Abstract A new member of the pavonite homologous series, sunshuite, ideally FeBi2S4, was discovered in the Jiawula-Chaganbulagen intermediate-sulfidation epithermal Ag-Pb-Zn ore-field, Inner Mongolia, China. The mineral occurs as anhedral grains, 5-20μm in size, in association with pyrrhotite, sphalerite, galena, chalcopyrite, native bismuth, bismuthinite, quartz, calcite, chlorite, and sericite, etc. Sunshuite forms from bluish-gray to light gray with metallic luster. The calculated density is 6.13 g·cm-3. Reflectance values for the four COM wavelengths of sunshuite in air Rmax, Rmin (%) (λ in nm) are 34.6, 36.4 (470); 33.2, 35.1 (546); 33.5, 35.1 (589); 33.7, 35.4 (650), respectively. The average composition (in wt%) of sunshuite was 1.44 Mn, 21.22 S, 7.46 Fe, 0.3 Pb, 0.11 Cu, 68.84 Bi, 0.41 Zn, 0.31 Ag, total 100.09, analyzed by electron microprobe analyses. The empirical formula is (Fe0.81Mn0.16Zn0.04Cu0.01Pb0.01Ag0.02) Σ1.05Bi1.99S4, on the basis of 4 S apfu. The crystal structure was determined by single-crystal X-ray diffraction. Sunshuite is monoclinic, with space group C2/m (#12). The unit-cell parameters are a = 12.576 (2) Å, b = 3.9100 (5) Å, c = 14.717 (2) Å, β = 115.04 (2)°, V = 655.7 (2) Å3 and Z = 4. The strongest X-ray diffraction lines d (I%) of sunshuite are 3.637 Å (54), 3.622 Å (59), 3.444 Å (100), 3.333 Å (47), 3.057 Å (63), 2.842 Å (74), 2.720 Å (87), 2.523 Å (46). Sunshuite is the Fe analogue of graţianite (MnBi2S4), 3P members of the pavonite homologous series. Sunshuite comprises two types of slabs, parallel to (001), namely type I thinner slabs have Fe-centered octahedra, flanked by Bi-centered square-pyramidal five-fold coordination; and type II thicker slabs comprise Fe-, Bi-centered octahedra. Both slabs are interconnected via common sulfur atoms. The Fe in sunshuite is divalent (Fe2+), and its association with pyrrhotite and native bismuth suggests that sunshuite has the potential to serve as an indicator of a reducing hydrothermal environment. The mineral is named after the late professor Shu Sun, a member of the Chinese Academy of Sciences on sedimentary geotectonics.
Hui et al. (Thu,) studied this question.