Environmental Geochemistry of Geophagic Materials from Free State Province in South Africa

Nine geophagic material samples were analysed in order to characterise their mineralogical and elemental constituents, and infer on their health threats. Most abundant mineral in the samples was quartz, followed by smectite, kaolinite and muscovite in minor; and microcline, plagioclase, and goethite in trace quantities. Dominant major oxides were SiO2 (43 - 74 wt%) and Al2O3(15 - 19 wt%). Chemical Indices of Alteration (79.37-99.34) and Weathering (94.38-99.92) values suggest moderate to extreme silicate weathering, and alkali and alkaline earth metals depletion. Based on molar proportions of Al2O3, CaO + Na2O, and K2O, weathering trend and mineralogical compositions of the soils showed more advanced argillic alteration with rare earth elements being more concentrated compared to Upper Continental Crust. Excessive amounts of quartz and heavy metals in the geophagic soils represent significant health threats to geophagic individuals, though heavy metals had low biaccessibility values. There is need for soils beneficiation before ingestion.