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Winter 2011 G&G Lab Notes

This section, from the Winter 2011 issue of Gems & Gemmology, is a compilation of interesting finds from GIA’s laboratories.

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Opal from the Shewa Province, Ethiopia

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

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Queensland Boulder Opal

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

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Treated Andamooka Matrix Opal
Treated Andamooka Matrix Opal

Matrix opal from Andamooka, in South Australia, is a precious opal-included porous rock that is commonly colour enhanced (carbon impregnated) to imitate the highly prized black opal from Lightning Ridge in northern New South Wales, Australia.

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"Opalite": Plastic Imitation Opal with True Play-Of-Colour

A plastic imitation opal that shows true play-of-colour was advertised as "new" and offered for sale under the trade name "Opalite" at the Gem and Lapidary Dealers Association (GLDA) Tucson show in February 1988.

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Opals from Opal Butte, Oregon
Opals from Opal Butte, Oregon

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

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Gemstone Durability: Design to Display

A treatise on the design, display, care and repair of fine gemstones.

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Green Opal From East Africa

Gemmological and chemical analysis of bright green gem-quality opal from Tanzania.

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Opal from Queretaro, Mexico: Occurrence and Inclusions

An examination of play-of-colour opal from Mexico and its variety of inclusions.

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Carving Gem-Quality Opal

An examination of the challenges of carving gem-quality opal.

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