Tatyanaite, a new platinum-group mineral, the Pt analogue of taimyrite, from the Noril'sk complex (northern Siberia, Russia)

Tatyanaite, a new mineral from Norir'sk (Siberia), is the Pt analogue of ta imyrite. It is defined as the member(s) of the tatyanaite-taimyrite solid-s olution series with Pt > Pd. Tatyanaite solid solution occurs in massive su lphide ore, which consists of chalcopyrite and subordinate pentlandite, pyr rhotite, and cubanite (or isocubanite). It occurs as central zones of large , elongate grains (up to similar to 1 mm) and as aggregates of smaller grai ns associated with Ag-Au alloys. The associated minerals include unusually Pt-rich taimyrite [(Pd1.25Pt0.86)(Cu0.85Ni<0.01)(Sn1.01Sb0.02)], atokite-ru stenburgite, paolovite, froodite, sperrylite, maslovite, and galena. Crypti c zoning (Pt increases and Pd decreases toward the centre) and polysyntheti c twins are characteristic. In reflected light, tatyanaite is pink with lil ac tinge in air. Bireflectance is weak to distinct, from brownish pink to p inkish lilac. Anisotropy is distinct to moderate, from light brown to dark blue. Reflectance percentages in air and tin oil) are, for R-1 and R-2, 470 nm 42.8, 44.1 (32.8, 33.3), 546 nm 49.5, 50.0 (37.6, 38.8), 589 nm 51.8, 5 4.6 (38.9, 39.9), and 650 nm 55.6, 56.8 (41.6, 44.2). It is ductile; the mi crohardness is VHN20 = 292-348, mean of 327 kg/mm(2). The average of nine e lectron-microprobe analyses gave Pt 45.38, Pd 19.53, Cu 10.62, Ni 0.15, Fe 0.03, Sn 23.02, Sb 0.27, sum 99.0 wt.%, corresponding to [(Pt4.76Pd3.75)(Si gma 8.51)Cu-0.48](Sigma 8.99)(Cu2.94Ni0.05Fe0.01)(Sigma 3.00)(Sn3.96Sb0.05) (Sigma 4.01) [or to (Pt1.19Pd0.94)(Cu0.85Ni0.01Fe<0.01) (Sn-0.99 Sb-0.01)] The powder pattern is similar to that of synthetic Pd9Cu3Sn4, and, by analo gy with the latter, it was indexed for an orthorhombic cell with a = 7.89(1 ) Angstrom, b = 4.07(1) Angstrom and c = 7.73(1) Angstrom, and V= 248(1) An gstrom(3). The three strongest lines in the pattern are 2.283 (10, 212), 2. 163 (4, 203) and 1.369 (3, 323). Tatyanaite-taimyrite formed from a late-st age liquid rich in noble metals, Cu and Sn.