mineral that is a naturally occurring form of strontium sulfate (SrSO₄). It resembles barite, barium sulfate, but is much less common. Barium is interchangeable with strontium in the crystal structure; there is a gradation between celestine and barite. Celestine occurs in sedimentary rocks, particularly dolomites and dolomitic limestones, throughout the world and also is present in hydrothermal veins and in cavities in basic eruptive rocks. Celestine is mined as a source of strontium for use in sugar-beet refining and in the manufacture of pyrotechnics. It is abundant in Sicily; Bristol, Eng.; on South Bass Island, Lake Erie, Ohio; and in San Bernardino county, Calif. For detailed physical properties, see sulfate mineral (table).