Zheshengite, Pb4ZnZn2(AsO4)2(PO4)2(OH)2: A New Mineral of the Dongchuanite Group and the Influence of As–P Isomorphic Substitution on Unit-Cell Parameters of Dongchuanite Group Minerals

Abstract

Zheshengite (IMA2022-011), Pb4ZnZn2(AsO4)2(PO4)2(OH)2, is a new mineral from Sanguozhuang Village in the eastern Dongchuan Copper Ore Field, Yunnan Province, China. The new mineral is named after Zhesheng Ma (1937–). Zheshengite occurs as prismatic single crystals with chisel-like terminations on hemimorphite, with crystal sizes ranging from 0.02 to 0.05 mm. It is a brittle mineral with irregular fractures, a Mohs hardness of 2½ to 3, perfect cleavage on {011}, and a calculated density of 6.26 g/cm3. The empirical formula of zheshengite, based on 18 O atoms per formula unit, is (Pb4.12Ca0.01)∑4.13(Zn0.83Cu0.23Fe0.04)∑1.10Zn2.00[(As0.90P0.10)∑1.00O4]2[(P0.94Si0.01)∑0.95O4]2(OH)2. Zheshengite exhibits a triclinic structure (space group P−1, no. 2), with unit-cell parameters: a = 4.7746(4) Å, b = 8.4920 (7) Å, c = 10.4056 (8) Å, α = 97.087 (7)°, β = 101.060 (7)°, γ = 92.996 (7)°, V = 409.66 (6) Å3, and Z = 1. As a member of the dongchuanite group, zheshengite features a dongchuanite-type structure. This study reveals the impact of As–P isomorphic substitution on unit-cell parameters in the dongchuanite group, identifying correlations between As content and changes in parameters a and V, which may serve as diagnostic indicators for dongchuanite group minerals. In addition, the structure studies of zheshengite may have implications for environmental protection.