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 ...

In August 2022, a team of GIA gemologists visited the ruby mines near Montepuez in the Cabo Delgado province of northern Mozambique (Fall 2022 GNI, pp. 383–386). This included a visit to the deposits ...

Established in 1931, the Gemological Institute of America (GIA) is the world’s foremost authority on diamonds, colored stones, and pearls. A public benefit, nonprofit institute, GIA is the leading ...

New York is a unique city. It’s one of the world'’s media, financial, entertainment, and fashion capitals. It’s home to the iconic landmarks like Wall Street and the Statue of Liberty, and to edgy ...

Figure 1. The color zoning of amethyst from Boudi often displays a characteristic hourglass shape. Photo by Abdelghani El Harfi and Salahaddine Mouaddib. For 25 years, the Moroccan locality of Boudi ...

Through extensive hands-on practice using gemstones, you will explore grading the color, clarity and cut quality of a wide range of colored stones. Coursework includes the study of the GIA Colored ...

The authors used Vis-NIR spectral measurements combined with LA-ICP-MS data to investigate the usefulness of absorption spectra for differentiating between copper and iron as sources of greenish blue ...

As a consumer, you will regularly encounter in the marketplace gems that have been treated to change their appearance. A topic that often comes up is whether a particular gemstone is or isn’t treated.

This large Australian light opal cabochon weighs 117.85 carats. Small play-of-color flashes of orange and green predominate in a pinfire pattern, with spots of a more muted blue over a grayish ...

Figure 1. The bright red faceted ruby in this gold ring is from the large and potentially productive Snezhnoe deposit in Tajikistan. Photo by Zamoniddin Z. Nasriddinov. Discovered during the late ...

Diamond color is usually the result of selective absorption of incident white light. The unabsorbed portion of this light is transmitted through the diamond and is interpreted by the human vision ...