Fritsch, Emmanuel and Shigley, James E. and Rossman, George R. and Mercer, Meredith E. and Muhlmeister, Sam M. and Moon, Mike (1990) Gem-Quality Cuprian-Elbaite Tourmalines from São José Da Batalha, Paraíba, Brazil. Gems and Gemology, 26 (3). pp. 189-205. ISSN 0016-626X. http://resolver.caltech.edu/CaltechAUTHORS:20130801-093000494
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Unusually vivid tourmalines from the state of Paraíba, in northeastern Brazil, have attracted great interest since they first appeared on the international gem market in 1989. This article describes what is known of the locality at this time, but focuses on the most striking characteristic of these gem tourmalines: the unusual colors in which they occur. Quantitative chemical analyses revealed that these elbaite tourmalines contain surprisingly high concentrations of copper, up to 1.92 wt.% Cu (or 2.38 wt.% CuO). Their colors are due to Cu^(2+) or a combination of Cu^(2+), Mn^(3+), and other causes. Some colors can be produced by heat treatment, but most also occur naturally.
|Additional Information:||© 1990 Gemological Institute of America. The authors appreciate the information provided by Gerhard Becker, Brian Cook, David Epstein, Robert van Wagoner, and Heitor Barbosa. Gemological information was provided by John Koivula, Robert Weldon, and Dona Dirlam, of GIA, and by Christopher Smith, Patricia Madison, Karin Hurwit, and Robert Kane, of the GIA Gem Trade Laboratory. X-ray crystal alignments were performed by William Schaeffer, and electron microprobe analyses were obtained by Paul Carpenter and John Armstrong, of the California Institute of Technology. X-ray powder patterns were obtained by Waldo Winterburn, Stanford University.|
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|Deposited By:||Ruth Sustaita|
|Deposited On:||01 Aug 2013 18:30|
|Last Modified:||01 Aug 2013 18:30|
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