mineral

Celestite

Celestine (Strontium Sulfate, SrSO4)

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

Hardness: 3-3
Color: Pale blue, colorless, or white
Luster: Vitreous to pearly

Identified May 24, 2026More mineral →

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Physical properties

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

Formation & geological history

Formed in sedimentary rocks, especially evaporites, and sometimes in hydrothermal veins or geodes. It often precipitates from sulfate-rich fluids in cavities of limestone or dolostone.

Uses & applications

Primary source of strontium for fireworks (red flames) and flare manufacturing. Also used in ceramic glazes, glassmaking, and is highly valued by mineral collectors for its delicate blue crystals.

Geological facts

The name is derived from the Latin word 'caelestis' meaning celestial or heavenly, referring to its characteristic blue color. The world's largest known geode is a celestite geode located in Ohio.

Field identification & locations

Identify by its distinct pale blue color, high density (heavy for its size), and relatively low hardness (can be scratched by a copper coin). Commonly found in Madagascar, Sicily, and Lake Erie, USA.