metamorphic
Epidote
Epidote (Ca2(Al2,Fe)(SiO4)(Si2O7)O(OH))
Hardness: 6-7 on Mohs scale. Color: Pistachio green, yellowish-green, or brownish-green. Luster: Vitreous to pearly. Crystal Structure: Monoclinic with prismatic crystals. Cleavage: Perfect in one direction.
- Hardness
- 6-7 on Mohs scale
- Color
- Pistachio green, yellowish-green, or brownish-green
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Pistachio green, yellowish-green, or brownish-green. Luster: Vitreous to pearly. Crystal Structure: Monoclinic with prismatic crystals. Cleavage: Perfect in one direction.
Formation & geological history
Formed through regional or contact metamorphism of calcium-rich rocks like basalt, gabbro, or limestone. Also found in hydrothermal veins. Typical geological age varies but often associated with Alpine metamorphic events.
Uses & applications
Used primarily as a minor gemstone, collector's specimen, and as an index mineral for geologists to identify metamorphic facies (greenschist facies).
Geological facts
The name comes from the Greek word 'epidosis', meaning 'addition', referring to one side of the prism being longer than the others. It is one of the few minerals with a distinct 'pistachio' green color that is a primary diagnostic tool.
Field identification & locations
Identify by its unique 'pistachio green' color and high hardness (it can scratch glass). Found in metamorphic belts, specifically in veins or cavities within basaltic rocks.
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