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Mining wastes containing sulfide minerals can generate contaminated waters as acid mine drainage (AMD) and contaminated neutral drainage (CND). This occurs when such minerals are exposed to oxygen and water. Nowadays, mineralogical work—when it is done—is independently and differentially done according to the needs of the exploration, geotechnics, metallurgy or environment department, at different stages in the mine development process. Moreover, environmental impact assessments (EIA) are realized late in the process and rarely contain pertinent mineralogical characterization on ores and wastes, depending on countries’ regulations. Contaminant-bearing minerals are often not detected at an early stage of the mine life cycle and environmental problems could occur during production or once the mine has come to the end of its productive life. This work puts forward a more reliable methodology, based on mineralogical characterization of the ore at the exploration stages, which, in turn, will be useful for each stage of the mining project and limit the unforeseen environmental or metallurgical issues. Three polymetallic sulfide ores and seven gold deposits from various origins around the world were studied. Crushed ore samples representing feed ore of advanced projects and of production mines were used to validate the methodology with realistic cases. The mineralogical methodology consisted in chemical assays and XRD, optical microscopy, SEM and EPMA were done. Five of the ores were also submitted to geochemical tests to compare mineralogical prediction results with their experimental leaching behavior. Major, minor, and trace minerals were identified, quantified, and the bearing minerals were examined for the polluting elements (and valuables). The main conclusion is that detailed mineralogical work can avert redundant work, save time and money, and allow detection of the problems at the beginning of the mine development phase, improving waste management and closure planning.

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Quantitative mineralogy has seen significant developments from the combination of scanning electron microscopy (SEM) with automatic image analysis and energy dispersive X-ray spectrometry (EDS). The mining industry is one of the fields that has benefited from this progress. In this paper, the authors present a newly developed quantitative method based on SEM-EDS and image analysis (IA), which is used to determine the mineralogical and environmental characteristics of mine tailings. The main objectives of the method are to be able to characterize sulphides and carbonates as monomineral particles, which control the acid generation from the tailings. Pure sulphides, calcite and quartz were blended to make mineralogical standards that represent typical mine tailings environmental behavior. The SEM-EDS-IA method achieved good mineralogical precision for medium (1-20 Wt%) and abundant (> 20 Wt%) minerals, with a relative error below 10 %. However, some corrections had to be applied to account for typical stereological effects (apparent particle diameter from polished surface) and preparation modes (particle segregation during resin hardening). Particle size analysis was used to calibrate the method and identify the corrections to be applied. Since mineralogical quantifications are based on the area of the observed particles, the most reliable particle size analyses (also obtained from particle area) typically lead to the best mineralogical characterization. However, the SEM based techniques may show some limitations for fine-grained particle quantification (< 10 µm), which required additional corrections. In this article, the technique is described, and it is applied to characterize fine-grained mine tailings with a size-by-size mineralogy (with