strontianite, a strontium carbonate mineral (SrCO3) that is the original and principal source of strontium. It occurs in white masses of radiating fibres, although pale green, yellow, or gray colours are also known. Strontianite forms soft, brittle crystals that are commonly associated with barite, celestine, and calcite in low-temperature veins. Notable deposits exist in North Rhine–Westphalia, Ger.; Strontian, Scot.; and Strontium Hills, Calif., U.S. Strontianite is used in pyrotechnics to impart a red colour and in sugar refining as a clarifying agent. For detailed physical properties, see carbonate mineral (table).