Quantitative mineralogical and textural analysis of particulate samples of Kiruna-type iron ores using X-ray computed microtomography (CT)

Process mineralogy studies of particulate materials aim to provide quantitative constraints, not only for the mineralogical composition, but also for microtextural data, including particle and mineral grain sizes and shapes, degree of liberation and mineral associations. Although optical microscopy and SEM-EDS based image analysis are standard techniques for mineralogical and textural analysis, they provide only 2D data associated inherently with stereological bias. This limitation can be overcome with X-ray computed tomography coupled to a recently developed particle-based methodology (MSPaCMAn), enabling 3D particle characterization for process samples with minerals having distinct densities. The approach is assessed and validated by a case study dedicated to massively textured, fine-grained, Kiruna-type iron ores from the Per Geijer deposit, Sweden. Particle data obtained by CT are compared to data obtained by SEM–EDS-based image analysis, quantitative X-ray powder diffraction, and chemical assays. The quantitative mineralogical data obtained by all methods closely agree. Significant deviations between SEM-based image analysis and CT data for key microtextural properties do, however, emphasize the advantages of incorporating CT measurements for achieving realistic predictions of particle behavior in mineral processing. The workflow developed in this study can also be applied to other iron ore types – and can be transferred to other ores with significant density differences between ore and gangue minerals. • Kiruna-type IOA-ores were characterized by a novel CT workflow. • Quantitative mineralogy by CT agrees well to complementary methods. • Effect of stereological bias on 2D measurements of particle shape. • 3D particle size distribution agrees well with sieving size classes. • The suggested CT workflow can be applied for other simple-textured ores.