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. 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 ...

Todd’s Gems Todd Wacks outlines how garnets believed to be “regular” Tanzanian rhodolite when discovered in the late 1980s turned out to be rare color-change pyropes instead. In this video, he ...

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. The five zircon samples used in this study, ranging in size from 0.56–21.92 ct, were analyzed for radioactive degradation of their crystal structure. Radioactive elements such as thorium and ...

Blue zircon is perhaps best known from Cambodia, with most if not all of the material recovered as brown stones that turn blue upon heating. Recently, Brent Smith of Phoenix Gems supplied us with a ...

Until recently, film was the preferred medium used for capturing images through the microscope, primarily due to resolution limitations of digital-format cameras. The image quality that can now be ...

Emerald, the birthstone for May, has been beloved for millennia, evoking rebirth and renewal. Widely regarded as the definition of green, emerald is the perfect color for spring. From the poetic ...

The Robert Mouawad Campus at GIA World Headquarters in Carlsbad offers world-class gem studies with advanced classrooms, a renowned lab, and an iconic museum.

GIA reports represent the highest standard of reliability, consistency and integrity. And now, GIA Report Check is available for all GIA reports, providing you with an additional level of assurance.

An Identification Report, with geographic origin added. For polished, loose or mounted natural alexandrite, demantoid, emerald, jade, opal, Paraíba tourmaline ...

Discusses the role of three-phase inclusions in emerald, in combination with spectroscopy and trace-element analysis, in determining geographic origin.