A chemical and spectroscopic comparison of two purple gem spinel samples, one of them the first reported example of a spinel with a saturated purple color caused predominantly by chromium and cobalt.

Greenish yellow to yellowish green HPHT-treated diamonds exhibited highly saturated body color, well-defined brown to yellow octahedral graining, and visual evidence of heating, among other ...

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The sapphire deposit at Penglai, on Hainan Island, is potentially the largest in China. Gem-quality sapphires, at least one as large as 35.5 ct, have been found in alluvial gravels approximately 2 km ...

GIA ensures accurate gemological measurements across its global laboratories through rigorous metrology practices, including systematic instrument calibration, validation from traceable standards, and ...

Blue diffusion-treated sapphires are becoming more prevalent than ever before. The diffusion technique, which involves the addition of color-causing chemicals during heat treatment, results in a thin ...

Field Report Gems & Gemology, Fall 2013, Vol. 49, No. 3 Three Occurrences of Oregon Sunstone Duncan Pay, Robert Weldon, Shane McClure, and Kevin Schumacher ...

Observing a water drop’s interaction with opal, as well as refractive index, can confirm a specimen’s hydrophane nature with less risk of breakage than total immersion.

Several diamonds were treated for the purposes of observation and report with a new laser technique which does not show the typical surface-reaching drill hole.

Learn more about the GIA Diamond Origin Report service which includes a country of origin opinion for eligible 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 ...

専門分野で次の段階に進もうとする方も、新しいキャリアを目指す方も、GIA のコースやディプロマプログラムを受講して成功への準備をすることができます。 GIA は、独自の画期的な研究から開発され、業界をリードする ...