Celestine

Celestine, a mineral bearing the same relation to Strontia (q.v.) that heavy spar bears to baryta. It is essentially sulphate of strontia, $\backslash text\{SrSO\}\_4$, with occasional admixture of sulphate of baryta, carbonate of lime, oxide of iron, &c., in small proportions. It much resembles heavy spar, but is not quite equal to it in specific gravity; is usually blue, often of a very beautiful indigo-blue; sometimes colourless, more rarely reddish or yellowish. Its crystallisation is rhombic, like that of heavy spar. Most beautiful specimens of crystallised celestine are found in Sicily. Celestine derives its name from its colour. It is the source from which nitrate of strontia, employed in the manufacture of fireworks, is derived.