hur, elemental sulphur and sulphate. The most important forms are sulphide, mainly as pyrite (Fe&), and organic sulphur. Sulphate sulphur usually occurs in small amounts, often in sulphate minerals formed during oxidation of coal. Pearson and Kwong (1979) suggest that, in coals with low pyrite concentrations, organic sulphur can oxidize to form gypsum, which can also be introduced by ground-water. Elemental sulphur occ”rs in trace amounts.