mineral

Prehnite

Prehnite (Ca2Al2Si3O10(OH)2)

Hardness: 6-6.5 on the Mohs scale. Color: Pale green to yellow-green. Luster: Vitreous to pearly. Crystal structure: Orthorhombic, usually occurring in botryoidal or globular habits. Cleavage: Good in one direction.

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

Identified May 24, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a secondary mineral in cavities of mafic volcanic rocks (basalt). It typically forms from hydrothermal activity during low-grade metamorphism.

Uses & applications

Used primarily as a gemstone for jewelry, carvings, and as a popular mineral specimen for collectors. It has minor historical use as an ornamental stone.

Geological facts

Prehnite was the first mineral to be named after a person, Colonel Hendrik Von Prehn, who discovered it at the Cape of Good Hope in South Africa in 1788.

Field identification & locations

Identify in the field by its distinct 'grape-like' (botryoidal) clusters and translucent pale green color. Often found associated with zeolites or epidote in basaltic vugs.