Studies on Tourmaline, Sapphire, Cultured Pearl, and a Reliquary of Legend…
Spring is always a time of renewal. For our industry, early February marks the Tucson gem shows, the first big event of the season, where buyers are tempted with colored gems of every type and price. Similarly, there is truly something for everyone in our Spring 2019 edition.
We begin with multicolored tourmalines; few gems encompass such a rich variety of colors. In our lead article, GIA’s Ziyin Sun, Aaron Palke, and Christopher Breeding join Louisiana State University’s Barbara Dutrow to present a simplified classification system for tourmaline species using laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) analysis of major trace elements.
Our second study unites researchers based in Switzerland, Bahrain, and Scotland. Age dating of sulfide inclusions in diamonds using radiogenic decay systems is well known, but for gemologists, applying similar analyses to zircon inclusions in corundum is an emerging practice. Lead author Emilie Elmaleh tells us more about the age and origin of sapphires from two Sri Lankan alluvial deposits.
Next, a team headed by Gerard Panczer of France’s Claude Bernard University Lyon 1 contributes the first scientific, gemological analysis of the fascinating Talisman of Charlemagne. This historical, bejeweled container of holy relics—or reliquary—is a rare masterpiece of the goldsmith’s art dating back to the ninth century.
The authors of our fourth paper use a combination of LA-ICP-MS and multivariate analysis to compare the trace-element concentrations of two groups of cultured freshwater pearls (one from China, one from the United States) with natural pearls found in the U.S. This study, by Artitaya Homkrajae and her GIA team, provides the prospect of greater confidence identifying pearls of freshwater origin.
In our fifth paper, regular contributor Karl Schmetzer investigates the color appearance of faceted alexandrite, where the quest for the best color change is complicated by this biaxial gem’s inherent pleochroism. Through direct observation of synthetic alexandrite samples, he documents the impact of the inevitable multiple internal reflections on placement of a faceted gem’s table facet and its perceived color change and pleochroism.
Our final paper is a field report on Ethiopia, a new land of opportunity for colored gems. The 2016 discovery of fine emerald at Shakiso in the southern part of the country, coupled with the 2017 news of sapphires from northern Tigray Province, prompted a 2018 GIA field expedition. Led by field gemologist Wim Vertriest, the group documented mining and processing, measured social impact, and collected samples for GIA’s reference collection.
Our regular columns also provide plenty of interest. Our Lab Notes section features the largest diamond ever discovered in North America, Burmese color-change sapphire, and a synthetic diamond containing a CVD layer grown on natural diamond. In Diamonds from the Deep, Karen Smit and Steven Shirey examine fundamental questions around the ages of natural diamonds and the lessons we can draw from this information, while Micro-World offers a glimpse into the internal world of condor agate from Argentina, grandidierite inclusions in sapphire, and a fossil insect in opal. Our Gem News International section has more than 30 pages covering the 2019 Tucson shows, blending market insights with a fascinating display of gems from around the world.
As is customary, this issue contains the annual G&G Challenge: We invite you to test your gemological knowledge and skills of recall in the 2019 quiz. Finally, congratulations to our 2018 Dr. Edward J. Gübelin Most Valuable Article Award winners.
Welcome to the 2019 Spring edition of Gems & Gemology!