Clear yellow Sulphur crystals from El Desierto mine in Potosi, Bolivia. Sulphur or sulfur (symbol S) is an abundant, non-metallic chemical element. In nature, sulphur can be found both as the pure element and as compounds, such as sulphides and sulphates. Elemental sulphur, whether amorphous or crystalline is most often found in volcanic environments Well developed crystals, as in this picture, are formed in voids and open surfaces, and are much in demand with mineral collectors for their bright yellow colours and polyhedral shapes. Actual height of specimen is 200 mm.