The role of ore and host rock mineralogy in the beneficiation of a VMS deposit: Insights from Rävliden North, northern Sweden

• Rävliden North VMS ore characterised and tested for mineral processing. • Massive sphalerite ore has the highest concentration efficiency. • Quartz, feldspar, and anorthite reduce grindability. • Sphalerite, carbonate, amphibole, and mica increase grindability. • Precious, critical, and deleterious element phases traced in flotation. The grinding and flotation performance of Zn-Pb-Cu-Ag ores is highly sensitive to ore mineralogy, host rock composition, and textural variability, factors that are often overlooked in favour of bulk grade values. This study examines the Rävliden North Zn-Cu-Pb-Ag volcanogenic massive sulphide deposit (VMS) deposit in northern Sweden. Two main ore types are identified: massive sphalerite- and galena-rich ore and chalcopyrite-rich vein-dominated ore that coupled with host rock type led to further 6 sub-types. Mineralogical and textural characterisation of flotation feed and products, using Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN®) and element to mineral conversion (EMC) based on multi-element chemical assays, reveals that fine-grained, sphalerite-dominated ore is more amenable to grinding and exhibit better liberation, enhancing flotation efficiency. In contrast, chalcopyrite-rich ore perform better in Cu-Pb flotation but is harder to grind due to its silicate-rich gangue (e.g., quartz). Minerals such as micas, amphiboles, and carbonates affect ore hardness, and ore mineralogy (sphalerite, galena, chalcopyrite and Ag mineralogy) directly affects flotation efficiency. Blending of poor grade and hard to grind (problematic) ores with better grade and softer to grind (fairly good to good) ore is recommended to improve concentrate quality. Precious, critical, and deleterious elements are mostly recovered in the chalcopyrite-galena flotation circuit in amalgams (Ag, Hg), dyscrasite (Ag, Sb), hessite (Ag), sulphosalts (Ag, Sb, Bi), native Bi, and tellurobismuthite (Bi). These minerals are fine-grained (< 20 µm) and poorly liberated, leading to recovery in both target and non-target flotation concentrates. Nevertheless, established metallurgical methods enable their efficient extraction maximising ore value. This study highlights the importance of process mineralogy for improved beneficiation in concentration circuits, and the understanding of by-products during processing of complex polymetallic ores.