The new mineral hermannroseite, CaCu(PO_4, AsO_4)(OH), the phosphate analogue of conichalcite, from Tsumeb, Namibia

摘要

The new mineral hermannroseite (IMA-CNMNC No. 2010-006) has the chemical formula CaCu(PO_4, AsO_4)(OH). It is the phosphate analogue of conichalcite, CaCu(AsO_4)(OH) and belongs to the adelite group where it represents the fi rst phosphate end-member of this group. Hermannroseite is orthorhombic with space group P2_12_12_1. X-ray powder diffraction studies gave a: 7.328(7), b: 9.123(7), c: 5.769(6) A, V = 385.7(6) A~3 , Z = 4. The strongest refl ections in the X-ray powder diffraction data are as follows d_(obs). (A) (I, hkl): 2.808 (100, 130), 2.571 (73, 112), 3.092 (63, 201), 5.710 (56, 110) and 4.057 (37, 111). Hermannroseite was found in the Tsumeb mine, Tsumeb, Namibia. With a mean grain size of 0.7 μm hermannroseite occurs within botryoidal aggegates and crusts of micro crystalline conichalcite in association with hydroxylapatite, whitlockite, pseudomalachite and amorphous manganese oxides/hydroxides. Hermannroseite is translucent with a vitreous green colour. The calculated density is 4.08 g/cm~3, the calculated mean refractive index is 1.77. Chemical analyses gave (wt.%): CaO 22.80, CuO 34.52, ZnO 0.58, P_2O_5 15.16, As_2O_5 21.88, V_2O_5 1.02, H_2O_((by difference)) 4.04, sum 100.00 wt.%. The resulting empirical formula based on 5 anions is Ca_(0.96)(Cu_(1.03)Zn_(0.02))(P_(0.51)As_(0.45)V_(0.03))O_(3.94)(OH)_(1.06).