mineral

Celestite (Celestine)

Strontium sulfate (SrSO4)

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

Hardness: 3 - 3
Color: Pale blue, colorless, white
Luster: Vitreous (glassy) to pearly

Identified March 19, 2026More mineral →

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Physical properties

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

Formation & geological history

Formed through sedimentary processes, typically in evaporite deposits or as geode linings in limestone and sandstone. Most blue specimens found today originate from the Late Cretaceous period in Madagascar.

Uses & applications

Primary source of the element strontium, which is used in fireworks, tracer bullets, and glass for television cathode ray tubes. High-quality clusters are mostly used as decorative display specimens and for gemstone collecting.

Geological facts

The largest celestite geode ever found is located in Put-in-Bay, Ohio, and is 35 feet (11 meters) in diameter at its widest point. The mineral gets its name from the Latin 'caelestis' meaning celestial or heavenly, referring to its sky-blue color.

Field identification & locations

Identify in the field by its distinct pale blue color, high density (heavy for its size), and brittle orthorhombic crystals. It is most commonly found in Madagascar, Sicily, and Ohio, USA. Collectors should be careful as it is very fragile and can fade in direct sunlight.