs by any means other than traditional photocopying techniques (Xerox, etc.) is prohibited with- COPYRIGHT out the express permission of the photographer (where listed) or author of the article in which the photo appears (where no pho- AND REPRINT tographer is listed). For other copying, reprint, or republication permission, please contact the Managing Editor. Gems & Gemology is published quarterly by the Gemological Institute of America, a nonprofit educational organiza- PERMISSIONS tion for the gem and jewelry industry. Postmaster: Return undeliverable copies of Gems & Gemology to GIA, The Robert Mouawad Campus, 5345 Armada Drive, Carlsbad, CA 92008. Any opinions expressed in signed articles are understood to be the opinions of the authors and not of the publisher. ABOUT In the past 25 years, rubies and sapphires have gone from rare, expensive gems to material spanning all qualities THE COVER and price points. The lead article in this issue, by Russell Shor and Robert Weldon, reviews the political, economic, and technological forces that have reshaped the corundum market worldwide. This sapphire necklace, designed by David Webb, has approximately 700 carats of sapphire beads. The large cabochon, with a GIA origin report stating Sri Lanka, is unheated and weighs 80.77 ct. Courtesy of Brice Jewelers, Houston, Texas; photo by Robert Weldon. Color separations for Gems & Gemology are by Pacific Plus, Carlsbad, California. Printing is by Allen Press, Lawrence, Kansas. © 2009 Gemological Institute of America All rights