metamorphic
Epidote in Matrix (Unakite-related)
Epidosite (Ca2(Al,Fe)3(SiO4)3(OH))
Hardness: 6-7 Mohs; Color: Pistachio-green to yellowish-green with dark matrix; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction.
- Hardness
- 6-7 Mohs
- Color
- Pistachio-green to yellowish-green with dark matrix
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 Mohs; Color: Pistachio-green to yellowish-green with dark matrix; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction.
Formation & geological history
Formed through hydrothermal metamorphism where plagioclase feldspar is altered by fluids into epidote. This commonly occurs in basaltic rocks or granite settings during low-to-medium grade metamorphism.
Uses & applications
Used primarily as decorative stone, for lapidary work (cabochons, beads), and as an ornamental architectural stone. It is highly valued by rock collectors for its unique green hue.
Geological facts
Epidote is a key component of Unakite, the state rock of Virginia. Its name comes from the Greek word 'epidosis', meaning 'addition', referring to its crystal geometry.
Field identification & locations
Identify in the field by its distinct 'pistachio' green color and high hardness (it will scratch glass). Often found in glacial till, stream beds, or near metamorphic contact zones.
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