mineral

Celestite (Celestine)

Strontium sulfate (SrSO4)

Hardness: 3-3.5 (Mohs); Color: Pale blue to sky blue, colorless, or white; Luster: Vitreous (glassy) to pearly; Crystal structure: Orthorhombic; Cleavage: Perfect; Specific gravity: 3.9-4.0

Hardness: 3-3
Color: Pale blue to sky blue, colorless, or white
Luster: Vitreous (glassy) to pearly

Identified March 15, 2026More mineral →

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Physical properties

Hardness: 3-3.5 (Mohs); Color: Pale blue to sky blue, colorless, or white; Luster: Vitreous (glassy) to pearly; Crystal structure: Orthorhombic; Cleavage: Perfect; Specific gravity: 3.9-4.0

Formation & geological history

Formed as a sedimentary mineral within evaporite deposits, in cavities of limestone and dolomite, or through hydrothermal processes. Most commercial specimens are from the Jurassic or Cretaceous periods.

Uses & applications

Primary source of Strontium used in fireworks (red flames), flare lights, and glass manufacturing; also used as a gemstone for collectors and in metaphysical practices.

Geological facts

The name comes from the Latin 'caelestis', meaning 'celestial' or 'heavenly', referring to its characteristic blue color. The largest celestite geode known is the Crystal Cave in Ohio, measuring 35 feet deep.

Field identification & locations

Identified by its pale blue hue, high density (heavy for its size), and brittle nature. Commonly found in Madagascar, Sicily, and the Lake Erie region of the US. Collectors should look for distinct crystalline faces and avoid washing with water as it can be slightly soluble.