Neumann, ReinerAvelar, Angela NairCosta, Geraldo Magela da2015-04-142015-04-142014NEUMANN, R.; AVELAR, A. N.; COSTA, G. M. da. Refinement of the isomorphic substitutions in goethite and hematite by the Rietveld method, and relevance to bauxite characterization and processing. Minerals Engineering, v. 55, p. 80-86, 2014. Disponível em: <http://www.sciencedirect.com/science/article/pii/S0892687513002938>. Acesso em: 02 fev. 2015.0892-6875http://www.repositorio.ufop.br/handle/123456789/5083Although bauxites usually have a quite simple mineralogy – gibbsite (+boehmite), quartz, kaolinite, hematite, goethite, anatase (+rutile) and minor or less common phases, fine particle size, low crystallinity and variable compositions of the iron minerals might render phase quantification difficult, as well as impairing bauxite processing. A reliable and complete characterisation is therefore necessary in order t predict processing performance and ensure compliance to plant specifications. X-ray diffraction is the most important single tool for bauxite characterisation, and the constrained refinement of the Al-for-Fe substitution in goethite during one-step phase quantification by fundamental parameters Rietveld method has been successfully used. The same method was developed to analyse the coupled Al-for-Fe and OH_-for-O2_ substitutions in hematite. The method was tested against Mössbauer spectroscopy iron distribution on bauxite samples with a large compositional range, and on bauxite Certified Reference Materials from the main Brazilian mines, with improved results and widened range of conclusions that can be drawn related to bauxite processing.en-USBauxiteX-ray diffractionRietveld methodMineral phase quantificationIsomorphous substitutionArtigo publicado em periodicoO periódico Minerals Engineering concede permissão para depósito deste artigo no Repositório Institucional da UFOP. Número da licença: 3577160367605.https://doi.org/10.1016/j.mineng.2013.09.020