mineral
Prehnite
Prehnite (Ca2Al2Si3O10(OH)2)
Hardness: 6-6.5; 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; Color: Pale green to yellow-green; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Specific Gravity: 2.80-2.90
Formation & geological history
Formed as a secondary or hydrothermal mineral in cavities within volcanic rocks (basalts and gabbros). Often associated with zeolites.
Uses & applications
Commonly used as a gemstone in jewelry, especially when cabochon cut, and as an ornamental stone for collectors.
Geological facts
It was the first mineral to be named after a person, Colonel Hendrik Von Prehn, who discovered it in 1774 at the Cape of Good Hope.
Field identification & locations
Identify by its translucent, 'bottled-water' green appearance and pearly luster on cleavage faces. Found in South Africa, USA, and Australia.
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Orthoclase (KAlSi3O8)
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Mineral
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Mineral/Rock