Cu and Zn Ordering in Aurichalcite

J. M. Charnock1, P. F. Schofield2, C. M. B. Henderson1, G. Cressey2 and B. A. Cressey3
1 Department of Earth Sciences, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
2 Department of Mineralogy, Natural History Museum, Cromwell Road, London, SW7 5BD, UK
3 Department of Geology, University of Southampton, Southampton Oceanography Centre, Southampton, SO14 3ZH, UK

Abstract: The advantages of X-ray absorption spectroscopy have been utilized to assess the Cu and Zn ordering in aurichalcite, (Cu5−xZnx)(OH)6(CO3)2. We have examined one hydrozincite sample and three aurichalcite samples in which the Cu:Zn ratios are in the range 1:3 to 2:3. Copper 2p XAS confirms that there is no monovalent copper in aurichalcite and that in each sample the copper might be distributed across more than one metal site. EXAFS, at the Cu and Zn K-edges, shows that the copper atoms preferentially enter the Jahn- Teller elongated, octahedral (M2) and trigonal bipyramidal (M4) sites, with the zinc atoms entering the more regular octahedral (M1) and tetrahedral (M3) site. Substantial solid solution towards the zinc rich region is facilitated by the substitution of copper by zinc on the M2 and M4 sites. This information, not easily obtained by X-ray diffraction, substantially enhances the understanding of the structure of aurichalcite.

Keywords: aurichalcite • hydrozincite • Cu and Zn ordering • EXAFS

Mineralogical Magazine; December 1996 v. 60; no. 403; p. 887-896; DOI: 10.1180/minmag.1996.060.403.04
© 1996, The Mineralogical Society
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