metamorphic
Epidote in Quartz
Epidote (Ca2(Al,Fe)3(SiO4)3(OH)) in Milky Quartz (SiO2)
Hardness: 6-7 (epidote) and 7 (quartz); Color: Pistachio-green to dark brownish-green center with white/opaque outer layer; Luster: Vitreous to greasy; Crystal Structure: Monoclinic and Hexagonal; Cleavage: Perfect in one direction for epidote.
- Hardness
- 6-7 (epidote) and 7 (quartz)
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 6-7 (epidote) and 7 (quartz); Color: Pistachio-green to dark brownish-green center with white/opaque outer layer; Luster: Vitreous to greasy; Crystal Structure: Monoclinic and Hexagonal; Cleavage: Perfect in one direction for epidote.
Formation & geological history
Formed through regional metamorphism of igneous rocks or hydrothermal alteration. Epidote typically crystallizes in alpine-type veins or as a secondary mineral in basaltic rocks during the low-grade metamorphism of basalt or gabbro.
Uses & applications
Used primarily as collector specimens and in jewelry as cabochons or tumbled stones. High-quality epidote is faceted for gemstones, while quartz has wide industrial uses in electronics and abrasives.
Geological facts
Epidote is named from the Greek word 'epidosis' which means 'addition' because one side of the prism is longer than the other. It is often found in the company of minerals like actinolite and chlorite.
Field identification & locations
Identify by its distinctive 'pistachio' green color against the white quartz matrix. Found commonly in metamorphic terrains globally, including the Alps, Norway, and the United States (California/Colorado). Look for the green coloration and vitreous luster when broken.
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