QUANTITATIVE DETERMINATION OF CRISTOBALITE, MULLITE AND CORUNDUM SIMULTANEOUSLY BY X-RAY POWDER DIFFRACTION

A database for the quantitative determination of minerals by X-ray powder diffraction has been developed. The method is based on the comparison of the diffraction pattern from an unknown sample with a database of diffraction patterns, made up of eight different compositions of the analysed minerals. A database was developed for the analysis of cristobalite (SiO2), mullite (3Al2O3.2SiO2), and corundum (Al2O3), using either an added reference (zinc oxide), or an internal reference (corundum). The amount of cristobalite, mullite and corundum present in the sample is calculated through regression analysis involving the correlation of the reference peak areas. Typical relative errors of calculation range between 2% and 4.5%.