metamorphic
Epidotite (Unakite-related)
Epidote-rich rock
Hardness: 6-7 (Mohs); Color: Pistachio green to olive green; Luster: Dull to vitreous when wet; Crystal structure: Monoclinic (fine-grained); Cleavage: Perfect in one direction, though rarely visible in pebbles; Specific gravity: 3.3-3.6
- Hardness
- 6-7 (Mohs)
- Color
- Pistachio green to olive green
- Luster
- Dull to vitreous when wet
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Physical properties
Hardness: 6-7 (Mohs); Color: Pistachio green to olive green; Luster: Dull to vitreous when wet; Crystal structure: Monoclinic (fine-grained); Cleavage: Perfect in one direction, though rarely visible in pebbles; Specific gravity: 3.3-3.6
Formation & geological history
Formed through the hydrothermal alteration of mafic igneous rocks or through regional metamorphism of calcium-rich rocks. It is common in alpine-type veins and contact metamorphic zones.
Uses & applications
Primarily used as a lapidary material for cabochons, beads, and decorative carvings. Some epidote-rich rocks are used as construction aggregate or road ballast.
Geological facts
Epidote gets its name from the Greek word 'epidosis' which means 'addition', referring to the crystal sides being longer than those at the base. It is a common indicator mineral for low-grade metamorphism.
Field identification & locations
Look for the characteristic 'pistachio' green color that distinguishes it from quartz or olivine. Often found as rounded river or beach pebbles near metamorphic terrains. It will not scratch with a pocket knife.
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