177-208 Sulphates

The basic feature of the sulphate minerals is that they contain the sulphide ion (SO4). Groups of these ions combine with metals to form the sulphate minerals. Barite, gypsum, and anhydrite are the most common sulphate minerals.

Minerals of the sulphate class have a glass-like lustre, average to above average density, average hardness, and are in some cases, soluble and fluorescent.

Sulphates form in evaporite deposits, layered rock where water once flowed but has since evaporated.

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