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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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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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Green Opal From East Africa

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

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Abstract Header from the 2009 issue of Gems & Gemology
Abstracts; Summer 2009

This article, from the Summer 2009 issue of Gems & Gemmology, is a compilation of abstracts of important gemmology-related articles published outside of Gems & Gemmology.

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Leopard Opal
Leopard Opal: Play-Of-Colour Opal in Vesicular Basalt from Zimapán, Hidalgo State, Mexico

“Leopard opal” consists of vesicular basalt impregnated with play-of-colour opal, and is known only from Zimapán, Hidalgo State, Mexico.

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Dyed Purple Hydrophane Opal

Opals with an unusual purple bodycolour and strong play-of-colour have recently appeared in the market.

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Play-of-colour opal from Wegel Tena, Wollo Province, Ethiopia
Play-of-colour opal from Wegel Tena, Wollo Province, Ethiopia

A new opal deposit was discovered in 2008 near the village of Wegel Tena, in the volcanic rocks of Ethiopia’s Wollo Province.

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Chrysoprase and Prase Opal from Haneti, Central Tanzania
Chrysoprase and Prase Opal from Haneti, Central Tanzania

Commercial quantities of gem-quality chrysoprase and green prase opal (nickel-bearing chalcedony and common opal, respectively) have been recovered from altered serpentinite deposits near Haneti, Tanzania.

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