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A precise and accurate method for the quantitative determination of carbonate minerals by X-Ray diffraction using a spiking technique

Published online by Cambridge University Press:  05 July 2018

H. A. Gunatilaka
Affiliation:
Sedimentology Research Laboratory, University of Reading, Reading, RG6 2AB, England
Roger Till
Affiliation:
Sedimentology Research Laboratory, University of Reading, Reading, RG6 2AB, England

Summary

A precise and accurate X-ray diffraction method has been developed whereby the weight percentages of aragonite and low- and high-magnesium calcite are determined from the integrated peak areas of spiked and unspiked samples. The spike mixture was prepared from organisms extracted from the samples to be analysed. Use of a spiking method also avoided the preparation of working curves from artificial mixtures of carbonate minerals, which may not have the same diffraction behaviour as the unknowns. A test of the precision of the method indicates the following coefficients of variation: aragonite, 1·4 %; low-magnesium calcite, 1·5 %; high-magnesium calcite, 7·8 %. A test of the accuracy of the method indicates no significant bias in any of the carbonate results, except in samples where high-magnesium calcite values are below 10 %. Quartz may also be determined by this method (coefficient of variation 23·9 %; positive bias in values greater than 10 %).

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1971

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