mineral

Prehnite

Prehnite (Ca2Al(AlSi3O10)(OH)2)

Hardness: 6-6.5 on Mohs scale; Color: Pale green, yellowish-green; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Good in one direction; Specific gravity: 2.80 - 2.95

Hardness: 6-6
Color: Pale green, yellowish-green
Luster: Vitreous to pearly

Identified June 4, 2026More mineral →

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Physical properties

Hardness: 6-6.5 on Mohs scale; Color: Pale green, yellowish-green; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Good in one direction; Specific gravity: 2.80 - 2.95

Formation & geological history

Formed primarily as a secondary mineral in veins and cavities of mafic volcanic rocks (basalt) and occasionally in low-grade metamorphic rocks. It results from low-temperature hydrothermal activity.

Uses & applications

Commonly used as a gemstone for jewelry (cabochons and beads), mineral specimens for collectors, and sometimes used as a decorative stone.

Geological facts

Prehnite was the first mineral to be named after a person, Colonel Hendrik Von Prehn, who discovered it in South Africa in the late 18th century. It is often found associated with zeolites.

Field identification & locations

Identify by its characteristic pale 'apple green' color and translucent, slightly waxy appearance. Commonly found in South Africa, Australia, and the United States (New Jersey/Connecticut). Look for 'prehnite with epidote' inclusions which are popular in the market.