SURVEY OF SULPHATE-BEARING MINERALS IN LKAB'S TAILING POND

This research project investigated the high concentration of sulphate in a tailing pond at LKAB and the characteristics and behavior of sulphate minerals in different areas of the pond. The sampling of the tailings was carried out at Nine stationary sampling points. Each sample was taken from the surface to a depth of one meter except for the underflow sample which was collected from the thickener in the processing plant (fresh tailings). Stereo microscopy and SEM-EDS analysis aid in identifying mineral grains and confirming the presence of Gypsum and/or Anhydrite, along with other minerals like Pyrite, Pyrrhotite, and Chalcopyrite. The difficulty in distinguishing between Gypsum and Anhydrite under SEM was noted due to their similar crystal shapes and chemical composition. Gypsum and/or Anhydrite were identified as the main minerals responsible for the high sulphate concentration based on elemental screening, sequential extraction, and mineralogical results. Sulfide minerals like Pyrite, Chalcopyrite, and Pyrrhotite were also present but did not show any signs of weathering characteristics and therefore probably not contributed to the high sulphate concentration in the pond. The quantitative mineralogy carried out confirmed the presence of Gypsum and/or Anhydrite, Pyrite, Pyrrhotite and Chalcopyrite as identified in the mineralogical analysis. The study concludes that Gypsum and/or Anhydrite are the main contributors to the high sulphate concentration in the LKAB tailings pond