mineral
Prehnite
Ca2Al2Si3O10(OH)2
AI-generated identification · may be incorrectHardness: 6-6.5 (Mohs scale); Color: Pale green to yellow-green, translucent to semi-transparent; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Good in one direction; Specific Gravity: 2.80-2.95.
- Hardness
- 6-6
- Color
- Pale green to yellow-green, translucent to semi-transparent
- Luster
- Vitreous to pearly
Identified More mineral →
Explore Prehnite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-6.5 (Mohs scale); Color: Pale green to yellow-green, translucent to semi-transparent; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Good in one direction; Specific Gravity: 2.80-2.95.
Formation & geological history
Commonly formed in the cavities of mafic volcanic rocks (basalt). It is a secondary or hydrothermal mineral resulting from low-grade metamorphism or hydrothermal alteration of plagioclase feldspars.
Uses & applications
Primarily used as a gemstone for jewelry (cabochons and beads) and as a collector's mineral specimen.
Geological facts
It was the first mineral to be named after a person, Colonel Hendrik Von Prehn, who discovered it in South Africa in 1788. It is sometimes called 'Cape Emerald' due to its color.
Field identification & locations
Look for the characteristic 'grape-like' (botryoidal) clusters and the unique 'inner glow' or oil-like translucency. Common locations include South Africa, Australia, Scotland, and the USA (New Jersey and Virginia).
More like this
Other mineral specimens
Gneiss or Schist
Gneiss or Mica Schist with Garnet
Metamorphic
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
igneous
Granite
Granite (Phaneritic intrusive igneous rock)
igneous
Septarian Pebble
Septarian nodule / Concretion
sedimentary