mineral

Celestine (or Celestite)

Strontium sulfate (SrSO4)

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

Hardness: 3-3

Identified May 15, 2026More mineral →

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Physical properties

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

Formation & geological history

Commonly formed in sedimentary rocks (limestones and dolomites) as geodes, veins, or replacement nodules. It precipitates from strontium-rich solutions during diagenesis or hydrothermal activity.

Uses & applications

Primary source of Strontium used in fireworks, tracer bullets (for red flames), glass manufacturing, and ferrites. Also highly valued as a specimen for mineral collectors and metaphysical practitioners.

Geological facts

The largest geode in the world, the Crystal Cave in Ohio, is composed entirely of celestine crystals. Its name is derived from the Latin word 'caelestis', meaning celestial or heavenly, in reference to its blue color.

Field identification & locations

Identify by its sky-blue color, high density (heavy for its size), and blocky crystal habit. Commonly sourced from large deposits in Madagascar and Poland. Collectors should be careful as it is brittle and the color can fade in UV light.