mineral

Prehnite

Prehnite (Ca2Al(AlSi3O10)(OH)2)

AI-generated identification · may be incorrect

Hardness: 6-6.5 on Mohs scale; Color: Pale green to yellow-green; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Specific Gravity: 2.80-2.90

Hardness: 6-6
Color: Pale green to yellow-green
Luster: Vitreous to pearly

Identified May 17, 2026More mineral →

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Physical properties

Hardness: 6-6.5 on Mohs scale; Color: Pale green to yellow-green; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Specific Gravity: 2.80-2.90

Formation & geological history

Formed in the cavities of mafic volcanic rocks (basalt) through low-grade metamorphism or hydrothermal activity. Often found in amygdules or fissures.

Uses & applications

Primarily used as a gemstone for jewelry (cabochons and beads) and as a decorative collector specimen. Occasionally used for small ornamental carvings.

Geological facts

Prehnite was the first mineral to be named after a person, Colonel Hendrik Von Prehn (1733–1785), who discovered the mineral in South Africa.

Field identification & locations

Identified by its signature 'apple green' color and often its globular (botryoidal) growth habit. Common locations include South Africa, Australia, and the USA (New Jersey).