mineral

Celestine (Celestite)

Strontium Sulfate (SrSO4)

Hardness: 3-3.5 (Mohs scale), Color: Sky blue to colorless/gray, Luster: Vitreous/pearly, Crystal Structure: Orthorhombic, Cleavage: Perfect, Specific Gravity: 3.9-4.0

Hardness: 3-3

Identified February 22, 2026More mineral →

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Physical properties

Hardness: 3-3.5 (Mohs scale), Color: Sky blue to colorless/gray, Luster: Vitreous/pearly, Crystal Structure: Orthorhombic, Cleavage: Perfect, Specific Gravity: 3.9-4.0

Formation & geological history

Formed in sedimentary rocks, often within geodes or as replacements in limestone/dolostone; precipitate from hydrothermal solutions or evaporite deposits throughout various geological ages.

Uses & applications

Primary source of strontium (used in fireworks for red colors, flares, and ceramics); also used as collector specimens and in metaphysical practices.

Geological facts

The largest known geode in the world, Crystal Cave in Ohio, is composed entirely of Celestine crystals. It is named after the Latin word 'caelestis' for celestial/heavenly due to its blue color.

Field identification & locations

Identified by its distinctive pale blue color, high density (heavy for its size), and blade-like or tabular crystal habits. Common locations include Madagascar, Sicily, and the Lake Erie region of the US.