The Summer 2017 issue of GIA’s Gems & Gemology offers seven diverse articles on topics including Russia’s Lomonosov diamond mine, carbonado diamond, photoluminescence (PL) mapping, Vietnamese tourmaline, nephrite color determination and Montana sapphire. It opens with “Geology and Development of the Lomonosov Diamond Deposit, Northwestern Russia,” written by GIA research scientist Karen Smit and GIA senior industry analyst Russell Shor. The article delves into the geology, operations and production of this diamond mine. Rooted in younger Proterozoic rocks, Lomonosov’s two kimberlite pipes produce a high proportion of gem-quality diamonds, including a tiny amount of highly valuable fancy-color material.

“Carbonado Diamond: A Review of Properties and Origin,” by Professor Stephen Haggerty of Florida International University, evaluates origin theories for unusual diamond aggregates based on hundreds of examples from the only known sources: Brazil and the Central African Republic.

“Photoluminescence Mapping of Optical Defects in HPHT Synthetic Diamond” explores GIA research associate Lorne Loudin’s study of an irradiated HPHT synthetic diamond of mixed type, confirming that the technique shows great promise for detecting sophisticated diamond color treatments. Researchers led by Nguy Tuyet Nhung of the Gemmological Center of the Vietnam Gemstone Association provide “An Update on Tourmaline from Luc Yen, Vietnam.” 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 in the article “Characterization of Mg and Fe Contents in Nephrite Using Raman Spectroscopy.”

The Summer 2017 issue of G&G also includes a wall chart on sapphire inclusions, the second in a series. The same team of specialists that created the emerald inclusion chart in the Winter 2016 issue of G&G, led by GIA’s Nathan Renfro, documents characteristic internal features of natural, treated and synthetic sapphire.

G&G technical editor Tao Hsu and her co-authors survey alluvial sapphire production in the U.S. state of Montana. “Big Sky Country Sapphire: Visiting Montana’s Alluvial Deposits,” notes the prevalence of small-scale mining and the importance of gem tourism, but indicates that larger, mechanized operations are expanding.

G&G’s Lab Notes section includes entries on melee-size CVD synthetics in parcels and jewelry, CVD synthetic overgrowth on natural diamond and non-nacreous “rosebud” conch pearls. The Micro-World column includes kyanite in diamond and molybdenite “phantoms” in quartz, while Gem News International features new gem finds such as Ethiopian sapphires and common opal from Mexico.