| Abstract: | Lisiguangite, CuPtBiS3, is a new mineral spedes discovered in a PEG-bearing, Co-Cu sulfide vein in garnet pyroxenite of the Yanshan Mountains, Chengde Prefecture, Hebei Province, China. It is associated with chaicopyrite and bornite, galena, minor pyrite, carrolite, molybdenite and the platinum-group minerals daomanite (CuPtAsS2), Co-bearing malanite (Cu(Pt, Co)2S4) sperrylite, moncheite, cooperite and malyshevite (CuPdBiS3), rare damiaoite (Pt2In3) and yixunite (Pt3In). Lisiguangite occurs as idiomorphic crystals, tabular or lamellae (010) and elongated 100] or as aggregates, up to 2 mm long and 0.5 mm wide. The mineral is opaque, has lead-gray color, black streak and metallic luster. The mineral is non-fluorescent. The observed morphology displays the following forms: pinacoids {100}, {010}, {001}, and prism {110}. No twining is observed. The a:b:c ratio, calculated from unit-cell parameters, is 0.6010:1:0.3836. Cleavage: {010} perfect, {001} distinct, {100} may be visible. H Mohs: 21/2; VHN25=46.7-49.8 (mean 48.3) kg/mm2. Tenacity: brittle. Lisiguangite is bright white with a yellowish tint. In reflected light it shows neither internal reflections nor bireflectance or pleochroism. It has weak to moderate anisotropy (blue-greenish to brownish) and parallel-axial extinction. The reflectance values in air (and in oil) for R3, R4 and (imR3,/imR4), at the standard Commission on Ore Mineralogy wavelengths are: 37.5, 35.7 (23.4, 22.3) at 470 nm; 38.6, 36.5 (23.6, 22.6) at 546 nm; 39.4, 37.5 (23.6, 22.7) at 589 nm and 40.3, 38.2 (23.7, 22.9) at 650 nm. The average of eight electron-microprobe analyses: Cu 12.98, Pt 30.04, Pd 2.69, Bi 37.65 and S 17.55, totaling 100.91%, corresponding to Cu1.10(Pt0.83, Pd0.14)∑0.97Bi0.97S2.96 based on six atoms apfu. The ideal formula is CuPtBiS3. The mineral is orthorhombic. Space group: P212121,a=7.7152(15)A, b=12.838(3) A, c=4.9248(10)A, V=487.80(17)A3, Z=4. The six strongest lines in the X-ray powder-diffraction pattern d in A (I) (h k l) are 6.40(30)(020), 3.24(80)(031), 3.03(100)(201), 2.27(40)(051), 2.14(50)(250), 1.865(60)(232). |
