Redetermination of olivenite from an untwinned single-crystal

Abstract

The crystal structure of olivenite, ideally Cu2(AsO4)(OH) [dicopper(II) arsenate(V) hydroxide], was redetermined from an untwinned and phosphate-containing natural sample, composition Cu2(As0.92P0.08O4), from Majuba Hill (Nevada, USA). Olivenite is structurally analogous with the important rock-forming mineral andalusite, Al2OSiO4. Its structure consists of chains of edge-sharing, distorted [CuO4(OH)2] octa-hedra extending parallel to [001]. These chains are cross-linked by isolated AsO4 tetra-hedra through corner-sharing, forming channels in which dimers of edge-sharing [CuO4(OH)] trigonal bipyramids are located. The structure is stabilized by medium to weak O - H⋯O hydrogen bonds. In contrast to the previous refinements from powder and single crystal X-ray data, all non-H atoms were refined with anisotropic displacement parameters and the H atom was located.