mineral

Blue Celestite (Celestine)

Strontium sulfate (SrSO4)

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

Hardness: 3-3

Identified May 9, 2026More mineral →

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Physical properties

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

Formation & geological history

Commonly forms in sedimentary rocks as geodes, nodules, and crystals in limestone, dolomite, and sandstone through the precipitation of strontium-bearing groundwater.

Uses & applications

Chief source of strontium used in fireworks (red flames), television glass, and magnets. Widely collected as a gemstone and metaphysical tower.

Geological facts

The world's largest known geode is a celestite geode located in Put-in-Bay, Ohio, measuring 35 feet at its widest point.

Field identification & locations

Identify by its distinct pale blue color, high density (heavy for its size), and orthorhombic crystal habit. Common locations include Madagascar, Sicily, and Lake Erie, USA. Avoid acidic cleaners as it is a soft mineral.