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Damaraite, a new lead oxychloride mineral from the Kombat mine, Namibia (South West Africa)

Published online by Cambridge University Press:  05 July 2018

A. J. Criddle
Affiliation:
Department of Mineralogy, The Natural History Museum, Cromwell Rd., London SW7 5BD, U.K.
P. Keller
Affiliation:
Institut für Mineralogie und Kristallchemie, Universität Stuttgart, D-700 Stuttgart, Germany
C. J. Stanley
Affiliation:
Department of Mineralogy, The Natural History Museum, Cromwell Rd., London SW7 5BD, U.K.
J. Innes
Affiliation:
CSIRO Division of Exploration Geoscience, Private Bag, Wembley, Western Australia 6014

Abstract

Damaraite, ideally 3PbO.PbCl2, is a new mineral which occurs with jacobsite, hausmannite, hematophanite, native copper, an unnamed Pb-Mo oxychloride, calcite, and baryte, in specimens from the Asis West section of the Kombat mine, Namibia (South West Africa). Damaraite is colourless and transparent with a white streak, and adamantine lustre. It is brittle with an irregular to subconchoidal fracture and a cleavage on (010). The mineral has a low reflectance, a weak bireflectance, barely discernible reflectance pleochroism, from grey to slightly bluish grey in some sections, and is weakly anisotropic. Reflectance data in air and in oil are tabulated. Colour values relative to the CIE illuminant C for the most strongly bireflectant grain are, for R1 and R2 respectively:

It has a VHN50 of 148 (range 145–154) with a calculated Mohs hardness of 3. X-ray powder diffraction studies give the following parameters refined from the powder data: orthorhombic; space group Pma2, Pmam or P21am; a 15.104(1), b 6.891(1), c 5.806 (1)Å; V is 604.3 (4)Å3 and Z = 3. Dcalc 7.84 g/cm3. The strongest six lines of the powder pattern are [d in Å (I) (hkl)]: 2.902 (10) (121,002); 2.766 (10) (510,221); 2.877 (9) (411); 3.164 (6) (401); 3.135 (6) (220); 1.747 (b) (313,721,531). The name is for the Damara sequence which hosts the Kombat deposit.

Type
Mineralogy and Petrology
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1990

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