Feature Gems & Gemology, Fall 1994, Vol. 30, No. 3

Copper and Tenorite Inclusions in Cuprian-Elbaite Tourmaline from Paraíba, Brazil

Franz Brandstätter and Gerhard Niedermayr

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Inclusions of native copper and tenorite (CuO) were found in grayish green elbaite from São José da Batalha, Paraíba, Brazil. Native copper forms strongly dendritic platelets (about 100 µ long, 1 µ thick) oriented parallel to the c-axis of the host crystal in a trigonal arrangement. The much less abundant tenorite forms 20-30 µplaty grains. Electron microprobe analyses revealed that the tourmaline is cuprian elbaite (1 wt. % CuO), with significant contents of iron (2.7-3.1 wt. % FeO) and manganese (0.9-1.4 wt. % MnO). The CuO content of tourmaline around the native copper decreases toward these inclusions up to a factor of two. No such decrease in CuO was observed for the tenorite inclusions.