metamorphic
Epidote (likely Unakite component or Epidosite)
Epidote (Ca2(Al2Fe)(SiO4)(Si2O7)O(OH))
Hardness: 6-7 Mohs; Color: Pistachio green to olive or yellowish-green; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 3.3-3.6
- Hardness
- 6-7 Mohs
- Color
- Pistachio green to olive or yellowish-green
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 Mohs; Color: Pistachio green to olive or yellowish-green; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 3.3-3.6
Formation & geological history
Formed through regional metamorphism or hydrothermal alteration of igneous rocks (calcium-rich plagioclase turning into epidote). Often found in greenschist facies or near contact metamorphic zones.
Uses & applications
Commonly used as a semi-precious gemstone for jewelry (pendants, beads), architectural stone, and as a mineral specimen for collectors.
Geological facts
The name comes from the Greek word 'epidosis' meaning 'addition', referring to the crystal base being longer on one side. It is a primary indicator mineral for geologists studying metamorphic grades.
Field identification & locations
Identified in the field by its unique 'pistachio' green color. Common locations include the Blue Ridge Mountains (USA), Norway, Brazil, and Pakistan. For collectors, look for the mossy-green swirls and hardness that prevents scratching by a steel knife.
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