mineral

Prehnite

Prehnite - Ca2Al(AlSi3O10)(OH)2

Hardness: 6-6.5 on Mohs scale; Color: Pale green to yellow-green, translucent to semi-transparent; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Good in one direction; Specific gravity: 2.80 - 2.95.

Hardness: 6-6
Color: Pale green to yellow-green, translucent to semi-transparent
Luster: Vitreous to pearly

Identified March 22, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a secondary mineral in hydrothermal veins and cavities within mafic volcanic rocks (like basalt). It typically occurs in low-grade metamorphic environments and is often associated with zeolites.

Uses & applications

Primarily used as a semi-precious gemstone in jewelry, such as beads, cabochons, and carvings. It is also highly sought after by mineral collectors for its unique globular or 'botryoidal' crystal habits.

Geological facts

Prehnite was the first mineral to be named after a person (Colonel Hendrik Von Prehn) and was first discovered in South Africa in the late 18th century. It is sometimes referred to as 'Grape Jade' due to its common round growth habit.

Field identification & locations

Identify by its distinct pale 'sea-foam' green color and its tendency to form in rounded, translucent aggregates. Common locations include South Africa, Australia (Wave Hill), USA (New Jersey), and Scotland.