mineral

Celestine (Celestite)

Strontium sulfate (SrSO4)

Hardness: 3-3.5 on Mohs scale; Color: typically pale blue, occasionally colorless or white; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Perfect; Specific gravity: 3.9-4.0

Hardness: 3-3
Color: typically pale blue, occasionally colorless or white
Luster: Vitreous to pearly

Identified March 20, 2026More mineral →

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Physical properties

Hardness: 3-3.5 on Mohs scale; Color: typically pale blue, occasionally colorless or white; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Perfect; Specific gravity: 3.9-4.0

Formation & geological history

Formed as a sedimentary precipitate through evaporation of sulfate-rich waters, or via hydrothermal mineral deposition in cavities and veins within limestone or sandstone. Commonly found in geodes.

Uses & applications

Primary source of the element strontium, which is used in pyrotechnics (red fireworks), glass for CRT monitors, and ferrite magnets. Highly popular as a display mineral for collectors.

Geological facts

The largest celestine geode in the world, 'Crystal Cave,' is located in Ohio, USA, and measures 35 feet deep. The blue color is often attributed to natural irradiation of the crystal lattice.

Field identification & locations

Field identification: Distinguished by its relatively high density (heavy for its size), distinct sky-blue color, and perfect cleavage. Common locations include Madagascar (home to high-quality blue geodes), Ohio, and Sicily.