Abstract
Zhonghongite (IMA2023-046), ideally Cu29(As,Sb)12S33, is a new mineral discovered in the high-sulfidation vein of the Jiama deposit (E 91°45′, N 29°42′), southern Tibet, China. It forms complex intergrowths with watanabeite and tennantite-tetrahedrite, creating veined or massive aggregates ranging from millimeters to centimeters. Single crystals of zhonghongite are anhedral, and their sizes range from several micrometers to ∼100 μm. The mineral is gray with a black streak and metallic luster. It is brittle, with uneven fractures, and has a calculated density of 4.925 g/cm3. The average values of electron microprobe analyses (wt%) are: Cu 42.19, As 11.11, Sb 16.09, S 25.45, Hg 3.73, Mn 0.67, and Te 0.28. The empirical formula, based on 33 sulfur apfu, is (Cu27.60Hg0.77Mn0.51Fe0.07Ag0.02)Σ28.97(As6.16Sb5.49Te0.09)Σ11.74S33. In zhonghongite, the substitution of Sb for As is limited, with the atomic ratio of As/(As+Sb) ranging from 0.457 to 0.629. Hg, Mn, and Fe, with minor Cu, are divalent and serve for charge balance. Zhonghongite is orthorhombic, space group F2mm (42), a = 10.37741(5) Å, b = 14.69821(9) Å, c = 36.7645(2) Å, and V = 5607.66(5) Å3. The crystal structure was solved and refined by single-crystal X-ray diffraction with a final R1 = 0.0235 for 27 028 (2467 unique) reflections. It is composed of individual AsS3 tripyramids and clustered As4S7 tripyramids, CuS4 tetrahedra, and CuS3 planar triangles, connected through corner S atoms in tetrahedral coordination and octahedral coordination with Cu and/or As. The structure is a derivative of a tetrahedrite-type structure. Zhonghongite was formed under high-temperature conditions and is classified as an intermediate-sulfidation state mineral.