gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1990.054.377.12 Mineralogy and Petrology Corkite from Aggeneys, Bushmanland, South Africa de Bruiyn H. van der Westhuizen W. A. Beukes G. J. Meyer T. Q. Department of Geology, University of the Orange Free State, PO Box 339, Bloemfontein 9300, South Africa 12 1990 54 377 603 608 8 1 1990 1 5 1990 Copyright © 1990, The Mineralogical Society 1990 Abstract

Corkite associated with plumbojarosite and goethite occurs in gossan and iron-formation at Black Mountain and Broken Hill, Aggeneys. Electron microprobe analyses indicate that there are two groups of corkite present in the area; one with high Cu and low (PO4)3− and the other with low Cu and high (PO and the other with low Cu and high (PO4)3− contents. This can be explained in terms of the general formula contents. This can be explained in terms of the general formula AB2(XO4)2(OH)6, where the incorporation of divalent ions in the B site is accompanied by the exchange of trivalent anions by divalent ones to retain charge balance. Complete solid-solution is inferred between (SO4)2−and (PO4)3− end members, indicating that the jarosite and beudantite groups form part of the same solid-solution series. The distribution of Zn in corkite also reflects the regional distribution of zinc grades in the area, becoming more zinc-rich from west to east. New X-ray diffraction parameters are also presented which update existing data.

 Keywords corkite EMP analyses solid-solution series X-ray diffraction data Bushmanland South Africa