metamorphic
Unakite
Unakite (Altered Granite consisting of Orthoclase KAlSi3O8, Epidote Ca2(Al,Fe)3(SiO4)3(OH), and Quartz SiO2)
Hardness: 6-7 on Mohs scale; Color: Mottled green and pink/salmon; Luster: Vitreous to dull; Crystal structure: Monoclinic/Hexagonal (aggregate); Cleavage: Indistinct; Specific Gravity: 2.85-3.20
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled green and pink/salmon
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Mottled green and pink/salmon; Luster: Vitreous to dull; Crystal structure: Monoclinic/Hexagonal (aggregate); Cleavage: Indistinct; Specific Gravity: 2.85-3.20
Formation & geological history
Formed through the hydrothermal metamorphic alteration of granite, where plagioclase feldspar is replaced by epdiote. Most specimens date back to the Proterozoic eon (over 1 billion years ago).
Uses & applications
Used primarily as a lapidary stone for beads, cabochons, and carvings. It is also used as an architectural stone for floor tiles, stairs, and decorative facing.
Geological facts
It was first discovered in the Unaka Range of the Blue Ridge Mountains in North Carolina and Tennessee, from which it derives its name. It is the state rock of Virginia.
Field identification & locations
Identify in the field by its distinct 'pistachio green' and 'salmon pink' mottling. It is commonly found as river stones in areas with glacial outwash or near the Appalachian Mountains. It does not react to acid.
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