mineral

Prehnite

Prehnite (Ca2Al(AlSi3O10)(OH)2)

Hardness: 6-6.5 on Mohs scale; Color: Pale green to yellow-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 to yellow-green
Luster: Vitreous to pearly

Identified April 11, 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; Cleavage: Good in one direction; Specific gravity: 2.80-2.95.

Formation & geological history

Formed as a secondary mineral in veins and cavities of mafic volcanic rocks (basalts and gabbros) through hydrothermal alteration. Most primary deposits are from the Mesozoic era.

Uses & applications

Used primarily as a gemstone for jewelry (cabochons and beads) and as a popular specimen for mineral collectors. Some industrial use in chemical research.

Geological facts

It was the first mineral to be named after a person (Colonel Hendrik Von Prehn) in 1788. It is often found associated with zeolites such as apophyllite and stilbite.

Field identification & locations

Identify by its distinctive 'bottle green' translucent color and botryoidal (grape-like) habit. It is commonly found in the Karoo dolerites of South Africa, the Paterson area of New Jersey, and parts of Australia.