mineral

Prehnite

Prehnite - Ca2Al(AlSi3O10)(OH)2

Hardness: 6-6.5 Mohs; Color: Pale green to yellow-green; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Specific Gravity: 2.8-2.95; Often found with black Epidote inclusions.

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

Identified July 18, 2026More mineral →

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Physical properties

Hardness: 6-6.5 Mohs; Color: Pale green to yellow-green; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Specific Gravity: 2.8-2.95; Often found with black Epidote inclusions.

Formation & geological history

Primarily formed in the cavities and veins of mafic volcanic rocks (basalt) via secondary hydrothermal mineralization. Common ages range from Precambrian to Mesozoic depending on the locale.

Uses & applications

Commonly used as a gemstone for jewelry (cabochons, beads) and as a decorative mineral specimen for collectors.

Geological facts

Prehnite was the first mineral to be named after a person, Colonel Hendrik Von Prehn, who discovered it in South Africa in 1788. It is often nicknamed Grape Jade due to its botryoidal growth habits.

Field identification & locations

Identify by its translucent 'glowy' green appearance and frequent needle-like black inclusions of Epidote. Commonly found in South Africa, Australia, China, and the USA (New Jersey).