TARKIANITE, (Cu, Fe)(Re, Mo)4S8, A NEW MINERAL SPECIES FROM THE HITURA MINE, NIVALA, FINLAND

Abstract

Tarkianite, a new mineral species of ideal composition (Cu,Fe)(Re,Mo)4S8, was recently discovered in sulfide concentrate from the Hitura Ni–Cu–PGE mine, Nivala, western central Finland. It is associated with pyrrhotite, pentlandite, valleriite, chalcopyrite, cubanite, mackinawite, chromite, and the PGE minerals sperrylite, michenerite, irarsite, froodite and hollingworthite. It is black, opaque with a metallic luster, a black streak, and is brittle with an irregular fracture. VHN15 is in the range 537–584, which corresponds to a Mohs hardness of 5½ to 6. Under reflected plane-polarized light, the mineral is light brown-gray and isotropic. The CIE color values (illuminant C) are: x 0.314 (air), 0.315 (oil); y 0.321 (air), 0.323 (oil) Y: 38.9 (air), 21.7 (oil); d: 575 (air), 573 (oil); Pe%: 2.1 (air), 3.2 (oil). The measured values of reflectance in air and oil for a single grain, respectively, are 38.02, 20.91 (470 nm), 37.87, 21.76 (546 nm), 39.18, 21.84 (589 nm), 39.30, 22.12 (650 nm) and values for 400–700 nm are