celestine

Celestine, also known as celestite, is a mineral composed of strontium sulfate with the chemical formula SrSO4. It is best known for its pale blue to colorless crystals, though colors range to gray or pink in rare specimens. The name derives from Latin caelestis meaning heavenly.

Celestine crystallizes in the orthorhombic system and commonly forms tabular to prismatic crystals, often in aggregates or geodes. It has a Mohs hardness of 3 to 3.5 and a specific gravity around 3.9. It is typically transparent to translucent with a vitreous luster.

The mineral occurs most often in sedimentary environments, particularly evaporite deposits where saline waters precipitate SrSO4. It is commonly associated with gypsum, anhydrite, and halite. Worldwide deposits exist, with notable sources in Madagascar, Spain, Mexico, and the United States.

Economic and scientific significance: Celestine is the principal ore of strontium, a metal used in manufacturing of strontium compounds, glass and ceramic glazes, and in pyrotechnics to produce red colors. It is also collected as a mineral specimen by crystallographers and enthusiasts, especially when formed into well-formed blue crystals.

History: Celestine was described in the late 18th century and named for its celestial color. It has since been investigated for its crystallography and applications in strontium production.