mineral

Celestite (Celestine)

Strontium sulfate (SrSO4)

Hardness: 3-3.5 on Mohs scale; Color: Pale blue, colorless, white, or reddish; Luster: Vitreous (glassy) to pearly; Crystal Structure: Orthorhombic; Cleavage: Perfect in one direction; Specific Gravity: 3.9-4.0.

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

Identified March 2, 2026More mineral →

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Physical properties

Formation & geological history

Formed primarily in sedimentary rocks such as limestones and dolostones, often occurring as geodes or within evaporate deposits. It precipitates from strontium-rich solutions during diagenesis.

Uses & applications

Used as the primary source of the element strontium, which is used in fireworks (to create red flames), metal alloys, and glass for CRT monitors. It is also highly prized as a mineral specimen for collectors and used in metaphysical practices.

Geological facts

The world's largest known geode is a celestite geode located in Put-in-Bay, Ohio, measuring 35 feet (10.7 meters) in diameter at its widest point.

Field identification & locations

Identify in the field by its distinct pale blue color, high density (it feels heavy for its size), and orthorhombic crystal habits. Common locations include Madagascar (well-known for blue geodes), Sicily, and Lake Erie regions of North America.