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; Cleavage: Good in one direction; Specific gravity: 2.80–2.90.

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

Identified June 2, 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; Cleavage: Good in one direction; Specific gravity: 2.80–2.90.

Formation & geological history

Formed through low-grade metamorphism or hydrothermal activity in cavities of mafic volcanic rocks (basalt). It often appears as an alteration product of plagioclase feldspars.

Uses & applications

Primarily used as a gemstone for jewelry (cabochons and beads) and as a prized specimen for mineral 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 1774. It is sometimes called 'New Jade' or 'Grape Jade' due to its botryoidal growth habits.

Field identification & locations

Identify by its distinct apple-green color, translucency, and often radiating fibrous orbicular habit. It is frequently found associated with zeolites in basaltic cavities or vugs.