mineral
Prehnite
Prehnite (Ca2Al(AlSi3O10)(OH)2)
AI-generated identification · may be incorrectHardness: 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; Often translucent with a 'sleepy' appearance.
- 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; Often translucent with a 'sleepy' appearance.
Formation & geological history
Formed as a secondary or hydrothermal mineral in cavities (vesicles) of mafic volcanic rocks like basalt. It is also found in metamorphic rocks and granites.
Uses & applications
Primarily used as a gemstone for jewelry (beads, cabochons) and as a popular collector's mineral specimen. Historically used for small decorative carvings.
Geological facts
Prehnite was the first mineral to be named after a person, Colonel Hendrik Von Prehn, who discovered it at the Cape of Good Hope in 1788. It is sometimes called 'Grape Jade' due to its common botryoidal (grape-like) growth habit.
Field identification & locations
Identify in the field by its distinctive pale green color, brittle tenacity, and occurrence in volcanic cavities. It is commonly found in South Africa, Australia, China, and the USA (New Jersey).
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