Kitagohaite, Pt_7Cu, a new mineral from the Lubero region, North Kivu, Democratic Republic of the Congo

摘要

Kitagohaite, ideally Pt_7Cu, is a new mineral from the Lubero region of North Kivu, Democratic Republic of the Congo. The mineral occurs as alluvial grains that were recovered together with other Pt-rich intermetallic compounds and Au. Kitagohaite is opaque, greyish white and malleable and has a metallic lustre and a grey streak. In reflected light, kitagohaite is white and isotropic. The crystal structure of kitagohaite is cubic, space group Fm3m, of the Ca_7Ge type, with a = 7.7891(3) A, V = 472.57(5) A~3 and Z = 4. The strongest diffraction lines [d in A(I)(M/)] are: 2.246 (100)(222), 1.948(8)(004), 1.377 (77)(044), 1.174(27)(622), 1.123 (31)(444) and 0.893 (13)(662). The Vickers hardness is 217 kg mm~(-2) (VHN_(100)), which is equivalent to a Mohs hardness of 314 and the calculated density is 19.958(2) g cm~(-3). Electron-microprobe analyses gave a mean value (n = 13) of 95.49 wt.% Pt and 4.78 wt.% Cu, which corresponds to Pt_(6.93)Cu_(1.07) on the basis of eight atoms. The new mineral is named for the Kitagoha river, in the Lubero region.