mineral

Prehnite

Prehnite (Ca2Al2Si3O10(OH)2)

Hardness: 6-6.5 on Mohs scale; Color: Pale green to yellow-green, sometimes white or gray; Luster: Vitreous to pearly; Crystal structure: Orthorhombic (often botryoidal or massive); Cleavage: Distinct in one direction; Specific Gravity: 2.8 - 2.95.

Hardness: 6-6
Color: Pale green to yellow-green, sometimes white or gray
Luster: Vitreous to pearly

Identified July 8, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a secondary or hydrothermal mineral in veins and cavities of mafic igneous rocks (such as basalt and gabbro). It is a product of low-grade metamorphism. Formed during various geological periods following volcanic activity.

Uses & applications

Used primarily as a gemstone for jewelry (cabochons and beads) and as a collector's mineral specimen. Historically used as a source of aluminum or 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 to Europe in the late 18th century. It is often found associated with zeolites such as apophyllite and stilbite.

Field identification & locations

Identify by its characteristic 'seafoam' green color and often rounded (botryoidal) or radiating crystal formations. Commonly found in South Africa, Australia (Northern Territory), and the Paterson, New Jersey area in the USA. Collectors look for translucency and 'epidote' inclusions.