Celestite is often found disseminated through limestone or sandstone, or lining cavities in such rocks. It is associated with calcite, dolomite, gypsum, sulphur, fluorite and is also found as a gangue mineral in lead veins. It is used to prepare nitrate of strontium for fireworks and tracer bullets, and in the refining of beet sugar. It has the formulae SrSO4 and a relative hardness of 4.
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