Optimized multi-stage gravity separation strategy for celestine beneficiation based on integrated characterization and process simulation

This study evaluates the chemical, mineralogical and processing behavior of celestine (SrSO 4 ) ores from the Montevive deposit in the Granada Basin, Spain, the largest strontium reserve in Europe. Four representative material streams, direct extraction (DE), waste dump (WD), coarse reject greater than 2 mm (ROA), and fine reject smaller than 2 mm (ROB), were characterized by particle size distribution, mineralogy using XRD with Rietveld refinement, bulk and superficial chemical composition by XRF and XPS, and microstructure by SEM and TEM coupled with EDS. Celestine is the dominant mineral phase in all samples, although DE and WD contain significant carbonate and silicate impurities, while ROA and ROB are strongly enriched in celestine. A color-based micrograph segmentation method was applied to quantify mineral area proportions in dense medium cyclone streams, supporting the enrichment trends identified by XRD. Processing performance was evaluated by MODSIM™ simulations of dense medium cyclones, spiral concentrators, and shaking tables. Coarse deslimed ROA shows excellent response to dense medium separation, achieving simulated celestine grades up to 96.36 percent in the underflow and 91.40 percent in semi-industrial validation tests. In contrast, ROB performs poorly in dense medium cyclones but shows improved separation using spirals and shaking tables, with grades of 85.33 and 83.57 (87.70 validated) percent, respectively. TEM analysis indicates that losses are mainly associated with ultrafine liberated celestine reporting to the overflow. Overall, celestine processing efficiency is controlled by particle size and mineral liberation, highlighting the need for optimized flowsheets based on pre-desliming, size classification, and device-specific operating conditions.