SPRING 2018 VOLUME LIV THE UARTERLY JOURNAL OF THE GEMOLOGICAL INSTITUTE OF AMERICA Characteristics of Natural-Color Green Diamonds Iridescence in “Rainbow” Hematite DNA Identification of Japanese P. Fucata Pearls Tucson Report 2018 2018 GIA SYMPOSIUM New Challenges. Creating Opportunities. Harvard Business Track Authentic Leadership, Disruptive Innovation and Customer Centricity GIA Research Track Scientific Findings and Industry Analysis GIA® is accepting abstract submissions for oral Inc. America, Gemological Institute of of trademarks registered are GIA® ©2018 GIA. and poster presentations through June 1. Join us October 7 – 9, 2018 in Carlsbad, California Seats are Limited. Register Now. symposium.GIA.edu ADT180033_G&G_Symposium_ADS_Both-FINAL.indd 2 4/6/18 3:16 PM Spring 2018 VOLUME 54, No. 1 EDITORIAL 1 The Beauty of Natural Green Diamonds Duncan Pay FEATURE ARTICLES 2 Natural-Color Green Diamonds: A Beautiful Conundrum Christopher M. Breeding, Sally Eaton-Magaña, and James E. Shigley Characterizes diamonds with exceptionally rare natural green color, based on GIA’s exten- sive database of samples. pg. 9 28 Iridescence in Metamorphic “Rainbow” Hematite Xiayang Lin, Peter J. Heaney, and Jeffrey E. Post Analyzes the substructures that cause the intense iridescence observed in “rainbow” hematite from Minas Gerais, Brazil. 40 DNA Techniques Applied to the Identification of Pinctada Fucata Pearls From Uwajima, Ehime Prefecture, Japan Kazuko Saruwatari, Michio Suzuki, Chunhui Zhou, Promlikit Kessrapong, and Nicholas Sturman Shows how genetic material extracted from small amounts of pearl powder can be a useful pg. 45 indicator of this akoya cultured pearl species. REGULAR FEATURES 52 The Dr. Edward J. Gübelin Most Valuable Article Award 54 2018 Gems & Gemology Challenge pg. 59 56 Lab Notes Fracture-filled diamond with “rainbow” flash effect • HPHT-processed diamond fraudu- lently represented as untreated • Cat’s-eye demantoid and brown andradite with horsetail inclusions • Unusual orange pyrope-spessartine-grossular garnet • New plastic opal imita- tion from Kyocera • Natural blister pearl from pearlfish within Pinctada maxima shell • Five CVD synthetics over three carats • Fancy Deep brown-orange CVD synthetic 66 G&G Micro-World Beryl crystal in fluorite • Diamond with extraordinary etch channels • Omphacite and chromite “bimineralic” inclusion in diamond • Agate-like banding in opal • Dendritic inclu- sion in Cambodian sapphire • Green crystals in yellow sapphires • Celestial inclusion scene in sapphire • Pink tourmaline in spodumene host • Quarterly crystal: Cr-diopside in pg. 68 diamond 74 Gem News International Tucson 2018 • Gem-cutting family from Idar-Oberstein • Updates on Namibian and Russian demantoid, Brazilian and Colombian emerald • Liddicoatite exhibit • Mexican and Australian opal outlook • Indonesian opal • Cultured pearl update • Secon dary gem market • Oregon sunstone • Kenyan tsavorite mining • Arkan sas tur quoise • Vi brant colors on display • Michael Dyber on carving • Rex Guo on recutting • Jewelry designs by Erica Courtney, Paula Crevoshay • Responsible practices • Supply chain transparency • Buccellati design award • Aquamarine from Pakistan • Phena kite from the Urals • Fresh - water pearls from Texas • Very small akoya • Irradiated, annealed blue type Ia diamond pg. 92 • Microscope upgrade kit • International Diamond School • Gem-A photography award Editorial Staff Editor-in-Chief Editors, Lab Notes Contributing Editors Duncan Pay Thomas M. Moses James E. Shigley gia.edu/gems-gemology [email protected] Shane F. McClure Andy Lucas Donna Beaton Subscriptions Managing Editor Editors, Micro-World Copies of the current issue may be purchased for Stuart D. Overlin Nathan Renfro Editor-in-Chief Emeritus $29.95 plus shipping. Subscriptions are $79.99 for one [email protected] Elise A. Skalwold Alice S. Keller year (4 issues) in the U.S. and $99.99 elsewhere. Cana- John I. Koivula dian subscribers should add GST. Discounts are avail- Editor Customer Service able for renewals, group subscriptions, GIA alumni, Jennifer-Lynn Archuleta Editors, Gem News Martha Erickson and current GIA students. To purchase print subscrip- [email protected] (760) 603-4502 tions, visit store.gia.edu or contact Customer Service. Emmanuel Fritsch For institutional rates, contact Customer Service. [email protected] Technical Editors Gagan Choudhary Tao Z. Hsu Christopher M. 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Nantes, France Lucerne, Switzerland Hamburg, Germany Our Canadian goods and service registration number is 126142892RT. Eloïse Gaillou Ren Lu Fanus Viljoen Paris, France Wuhan, China Johannesburg, South Africa Any opinions expressed in signed articles are under- stood to be opinions of the authors and not of the Gaston Giuliani Thomas M. Moses Wuyi Wang publisher. Nancy, France New York, New York New York, New York Jaroslav Hyršl Aaron Palke Christopher M. Welbourn Prague, Czech Republic Carlsbad, California Reading, UK About the Cover Colored by atomic-level defect arrangments, natural-color green diamonds are among the rarest gemstones found on Earth. The cover photo showcases diamonds that display a range of green hues. The diamonds in the rings (clockwise from top) are a 4.17 ct Fancy Vivid yellowish green, a 10.18 ct Fancy Intense yellow-green, and a 3.88 ct Fancy Vivid green, respectively. The unmounted diamonds in the top row are a 1.42 ct Fancy Vivid bluish green, a 1.01 ct Fancy Vivid yellowish green, and a 2.06 ct Fancy Vivid green-blue. In the bottom row are a 0.55 ct Fancy Vivid green and a 0.55 ct Fancy Vivid bluish green. Photo by Robert Weldon/GIA, courtesy of Optimum Diamonds. Printing is by L+L Printers, Carlsbad, CA. GIA World Headquarters The Robert Mouawad Campus 5345 Armada Drive Carlsbad, CA 92008 USA © 2018 Gemological Institute of America All rights reserved. ISSN 0016-626X The Beauty of Natural Green Diamonds Naturally colored green diamonds are among the most rare and enigmatic of gems, and those with saturated hues—like the stunning examples on our spring issue cover—are highly coveted. Their color origin remains extremely challenging for gemological laborato- ries to determine. In our lead paper, Drs. Christopher Breeding, Sally Eaton-Magaña, and James Shigley review these extraordinary gems, identifying four distinct causes of their green colors— radiation damage defects, luminescence from H3 defects, and absorptions by hydrogen- and nickel-related defects— and discuss the difficulties of “Determining origin of color in green diamonds separating these gems from is a major challenge for gemological laboratories.” those colored by manmade irradiation treatments. Using data and observations based on thousands of samples from GIA’s research database, the authors offer an unrivaled gemological characterization of these remarkable gems. We’re delighted to present this article,