The role of automated mineralogy in geometallurgy: two case studies

SEM-based automated mineralogy is well established as a key tool in geometallurgical assessments, as it provides quantitative data on mineralogy and microstructure. It is widely used to improve the recovery of those constituents (ore minerals) that contain the major products (metals) of existing or planned mining operations and processing plants. Less common, however, is the use of automated mineralogy to study the presence and distribution of possible by-product or even penalty constituents. In this contribution, we present the results of two case studies that reveal the benefit of application of automated mineralogy to define beneficiation potential for economically significant by-products in large operations. Systematic plant surveys were carried out at one fluorite mine and one porphyry copper deposit. For the fluorite deposit, the plant survey was combined with an assessment of the undisturbed feed material.
Case study 1: For the recovery of REE as a potential by-product in a fluorite mine, blocks were sampled before mining, the material was subsequently followed through the flotation plant, sampling all crucial steps. Samples illustrate that the material from the tailings stream, i.e., the material being considered as waste, is strongly enriched in the two dominant REE-bearing minerals contained in the ore: monazite and xenotime. These REE-bearing minerals are well liberated, thus leading to the conclusion that it may be feasible to produce a REE concentrate as a by-product by only slight modification of the current flow sheet.
Case study 2 focused on the improvement of Mo recovery of a world-class porphyry copper deposit. Samples were taken systematically from the flotation plant also considering residence times. Particular flotation stages accounting for significant Mo losses due to bad molybenite liberation were identified. Lab-scale flotation tests were carried out to improve Mo recovery. Results indicate a clear influence of grain shape, grain size and residence time on the recovery.