Kansanshi mine is the largest copper producer in Africa. The deposit is mineralogically and texturally complex due to supergene enrichment resulting in the presence of a variety of primary and secondary copper minerals. This necessitates the processing of ore through three separate circuits: sulphide flotation, mixed flotation and oxide leach, followed by solvent extraction and electro-winning. This study revisits the process mineralogy of the ore using modern mineralogy tools, which for such a large and complex deposit cannot but deliver significant value. Specific focus is given to copper mineralisation and the flotation of the sulphide ores in compliment to another MSc study from the Centre for Minerals Research focusing on mixed ore flotation (Kalichini, 2015). A series of hand samples and grab samples representing the variation in mineralogy and texture of the Kansanshi ore, as well as two run of mine sulphide ore flotation feed samples were used for this investigation. Process mineralogical characterisation entailed optical microscopy, XRF, QXRD, QEMSCAN and EPMA investigations, alongside a series of laboratory scale batch flotation tests of two sulphide ores at two grinds (80% passing 150 μm, 80% passing 212 μm). Copper mineralisation at Kansanshi occurs as both vein-hosted mineralisation, and to a lesser extent sediment-hosted mineralisation. Later breccia-hosted and supergene mineralisation have overprinted all previous mineralisation styles. Chalcopyrite is the main ore mineral for both vein-hosted and sediment-hosted mineralisation styles. Vein-hosted mineralisation is characterized by an overall coarse-grained texture (>0.5 mm), compared to sediment-hosted mineralisation that is characterised by fine-grained disseminated textures that occur parallel to the bedding and foliation planes. Breccia-hosted and supergene related mineralisation have led to the formation of an array of secondary copper minerals, such as chalcocite, covellite, malachite and chrysocolla. These minerals show a variety of complex intergrowth textures between one another. Secondary copper oxide mineralisation is commonly associated with distinctive stockwork and boxwork textures, with replacement being partial or complete depending on the extent of oxidation. The variety of textures related to the replacement reactions result in grain size variations that cause a decrease in the chalcopyrite grain size and produce secondary copper sulphides that are of equivalent to or of a finer grain size (< 0.2 mm) than that of the primary copper sulphide. Mineralogical investigations of two run of mine sulphide flotation feed samples showed that the dominant ore mineral is chalcopyrite with an overall coarse-grained (> 0.5 mm) texture with minimal fine composite particles, which results in good chalcopyrite liberation. Results of this laboratory study show good copper recoveries (~89%) during rougher flotation, because chalcopyrite liberation was over 90% at a grind of 80% passing 150 μm. The effect of coarsening the grind caused an insignificant loss of copper recovery. This good performance during flotation can be attributed to a number of mineralogical characteristics, including minimal fine composite particles, the natural hydrophobicity of chalcopyrite and the high degree of liberation of chalcopyrite associated with the overall coarse texture of the sulphide ore. Mineralogical investigations suggest that the relatively low copper grades from batch flotation cannot be attributed to the presence of composite particles, and can potentially be improved using a series of cleaner floats. The effects of supergene enrichment on mineralogy and texture, and its influence on processing, have been used to develop a simplified process mineralogy matrix for Kansanshi. The matrix demonstrates the continuum of mineralogy and textures due to supergene enrichment and their potential influences on mineral processing. Some ideas for regular on-site use of mineralogical analyses at Kansanshi have also been proposed. Ultimately, this information can be incorporated into the existing geometallurgical framework at Kansanshi, adding to the understanding and predictability of the ore being fed into each circuit.

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