RIETVELD REFINEMENT OF THE CRYSTAL STRUCTURE OF OLIVENITE: A TWINNED MONOCLINIC STRUCTURE

PETER C. BURNS* and FRANK C. HAWTHORNE
Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2
* Present address: Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, U.K.

Abstract

The crystal structure of olivenite, Cu2AsO4(OH), has been refined by the Rietveld method in the space groups Pnnm and P21/n (x axis unique). In the latter refinement, the angle, 90.088(3) , is significantly different from 90 , and some atomic positions are significantly different from the ideal positions in a structure with orthorhombic symmetry. Thus olivenite has P21/n symmetry, as indicated by Toman (1977). Examination of previous structural work on libethenite suggests that this mineral may be monoclinic as well.

Keywords: olivenite, structure refinement, Rietveld method, arsenate.