Commercial quantities of gem-quality benitoite are known from a single location in the world, the Benitoite Gem mine in the New Idria district of San Benito County, California.

An investigation of the difference between synthetic opal and opal simulant.

New mining techniques have combined state-of-the-art equipment and technology to detect and extract large, fine-quality rhodochrosite specimens and gem rough.

Examination of 51 colorless to near-colorless synthetic diamonds from all known sources of production confirms that they can be distinguished from similar-appearing natural diamonds on the basis of their gemological properties.

Ruby crystals from Southeast Asia with a fixed six-rayed star, similar in effect to trapiche emeralds from Colombia, are described.

The Capão mine is one of the oldest and most productive fully mechanized Imperial topaz mines in the historic Ouro Preto area of Minas Gerais, Brazil.

Among the most difficult gems to identify are those that are black and opaque (or nearly so).

Two instruments have been developed at De Beers DTC Research Centre, Maidenhead, to distinguish synthetic diamonds from natural diamonds.

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

Demantoid, green andradite garnet, was discovered in the Central Ural Mountains of Russia in the mid-19th century.

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

A compilation of gem news from around the world, covering topics such as localities, unusual gem materials, market news, new products, discoveries, jewelry manufacturing techniques, and industry trends.

A new type of Russian hydrothermal synthetic emerald is produced by seeded growth in steel autoclaves without noble-metal inserts; the seed slices have been cut parallel to a face of the second-order hexagonal dipyramid s (1121).

This article explores the mining developments and new diamond occurrences in Africa that led to many of the key concepts in modern geology.

Exploration of a chart designed to give jewelers and gemologists a practical guide to identifying synthetic diamonds as they enter the jewelry trade.

For more than 100 years, Africa has produced large commercial quantities of diamonds and important individual stones.

One of the most interesting of the commercially available Czochralski pulled synthetic corundums is pink “Ti-sapphire.”

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

The emeralds of the Ural Mountains, in what is now called the Russian Federation, have been known for more than 160 years.

The history of Baja California has been closely tied to the exploitation of pearls since the 16th century.