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Type of rock and how it forms:
Gneiss is a metamorphic rock, meaning that it was transformed from a different type of rock into Gneiss by intense heat and pressure. Often times, this heat and pressure is created in a mountain building event, or an orogeny.
The protolith, or original rock, that turns into Gneiss is often shale, a sedimentary rock.
Check out this video on how to identify gneiss!
Minerals in gneiss and variations in appearance:
Gneiss has foliation, or layering, with light and dark minerals alternating.
Gneiss often contains these minerals:
Feldspar: a silicate mineral that makes up around 50% of the Earth's crust! Feldspar usually makes up the darker layers of gneiss.
Quartz: the most abundant mineral on the Earth's surface! Quartz is usually transparent or translucent and makes up the lighter layers of gneiss.
Gneiss can contain a wide variety of minerals, including garnet, muscovite, hornblende, and biotite.
Where gneiss is found in NC:
Gneiss is found in Jackson, Mitchell, Yancey, Transylvania, Buncombe, Rutherford, Henderson, Watauga, Wake, Gaston, Lincoln, Warren, Macon, Avery, Madison, Haywood, Caldwell, and Wilkes counties.
Gneiss is durable, making it useful for infrastructure!
It is often used in:
road construction
landscaping
floor tiles
countertops
Fun facts:
Gneiss is pronounced as "nice"
Some of the oldest rocks on Earth are gneisses!
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