Following up on Nassau's 1981 article on the technical aspects of heat treating ruby and sapphire, the author reports his personal observations of the actual heat treatment process in Bangkok. He ...

Cultured pearls come in different sizes, shapes, and colors. Perhaps the best-loved gems of all time, pearls—both natural and modern cultured pearls—occur in a wide variety of colors. The most ...

A look at the history of analytical instruments used for gem testing. UV-Vis-NIR spectroscopy measures how gemstones absorb and interact with light across the ultraviolet, visible, and near-infrared ...

Since Robert Crowningshield's discovery in the late 1950s that diamonds that have been artificially colored by irradiation and subsequent annealing could be identified by their characteristic ...

Although the Art Deco period extends roughly from 1910 to well into the 1930s, it was primarily a product of the "Roaring '20s." This was a wonderfully decadent era. It was an age of Prohibition and ...

Since late 2007, rubies and sapphires have been mined by hand methods from both eluvial and primary deposits at Winza in central Tanzania. The gem corundum is related to “dikes” of amphibolitic rocks ...

During the past 25 years, the corundum market has been transformed from one of medium to high-priced gems to one that encompasses nearly all price ranges. This transformation was caused by the ...

The refractive indices of the synthetic overgrowth on the beryl seeds of Lechleitner synthetic emeralds show a linear correlation with the chromium content of the coating. In a sample with refractive ...

The various techniques in use today to alter colorless topaz to produce brown, pink, and most commonly, blue stones are discussed. Special attention is given to the three irradiation sources -gamma ...

Brazil is currently the leader in overall production of amethyst. This article describes the author's visits to three of Brazil’s most important mining areas: Marabá, Pau d’Arco, and Rio Grande do Sul ...

A necklace of round beads offered as "blue quartz from India" was analyzed by gemological and additional advanced techniques. The violet-blue ornamental material, which resembled fine-quality lapis ...