Fall 1996 Gems & Gemology Gemological Abstracts
REVIEW BOARD Emmanuel Fritsch Marv L. Johnson Himiko Naka University of Nantes, France GIAG~~Trade Lab, Santa Monica Pacific Palisades, California Charles E, Ashbaugh Ill Isotope Products Laboratories Michael Gray A. A. Levinson Gary A. Roskin Burbank, California Missoula, Montana University 01 Calgary European Gemological Laboratory Calgary, Alberta, Canada Los Angeles, California Andrew Christie Patricia A, S, Gray Loretta B, Loeb James E. Shigley GIA, Santa Monica GIA, Santa Monica Missoula, Montana Visalia, California Carol M. Stockton Jo Ellen Cole Elise B. Misiorowski GIA, Santa Monica Professor R. A. Howie GIA, Santa Monica Alexandria, Virginia Royal Holloway Rolf Tatje Maha DeMaggio University of London Jana E. Miyahira Duisburg University GIA Gem Trade Lab, Santa Monica United Kingdom GIA, Santa Monica Duisburg, Germany COLORED STONES AND Townsendl. In disagreement- with traditional theories of ORGANIC MATERIALS opal formation, Len Cram offers a surprising new model, based on ion exchange, that he demonstrated by growing Cretaceous mushrooms in amber. D. S. Hibbett, D. synthetic opal out of "opal dirt" in a bottle in just three Grimaldi, and M. J. Donaghue, Nature, October 12, months. Jiirgen Schutz describes the long history of 1995, p. 487. Mexican opals, their varieties, and the present mining sit- Recently, two mushrooms were discovered in amber of uation. Jochen Knigge recounts the history and produc- Turonian age (90-94 million years old, mid-Cretaceous] in tion of opals from Pedro 11, Piaui, Brazil. Klaus Eberhard central New Jersey. One specimen is nearly complete, with Wild portrays another important locality-Kirschweiler, an intact cap, distinct gills, and a central stalk (itis the old- near Idar-Oberstein-which was (and perhaps still is] one est known such mushroom, by about 60 donyears); the of the most important centers of opal fashioning and other is a wedge-shaped fragment of a mushroom cap.
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