Hodgesmithite, (Cu,Zn)6Zn(SO4)2(OH)10·3H2O, a new copper zinc sulfate mineral with a unique, decorated, interrupted-sheet structure

Abstract

Hodgesmithite, ideally (Cu,Zn)6Zn(SO4)2(OH)10·3H2O, is a new copper zinc sulfate mineral from the Block 14 Opencut, Broken Hill, New South Wales, Australia. Electron microprobe analysis provided the empirical formula Cu4.84,Zn2.16,Cd0.04[(SO4)1.89,(SiO4)0.12]2.01(OH)9.82·3.15H2O based on 21 oxygen atoms per formula unit. Hodgesmithite is trigonal, space groupP3, witha= 8.1905 (12),c= 7.0990 (14) Å,V= 412.43 (12) Å3andZ= 1. The crystal structure of hodgesmithite,R1= 0.0272 for 5145 reflections withFo> 4σ(Fo) measured with synchrotron X-ray radiation (λ = 0.71080 Å), contains interrupted sheets of edge-sharing Cu(O,OH)6octahedra in the (001) plane. Every seventh octahedral site is vacant and capped by a ZnO4tetrahedron and an SO4tetrahedron which are attached to the sheet above and below this position. The sheets are additionally decorated on one side by SO4tetrahedra that share a vertex incident to three Cu—O(apical) bonds. Interstitial H2O groups lie between the sheets. ZnO4tetrahedra share vertices with SO4tetrahedra from the adjacent sheet to provide linkage between the sheets in thecdirection.