Figure 1. Spinel is available in a wide range of colors, as seen in this suite of round gems weighing 1.47–6.70 ct faceted by Bill Vance. Photo by Robert Weldon/GIA; courtesy of Vance Gems. Spinel has ...

Figure 1. Sapphires from Madagascar: a beautiful 3.29 ct untreated faceted stone and an assortment of rough in the background. Madagascar has produced many high-quality stones in the last few years ...

This chart focuses primarily on the types of natural inclusions found in tourmaline, as well as the minerals in which tourmaline can be found as an inclusion. Treatments such as enhancement of ...

Jadeite jade is one of the most important aggregate gems in today’s global marketplace, with known sources in Myanmar, Japan, Russia, and Guatemala. Among them, Myanmar is the most legendary and still ...

At the earth’s surface, graphite is the stable crystalline form of carbon, with a density of 2.26 g/cm 3. Diamond is a much more compact form of carbon, with a density of 3.52 g/cm 3, 56% higher than ...

Figure 1. The GIA 7 Pearl Value Factors system classifies pearls according to size, shape, color, luster, surface, nacre, and matching. Composite photo by GIA staff. Prized by many cultures throughout ...

Prior to the discovery of kimberlites, diamonds were all mined from secondary alluvial sources: river environments where diamonds had been eroded from their primary source. Historical diamonds from ...

Rough pink diamonds are rarely found, and although the cause of color has been correlated with plastic deformation, the precise mechanism and atomic configuration for the resulting color are topics of ...

The fee for the GIA Laboratory-Grown Diamond Quality Assessment is US$15 per carat, with a minimum fee of $15. Submissions that do not meet the minimum criteria for assessment will be charged a US$5 ...

Fluorescence and phosphorescence can assist in revealing whether a gemstone is natural, laboratory-grown or treated. GIA developed this guide so retailers can use fluorescence tests to help identify ...

The Karowe Diamond Mine in Botswana, owned and operated by Lucara Diamond Corp., has gained international recognition for producing large, high-quality type IaB or coexistence of IaB with IIa diamonds ...

Raman spectroscopy confirmed the identity of the material as pezzottaite by an intense peak at ~1100 cm –1, which is not present in beryl. Fourier-transform infrared spectroscopy showed features ...