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.
The authors have encountered hundreds of polymer-filled aquamarines in the Chinese jewelry market.
“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.
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.
On the Identification of Various Emerald Filling Substances
Criteria for distinguishing emerald filling substances were investigated.
Reactor-Irradiated Green Topaz
Examination of samples of faceted "Ocean green" topaz reveals that this material has been irradiated in a nuclear reactor.
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.
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.
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.
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.