Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Résumé Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Jambor, J. L. Articles by Feinglos, M. N. Search for Related Content GeoRef GeoRef Citation

CALVERTITE, Cu₅Ge_0.5S₄, A NEW MINERAL SPECIES FROM TSUMEB, NAMIBIA

John L. Jambor^1,, Andrew C. Roberts², Lee A. Groat³, Chris J. Stanley⁴, Alan J. Criddle^4, and Mark N. Feinglos⁵

¹ Leslie Research and Consulting, 316 Rosehill Wynd, Tsawwassen, British Columbia V4M 3L9, Canada
² Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada
³ Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
⁴ Department of Mineralogy, Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom
⁵ Duke University Medical Center, Box 3921, Durham, North Carolina 27710, U.S.A.

E-mail address: jljambor{at}aol.com

The sulfide-rich matrix of a partly oxidized specimen from the Tsumeb mine, Tsumeb, Namibia, consists mainly of renierite, tennantite, gallite, chalcocite, and the new mineral calvertite, simplified as Cu₅Ge_0.5S₄, which is named after Lauriston D. Calvert (1924–1993) of the National Research Council, Ottawa, Canada. Calvertite occurs as anhedral grains, up to 100 µm across, that are outlined by a network of chalcocite veinlets of micrometric width. In reflected light, calvertite is opaque, pale bluish grey, and isotropic. Reflectance percentages in air are 26.3 (470 nm), 23.1 (546), 22.2 (589), and 21.5% (650). The mineral is brittle, macroscopically black with a black streak, and has a hardness of 4 to 5, a conchoidal to uneven fracture, and no cleavage. Single-crystal X-ray study indicated F-centered cubic symmetry, a 5.337(3) Å; the structure has not been solved, and the powder-diffraction pattern has only four lines [d in Å(I)(hkl)]: 3.053(100)(111), 2.639(10)(200), 1.869(90)(220), and 1.595(30) (311). An electron-microprobe analysis gave Cu 63.10, Fe 1.66, Zn 0.55, Ge 5.76, As 1.50, Ga 0.36, V 0.05, S 26.63, total 99.60 wt.%, corresponding to (Cu_4.782Fe_0.143Zn_0.041Ga_0.025V_0.005)_S4.996(Ge_0.382As_0.096)_S0.478S₄ on the basis of S = 4 atoms and Z = 1. It is likely that the structure is disordered, and the measured unit-cell is the subcell of a compound whose ordered equivalent has the simplified formula Cu₁₀GeS₈.

Keywords: calvertite, new mineral species, Cu–Ge sulfide, electron-microprobe analysis, reflectance data, Tsumeb mine, Namibia.