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Raman spectroscopy of the arsenates and sulphates of the tsumcorite mineral group

2004; Wiley; Volume: 35; Issue: 1 Linguagem: Inglês

10.1002/jrs.1076

1097-4555

Ray L. Frost, J. Theo Kloprogge, Wayde N. Martens,

Mineralogy and Gemology Studies

Abstract The structure of a selection of arsenate‐and sulphate‐based minerals of the tsumcorite group was studied by the combination of Raman and infrared spectroscopy. A comparison is made with the sulphate‐bearing mineral natrochalcite. Isomorphic substitution of sulphate for arsenate is observed for gartrellite and thometzekite. The positions of the hydroxyl and water stretching vibrations are related to the strength of the hydrogen bond formed between the OH unit and the AsO 4 anion. Estimates of the hydrogen bond distances are calculated using a Libowitzky‐type function. Characteristic Raman spectra of the minerals allow the assignment of the bands to specific vibrational modes. Copyright © 2004 John Wiley & Sons, Ltd.