metamorphic
Epidote
Epidote (Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH))
Hardness: 6-7 on Mohs scale; Color: Pistachio green to dark 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 dark green
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Pistachio green to dark green; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 3.3-3.6
Formation & geological history
Commonly formed in metamorphic rocks during low-to-medium grade regional metamorphism. It is often a hydrothermal alteration product of calcium-rich minerals such as plagioclase feldspar, pyroxene, or amphibole.
Uses & applications
Used primarily as a minor gemstone and for decorative carvings or cabochons. It is also of great interest to mineral collectors and as a geological indicator of low-grade metamorphic facies.
Geological facts
The name 'epidote' comes from the Greek word 'epidosis', meaning 'increase' or 'addition', referring to the unequal sides of the crystal prism. Its distinctive pistachio green color is unique among common minerals.
Field identification & locations
Identifiable by its signature green color (often called 'pistachio green'), its hardness, and its association with quartz and feldspar. Look for it in metamorphic terrains such as greenschists or in hydrothermally altered basalt.
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