Lisiguangite,CuPtBiS3, a New Platinum‐Group Mineral from the Yanshan Mountains,Hebei, China

Lisiguangite, CuPtBiS₃, is a new mineral species 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 chalcopyrite 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: 2½ 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 Cu_1.10(Pt_0.83, Pd^0.14)_Σ0.97Bi_0.97S_2.96 based on six atoms apfu. The ideal formula is CuPtBiS₃. The mineral is orthorhombic. Space group: P2₁2₁2₁, a= 7.7152(15)Å, b= 12.838(3) Å, c= 4.9248(10)Å, V= 487.80(17)ų, Z= 4. The six strongest lines in the X‐ray powder‐diffraction pattern d in Å (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).