QUANTITATIVE MINERALOGICAL ANALYSIS OF COALS FROM THE CALLIDE BASIN, QUEENSLAND, AUSTRALIA USING X-RAY-DIFFRACTOMETRY AND NORMATIVE INTERPRETATION

Comparisons are presented between the results of quantitative X-ray di ffractometry using a Rietveld-based computational method (SIROQUANT) o n low-temperature ash (LTA) and normative calculation from chemical an alysis of high-temperature ash for a series of coal samples from the C allide Basin of Queensland. Mineral percentages indicated by each meth od are also compared to the results of conventional X-ray diffractomet ry on low-temperature ash spiked with a known proportion of corundum, evaluated in conjunction with detailed clay mineral analysis of the < 2 mu m fraction of each sample by oriented-aggregate X-ray diffraction methods. For species where direct comparison is possible, the proport ions of the different minerals in the crystalline fraction indicated b y SIROQUANT are similar to those indicated by normative analysis using a computational procedure referred to as SEDNORM. More conventional X RD study of spiked LTA materials, with the samples studied, seems to u nderestimate quartz and siderite content, and by default overestimate kaolinite. SIROQUANT, on the other hand, tends to overestimate the pro portion of Ca-bearing minerals, relative to the Ca content of the high -temperature ash, processed using the SEDNORM computation. Both the SI ROQUANT analysis and the normative evaluation of SEDNORM provide signi ficantly more quantitative information on coal mineralogy than other m ore commonly used techniques.