Provides a visual guide to the internal features of natural, synthetic, and treated spinel, as well as inclusions of spinel in other gemstones.

GIA developed this guide so retailers can use fluorescence tests to help identify gems right in their own stores.

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.

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 ...

Zambia is considered the world’s second most important source of emeralds by value (after Colombia). The deposits are located near the Kafubu River in the Ndola Rural Restricted Area. Emeralds have ...

The micro-world of gems lies at the very core of gemology. Information gathered from observations through the microscope serves as the very foundation for many conclusions drawn on a specimen, ...

“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.

GIA has been performing color stability testing on some sapphires for decades (Crowningshield, 1969). More recently, the stability test has been implemented to identify pink sapphires that can be ...

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.