metamorphic
Epidosite
Epidosite (Metasomatic calcium-aluminum silicate rock)
Hardness: 6-7 (Mohs scale); Color: Pistachio-green to yellowish-green with gray or white quartz zones; Luster: Vitreous to dull; Crystal structure: Monoclinic (epidote component); Cleavage: Perfect (one direction in epidote grains); Specific gravity: 3.2-3.5
- Hardness
- 6-7 (Mohs scale)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Pistachio-green to yellowish-green with gray or white quartz zones; Luster: Vitreous to dull; Crystal structure: Monoclinic (epidote component); Cleavage: Perfect (one direction in epidote grains); Specific gravity: 3.2-3.5
Formation & geological history
Formed through hydrothermal alteration (metasomatism) of mafic igneous rocks like basalt. It occurs in subduction zones and ophiolite complexes where hot calcium-rich fluids replace original feldspars and pyroxenes.
Uses & applications
Used primarily as decorative stone, lapidary material for cabochons, and as a geological indicator for mineralized zones including copper and gold deposits.
Geological facts
Epidosite is a key component of the deep 'sheeted dike' complexes found in the ocean floor. The distinctive pistachio green color is caused by the presence of iron (Fe3+) in the epidote mineral structure.
Field identification & locations
Identify in the field by its characteristic 'pistachio' green color combined with hard, granular quartz. Frequently found in creek beds within mountainous, formerly volcanic regions or along tectonic plate boundaries.
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