mineral

Prehnite

Prehnite (Ca2Al(AlSi3O10)(OH)2)

Hardness: 6-6.5; Color: pale green to yellow; Luster: vitreous to pearly; Crystal structure: Orthorhombic; Specific gravity: 2.80-2.90

Hardness: 6-6
Color: pale green to yellow
Luster: vitreous to pearly

Identified May 9, 2026More mineral →

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Physical properties

Hardness: 6-6.5; Color: pale green to yellow; Luster: vitreous to pearly; Crystal structure: Orthorhombic; Specific gravity: 2.80-2.90

Formation & geological history

Commonly forms as a secondary mineral in vesicular cavities of mafic volcanic rocks like basalt; often associated with zeolites. Formatively typically hydrothermal or metamorphic in age.

Uses & applications

Used primarily as a gemstone for jewelry (cabochons or beads) and as a decorative mineral specimen for collectors.

Geological facts

It was the first mineral to be named after a person, Colonel Hendrik Von Prehn, who discovered it in South Africa in 1788.

Field identification & locations

Identified by its distinctive 'apple-green' color and botryoidal (grape-like) habit in the field. Found in South Africa, Australia, and the USA.

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