mineral

Prehnite with Epidote inclusions

Ca2Al(AlSi3O10)(OH)2

AI-generated identification · may be incorrect

Hardness: 6-6.5 on Mohs scale; 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 July 14, 2026More mineral →

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Physical properties

Hardness: 6-6.5 on Mohs scale; 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 as a secondary or hydrothermal mineral in cavities of mafic volcanic rocks (basalts and volcanic tuffs). It is often found associated with zeolites and formed during low-grade metamorphism.

Uses & applications

Mostly used as a gemstone for jewelry (cabochons or beads), ornamental carvings, and as a popular 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 the late 18th century. It is often called 'Grape Jade' in the trade due to its botryoidal growth habit.

Field identification & locations

Identified by its specific 'oily' or pearly luster and distinctive pale green color, often containing dark needle-like inclusions of Epidote. Commonly found in South Africa, Australia, and the United States (New Jersey/Connecticut).