mineral

Prehnite

Prehnite (Ca2Al2Si3O10(OH)2)

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

Identified April 3, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a secondary or hydrothermal mineral in cavities and veins of mafic volcanic rocks (like basalt). It often occurs alongside zeolites and is associated with low-grade metamorphism.

Uses & applications

Primarily used as a gemstone for jewelry (cabochons and beads) and as a popular specimen for mineral collectors. Occasionally used as a minor source of aluminum or calcium.

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 1788. It often forms 'botryoidal' (grape-like) clusters.

Field identification & locations

Identify by its distinct pale 'apple-green' color and translucent vitreous luster. It is commonly found in basaltic terrains such as the Paterson region of New Jersey, USA, or the Wave Hill station in Australia.