If variety is the spice of life, you’ll appreciate our Summer 2017 issue. We offer six diverse articles featuring Russia’s Lomonosov diamond mine, carbonado, photoluminescence (PL) mapping, Vietnamese tourmaline, nephrite color determination, and Montana sapphire. In addition, we provide a full-color wall chart of characteristic sapphire inclusions.
Photoluminescence mapping shows great promise for detecting sophisticated diamond color treatments.
In August 2016, GIA’s Dr. Karen Smit and Russell Shor were fortunate enough to visit Russia’s Lomonosov diamond mine. This deposit is located about 60 miles (100 km) north of the historic port of Arkhangelsk, at a northerly latitude much like Canada’s Diavik mine. In our lead article, they share insight into its geology, operations, and diamond production. Rooted in younger Proterozoic rocks—similar to Australia’s off-craton Argyle lamproite pipe— Lomonosov’s two kimberlite pipes produce a high proportion of small gem-quality diamonds, including a tiny amount of highly valuable fancy colors, including pink. Named for its resemblance to charcoal, carbonado is one of the most intriguing diamond forms. In our second paper, Prof. Stephen Haggerty of Florida International University reviews his findings from a study of hundreds of examples from the only known sources: Brazil and the Central African Republic. He evaluates origin theories, including terrestrial and extraterrestrial models.
High-speed PL mapping can plot the distribution of optical centers in diamond. In his study, GIA research associate Lorne Loudin examines an unusual irradiated HPHT synthetic diamond of mixed type. He demonstrates a clear correlation between concentration of optical centers and diamond growth sectors, confirming that the technique shows great promise for detecting sophisticated diamond color treatments.
Luc Yen tourmaline is the subject of our next paper, from Nguy Tuyet Nhung of the Gemmological Center of the Vietnam Gemstone Association and a team of researchers. They survey the gem’s distribution in the area, its geology, and suitability for use as gems, carvings, or mineral specimens.
In our fifth paper, Xiaoyan Feng, senior engineer at NGTC in Beijing, and her research team use Raman spectroscopy to investigate and define color boundaries in nephrite from China and Taiwan.
Following the Winter 2016 emerald wallchart, we present the next in the series, which features some characteristic internal features of natural, treated, and synthetic sapphire. The chart is from the same team of inclusion specialists, led by GIA’s Nathan Renfro and John Koivula.
In our final article, Tao Hsu and her coauthors survey alluvial sapphire production in the U.S. state of Montana. They note the prevalence of small-scale mining and the importance of gem tourism, but indicate that larger, mechanized operations are expanding production at these sources.
Our Lab Notes section offers entries on melee-size CVD synthetics in parcels and jewelry, CVD synthetic overgrowth on natural diamond, and non-nacreous “rosebud” conch pearls. Topics in our Micro-World section include kyanite in diamond and molybdenite “phantoms” in quartz, while GNI features new gem finds such as Ethiopian sapphires and common opal from Mexico.
Please enjoy the Summer edition!