mineral

Prehnite

Prehnite (Ca2Al2Si3O10(OH)2)

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

Identified June 24, 2026More mineral →

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Physical properties

Formation & geological history

Formed through low-grade metamorphism or hydrothermal activity in the cavities of mafic volcanic rocks (basalt). It is primarily associated with zeolites across various geological eras.

Uses & applications

Commonly used as a gemstone for jewelry (cabochons and beads) and highly valued as a specimen by mineral collectors.

Geological facts

Prehnite was the first mineral to be named after a person (Colonel Hendrik Von Prehn, 1788). It is often found in globe-like (botryoidal) clusters that look like grapes, earning it the nickname 'Grape Jade' in some markets.

Field identification & locations

Identified in the field by its distinctive 'bottle-glass' green color and rounded, translucent habit. Commonly found in South Africa, Australia (Wave Hill), and the United States (New Jersey/Connecticut). Collectors look for clarity and needle-like inclusions of epidote.