mineral

Celestite (Celestine)

Strontium Sulfate (SrSO4)

Hardness: 3-3.5 (Mohs); Color: Pale blue to colorless, sometimes white; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Perfect; Specific gravity: 3.9-4.0

Hardness: 3-3
Color: Pale blue to colorless, sometimes white
Luster: Vitreous to pearly

Identified March 24, 2026More mineral →

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Physical properties

Hardness: 3-3.5 (Mohs); Color: Pale blue to colorless, sometimes white; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Perfect; Specific gravity: 3.9-4.0

Formation & geological history

Formed most commonly in sedimentary rocks (limestones and dolomites) as a result of chemical precipitation from strontium-rich groundwater. It often occurs as geodes or cavity linings within evaporite deposits.

Uses & applications

Primary source of the element strontium, used in the manufacturing of glass for TV screens, fireworks (red flames), and metal alloys. Also popular in the gem and mineral trade for healing and aesthetic display.

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 name is derived from the Latin 'caelestis', meaning 'heavenly' or 'celestial', referring to its sky-blue color.

Field identification & locations

Identify in the field by its high density (feels heavy for its size), distinct pale blue color, and rectangular crystal habits. Commonly found in Madagascar, Sicily, and the Lake Erie region of the USA.