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

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

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.