GEOCHEMICAL EVALUATION OF THE LUESHE NIOBIUM DEPOSIT (ZAIRE) BY RIETVELD QUANTITATIVE X-RAY-DIFFRACTION

The Lueshe Nb deposit is used as an example to show that a modal analy sis of fine-grained samples can readily be obtained by X-ray powder di ffraction and the Rietveld method. This permits applications such as t he visualisation of the weathering profile, the calculation of enrichm ent factors and estimation of the amount of nondiffracting material. T his quantification method is based on the knowledge of the structural parameters of all the phases present in the sample and, in the case of geological material (especially secondary minerals), it sometimes req uires structure refinement to optimize the results. (C) 1997 Elsevier Science Ltd.