Over the last 10 years, millions of carats of turquoise have been enhanced by a proprietary process called the Zachery treatment.

Greater amounts of colorless sapphire—promoted primarily as diamond substitutes, but also as natural gemstones—have been seen in the gem market during the past decade.

More than 400 blue diamonds were studied at the GIA Gem Trade Laboratory over several years to reveal additional information about the relationships between their color, clarity, and other gemological properties.

A mathematical model which can analyze how appearance factors depend on proportions.

The successful culturing of abalone pearls has been known since French scientist Louis Boutan’s experimentation in the late 1890s, but commercial production has been achieved only in recent decades.

Natural and synthetic gem rubies can be separated on the basis of their trace-element chemistry.

Two ecclesiastical objects of the late Gothic period (1350–1520) were investigated to identify the gemstones that adorn them.

This article reviews the rise of the modern diamond cutting industry in India and its impact on the world diamond trade.

Some gem diamonds fluoresce, most commonly blue, to the concentrated long-wave ultraviolet radiation of a UV lamp.

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.

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.

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

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.

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

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

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

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