metamorphic
Epidote
Epidote (Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH))
Hardness: 6-7 on Mohs scale; Color: Pistachio-green to olive; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect on {001}; Specific gravity: 3.3 to 3.5
- Hardness
- 6-7 on Mohs scale
- Color
- Pistachio-green to olive
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Pistachio-green to olive; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect on {001}; Specific gravity: 3.3 to 3.5
Formation & geological history
Formed through low-to-medium grade regional metamorphism of calcium-rich rocks like basalt, or through hydrothermal alteration. Commonly found in schists and contact metamorphic zones.
Uses & applications
Primarily used as a minor gemstone, for ornamental lapidary work (tumbled stones), and as a mineral specimen for collectors. It has no major industrial uses.
Geological facts
Epidote gets its name from the Greek word 'epidosis' which means 'addition', referring to its characteristic crystal geometry where one side of the prism is longer than the other. It is the defining mineral of the 'epidote facies' in metamorphic petrology.
Field identification & locations
Identify by its unique 'pistachio' green color and hardness. It is often found associated with quartz, feldspar, and chlorite in metamorphic terrains. Common in the Alps, Alaska, and Norway.
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