Feature
Gems & Gemology, Fall 1990, Vol. 26, No. 3
Gem-Quality Cuprian-Elbaite Tourmalines from São José Da Batalha, Paraíba, Brazil
Emmanuel Fritsch, James E. Shigley, George R. Rossman, Meredith E. Mercer, and Sam M. Muhlmeister, and Mike Moon
Unusually vivid tourmalines from the state of Paraiba, in north eastern 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 the se 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 Cu2 + or a combination of Cu2 +, Mn3 +, and other causes. Some colors can be produced by heat treatment, but most also occur naturally.
