mineral

Celestite (Celestine)

Strontium sulfate (SrSO4)

Hardness: 3-3.5 (Mohs); Color: Sky blue, colorless, or white; Luster: Vitreous/Pearly; Crystal structure: Orthorhombic; Cleavage: Perfect; Specific gravity: 3.9-4.0

Hardness: 3-3
Color: Sky blue, colorless, or white
Luster: Vitreous/Pearly

Identified March 15, 2026More mineral →

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Physical properties

Hardness: 3-3.5 (Mohs); Color: Sky blue, colorless, or white; Luster: Vitreous/Pearly; Crystal structure: Orthorhombic; Cleavage: Perfect; Specific gravity: 3.9-4.0

Formation & geological history

Formed as a sedimentary mineral in cavity fillings of limestone and dolostone via evaporation or hydrothermal activity; often occurs in geodes. Primarily found in Cretaceous and Jurassic formations.

Uses & applications

Primary source of Strontium for fireworks (adds red color) and metal alloys; used in crystal healing, home decor, and mineral collecting.

Geological facts

Derived its name from the Latin 'caelestis' meaning celestial or heavenly due to its sky-blue color. The Sakoany mine in Madagascar produces the world's most iconic blue geodes.

Field identification & locations

Identify by its sky-blue translucence, tabular crystal habits, and heavy weight (high specific gravity). Common in Madagascar, Sicily, and Ohio (USA). It is very soft and brittle; do not clean with water for long periods.