Metamorphic
Unakite (Epidotized Granite)
Unakite; primarily composed of Epidote (Ca2(Al,Fe)3(SiO4)3(OH)), Orthoclase (KAlSi3O8), and Quartz (SiO2)
Hardness: 6-7 (Mohs scale); Color: Mottled green (epidote), pink (feldspar), and grey (quartz); Luster: Vitreous to dull; Crystal structure: Monoclinic/Triclinic mixture; Cleavage: Fragmentary; Specific gravity: 2.55 - 2.85.
- Hardness
- 6-7 (Mohs scale)
- Color
- Mottled green (epidote), pink (feldspar), and grey (quartz)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Mottled green (epidote), pink (feldspar), and grey (quartz); Luster: Vitreous to dull; Crystal structure: Monoclinic/Triclinic mixture; Cleavage: Fragmentary; Specific gravity: 2.55 - 2.85.
Formation & geological history
Formed through the hydrothermal metamorphism of granite, where plagioclase feldspar is replaced by epidote. Usually associated with Precambrian or Paleozoic geological ages in basement complexes.
Uses & applications
Commonly used as a lapidary stone for beads, cabochons, and decorative carvings. In industry, it is sometimes used as crushed stone for road construction or architectural facing.
Geological facts
It was first discovered in the Unaka Range of North Carolina, USA, from which it derives its name. It is the state rock of Virginia and is unique because it is one of the few metamorphic rocks used widely in jewelry without being a 'pure' mineral.
Field identification & locations
Identify in the field by its distinct 'pistachio green' and 'salmon pink' mottled appearance. Commonly found in river beds as pebbles (especially in the Blue Ridge Mountains) or in glacial till in the Great Lakes region. Collectors should look for balanced color distribution.
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