Environmental mineralogy of soils around Selebi Phikwe nickel-copper plant, Botswana

This study determined mineralogical changes in soils as a result of mining and smelting of nickel-copper (Ni-Cu). Soil samples obtained around the Selebi Phikwe Ni-Cu plant, Botswana were studied using petrographic microscopy and X-ray Powder Diffraction (XRPD) technique. Bulk soil samples contained actinolite, albite, quartz, microcline, pyrrhotite, silicon sulfide and cobalt oxide, whereas the < 2 μm fraction was made of kaolinite, illite, smectite, anorthite and quartz. Heavy minerals fraction of soil samples ranged between 5 wt% and 43 wt% with higher values occurring at sites close to either the mines or the smelter plant. Cobalt oxide and silicon sulfide identified in surface soils are indicative of mineralogical alteration of mining waste deposited on soils. Consequently, aspects of pollution management such as phytoremediation and phytomining, and environmental desulfurization could be introduced as pollution control measures at Selebi Phikwe.