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: 2.80-2.90; Often translucent with a 'sleepy' appearance.

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

Identified May 7, 2026More mineral →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Formed as a secondary or hydrothermal mineral in cavities (vesicles) of mafic volcanic rocks like basalt. It is also found in metamorphic rocks and granites.

Uses & applications

Primarily used as a gemstone for jewelry (beads, cabochons) and as a popular collector's mineral specimen. Historically used for small decorative carvings.

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

Field identification & locations

Identify in the field by its distinctive pale green color, brittle tenacity, and occurrence in volcanic cavities. It is commonly found in South Africa, Australia, China, and the USA (New Jersey).