mineral
Prehnite
Calcium aluminum silicate hydroxide, Ca2Al(AlSi3O10)(OH)2
Hardness: 6-6.5 on the Mohs scale; Color: Light green, yellow-green, white, grey; Luster: Vitreous to pearly; Crystal structure: Orthorhombic, often found in botryoidal or globular aggregates; Cleavage: Good on [001], distinct on [110]; Specific gravity: 2.80-2.95
- Hardness
- 6-6
- Color
- Light green, yellow-green, white, grey
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-6.5 on the Mohs scale; Color: Light green, yellow-green, white, grey; Luster: Vitreous to pearly; Crystal structure: Orthorhombic, often found in botryoidal or globular aggregates; Cleavage: Good on [001], distinct on [110]; Specific gravity: 2.80-2.95
Formation & geological history
Forms in low-temperature hydrothermal environments, typically in cavities and veins of mafic igneous rocks such as basalts, as well as in metamorphic rocks.
Uses & applications
Used primarily as a gemstone, often cut as cabochons or beads, and highly sought after by mineral collectors.
Geological facts
Prehnite was the first mineral to be named after a military person, being described by Abraham Gottlob Werner in 1788 after Colonel Hendrik Von Prehn, who discovered it in South Africa.
Field identification & locations
Easily identified by its characteristic pale apple-green color and botryoidal (bubble-like) habit. Commonly found in South Africa, Australia, the USA, and China.
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