Use of weighted X-ray diffraction data for semi-quantitative estimation of minerals in low temperature ashes of bituminous coal and in shale

The intensity of x-rays diffracted from a component of a mixture is proportional to the concentration of that component in the mixture. The proportionality constant is however affected by various parameters including sample preparation and mounting, equipment operation, the composition and crystallinity of the component and the overall composition of the mixture to name just a few. Assuming critical control of sample preparation, mounting and equipment operation, for a specific sample type, weighting factors were determined which when applied to the observed x-ray intensities of the individual minerals allowed a reasonably accurate semiquantitative estimation of the mineral abundances to be calculated. The effectiveness of the weighting factors was evaluated using both parametric and non-parametric statistical comparisons with other conventional analytical procedures. Because the sample preparation and mounting procedures are critical for the success of this or any other analytical technique, the procedures used are detailed.