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; Specific Gravity: 2.80-2.95

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

Identified July 19, 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: 2.80-2.95

Formation & geological history

Typically forms as a secondary or hydrothermal mineral in cavities of mafic volcanic rocks like basalt. It often occurs as a result of low-grade metamorphism.

Uses & applications

Primarily used as a gemstone for jewelry (beads, cabochons) and as a collector's mineral specimen.

Geological facts

Prehnite was the first mineral to be named after a person, Colonel Hendrik Von Prehn, who discovered it in South Africa in 1788. It is often found associated with zeolites.

Field identification & locations

Identified by its distinct oil-green color and 'grape-like' (botryoidal) habit in its natural state. Commonly found in South Africa, Australia, and the United States (New Jersey).