metamorphic
Epidosite
Epidosite (composed mainly of Epidote - {Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH))
Hardness: 6-7 Mohs; Color: Pistachio green to olive green; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Specific Gravity: 3.3-3.6
- Hardness
- 6-7 Mohs
- Color
- Pistachio green to olive green
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 Mohs; Color: Pistachio green to olive green; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Specific Gravity: 3.3-3.6
Formation & geological history
Formed through hydrothermal alteration of mafic volcanic rocks (metasomatism) where calcium-rich fluids replace original plagioclase and pyroxene. Commonly associated with regional metamorphism.
Uses & applications
Primarily used as a lapidary material for cabochons or decorative carvings; also studied by geologists to understand hydrothermal fluid flow in the crust.
Geological facts
Epidosite is the state rock of some specific geological regions and is often found in ophiolite complexes representing ancient seafloors. Its distinctive 'pistachio' color is caused by the inclusion of iron in its crystal structure.
Field identification & locations
Identify by its characteristic yellowish-green color and high hardness (cannot be scratched by a steel knife). Commonly found in riverbeds or coastal areas near metamorphic belts, particularly in California, the Appalachian mountains, and the Alps.
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