metamorphic
Epidote with Feldspar/Quartz (Unakite-like)
Epidotized Granite (Ca2(Al,Fe)3(SiO4)3(OH) + KAlSi3O8)
Hardness: 6-7 on Mohs scale. Color: Mottled pistachio green (epidote), pink to orange-brown (orthoclase feldspar), and gray (quartz). Luster: Vitreous to dull. Crystal structure: Monoclinic (epidote). Cleavage: Perfect in one direction (feldspar), non-existent (quartz). Specific gravity: 2.85-3.20.
- Hardness
- 6-7 on Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Mottled pistachio green (epidote), pink to orange-brown (orthoclase feldspar), and gray (quartz). Luster: Vitreous to dull. Crystal structure: Monoclinic (epidote). Cleavage: Perfect in one direction (feldspar), non-existent (quartz). Specific gravity: 2.85-3.20.
Formation & geological history
Formed through the hydrothermal metamorphism of granite, where plagioclase feldspar is replaced by green epidote. This process, known as epidotization, typically occurs in tectonic mountain-building zones during the Proterozoic to Paleozoic eras.
Uses & applications
Commonly used as a lapidary material for cabochons, beads, and carvings. Also used as decorative architectural stone, floor tiles, and as a lower-tier gemstone for collectors due to its unique patterns.
Geological facts
Unakite takes its name from the Unaka Range of North Carolina, where it was first discovered. While it looks like a simple rock, it is unique because the presence of epidote indicates high-pressure, low-temperature metamorphic conditions within granite batholiths.
Field identification & locations
Identified in the field by its distinct 'Christmas color' combination of green and pink. Found commonly in riverbeds where mountain runoff carries eroded granite. Major locations include the Blue Ridge Mountains (USA), South Africa, Sierra Leone, and Brazil.
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