mineral

Prehnite

Prehnite (Ca2Al(AlSi3O10)(OH)2)

Hardness: 6-6.5 Mohs scale; Color: Pale green to yellow-green; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Good; Specific Gravity: 2.80-2.95

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

Identified April 6, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6-6.5 Mohs scale; Color: Pale green to yellow-green; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Good; Specific Gravity: 2.80-2.95

Formation & geological history

Formed primarily in the cavities of mafic volcanic rocks (like basalts). Created by low-grade metamorphism or hydrothermal activity as a secondary mineral. Often occurs in botryoidal or globular habits.

Uses & applications

Popular as a semi-precious gemstone for jewelry (beads, cabochons), a collector's specimen, and occasionally used as an ornamental stone.

Geological facts

Prehnite was the first mineral to be named after a person, Colonel Hendrik Von Prehn, who brought the mineral from South Africa in 1774. It is sometimes called 'Cape Emerald' due to its color.

Field identification & locations

Identified by its distinctive light green color and bubbly 'botryoidal' appearance. Often found associated with Zeolites. Notable locations include South Africa, Australia, and Paterson, New York.