Veselovskyite, triclinic (Zn,Cu,Co)Cu4(AsO4)2(AsO3OH)2 • 9H2O, a Zn-dominant analogue of lindackerite

Veselovskyite, (Zn,Cu,Co)Cu-4(AsO4)(2)(AsO3OH)(2) center dot 9H(2)O, is a new supergene mineral from the Geister vein, Mine Rovnost at the Jachymov ore district (St. Joachimsthal), Czech Republic, commonly associated with strashimirite and blue amorphous Cu arsenate. It forms aggregates, up to 8 x 5 x 1 mm in size, consisting of lath-like to thin-tabular crystals, up to 1 mm long, commonly forming complicated intergrowths, no twinning was observed. Veselovskyite is translucent (aggregates) to transparent (crystals), colourless to greyish white (with a slight greenish tint). It has a greyish white streak with a greenish tint, a vitreous luster, does not fluoresce under both short- and long-wave ultraviolet light. Cleavage on {001} is perfect, Mohs hardness is similar to 2-3, and veselovskyite is very brittle with an irregular fracture and calculated density 3.28 g/cm(3). Veselovskyite is biaxial positive, the indices of refraction are nx(') 1.645(3), ny(') 1.68(1), nz(') similar to 1.72, 2V(calc) approximative 88 degrees, it is strongly pleochroic (nx = greenish, ny = pale green, nz = green), and the optical orientation is as follows: nx(') versus elongation (c) = 15(1)degrees. Veselovskyite is triclinic, space group P-1, a 6.4022(4), b 8.0118(4), c 10.3665(4) angstrom, alpha 85.491(3)degrees, beta 79.377(4)degrees, gamma 84.704(5)degrees, V 519.34(4) angstrom(3), Z = 1, a:b:c = 0.7991:1:1.2939. The eight strongest lines in the X-ray powder diffraction pattern are as follows: d (angstrom), I, (hkl): 10.185, 100 (001), 7.974, 12 (010), 3.987, 13 (020), 3.637, 15 (0-21), 3.395, 37 (003), 3.238, 15 (022), 2.910, 12 (202), 2.668, 16 (023). The chemical analyses by electron microprobe yielded MgO 0.05, CaO 0.04, MnO 0.22, NiO 0.30, CoO 0.96, CuO 32.98, ZnO 3.39, Al2O3 0.24, P2O5, As2O5 43.16, H2O 17.90, total (100.00) wt.%. The resulting empirical formula on the basis of 25 (O, OH, H2O) anions is (Zn0.43Cu0.24Co0.13Al0.05Ni0.04Mn0.03Mg0.01Ca0.01)(Sigma 0.94)Cu-4.00 [(AsO4)(1.92)(PO4)(0.11)(AsO3OH)(1.92)] center dot 9.20H(2)O. The ideal end-member formula ZnCu4[(AsO4)(2)(AsO3OH)(2)] center dot 9H(2)O requires ZnO 7.83, CuO 30.61, As2O5 44.22, H2O 17.34, total 100.00 wt.%. Veselovskyite is isostructural with lindackerite and represents Zn-dominant analogue of lindackerite and pradetite. The name veselovskyite is in honor of Frantisek Veselovsky (*1948), an outstanding Czech mineralogist, who described several new minerals from the Jachymov ore district.