mineral

Prehnite

Ca2Al(AlSi3O10)(OH)2 (Calcium Aluminum Silicate hydroxide)

AI-generated identification · may be incorrect

Hardness: 6-6.5 on the Mohs scale; Color: typically pale green to yellow-green; Luster: vitreous to pearly; Crystal structure: Orthorhombic (often occurs in botryoidal or globular habits); Cleavage: Distinct in one direction; Specific Gravity: 2.80 - 2.95.

Hardness: 6-6
Color: typically pale green to yellow-green
Luster: vitreous to pearly

Identified March 16, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a secondary or hydrothermal mineral in cavities (vugs) of mafic volcanic rocks like basalt. It often occurs as a product of low-grade metamorphism. Typical geological ages range from Jurassic to the present depending on the host rock formation.

Uses & applications

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

Geological facts

Prehnite was the first mineral to be named after an individual, Colonel Hendrik Von Prehn, who discovered it in South Africa in 1788. It is sometimes called 'Grape Jade' due to its common rounded, translucent green appearance.

Field identification & locations

Identify by its 'oily' or pearly luster and distinctive pale mint-green color. In the field, look for bubble-like (botryoidal) clusters inside volcanic rock cavities. Common locations include South Africa, Australia (Northern Territory), and the USA (New Jersey and Virginia).