The gemological properties of a new ruby imitation, produced by dyeing natural colorless to pale-colored corundum, are described.

The East African nation of Tanzania has great gem wealth.

The stony-iron meteorites known as pallasites are famed for the areas of yellowish green olivines they contain.

A series of cuts, designed by the author, exhibit extraordinary optical effects that result from a combination of curved surfaces and plane facets placed to take advantage of internal reflection.

The Ponderosa mine is now producing commercial quantities of the gem-quality labradorite feldspar known as sunstone.

Gem-quality rubies and pink to purple sapphires are being recovered from the Luc Yen and Quy Chau mining regions of Vietnam.

This section, from the Spring 1991 issue of Gems & Gemology, is a compilation of interesting finds from GIA’s laboratories.

Although certain concepts about the age and formation of diamonds have been known for some time, this overview of advances over the decade leading up to the early 1990s have expanded the scientific understanding of this fascinating topic exponentially.

This article reports on the gemological properties of six large black diamonds set in a suite of jewelry.

Today, only by combining different gemological tests with years of practical experience, can a conclusive determination of the origin of a sapphire be made.

In addition to its rich history, the Dresden Green offers an opportunity to gain information about how to distinguish natural from laboratory-irradiated green diamonds.

Physical, chemical, spectroscopic, and microscopic characteristics of a sample of hydrothermally grown synthetic aquamarine from the USSR are presented.

Unusually vivid tourmalines from the state of Paraiba, in north eastern Brazil, have attracted great interest since they first appeared on the international gem market in 1989.

This article discusses the history of the Majorica imitation pearl, the manufacturing and marketing processes, and the separation of the Majorica product from its cultured counterparts.

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

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

The 1980s saw major developments in new sources for diamonds and colored stones, as well as expanded production at many existing mines.

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.