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Cuprodongchuanite, Pb 4 CuZn 2 (PO 4 ) 2 (PO 4 ) 2 (OH) 2 : a new mineral from Yunnan Province, China, and the Jahn-Teller effect in dongchuanite-group minerals

Year: 2025
Type: article
Abstract: Cuprodongchuanite (IMA2021-065), Pb 4 CuZn 2 (PO 4 ) 2 (PO 4 ) 2 (OH) 2 , is a new mineral from Sanguozhuang Village, Yunnan Province, China. It occurs as striking apple green crust-like radial or spherical aggregates of microscopic blade-like crystals on hemimorphite. Cuprodongchuanite is brittle with an irregular fracture, a Mohs hardness of 2½–3, and perfect cleavage on {011}. The calculated density is 6.10 g/cm 3 . The empirical chemical formula is (Pb 4.06 Ca 0.02 ) Σ4.08 (Cu 1.07 Cd 0.01 ) Σ1.08 Zn 2.03 [(P 0.74 As 0.20 S 0.01 Si 0.01 ) Σ0.96 O 4 ] 2 (PO 4 ) 2 (OH) 2 based on 18 O atoms per formula unit. Cuprodongchuanite is triclinic, space group P 1 bar $\bar 1$ 1 ¯ (#2), with unit-cell parameters. a = 4.7405(3) Å, b = 8.5023(5) Å, c = 10.2897(6) Å, α = 97.206(5)°, β = 101.877(5)°, γ = 91.786(5)°, V = 401.95(4) Å 3 and Z = 1. Cuprodongchuanite’s name combines the prefix ‘cupro’ (for copper) with the root ‘dongchuanite’. As a member of the dongchuanite group, cuprodongchuanite features a dongchuanite-type structure with the general formula A 4 VI B IV B 2 ( X 1O 4 ) 2 ( X 2O 4 ) 2 (OH) 2 . In addition to providing a detailed characterisation of cuprodongchuanite, this study delves deeper into exploring the Jahn-Teller effect of Cu 2+ ions at the VI B site, an important factor in the mineral’s crystallography. Employing the Δ oct parameter, the study quantitatively links the degree of octahedral distortion to the Cu-Zn ratio. This method provides a refined understanding of the dongchuanite-type structure and offers an example for assessing similar mineral compositions where cations exhibit closely related properties.
DOI: 10.1180/mgm.2025.10154
Language: English
Open Access status: bronze
OpenAlex ID: W4414366712
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