metamorphic
Unakite
Epidotized Granite (SiO2 with Ca2(Al,Fe)3(SiO4)3(OH) and KAlSi3O8)
Hardness: 6-7 (Mohs scale); Color: Mottled green, pink, and gray; Luster: Vitreous to dull; Crystal Structure: Monoclinic/Triclinic mixture; Cleavage: None/Irregular; Specific Gravity: 2.85-3.20.
- Hardness
- 6-7 (Mohs scale)
- Color
- Mottled green, pink, and gray
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Mottled green, pink, and gray; Luster: Vitreous to dull; Crystal Structure: Monoclinic/Triclinic mixture; Cleavage: None/Irregular; Specific Gravity: 2.85-3.20.
Formation & geological history
Formed through the hydrothermal metamorphism of granite, where plagioclase feldspar is replaced by epidote. It is often found as river pebbles or in large outcroppings in ancient mountain ranges (Precambrian to Paleozoic).
Uses & applications
Primarily used as a lapidary stone for beads, cabochons, and decorative carvings. It is also used in construction as crushed stone or architectural facing.
Geological facts
It was first discovered in the Unaka Range of the Blue Ridge Mountains in the United States, which is where it gets its name. It is the state rock of Virginia.
Field identification & locations
Identify in the field by its distinct 'pistachio' green and 'salmon' pink mottled appearance. Commonly found in the Blue Ridge Mountains (USA), South Africa, Sierra Leone, and Brazil. Collectors look for high contrast between the green epidote and pink orthoclase.
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