Evaluation of quantitative X-ray diffraction for possible use in the quality control of granitic pegmatite in mineral production

To test the reliability of Quantitative X-ray diffraction for possible use in quality control of granitic pegmatite in mineral production, a quantitative Rietveld XRD method has been developed for feldspar and quartz quantification. The results of the Rietveld XRD method are compared with regular semi-quantitative XRD, a semi-quantitative combination method using XRD-XRF and element to mineral conversion using data from XRF and EPMA. Three of the methods have proven to be accurate and precise; the semi-quantitative combination method using XRD and XRF data, the Rietveld XRD quantification and the element to mineral conversion. The semi-quantitative XRD method is less accurate. The prerequisite for successful Rietveld quantification is the correct input in terms of crystallographic information of the minerals and limits to the variation in cell parameters and crystal sizes, as well as correct sample preparation. A combination of the methods including both mineralogy and chemistry as part of the daily quality control management gives the best outcome concerning accuracy. Because the project presented here has an industrial motive, the methods are tested according to accuracy and user friendliness.