Spring 2007 Gems & Gemology
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G EMS & G VOLUME XLIV SPRING 2008 EMOLOGY S PRING 2008 P AGES 1–106 Paraíba-type Tourmaline from Mozambique History of Diamond Treatments V OLUME Purple Diamonds 44 N O. 1 THE QUARTERLY JOURNAL OF THE GEMOLOGICAL INSTITUTE OF AMERICA ® Spring 2008 VOLUME 44, NO. 1 EDITORIAL ________ 1 The Dr. Edward J. Gübelin Most Valuable Article Award FEATURE ARTICLES _____________ 4 Copper-Bearing (Paraíba-type) Tourmaline from Mozambique Brendan M. Laurs, J. C. (Hanco) Zwaan, Christopher M. Breeding, William B. (Skip) Simmons, Donna Beaton, Kenneth F. Rijsdijk, Riccardo Befi, and Alexander U. Falster The geology, mining, and properties are described for this tourmaline, which typically yields bright Paraíba-like blue-to-green hues on heat treatment. 32 A History of Diamond Treatments pg. 14 Carat Points Thomas W. Overton and James E. Shigley Reviews the history, characteristics, and identification of diamond color and clarity enhancement techniques. NOTES AND NEW TECHNIQUES ________ Natural-Color Purple Diamonds from Siberia 56 Sergey V. Titkov, James E. Shigley, Christopher M. Breeding, Rimma M. Mineeva, Nikolay G. Zudin, and Aleksandr M. Sergeev A gemological and spectroscopic investigation of rare purple diamonds from Siberia to better understand their color and its causes. pg. 40 REGULAR FEATURES _____________________ 66 Lab Notes Aquamarine with kelp-like inclusions • Diamond with repeating growth/ dissolution features • First CVD synthetic diamond submitted for Dossier grading • Interesting filled voids • Glass with devitrified inclusions • White clam pearl with original shell • Large baroque multicolored conch pearl • Green synthetic sapphire with vibrant blue inclusions • High-temperature heat-treated zircon 74 Gem News International pg. 71 Tucson report • Emerald-bearing gem pockets from North Carolina • Spessartine from Loliondo, Tanzania • Gem-quality afghanite and haüyne from Afghanistan • A blue manganaxinite • Gem news from Myanmar • Gems on the market in Taunggyi, Myanmar • Large gem pocket discovered in San Diego County, California • Green sodic plagioclase from East Africa • A blue topaz with 2500+ facets • An imitation “elephant pearl” • An interesting synthetic sapphire • Lead glass–filled color-change sapphire • Myanma Gem Emporium offerings for 1992–2007 • Conference reports 95 2008 Gems & Gemology Challenge 97 Book Reviews 100 Gemological Abstracts pg. 83 he first-place article was “Durability Testing of Filled T Emeralds” (Summer 2007), a long-term study of the stability and durability of nine common emerald-filling substances. Receiving second place was “Serenity Coated Colored Diamonds: Detection and Durability” (Spring 2007), which examined a new multi-layer diamond coating technique that produces evenly distributed, natural-looking fancy colors. Third place went to “Latest-Generation CVD-Grown Synthetic Diamonds from Apollo Diamond Inc.” (Winter 2007), a report on the compa- ny’s latest products, which showed significant improve- ments in size, color, and clarity. The authors of these three articles will share cash prizes of $2,000, $1,000, and $500, respectively. Following are brief biographies of the winning authors. DURABILITY TESTING OF FILLED EMERALDS Mary L. Johnson Mary L. Johnson is the principal of Mary Johnson Consulting in San Diego, California. Formerly manager of research and development at GIA, Dr. Johnson received her Ph.D. in mineralogy and crystallography from Harvard University. Mary L. Johnson SERENITY COATED COLORED DIAMONDS: DETECTION AND DURABILITY Andy H. Shen, Wuyi Wang, Matthew S. Hall, Steven Novak, Shane F. McClure, James E. Shigley, and Thomas M. Moses Andy H. Shen is a research scientist at the GIA Laboratory in Carlsbad, Andy H. Shen Wuyi Wang California. Dr. Shen holds a Ph.D. from Cornell University and has conducted MOST VALUABLE ARTICLE AWARD GEMS & GEMOLOGY SPRING 2008 1 research in mineral physics in the United States, Germany, and the United Kingdom for more than 15 years. Wuyi Wang is manager of research projects at the GIA Laboratory in New York. Dr. Wang holds a doctorate in geology from the University of Tsukuba in Japan. He has considerable research expe- rience in diamond geochemistry and diamond treatment. Matthew S. Hall is manager of identification services at the GIA Laboratory in New York. Mr. Hall has a bachelor’s degree in geology from Franklin and Marshall College and a master’s in geology and geochemistry from the University of Maryland. Matthew S. Hall Steven Novak Steven Novak is senior specialist at the Evans Analytical Group in East Windsor, New Jersey. Dr. Novak has a Ph.D. in geology from Stanford University. Shane F. McClure is director of identification services at the GIA Laboratory in Carlsbad. Well-known for his many articles and lectures on gem identification, Mr. McClure is coeditor of G&G’s Lab Notes section. James E. Shigley is distinguished research fellow at the GIA Laboratory in Carlsbad. The editor of the Gems & Gemology in Review series and contributing edi- tor to the journal, Dr. Shigley received his doctorate in geology from Stanford Shane F. McClure James E. Shigley University. Thomas M. Moses is senior vice president of the GIA Laboratory and Research, New York. Thomas M. Moses LATEST-GENERATION CVD-GROWN SYNTHETIC DIAMONDS FROM APOLLO DIAMOND INC. Wuyi Wang, Matthew S. Hall, Kyaw Soe Moe, Joshua Tower, and Thomas M. Moses Wuyi Wang, Matthew S. Hall, and Thomas M. Moses were profiled in the sec- ond-place entry. Kyaw Soe Moe, formerly a research technician at the GIA Laboratory in New York, holds a bachelor’s degree in geology from the University of Yangon in Myanmar. Mr. Moe resides in West Melbourne, Florida. Joshua Tower, senior scientist at Apollo Diamond Inc. in Boston, has 20 years of experience in crystal growth, materials characterization, and semiconductor Kyaw Soe Moe Joshua Tower metrology. Mr. Tower received a bachelor’s degree from Middlebury College and a master’s degree from the University of Maryland, both in physics. Congratulations to Dr. Edward Blomgren of Owls Head, New York, whose ballot was drawn from the many entries to win a three-year subscription to GEMS & GEMOLOGY, and copies of the two GEMS & GEMOLOGY IN REVIEW volumes, COLORED DIAMONDS and SYNTHETIC DIAMONDS. 2 MOST VALUABLE ARTICLE AWARD GEMS & GEMOLOGY SPRING 2008 COPPER-BEARING (PARAÍBA-TYPE) TOURMALINE FROM MOZAMBIQUE Brendan M. Laurs, J. C. (Hanco) Zwaan, Christopher M. Breeding, William B. (Skip) Simmons, Donna Beaton, Kenneth F. Rijsdijk, Riccardo Befi, and Alexander U. Falster Copper-bearing tourmaline from Mozambique was first recovered in 2001, but its Cu content was not recognized until 2003, and it was not widely sold with its Mozambique origin disclosed until 2005. It has been mined from alluvial deposits in an approximately 3 km2 area near Mavuco in the eastern portion of the Alto Ligonha pegmatite district. Most of the production has come from arti- sanal mining, with hand tools used to remove up to 5 m of overburden to reach the tourmaline- bearing layer. The stones exhibit a wide range of colors, typically pink to purple, violet to blue, and blue to green or yellowish green. Heat treatment of all but the green to yellowish green stones typi- cally produces Paraíba-like blue-to-green hues by reducing absorption at ~520 nm caused by the presence of Mn3+. The gemological properties are typical for Cu-bearing tourmaline (including material from Brazil and Nigeria); the most common inclusions consist of partially healed fractures and elongate hollow tubes. With the exception of some green to yellow-green stones, the tourma- lines examined have relatively low Cu contents and very low amounts of Fe and Ti. Mechanized mining is expected to increase production from this region in the near future. opper-bearing tourmaline, in bright blue- deposit of Cu-bearing tourmaline, and the “neon” to-green hues, is one of the most sought- blue and green shown by the finest stones closely after colored stones in the gem market. Soon resembles the most sought-after material from Cafter its discovery in Brazil’s Paraíba State in the Paraíba (figure 1). Mavuco actually produces a wide late 1980s (Koivula and Kammerling, 1989), the variety of colors, including unusual deep purple material gained notoriety for its beautiful “neon” amethyst-like hues and steely violetish blues (figure colors, and prices escalated rapidly. Additional 2). Of the several hundred kilograms of tourmaline deposits were found in Paraíba and in neighboring rough mined to date in the Mavuco area, about 10% Rio Grande do Norte State during the 1990s show blue-to-green Paraíba-like colors without heat (Shigley et al., 2001). Then, in 2001, Cu-bearing treatment (M. Konate, pers. comm., 2007). tourmaline was discovered in Nigeria (Smith et al., The Cu-bearing tourmaline from this area may 2001). At least three Nigerian localities were subse- have been sold initially as Brazilian material (in var- quently recognized (Furuya and Furuya, 2007; ious countries around the world, including Brazil), Breeding et al., 2007). The newest source of Cu- since the Mozambique origin was not correctly and bearing tourmaline is Mozambique, which was first described in 2004 (Wentzell, 2004). Eventually, the gem trade learned that the source was the Mavuco See end of article for About the Authors and Acknowledgments. (or Chalaua) area in the Alto Ligonha pegmatite dis- GEMS & GEMOLOGY, Vol. 44, No. 1, pp. 4–30. trict. It is probably the world’s largest known © 2008 Gemological Institute of America 4 COPPER-BEARING TOURMALINE FROM MOZAMBIQUE GEMS & GEMOLOGY SPRING 2008 Figure 1. Copper-bearing tourmaline from Mozambique is found as alluvial pebbles (upper left, approximately 11 g) and is faceted into a variety of bright colors, including the most desirable “neon” blue and green. The center stone in the ring weighs approximately 5 ct, and the other faceted tour- malines weigh 6.73–15.77 ct; the blue teardrop in the center and the stone in the ring have been heat treated.