mineral

Prehnite

Prehnite (Ca2Al(AlSi3O10)(OH)2)

Hardness: 6-6.5 (Mohs scale); Color: Light green to yellow-green, white, or colorless; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Good in one direction.

Hardness: 6-6
Color: Light green to yellow-green, white, or colorless
Luster: Vitreous to pearly

Identified June 7, 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: Light green to yellow-green, white, or colorless; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Good in one direction.

Formation & geological history

Formed as a secondary or hydrothermal mineral in cavities (vugs) of mafic igneous rocks like basalt. It often occurs as a result of low-grade metamorphism.

Uses & applications

Used primarily as a gemstone for jewelry (cabochons) and as a popular specimen for mineral collectors. Historically used as a minor decorative stone.

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 1774. It is sometimes called 'Grape Jade' due to its common botryoidal (grape-like) habit.

Field identification & locations

Identified in the field by its distinctive pale green color, brittle nature, and frequent occurrence in radiating fibrous or botryoidal clusters. Commonly found in South Africa, Australia, and the United States (New Jersey).