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Redefinition of arhbarite, Cu2Mg(AsO4)(OH)3

  • W. Krause (a1), H.-J. Bernhardt (a2), H. Effenberger (a3), U. Kolitsch (a3) and CH. Lengauer (a3)...

Abstract

Arhbarite was described in 1982 as a new copper arsenate, Cu2(OH)AsO4·6H2O, from the Arhbar mine, Morocco. Due to the very small grain size no crystallographic data other than the X-ray powder diffraction data could be given. Reinvestigation of the type material and of new finds from the El Guanaco mine, Chile, is based on Rietveld refinement of X-ray powder data, electron microprobe investigations, optical studies as well as infrared and Raman spectra. The main results are: (1) arhbarite has the ideal formula Cu2Mg(AsO4)(OH)3 with magnesium oxide as an additional constituent and (2) arhbarite is isotypic with gilmarite, Cu3(AsO4)(OH)3. Arhbarite is triclinic, space group P1 (no. 1), unit-cell parameters (type material; refined from powder data) a= 5.315(4), b= 5.978(6), c= 5.030(6)Å, α = 113.58(6), β = 97.14(7), γ = 89.30(8)°, V= 145.2(1)Å3, Z= 1. Microprobe analyses of the type material gave MgO 10.20, CuO 47.46, NiO 0.20, CoO 0.24, As2O5 33.85, SiO2 0.10, H2O 7.58 (calc.), total 99.63 wt.%. The empirical formula is Cu1.98(Mg0.88Cu0.09Ni0.01Co0.01)S0.99(AsO4)1.02(OH)2.92, based on 7 O atoms. The Chilean arhbarite shows a slightly higher Cu content than the type material; it has the formula Cu1.99(Mg0.73Cu0.25Zn0.01)∑0.99[(AsO4)1.01(SiO4)0.01]∑1.02(OH)2.92. The formal redefinition of arhbarite has been approved by the CNMMN of the IMA.

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Eby, R.K. and Hawthorne, F.C. (1990 Clinoclase and the geometry of [5]-coordinate Cu + in minerals. Ada Crystallographica, C46, 22912294.
Farber, G., Witzke, T., Neumeier, G. and WeiB, S. (1998 Die besten Stufen des seltenen Kupferarsenat es Arhbarit - ein sensationeller Neufund aus Chile. Lapis, 23(10, 4951.
Kolitsch, U., Witzke, T. and Wiechowski, A. (2000 A new Cu-Mg-arsenate from El Guanaco, near Taltal, Chile: crystal structure and preliminary data. European Journal of Mineralogy, 12, Beih. No. 1, 102.
Mandarino, J.A. (1981a) The Gladstone-Dale relation-ship: part IV. The compatibility concept and its application. The Canadian Mineralogist, 19, 441450.
Mandarino, J.A. (1981b) Comments on the calculation of the density of minerals. The Canadian Mineralogist, 19, 531534.
Rietveld, H.M. (1969 A profile refinement method for nuclear and magnetic structures. Journal of Applied Crystallography, 2, 65—71.
Sarp, H. and Cerny, R. (1999 Gilmarite, Cu3(AsO4)(OH)3, a new mineral: its description and crystal structure. European Journal of Mineralogy, 11, 549555.
Schmetzer, K., Tremmel, G. and Medenbach, O. (1982 Arhbarit, Cu2[OHIAsO4]-6H2O, ein neues Mineral von Bou-Azzer, Marokko. Neues Jahrbuch fur Mineralogie, Monatshefte, 529— 533.
Visser, J.W. (1969 A fully automatic program for finding the unit cell from powder data. Journal of Applied Crystallography, 2, 8995.
Yvon, K., Jeitschko, W. and Parthe, E. (1977 LAZY PULVERIX, a computer program, for calculating X-ray and neutron diffraction powder patterns. Journal of Applied Crystallography, 10, 7374.

Keywords

Redefinition of arhbarite, Cu2Mg(AsO4)(OH)3

  • W. Krause (a1), H.-J. Bernhardt (a2), H. Effenberger (a3), U. Kolitsch (a3) and CH. Lengauer (a3)...

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