ALBERT

Description: Nisnite, ideally Ni3Sn, was found during a re-examination of heazlewoodite crystals in rodingite samples from the Jeffrey mine, Asbestos, Quebec. It occurs as bronze-colored metallic, striated, blocky and square to rectangular tabular crystals of up to 100 {micro}m in length, with groupings of [≤]1 mm growing on heazlewoodite. Crystal groupings exhibit a boxwork-like habit. Reflectance measurements in air gave 43.2 (470 nm), 49.1 (546 nm), 53.2 (589 nm), and 59.0% (650 nm). Minerals closely associated with nisnite are chromite, diopside, grossular, heazlewoodite and shandite. The mineral is cubic, P4/m[IMG]f1.gif" ALT="Formula" BORDER="0"〉2/m, with unit-cell parameter refined using powder-diffraction data: a 3.7349(6) A, V 52.10(3) A3, Z = 1, Dcalc = 9.41 g/cm3. The average results of five and three electron-microprobe analyses on separate crystals gave Ni 57.88, Sn 40.17, sum 98.05 wt.% and Ni 59.24, Sn 41.00, sum 100.24 wt.%, corresponding to Ni2.98Sn1.02 on the basis of 4 apfu. The structure has been refined to an R index of 0.008% on the basis of 30 unique reflections. The structure of nisnite contains 12-coordinated Sn atoms (12 Ni) and 12-coordinated Ni atoms (8 Ni and 4 Sn). Among the three synthetic Ni3Sn phases known, nisnite corresponds to the ccp structure that has been synthesized at high pressure and high temperature.