In South Africa, the majority of rural water supply comes from groundwater hosted within the weathered and fractured crystalline rocks. The main minerals that are responsible for arsenic release into groundwater in South Africa are arsenopyrite (FeAsS), lollingite (FeAs2) and scorodite (FeAsO4.2H2O), where scorodite is an alteration product of arsenopyrite due to prolonged water-rock interaction process. Owing to the release of arsenic from highly mineralized rocks, its concentration in the groundwater reaches up to 253 μg L−1 (south western part of the country), 6150 μg L−1 (west of Johannesburg), about 500 μg L−1 in the Karoo aquifers. Acid mine drainage is also found to be important source of arsenic and other toxic metals in the environment.