mineral
Prehnite
Prehnite (Ca2Al(AlSi3O10)(OH)2)
Hardness: 6-6.5 on Mohs scale; Color: Pale green to yellow-green; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Specific Gravity: 2.80-2.90
- Hardness
- 6-6
- Color
- Pale green to yellow-green
- Luster
- Vitreous to pearly
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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; Specific Gravity: 2.80-2.90
Formation & geological history
Formed in the cavities of mafic volcanic rocks (basalt) through low-grade metamorphism or hydrothermal activity. Often found in amygdules or fissures.
Uses & applications
Primarily used as a gemstone for jewelry (cabochons and beads) and as a decorative collector specimen. Occasionally used for small ornamental carvings.
Geological facts
Prehnite was the first mineral to be named after a person, Colonel Hendrik Von Prehn (1733–1785), who discovered the mineral in South Africa.
Field identification & locations
Identified by its signature 'apple green' color and often its globular (botryoidal) growth habit. Common locations include South Africa, Australia, and the USA (New Jersey).
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