metamorphic
Epidote (Greenstone)
Epidote (Ca2(Al2,Fe)(SiO4)(Si2O7)O(OH))
Hardness: 6-7 on Mohs scale; Color: Pistachio green to blackish-green; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 3.3-3.6
- Hardness
- 6-7 on Mohs scale
- Color
- Pistachio green to blackish-green
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Pistachio green to blackish-green; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 3.3-3.6
Formation & geological history
Formed by low-to-medium grade regional metamorphism of igneous rocks like basalt or gabbro, or through hydrothermal alteration. It is common in alpine-type veins and skarns.
Uses & applications
Primarily used as a minor gemstone for jewelry when transparent, a decorative stone (Unakite component), and highly valued by mineral collectors for its unique green color.
Geological facts
The name 'Epidote' comes from the Greek word 'epidosis', meaning 'addition', referring to the crystal's geometry where one side of the base is longer than the other. It is the signature mineral of the greenschist metamorphic facies.
Field identification & locations
Identify by its characteristic 'pistachio green' color and relative hardness. Commonly found in metamorphic terrains such as the Alps, Norway, or the Blue Ridge Mountains in the USA. Collectors look for well-formed prismatic crystals or solid green river-worn pebbles.
