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.

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

Field Report Gems & Gemology, Winter 2016, Vol. 52, No. 4 Update on Gemstone Mining in Northern Mozambique Wim Vertriest and Vincent Pardieu ...

Reports on a visit to a shell nucleus manufacturer and two pearl farms in northern Vietnam, which is emerging as a notable producer.

CARLSBAD, Calif. – June 2, 2025 – Beginning later this year, GIA (the Gemological Institute of America) will start using descriptive terms to characterize the quality of laboratory-grown diamonds and ...

Shows how the color of Madagascar sapphire is lightened with heating to relatively low temperatures below 1350°C.

Diamonds have a long history as a premier gemstone—a natural consequence of their beauty, rarity, and superlative physical properties such as extreme hardness. Diamonds that are mined for use as ...

“Rabbit hair” quartz is a commercial variety of quartz with special inclusions. These inclusions resemble rabbit fur and are shorter and thinner than the typical rutile, tourmaline, or other acicular ...

The quality and size of this 4.04 ct CVD-grown diamond ring demonstrate the advancing technology in laboratory-grown diamonds.

At the AGTA show, we spoke with Alex Skachkov of Misfit Diamonds (Vancouver, Canada) about some of their unusual diamonds (figure 1). When asked what was popular, he showed us their aptly named “salt ...

GIA researchers report on a new nickel-diffusion treatment used to modify color in spinel and present criteria for identification.

This installment of “Colored Stones Unearthed” explores inclusions in gems—how they form, how they are studied, and what they mean for gemologists and geoscientists.