mineral

Prehnite

Prehnite (Ca2Al2Si3O10(OH)2)

Hardness: 6-6.5 on Mohs scale; Color: Light green, yellow-green, white, gray; Luster: Vitreous to pearly; Crystal System: Orthorhombic, often forming botryoidal or stalactitic aggregates with distinct radiating crystal sprays; Cleavage: Good on [001]; Specific Gravity: 2.80-2.95.

Hardness: 6-6
Color: Light green, yellow-green, white, gray
Luster: Vitreous to pearly

Identified August 1, 2026More mineral →

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Physical properties

Formation & geological history

Formed in low-temperature hydrothermal environments, typically filling cavities and veins in mafic volcanic rocks such as basalts, as well as in metamorphic environments.

Uses & applications

Used as a gemstone, frequently cut as cabochons or carved into decorative objects, and highly sought after by mineral collectors.

Geological facts

Prehnite was the first mineral to be named after a military officer, Dutch Colonel Hendrik von Prehn, who discovered it in South Africa in the late 18th century.

Field identification & locations

Easily identified by its distinctive pale apple-green color, characteristic botryoidal habit with radiating crystalline inclusions visible under close inspection, and a hardness that easily scratches glass.