Raman spectroscopic study of the mixed anion sulphate-arsenate mineral parnauite Cu9 [(OH)10|SO4|(AsO4)2]·7H2O

Abstract

The mixed anion mineral parnauite Cu9 [(OH)10|SO4|(AsO4)2]·7H2O has been studied by Raman spectroscopy. Characteristic bands associated with arsenate, sulphate and hydroxyl units are identified. Broad bands are observed and are resolved into component bands. Two intense bands at 859 and 830 cm-1 areas signed to the ν1 (AsO4)3- symmetric stretching and ν3 (AsO4)3- antisymmetric stretching modes. The comparatively sharp band at 976 cm-1 is assigned to the ν1 (SO4)2- symmetric stretching mode and a broad-spectral profile centered upon 1097 cm-1 is attributed to the ν3 (SO4)2- antisymmetric stretching mode. A comparison of the Raman spectra is made with other arsenate-bearing minerals such as carminite, clinotyrolite, kankite, tilasite and pharmacosiderite. © 2009 John Wiley & Sons, Ltd.