Blue diffusion-treated sapphires are becoming more prevalent than ever before.

Many deposits of jadeite have been found in Guatemala during the last two decades.

Gem-quality zircon from a relatively underdeveloped locality in the Harts Range of central Australia is described.

During the 1970s and 1980s, treasure hunters discovered the centuries-old remains of the sunken Spanish galleons Nuestra Señora de Atocha and Santa Margarita.

One of the most popular exhibits at the Smithsonian Institution, the stunning Fancy Dark grayish blue Hope diamond was formally graded by GIA’s gem laboratory.

The world-renowned Sinkankas collection of books and other publications is now available to the public as part of the Richard T. Liddicoat Gemological Library and Information Center at GIA Santa Monica.

Recent mining at Opal Butte in northeastern Oregon has produced a wide variety of large flawless opals.

With the increasing use of radiation to color enhance gemstones, the issue of radioactivity has become a source of concern for gemologists worldwide.

The final part of this series is concerned with colors explained by band theory, such as canary yellow diamonds, or by physical optics, such as play-of-color in opal.