metamorphic
Epidote (Unakite-related)
Epidote (Ca2(Al,Fe)3(SiO4)3(OH))
Hardness: 6-7 Mohs; Color: Pistachio green to yellowish-green with dark inclusions; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 3.3 - 3.5
- Hardness
- 6-7 Mohs
- Color
- Pistachio green to yellowish-green with dark inclusions
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 Mohs; Color: Pistachio green to yellowish-green with dark inclusions; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 3.3 - 3.5
Formation & geological history
Formed through regional or contact metamorphism of calcium-rich rocks like basalt or limestone. Often found as an alteration product of plagioclase feldspar. Geological age varies significantly from Precambrian to Cenozoic depending on the host rock formation.
Uses & applications
Used primarily as a decorative stone, in lapidary for cabochons and beads, and as a minor gemstone. Also used in construction as an ornamental building stone when found in larger masses like Unakite.
Geological facts
The name 'Epidote' comes from the Greek word 'epidosis', meaning 'addition', referring to the crystal's unequal sides. It is a key indicator mineral for the greenschist metamorphic facies.
Field identification & locations
Identify in the field by its distinctive 'pistachio green' color and relative hardness (it will scratch glass). Commonly found in hydrothermal veins and metamorphic terrains like the Appalachian Mountains or the Alps.
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