mineral
Prehnite
Calcium aluminum silicate hydroxide, Ca2Al(AlSi3O10)(OH)2
Hardness: 6-6.5 on the Mohs scale; Color: Light green, yellow-green, white, gray; Luster: Vitreous to pearly; Crystal System: Orthorhombic; Cleavage: Good on [001], poor on [110]; Specific Gravity: 2.80-2.95
- Hardness
- 6-6
- Color
- Light green, yellow-green, white, gray
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-6.5 on the Mohs scale; Color: Light green, yellow-green, white, gray; Luster: Vitreous to pearly; Crystal System: Orthorhombic; Cleavage: Good on [001], poor on [110]; Specific Gravity: 2.80-2.95
Formation & geological history
Forms primarily in cavities of mafic igneous rocks, such as basalt, as a secondary mineral through hydrothermal processes. Can also form in metamorphic rocks.
Uses & applications
Commonly used as a gemstone, frequently cut into cabochons, carved into ornamental objects, and collected by mineral enthusiasts.
Geological facts
Prehnite was the first mineral to be named after a military officer, Colonel Hendrik von Prehn, who discovered it in South Africa in the late 18th century.
Field identification & locations
Identified by its distinctive pale apple-green or yellow-green color, botryoidal or globular habit, and vitreous to pearly luster. Found worldwide including South Africa, Australia, the USA, and China.
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