mineral

Blue Celestite (Celestine) Cluster

Strontium sulfate (SrSO4)

Hardness: 3 - 3.5 on Mohs scale; Color: Pale sky blue to colorless; Luster: Vitreous to pearly; Crystal Structure: Orthorhombic; Cleavage: Perfect; Specific Gravity: 3.9 - 4.0

Hardness: 3 - 3
Color: Pale sky blue to colorless
Luster: Vitreous to pearly

Identified March 17, 2026More mineral →

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Physical properties

Hardness: 3 - 3.5 on Mohs scale; Color: Pale sky blue to colorless; Luster: Vitreous to pearly; Crystal Structure: Orthorhombic; Cleavage: Perfect; Specific Gravity: 3.9 - 4.0

Formation & geological history

Usually forms in sedimentary rocks like limestone, dolostone, and evaporites through the precipitation of strontium-rich fluids. Most high-quality blue specimens are from the Sakoany Mine in Madagascar and are millions of years old (Phanerozoic Eon).

Uses & applications

Primary source for strontium, used in pyrotechnics (red fireworks), glass manufacturing, and metallurgy. Also highly popular as a metaphysical healing stone and decorative collector's specimen.

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. The mineral's name is derived from the Latin 'caelestis,' meaning 'celestial' or 'heavenly' in reference to its characteristic blue color.

Field identification & locations

Identify in the field by its distinct pale blue color, high density (heavy for its size), and blocky or tabular crystal habits. Common locations include Madagascar, Sicily, and the Lake Erie region of the USA. Note: It is brittle and sensitive to sunlight, which can cause the blue color to fade.

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