The Surface Properties of Bornite

David J. Vaughan, John A. Tossell and Chris. J. Stanley
Department of Geological Sciences, Aston University, Birmingham B4 7ET, U.K.
Department of Chemistry, University of Maryland, College Park, Maryland 20742, U.S.A
Department of Mineralogy, British Museum (Natural History), Cromwell Road, London SW7 5BD, U.K.

Abstract: The surfaces of fresh and tarnished (through exposure to the atmosphere) bornite have been studied by measurement of reflectance and quantitative colour parameters in the visible region, X-ray photoelectron and Auger electron spectroscopy, and conversion electron Mössbauer spectroscopy. The results of these studies, in combination with those of previous workers, indicate that a surface coating of an iron hydroxy-oxide forms on bornite, leaving beneath it a layer with a copper sulphide composition. A model to explain this alteration process is proposed based on a suggested surface reconstruction in bornite, leading to metals in essentially trigonal planar coordination. Resulting destabilization of iron relative to copper in this crystal chemical environment is suggested to account for its preferential oxidation.

Keywords: bornite • surface properties • tarnish • sulphides

Mineralogical Magazine; June 1987 v. 51; no. 360; p. 285-293; DOI: 10.1180/minmag.1987.051.360.11
© 1987, The Mineralogical Society
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