mineral

Celestite (Celestine)

Strontium sulfate (SrSO4)

Hardness: 3-3.5 on Mohs scale; Color: Pale blue, colorless, or white (rarely yellow/red); Luster: Vitreous (glassy) to pearly; Crystal Structure: Orthorhombic; Cleavage: Perfect in one direction; Specific Gravity: 3.9-4.0 (conspicuously heavy for its looks).

Hardness: 3-3
Color: Pale blue, colorless, or white (rarely yellow/red)
Luster: Vitreous (glassy) to pearly

Identified March 18, 2026More mineral →

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Physical properties

Formation & geological history

Formed in sedimentary rocks, often within geodes or evaporation cavities. Common in limestones and dolomites as a result of hydrothermal activity or precipitation from strontium-rich groundwater. Most high-quality blue specimens are found in Madagascar.

Uses & applications

Primary source of the element Strontium, used in fireworks (to create red flames), metal alloys, and glass for cathode ray tubes. Widely popular in the metaphysical and crystal collecting market as display specimens.

Geological facts

The name is derived from the Latin 'caelestis', meaning 'heavenly', referring to its characteristic sky-blue color. While it is the main ore of strontium, it is very fragile and sensitive to heat, often losing its color if left in direct sunlight for extended periods.

Field identification & locations

Identify in the field by its distinct pale blue color, high density (heaviness), and flat, blocky crystal terminations. It is most commonly found in Madagascar, Sicily, and parts of the United States (Ohio and Michigan). Collectors should look for intact geode linings.