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VOLUME XLII WINTER 2006 Impact of Graining on Diamond Clarity Grading . “Chocolate Pearls”. Leopard Opal . Rainbow Andradite from Japan THE QUARTERLY JOURNAL OF THE GEMOLOGICAL INSTITUTE OF AMERICA ® Winter 2006 VOLUME 42, NO. 4 EDITORIAL _____________ 205 Remembering G. Robert Crowningshield Alice S. Keller FEATURE ARTICLES _____________ 206 The Impact of Internal Whitish and Reflective Graining on the Clarity Grading of D-to-Z Color Diamonds at the GIA Laboratory Carat Points John M. King, Thomas M. Moses, and Wuyi Wang A study of two important types of graining and how GIA determines their impact on a diamond’s clarity grade. pg. 216 222 Identification of “Chocolate Pearls” Treated by Ballerina Pearl Co. Wuyi Wang, Kenneth Scarratt, Akira Hyatt, Andy Hsi-Tien Shen, and Matthew Hall Examines the “chocolate” color treatment process for cultured pearls and techniques for identifying these products. 236 Leopard Opal: Play-of-Color Opal in Vesicular Basalt from Zimapán, Hidalgo State, Mexico Robert Raymond Coenraads and Alfonso Rosas Zenil A look at the origin and properties of this colorful ornamental stone, which is known from only one source. 248 The Cause of Iridescence in Rainbow Andradite from Nara, Japan Thomas Hainschwang and Franck Notari Characterizes this iridescent garnet from Japan and explains the cause of pg. 223 its unusual color phenomenon. REGULAR FEATURES _____________________ 260 Lab Notes Lizards in imitation amber • Large demantoid of exceptional color • A large Fancy white diamond with whitish banding • Prolonged change of color in a pink diamond • Strand of natural nacreous and non-nacreous pearls • Poudretteite • Unusual gem pyroxmangite 268 Gem News International Diamond trading in Sierra Leone • Jewelry repair damages a diamond • Green pg. 260 augelite from Peru • Bicolored beryl from Namibia • Diopside from Afghanistan • California jadeite with copper inclusions • Labradorite from Mexico • Gem news from Mogok, Myanmar • Moonstone from Madagascar • Phenomenal fire opal • “Sunset” quartz from Brazil • Swedish Blue (slag) and Swedish Iron Ore • Tourmaline mining at Nandihizana, Madagascar • Green uvite from Afghanistan • Synthetic corundum “gem rough” in Tanzania • Small treated synthetic pink diamonds • “Chocolate” Tahitian cultured pearls • Treated violetish blue quartz from Brazil • Circular inclusions in a diffusion-treated sapphire • Diffusion-treated synthetic sapphire with unusual fluorescence 293 2006 Challenge Winners 294 Book Reviews 297 Gemological Abstracts 309 2006 Index pg. 269 EDITORIAL Editor-in-Chief Editor Editors, Lab Notes STAFF Alice S. Keller Brendan M. Laurs Thomas M. Moses [email protected] The Robert Mouawad Campus Shane F. McClure 5345 Armada Drive Managing Editor Carlsbad, CA 92008 Editor, Gem News International Thomas W. Overton (760) 603-4503 Brendan M. Laurs [email protected] [email protected] Technical Editor Editors, Book Reviews Associate Editor Sally Magaña Susan B. Johnson Stuart Overlin [email protected] Jana E. Miyahira-Smith [email protected] Stuart Overlin Consulting Editor Circulation Coordinator Carol M. Stockton Debbie Ortiz Editors, Gemological Abstracts Contributing Editor (760) 603-4000, ext. 7142 Brendan M. Laurs James E. Shigley [email protected] Thomas W. Overton PRODUCTION Art Director Production Assistant Website: STAFF Karen Myers Allison DeLong www.gia.edu EDITORIAL Shigeru Akamatsu Alan Jobbins George Rossman REVIEW BOARD Tokyo, Japan Caterham, United Kingdom Pasadena, California Alan T. Collins Mary L. Johnson Kenneth Scarratt London, United Kingdom San Diego, California Bangkok, Thailand John Emmett Anthony R. Kampf James E. Shigley Brush Prairie, Washington Los Angeles, California Carlsbad, California Emmanuel Fritsch Robert E. Kane Christopher P. Smith Nantes, France Helena, Montana New York, New York Henry A. Hänni Lore Kiefert Christopher M. Welbourn Basel, Switzerland New York, New York Reading, United Kingdom A. J. A. (Bram) Janse Thomas M. Moses Perth, Australia New York, New York SUBSCRIPTIONS Subscriptions to addresses in the U.S. are priced as follows: $74.95 for one year (4 issues), $194.95 for three years (12 issues). Subscriptions sent elsewhere are $85.00 for one year, $225.00 for three years. Canadian subscribers should add GST. Special rates are available for GIA alumni and current GIA students. One year: $64.95 to addresses in the U.S., $75.00 else- where; three years: $179.95 to addresses in the U.S., $210.00 elsewhere. Please have your student or Alumni number ready when ordering. Go to www.gia.edu or contact the Circulation Coordinator. Single copies of this issue may be purchased for $19.00 in the U.S., $22.00 elsewhere. Discounts are given for bulk orders of 10 or more of any one issue. A limited number of back issues are also available for purchase. Please address all inquiries regarding subscriptions and single copy or back issue purchases to the Circulation Coordinator (see above) or visit www.gia.edu. To obtain a Japanese translation of Gems & Gemology, contact GIA Japan, Okachimachi Cy Bldg., 5-15-14 Ueno, Taitoku, Tokyo 110, Japan. Our Canadian goods and service registration number is 126142892RT. MANUSCRIPT Gems & Gemology welcomes the submission of articles on all aspects of the field. Please see the Guidelines for Authors on our SUBMISSIONS Website, or contact the Managing Editor. Letters on articles published in Gems & Gemology are also welcome. Abstracting is permitted with credit to the source. Libraries are permitted to photocopy beyond the limits of U.S. copyright law COPYRIGHT for private use of patrons. Instructors are permitted to photocopy isolated articles for noncommercial classroom use without fee. AND REPRINT Copying of the photographs by any means other than traditional photocopying techniques (Xerox, etc.) is prohibited without the express permission of the photographer (where listed) or author of the article in which the photo appears (where no photographer PERMISSIONS 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 organization for the gem and jewelry industry, The Robert Mouawad Campus, 5345 Armada Drive, Carlsbad, CA 92008. Postmaster: Return undeliverable copies of Gems & Gemology to 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 Treated-color “chocolate” cultured pearls created from Tahitian cultured pearls have become a popular segment of the pearl THE COVER market in recent years. The article by Dr. Wuyi Wang and co-authors on pp. 222–235 of this issue examines a selection of “chocolate pearls” treated by Ballerina Pearl Co. in order to determine the basic process used and means of identifying these treated pearls. The “chocolate pearls” in the necklace range from ~12.0 to 13.7 mm; those in the earrings are 12.1 mm (left) and 12.3 mm (right). Jewelry courtesy of Emiko Pearls International; photo by Robert Weldon. Color separations for Gems & Gemology are by Pacific PreMedia, Carlsbad, California. Printing is by Allen Press, Lawrence, Kansas. © 2006 Gemological Institute of America All rights reserved. ISSN 0016-626X emology lost one of its original pioneers with the pass- G&G article, from the ing of G. Robert Crowningshield on November 8 at the Summer 1989 issue, age of 87. During a career that spanned six decades, his was on the first formal wide-reaching achievements as a researcher, author, and grading of the famed educator helped shape modern gemology. Hope diamond. Born in Colorado Springs, Colorado, Bob Crowningshield graduat- Many other discover- ed from San Diego State College (now San Diego State University) ies were set forth in with a degree in natural science. As an officer in the U.S. Navy Crowningshield’s from 1942 to 1946, he read books on gems to pass the long hours long-running G&G at sea and even arranged an unscheduled stop in Colombo, the column, which con- capital of Ceylon (now Sri Lanka) and a bustling trade center for tained brief notes gems. As fate would have it, the owner of the first jewelry store he from the New York visited had a son who had graduated from GIA’s resident program lab (and eventually in Los Angeles in 1939. When the young man told Crowningshield became the journal’s present-day Lab Notes section). Between of a school dedicated to the science of gems, his destiny became 1957 and 1999, he turned out more than 1,000 observations of clear, and he enrolled at GIA once his tour of duty was over. interesting and unusual gems. His 1970 note on “milky” graining in diamonds was the first articulation of what has become an After graduating from the Institute in 1947, Crowningshield stayed important feature in the clarity grading of diamonds, as described on campus in Los Angeles as an instructor. Two years later, he was in the lead article in this issue. sent to New York to help start up GIA’s East Coast office, where he worked for more than four decades, rising to the position of vice His scientific achievements alone would have earned Bob president. Crowningshield a place in gemological history, but they don’t tell the whole story. His reputation for accuracy and integrity played a Crowningshield championed the spectroscope as a tool for gemo- key role in establishing GIA’s diamond grading reports as an indus- logical research. Pencil in hand, he sketched absorption spectra for try standard. Crowningshield was also a respected educator who every stone he examined. His collection of hand-drawn illustra- taught scores of jewelers across the United States and presented at tions, first published in Richard T. Liddicoat’s 1962 edition of the all but two American Gem Society (AGS) Conclaves from 1951 to Handbook of Gem Identification, demonstrated the value of the 1993. (A complete review of his career can be found in Thomas spectroscope to gemologists.
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  • Gems and Placers—A Genetic Relationship Par Excellence

    Gems and Placers—A Genetic Relationship Par Excellence

    Article Gems and Placers—A Genetic Relationship Par Excellence Dill Harald G. Mineralogical Department, Gottfried-Wilhelm-Leibniz University, Welfengarten 1, D-30167 Hannover, Germany; [email protected] Received: 30 August 2018; Accepted: 15 October 2018; Published: 19 October 2018 Abstract: Gemstones form in metamorphic, magmatic, and sedimentary rocks. In sedimentary units, these minerals were emplaced by organic and inorganic chemical processes and also found in clastic deposits as a result of weathering, erosion, transport, and deposition leading to what is called the formation of placer deposits. Of the approximately 150 gemstones, roughly 40 can be recovered from placer deposits for a profit after having passed through the “natural processing plant” encompassing the aforementioned stages in an aquatic and aeolian regime. It is mainly the group of heavy minerals that plays the major part among the placer-type gemstones (almandine, apatite, (chrome) diopside, (chrome) tourmaline, chrysoberyl, demantoid, diamond, enstatite, hessonite, hiddenite, kornerupine, kunzite, kyanite, peridote, pyrope, rhodolite, spessartine, (chrome) titanite, spinel, ruby, sapphire, padparaja, tanzanite, zoisite, topaz, tsavorite, and zircon). Silica and beryl, both light minerals by definition (minerals with a density less than 2.8–2.9 g/cm3, minerals with a density greater than this are called heavy minerals, also sometimes abbreviated to “heavies”. This technical term has no connotation as to the presence or absence of heavy metals), can also appear in some placers and won for a profit (agate, amethyst, citrine, emerald, quartz, rose quartz, smoky quartz, morganite, and aquamarine, beryl). This is also true for the fossilized tree resin, which has a density similar to the light minerals.
  • Diamond Clarity Scale Guide

    Diamond Clarity Scale Guide

    Diamond Clarity Scale Guide Buckram and contrite Carson foreknew almost playfully, though Lukas shaft his majesty quash. One-piece Deryl andpinged Londony some sunhatsClair grieved and candlingquite perceptibly his perchers but imposts so abusively! her puddler Deuced purposefully. Bernhard still disemboguing: premosaic An h color grade clarity diamond guide on the flash does the surface The diamond and then tested by taking more graders who conceal their own findings and soul note any clarity characteristics. In the best way to the majority of lustre, really interesting names for this gemstone available use loupes or treatment is fairly common. A cavity to diamond clarity grade and bare it will cancel the overall appearance of fine diamond engagement ring. When diamonds clarity scale was this page and scales and effort. The term VS is used for diamonds in which it is difficult for a qualified observer, under observation conditions as described, to find either a few somewhat larger internal characteristics or several very small ones. Because it comes down to avoid diamonds are perpetual, we have reduced by no internal characteristics like a diamond online diamond in. URL and Selector in the configuration of the extension. Diamonds without such impurities are very rare. The 4Cs Carat Color Clarity and Cut Kay Kay Jewelers. Couples looking at round, oval, princess, radiant, heart, and pear can consider G and H color grades for a great value! The wheat is far outdated that. Why do we do this? However, such diamonds may or may not cover surface flaws or blemishes. In these cases, since each individual inclusion is very small, blue diamond looks clean to watch naked eye.