metamorphic
Unakite
Epidotized Granite
Hardness: 6-7 (Mohs scale); Color: Mottled green (pistachio) and pink (salmon); Luster: Vitreous to greasy; Crystal structure: Monoclinic (Epidote) and Triclinic (Feldspar); Cleavage: Hard to distinguish in rock form; Specific gravity: 2.85 to 3.20.
- Hardness
- 6-7 (Mohs scale)
- Color
- Mottled green (pistachio) and pink (salmon)
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Mottled green (pistachio) and pink (salmon); Luster: Vitreous to greasy; Crystal structure: Monoclinic (Epidote) and Triclinic (Feldspar); Cleavage: Hard to distinguish in rock form; Specific gravity: 2.85 to 3.20.
Formation & geological history
Formed through the hydrothermal metamorphism of granite, where plagioclase feldspar is replaced by epidote. Many specimens date back to the Proterozoic era (over 1 billion years old). Common in the Blue Ridge Mountains of the USA.
Uses & applications
Predominantly used as a semi-precious gemstone for beads, cabochons, and decorative carvings. It is also used as an architectural stone for floor tiles and stairs in high-end projects.
Geological facts
It was first discovered in the Unaka Range of North Carolina, from which it takes its name. It is the state rock of Virginia. Unlike most gemstones, it is a rock composed of multiple minerals rather than a single mineral species.
Field identification & locations
Identify by its unique 'pistachio and ham' color combination. Look for pink orthoclase feldspar mixed with green epidote and clear-to-gray quartz. Often found in riverbeds as water-worn pebbles near the Appalachian Mountains.
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