mineral

Prehnite

Prehnite (Ca2Al2Si3O10(OH)2)

Hardness: 6-6.5 on Mohs scale; Color: Pale green to yellow-green; Luster: Vitreous to pearly; Crystal System: Orthorhombic; Cleavage: Good in one direction; Specific Gravity: 2.80 - 2.95.

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

Identified April 4, 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 System: Orthorhombic; Cleavage: Good in one direction; Specific Gravity: 2.80 - 2.95.

Formation & geological history

Formed as a secondary or hydrothermal mineral in cavities and veins within mafic volcanic rocks (basalt). It often forms through the low-grade metamorphism of calcium-rich rocks.

Uses & applications

Commonly used as a gemstone in jewelry (cabochons and beads) and highly valued by mineral collectors for its unique mammillary or botryoidal formations.

Geological facts

Prehnite was the first mineral to be named after a specific person, Colonel Hendrik Von Prehn, who discovered it in South Africa in 1788.

Field identification & locations

Identify in the field by its characteristic 'seafoam' green color and translucent appearance. It often occurs alongside zeolites like apophyllite. Major sources include Australia, South Africa, and the USA.