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.
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.
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.
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.
"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.
Opals from Opal Butte, Oregon
Recent mining at Opal Butte in northeastern Oregon has produced a wide variety of large flawless opals.
Gemstone Durability: Design to Display
A treatise on the design, display, care and repair of fine gemstones.
Green Opal From East Africa
Gemmological and chemical analysis of bright green gem-quality opal from Tanzania.
Opal from Queretaro, Mexico: Occurrence and Inclusions
An examination of play-of-colour opal from Mexico and its variety of inclusions.
Carving Gem-Quality Opal
An examination of the challenges of carving gem-quality opal.