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Unakite is an metamorphic rock that is altered granite composed of pink orthoclase feldspar, green epidote, and generally colorless quartz.
R. V. Dietrich ''Gemrocks: Unakite''Unakite on Geology.com
Granite Gemstones {{petrology-stub
Unakite is an metamorphic rock that is altered granite composed of pink orthoclase feldspar, green epidote, and generally colorless quartz.
Discovery
It was first found in the United States in the Unaka mountain range of North Carolina from which it gets its name. Unakite exists in various shades of green and pink and is usually mottled in appearance.Use
A good quality unakite is considered a semiprecious stone; it will take a good polish and is often used in jewelry as beads or cabochons and other lapidary work such as eggs, spheres and animal carvings. It is also referred to as epidotized or epidote granite.Structure
In some of the Blue Ridge occurrences, an epidotizedaugen
Augen (from German "eyes") are large, lenticular eye-shaped mineral grains or mineral aggregates visible in some foliated metamorphic rocks. In cross section they have the shape of an eye.
Feldspar, quartz, and garnet are common minerals whic ...
gneiss is present exhibiting foliation structures.
The dominant green epidote in unakite rocks is the metasomatic alteration product of plagioclase feldspar, while the orthoclase and quartz crystals remain unaffected.
Distribution
Unakite can be found as pebbles and cobbles fromglacial drift
In geology, drift is a name for all sediment (clay, silt, sand, gravel, boulders) transported by a glacier and deposited directly by or from the ice, or by glacial meltwater. Drift is often subdivided into (unsorted and) unstratified drift (glaci ...
in the beach rock on the shores of Lake Superior. It also occurs in Virginia where it is found in the river valleys after having been washed down from the Blue Ridge Mountains. Unakite is not limited to the United States, and has also been reported in South Africa, Sierra Leone, Brazil, China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
and Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
Some material labeled ''unakite'' lacks the feldspar and is more properly called epidosite, and is also used as beads and cabochons.
References
R. V. Dietrich ''Gemrocks: Unakite''
Granite Gemstones {{petrology-stub