Celestine

Celestine, a naturally occurring sulphate of strontium. It crystallises in white translucent, or transparent prisms of the rhombic system, or may occur in fibrous or granular masses. It is very brittle, and has a sp. gr. 3.9. It is found in a few localities in England and Scotland, in the Tyrol, Hungary, Pennsylvania, and Strontian Island; and is frequently associated with gypsum and rock salt, and, in volcanic regions, with sulphur.