mineral

Prehnite

Prehnite, Ca2Al2Si3O10(OH)2

Hardness: 6-6.5 on the Mohs scale. Color: Pale green to yellow-green, occasionally white or colorless. Luster: Vitreous to pearly. Crystal Structure: Orthorhombic, often occurring in botryoidal (grape-like) or radiating habits.

Hardness: 6-6
Color: Pale green to yellow-green, occasionally white or colorless
Luster: Vitreous to pearly

Identified May 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a secondary or hydrothermal mineral in cavities of mafic volcanic rocks (basalts and dolerites) and sometimes in low-grade metamorphic rocks.

Uses & applications

Used primarily as a gemstone for jewelry (cabochons and beads) and is a popular specimen for mineral collectors.

Geological facts

It was the first mineral to be named after a person, Colonel Hendrik Von Prehn, who discovered it in South Africa in 1788. It was once considered rare but is now well-documented worldwide.

Field identification & locations

Identified by its distinct green color and often 'bumpy' or botryoidal surface texture. Commonly found in South Africa, Australia, and Paterson, New Jersey, USA.