metamorphic
Unakite (Epidote in Feldspar/Quartz)
Unakite (composed of Epidote {Ca2(Al,Fe)3(SiO4)3(OH)}, Orthoclase {KAlSi3O8}, and Quartz {SiO2})
Hardness: 6-7 (Mohs); Color: Pistachio green, pink, and gray; Luster: Vitreous to dull; Crystal structure: Monoclinic/Hexagonal components; Cleavage: Poor/none; SG: 2.85-3.2
- Hardness
- 6-7 (Mohs)
- Color
- Pistachio green, pink, and gray
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 (Mohs); Color: Pistachio green, pink, and gray; Luster: Vitreous to dull; Crystal structure: Monoclinic/Hexagonal components; Cleavage: Poor/none; SG: 2.85-3.2
Formation & geological history
Formed through the hydrothermal alteration of granite where plagioclase feldspar is replaced by epidote. Usually associated with Proterozoic orogenic belts.
Uses & applications
Commonly used for lapidary work including beads, cabochons, and small carvings. Also used as decorative stone in architecture and as a semi-precious gemstone.
Geological facts
First discovered in the Unaka Mountains of North Carolina, USA. It is unique among rocks for its distinct pistachio-green and salmon-pink color combination.
Field identification & locations
Identify by its 'Christmas-like' combination of green epidote and pink feldspar. Commonly found in riverbeds around the Blue Ridge Mountains and Lake Superior shores.
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