mineral

Celestine (Celestite)

Strontium sulfate (SrSO4)

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

Hardness: 3-3

Identified May 31, 2026More mineral →

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Physical properties

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

Formation & geological history

Commonly occurs in sedimentary rocks (limestones and dolomites) as geodes or nodules, or in hydrothermal veins and evaporite deposits. Most gem-quality blue specimens form in sedimentary geodes.

Uses & applications

Primary source of Strontium for pyrotechnics (red flares) and metal alloys. Also popular in crystal healing, metaphysical collecting, and as ornamental mineral specimens.

Geological facts

The largest celestine geode in the world, 'Crystal Cave', is located in Ohio and measures 35 feet in diameter at its widest point. The mineral is named from the Latin 'caelestis' meaning celestial, referring to its sky-blue color.

Field identification & locations

Identified by its heavy weight for its size (high specific gravity), distinctive pale sky-blue color, and bladed or tabular crystal habit. Frequently found in Madagascar, USA, and Italy.