Copper-Bearing (“Paraíba”) Tourmaline from Abuloo, Ethiopia: Preliminary Results

A series of tourmalines from Abuloo, Oromia regional state, Ethiopia, was studied to describe their chemical and spectroscopic characteristics. Data from the seven samples were consistent with elbaite. Several specimens contained significant concentrations of copper (up to 2.29 wt%) and iron up to 0.81 wt%. Visible absorption spectroscopy indicated that the blue coloration in most samples is primarily related to Cu, with Mn and Fe contributing to a lesser extent, whereas in some specimens, Fe is the chromophore dominating Cu. The Cu-dominant tourmalines exhibited characteristics that correspond to the gemological definition of Paraíba tourmaline. Elements such as Ga, Pb, Bi, Zn, and V, as well as REE and Cu, could help to distinguish Ethiopian samples from copper-bearing tourmalines from Brazil, Mozambique, and Nigeria. These results suggest that the Abuloo occurrence represents a potentially significant source of gem-quality, unheated Cu-bearing tourmaline with distinctive features that may aid in its identification.