mineral
Epidote
Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)
AI-generated identification · may be incorrectHardness: 6-7 on Mohs scale. Color: Pistachio-green to brownish-black. Luster: Vitreous to pearly. Crystal structure: Monoclinic, often prismatic or acicular. Cleavage: Perfect in one direction. Specific gravity: 3.3-3.6.
- Hardness
- 6-7 on Mohs scale
- Color
- Pistachio-green to brownish-black
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Pistachio-green to brownish-black. Luster: Vitreous to pearly. Crystal structure: Monoclinic, often prismatic or acicular. Cleavage: Perfect in one direction. Specific gravity: 3.3-3.6.
Formation & geological history
Formed in low- to medium-grade metamorphic rocks (schists and gneisses) or through hydrothermal alteration of igneous rocks like basalt and gabbro. Most specimens are from the Phanerozoic eon, typically found in contact metamorphic zones.
Uses & applications
Predominantly used as a semi-precious gemstone (when high quality) and as a collector's mineral specimen. It has minor industrial use as an indicator mineral in mineral exploration.
Geological facts
The name comes from the Greek 'epidosis' meaning 'increase', referring to the crystal base being longer on one side. It is the defining mineral for the 'Epidote Facies' in metamorphic petrology.
Field identification & locations
Identify in the field by its characteristic 'pistachio-green' color and prismatic crystals with longitudinal striations. Common locations include Knappenwand (Austria), Alaska, and Pakistan. Collectors should look for luster and well-defined crystal terminations.
