gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1985.049.350.03 An Extended X-ray Absorption Fine Structure (EXAFS) Study of the Calcium Site in a Model Basaltic Glass, Ca3Mg4Al2Si7O24 Hardwick A. * Whittaker E. J. W. Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR Diakun G. P. SERC Daresbury Laboratory, Daresbury, Warrington WA4 4AD

Present address: BP Research Centre, Chertsey Road, Sunbury-on-Thames, TW16 7LN.

 3 1985 49 350 25 29 9 5 1984 17 9 1984 Copyright © 1985, The Mineralogical Society 1985 Abstract

Short-range order in the oxygen co-ordination shell of the Ca ion in a glass of composition Ca3Mg4Al2Si7O24 is investigated by analysis of the extended X-ray absorption fine structure. The estimate of disorder in the short-range oxygen co-ordination is no greater than that for crystalline samples of diopside and bytownite. An estimate of the oxygen environment of calcium in the particular glass is included.

 Keywords EXAFS basaltic glass short-range order diopside bytownite