Opal occurs as nodules in volcanic rocks at a new gem opal locality in the Menz Gishe district of Shewa Province, Ethiopia.

Since 1993, large amounts of gem-quality sapphires from the Andranondambo region of southern Madagascar have entered the international gem market.

This article illustrates the various features in filled diamonds and explores the best techniques for examining them.

Yogo Gulch, discovered more than 100 years ago, is one of four major sapphire-producing areas in Montana, United States.

Northern Vietnam began producing significant quantities of rubies and fancy sapphires in the late 1980s.

Renewed interest in large-scale commercial mining of Montana sapphires motivated a detailed study of the heat treatment of sapphire from the Rock Creek deposit.

Blue diffusion-treated sapphires have become a subject of considerable controversy since their introduction in significant quantities a few years ago.

After almost 75 years of inactivity, the deposits of boulder opal in Queensland, Australia, began to attract new interest in the 1960s and 1970s.

Burma, now named Myanmar, has for centuries been considered the world's preeminent source of fine rubies.

The East African nation of Tanzania has great gem wealth.

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

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.

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.

The Coscuez mine, one of a number in Colombia, is rapidly gaining significance as a major source of fine emeralds.

A review of the history of this area, its geology, and the mining methods that have predominated.

This article focuses on Colombian emeralds and gives a detailed explanation of the oiling process as observed by the author.

This article examines the history of the Ouro Preto district as well as the geology of the area and occurrence of the topaz.

Thailand has become the world's major source of gem ruby.

Marketed throughout the world, San Carlos material is often confused with, and sold as, peridot from localities that are better known and documented.

A comprehensive review of the history and geology of Colombian emeralds together with descriptions of some of the most famous gems to come from this locality.