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Feinglosite, a new mineral related to brackebuschite, from Tsumeb, Namibia

Published online by Cambridge University Press:  05 July 2018

A. M. Clark ,
A. J. Criddle ,
A. C. Roberts ,
M. Bonardi  and
E. A. Moffatt
A. M. Clark
Affiliation:
Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
A. J. Criddle
Affiliation:
Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
A. C. Roberts
Affiliation:
Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, Canada KIA 0E8
M. Bonardi
Affiliation:
Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, Canada KIA 0E8
E. A. Moffatt
Affiliation:
Canadian Conservation Institute, 1030 Innes Road, Ottawa, Ontario, Canada K1A 0C8
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Abstract

Feinglosite, the zinc analogue of arsenbrackebuschite, was found lining a cavity in a sample of massive chalcocite from Tsumeb, Namibia. In this cavity it is associated with wulfenite, anglesite and goethite. The mean of seven electron-microprobe analyses (wt.%) is: PbO 61.4, ZnO 7.3, FeO 1.8, As2O5 22.1, SO3 5.3, H2O (by difference) [2.1], total = [100.00]%, leading to the ideal formula: Pb2(Zn,Fe)[(As,S)O4]·H2O. Feinglosite is monoclinic, space group P21 or P21/m, a 8.973(6), b 5.955(3), c 7.766(6) Å, β 112.20(6)°, with Z = 2. The strongest five reflections of the X-ray powder diffraction pattern are [d in Å (I) (hkl)]: 4.85 (50) (110), 3.246 (100) (112), 2.988 (60) (301), 2.769 (60) (300/211), 2.107 (50) (321). The mineral is pale olive-green, transparent, sectile, and has a white streak and adamantine lustre. It overgrows clusters of goethite crystals and forms globular microcrystalline aggregates up to 0.5–0.75mm in size. The hardness on Mohs' scale is 4–5: the mean micro-indentation hardness is 263 at VHN100. Its calculated density is 6.52 g cm−3. The mineral is pale brownish grey in reflected light (when compared with goethite). Visible spectrum reflectance data are presented. Feinglosite is named for Mark N. Feinglos who first recognised the mineral on a specimen in his collection.

Keywords

feinglositenew mineralbrackebuschite grouplead-zinc arsenate hydrateX-ray dataelectron-microprobe datareflectance dataTsumeb, Namibia
Type
Mineralogy
Information
Mineralogical Magazine , Volume 61 , Issue 405 , April 1997 , pp. 285 - 289
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1997

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Footnotes

*

Present address: I.S.D.G.M., S. Polo 1364, 30125 Venice, Italy

References

Abraham, K., Kantz, K., Tillmanns, E. and Walenta, K. (1978) Arsenbrackebuschite, Pb2(Fe,Zn)(OH,H2O) [AsO4]2, a new arsenate mineral. Neues Jahrb. Mineral., Mh., 193-6.Google Scholar
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