mineral
Prehnite
Ca2Al(AlSi3O10)(OH)2
Hardness: 6-6.5 on Mohs scale; Color: Pale green to yellow-green, sometimes white or colorless; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Good in one direction; Translucent to semi-transparent.
- Hardness
- 6-6
- Color
- Pale green to yellow-green, sometimes white or colorless
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-6.5 on Mohs scale; Color: Pale green to yellow-green, sometimes white or colorless; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Good in one direction; Translucent to semi-transparent.
Formation & geological history
Formed as a secondary or hydrothermal mineral in cavities and veins of mafic volcanic rocks (like basalt). It is typically found in low-grade metamorphic environments.
Uses & applications
Mostly used as a gemstone for jewelry (cabochons and beads) and as a collector's mineral specimen. In some cultures, it is used as a stone for meditation.
Geological facts
Prehnite was the first mineral to be named after a person (Colonel Hendrik von Prehn) in 1788. It is often found associated with minerals like zeolites, calcite, and epidote.
Field identification & locations
Identifiable by its characteristic 'milky' or 'oily' pale green color and its tendency to form radiating botryoidal (grape-like) clusters. Common locations include South Africa, Australia, Mali, and the USA (New Jersey).
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Other mineral specimens
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Schist
Schist
Metamorphic
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock
Granite
Granite (Phaneritic intrusive igneous rock)
igneous