The Spring 2008 issue of Gems & Gemology (G&G), which is available now, features Paraíba-type tourmaline from Mozambique, a history of diamond treatment methods, purple diamonds from Siberia and the annual G&G Challenge quiz.
Vivid blue-to-green copper-bearing tourmaline has been one of the most sought-after colored stones since its discovery in Brazil's Paraíba state two decades ago. In the lead article, "Copper-Bearing (Paraíba-type) Tourmaline from Mozambique," G&G editor Brendan Laurs and co-authors explore the newest source of similar material. Produced mainly since 2005, copper-bearing tourmalines from the Mavuco area have been recovered in large sizes and can attain Paraíba-like hues, most commonly when heat treated. The article reports on the material's gemological properties as well as on mining operations at Mavuco.
"A History of Diamond Treatments," by Thomas Overton and James Shigley, explores early coatings and dyes as well as modern techniques of color alteration through irradiation and high-pressure, high-temperature (HPHT) annealing. It also reviews the development of clarity enhancement, from laser drilling to glass filling. For each of these diamond treatments, the authors summarize the key identification procedures.
Rounding out the Spring issue lineup is "Natural-Color Purple Diamonds from Siberia," in which Dr. Sergey Titkov of the Russian Academy of Sciences and a team of researchers use spectroscopic methods to better understand the causes of this rare color.
The Lab Notes column provides the latest reports from the GIA Laboratory, including unusual inclusions in aquamarine, high-temperature heat-treated zircon, and the first CVD synthetic diamond submitted for Dossier grading. The Gem News International section gives highlights from this year's Tucson gem and mineral shows, such as spessartine from a new mine in Tanzania, plus updates from around the world, with reports on various gems from Afghanistan, green plagioclase from East Africa, and more.
Two special features are the announcement of this year's Dr. Edward J. Gübelin Most Valuable Article Awards and the G&G Challenge, a 25-question multiple-choice quiz based on articles from the 2007 issues. Successful Challenge participants will receive a GIA Continuing Education Certificate and, if they score 100 percent, recognition in an upcoming issue of G&G.
To purchase a copy of the Spring issue or any of the 2007 issues, or to subscribe to G&G, click here or contact Circulation Coordinator Debbie Ortiz, by calling toll-free (800) 421-7250, ext. 7142. From outside the U.S. and Canada, dial (760) 603-4000, ext. 7142.
19th May 2008