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The quantification of lateritic bauxite minerals using X-ray powder diffraction by the Rietveld method

Published online by Cambridge University Press:  10 January 2013

Mark G. Aylmore
Affiliation:
Special Research Centre for Advanced Mineral and Materials Processing, University of Western Australia, Nedlands, Western Australia, 6907, Australia
Graham S. Walker*
Affiliation:
CSIRO Division of Minerals, P.O. Box 90 Bentley, Western Australia, 6102, Australia
*
a) Author to whom all correspondence should be sent.

Abstract

The application of the Rietveld method to quantify mineral components of bauxite and lateritic samples was carried out in order to determine the ability of the method to obtain accurate mineralogical abundances for these materials. The method was initially applied to synthetic mixtures using both Cu and Co Kα radiations, and it was shown that Rietveld-derived data compared favourably with the weighed compositions. Application to two types of natural bauxite resulted in a high correlation between Rietveld predicted values and those calculated by proportioning peak intensities with chemical assays. The use of the whole pattern rather than selected peak intensities gives greater accuracy, confirmed by a strong correlation between derived oxide concentrations from XRF assays. Accuracy and precision were improved by the determination of isomorphous substitution of aluminum in goethite and hematite by refinement of unit cell dimensions. Importantly, the ability of the Rietveld program to successfully model several goethites with different levels of isomorphous substitution improved the correlation between predicted and calculated values. In addition, crystallinity and crystallite size that influence the reactivity of the mineral components can be derived from refined peak profiles.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1998

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