- Morton Gneiss
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The Morton Gneiss is an Archean-age migmatitic gneiss found in southwestern Minnesota. It has been dated to 3.6 billion years ago, making it one of the oldest rock units on the planet. It is believed to have originally been a granite before it was metamorphosed.
Its type locality is in Morton, Minnesota.
It is also known as "Rainbow Gneiss", and is quarried as a facing stone for buildings.
References
Gneiss, Minnesota Geological Survey, University of Minnesota.
Categories:- Geology of Minnesota
- United States geology stubs
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