Gemology

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by Amy Cooper and Phil York GIA, Carlsbad
Any gem with elongated needle inclusions or a fibrous structure can produce chatoyancy when cut as a cabochon with the proper orientation. ...»
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by Nathan Renfro GIA, Carlsbad
Recently examined in the Carlsbad laboratory was an 11.52 ct purplish red cushion mixed cut. Gemological testing confirmed the material was corundum ...»
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by Kyaw Soe Moe GIA, New York
At the 2012 Tucson gem shows, Mark Kaufman (Kaufman Enterprises, San Diego, California) revealed a relatively new find of yellow opal. According to his supplier, the opal reportedly came from West Africa, ...»
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by Gagan Choudhary Gem Testing Laboratory, Jaipur, India
Mehul Durlabhji, co-convener of the Gem Testing Laboratory of Jaipur, India, recently brought two cabochons to this contributor for identification. The specimens, one green and one orangy yellow, ...»
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by Sally Eaton-Magaña GIA, Carlsbad
em-quality synthetic diamond grown by chemical vapor deposition (CVD) is rarely encountered among the stones submitted for a GIA diamond report. Rarer still are type IIb CVD specimens—most are type IIa. ...»
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by Akira Hyatt GIA, New York
In July 2012, the New York laboratory received a most unusual pearl for examination. The 26.99 x 17.90 x 7.25 mm specimen bore an uncanny likeness to a mushroom, consisting of a bell-shaped cap atop a narrower stem. ...»
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Among the many elements represented on the Chart of Elements is a group known as the "Noble Metals." These metals distinguish themselves by being remarkably resistant to chemical reactions, corrosion and oxidation ...»
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Platinum is a member of a suite of similar white or gray colored metals, including platinum, ruthenium, rhodium, osmium, iridium and palladium, and are collectively known as the Platinum Metal Group ...»
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Pearls have a rich inner glow that seems to come from deep within. That’s luster. It’s an effect caused by light reflecting and diffusing through the layers of nacre. High luster tends to make a pearl more valuable. ...»
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Opals are composed of a desiccated silica gel that, upon drying, forms spheres on a microscopic structural level. The size, roundness and space between these spheres dictate the ultimate quality of play of color that appears in each individual stone. ...»
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Long valued for its beauty and allure, the history of the emerald reaches across the ages and spans civilizations, from the Babylonians and Egyptians to the Romans and Aztecs. ...»
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Ever since humankind began culling gemstones for a myriad of purposes—to adorn the body, as a talisman ornament, even for an accompaniment on the journey to the afterlife, for example—so have people been collecting mineral specimens. ...»
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Grading the quality of pearls consists of examining the size, shape, surface, color, luster, orient, nacre thickness, and, if appropriate, matching ...»
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Fancy color diamonds are the diamond lovers’ new frontier, due to the variety of color options and because they now offer an affordable change from their more traditional counterparts ...»
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The Diamond is known as the “King of Gems,” and justifiably so. The ancient Greeks called it adamas, meaning unconquerable,” to convey the phenomenal hardness of this material. ...»

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