List the important source of sulphur.

The abundance of sulphur in the earth crust is 0.03-0.1%. Combined sulphur exist primarily as sulphates such as gypsum CaSO₄. 2H₂,O, epsom salt MgSO₄.7H₂ O, baryte BaSO₄ and sulphides such as galena PbS, zinc blende ZnS copper pyrite CuFeS₂. Traces of sulphur occur as hydrogen sulphide in volcano. Organic minerals such as eggs, proteins, garlic, onion, mustard, hair and wool contain sulphur.