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UV/Vis/NIR Absorption Spectrum
Spectroscopic Evidence of GE POL HPHT-Treated Natural Type IIA Diamonds

Results from spectroscopic analyses of GE POL high-pressure high-temperature (HPHT) annealed nominally type IIa diamonds are presented, and these spectral characteristics are compared with those of untreated diamonds of similar appearance and type.

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Filled Aquamarine Jewelry
Polymer-Filled Aquamarine

The authors have encountered hundreds of polymer-filled aquamarines in the Chinese jewelry market.

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0.76 ct HPHT-treated Diamond
“Fluorescence Cage”: Visual Identification of HPHT-Treated Type I Diamonds

HPHT-treated type I diamonds of various colors may exhibit unusually intense fluorescence at the facet edges and junctions.

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Clues to the Process Used by General Electric to Enhance the GE POL Diamonds

General Electric has developed a variety of high-temperature annealing techniques at different pressures for enhancing the optical properties of polycrystalline synthetic diamond films and single-crystal synthetic diamond.

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On the Identification of Various Emerald Filling Substances

Criteria for distinguishing emerald filling substances were investigated.

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Reactor-Irradiated Green Topaz

Examination of samples of faceted "Ocean green" topaz reveals that this material has been irradiated in a nuclear reactor.

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Confusing, Triangular Inclusions in an Art Deco-Style Pin
Spring 1991 G&G Lab Notes

This section, from the Spring 1991 issue of Gems & Gemology, is a compilation of interesting finds from GIA’s laboratories.

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Gemstone Irradiation and Radioactivity

With the increasing use of radiation to color enhance gemstones, the issue of radioactivity has become a source of concern for gemologists worldwide.

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An Update on Color in Gems. Part 1: Introduction and Colors Caused by Dispersed Metal Ions

This three-part series of articles reviews our current understanding of gemstone coloration.

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Emeralds of the Panjshir Valley, Afghanistan
Emeralds of the Panjshir Valley, Afghanistan

With the withdrawal of Soviet troops from Afghanistan, villagers in the Panjshir Valley are turning their attention to the emerald riches of the nearby Hindu Kush Mountains.

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