metamorphic
Epidote (Unakite variety)
Epidosite (Metasomatic rock containing Ca2(Al,Fe)3(SiO4)3(OH))
Hardness: 6-7 Mohs; Color: Pistachio-green to olive-green mixed with salmon-pink feldspar; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 3.3 - 3.5
- Hardness
- 6-7 Mohs
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 Mohs; Color: Pistachio-green to olive-green mixed with salmon-pink feldspar; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 3.3 - 3.5
Formation & geological history
Formed through hydrothermal metasomatism where plagioclase feldspar is replaced by epidote. Generally found in metamorphic belts or altered igneous rocks. Geological age varies widely based on site, often Precambrian to Paleozoic.
Uses & applications
Commonly used for lapidary work like cabochons, beads, and animal carvings. In construction, it is occasionally used as an ornamental building stone or decorative gravel.
Geological facts
The name 'Epidote' comes from the Greek 'epidosis' meaning 'increase' or 'addition,' referring to the unequal sides of the crystal base. When combined with pink orthoclase and quartz, it is specifically called Unakite.
Field identification & locations
Identify by its distinctive 'pistachio' green color and high hardness (it will scratch glass). Commonly found in the Blue Ridge Mountains of the USA, South Africa, and Brazil. Collectors should look for vibrant, contrasting colors.
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