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Gneiss formed by metamorphism of preexisting granite. Dark minerals are mica; light-colored minerals are quartz and feldspar. The streaky nature of banding is typical of gneisses. The sample is from the Great Smoky Mountains of North Carolina.
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www.answers.com/topic/gneiss
www.answers.com/topic/gneiss
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(petrology) A gneiss formed as a result of or modified by the passage of geochemically mobile materials through or into solid rock. ... Sci-Tech Dictionary: permeation gneiss...
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www.answers.com/topic/permeation-gneiss
www.answers.com/topic/permeation-gneiss
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Gneiss is formed from pre-existing rocks that are subjected to intense directional pressure and heat, causing an alignment of their constituent minerals into parallel bands, a texture that is referred to as foliation.
http://wiki.answers.com/Q/How_is_gneiss_formed
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More on gneiss from Fact Monster: ... See more Encyclopedia articles on: Geology and Oceanography ... schist - schist schist , metamorphic rock having a foliated, or plated, structure called schistosity in ...
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www.factmonster.com/ce6/sci/A0821075.html
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Plate 4. Selected key textural relationships in the pelitic and migmatite gneiss. 5. Mutual intergrowths between cordierite (Cd) and the granitic matrix, composed by K-feldspar (K), quartz, and minor plagioclase phenocrysts.
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www-odp.tamu.edu/publications/161_SR/chap_19/p4_5.htm
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Plate 4. Selected key textural relationships in the pelitic and migmatite gneiss. 3. Rounded andalusite porphyroblasts (A) included with disharmonious fibrolitic sillimanite (S) in a large K-feldspar phenocryst (K). Sample 161-976B-101R-2, 38-41 cm. Plane-polarized light.
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www-odp.tamu.edu/publications/161_SR/chap_19/p4_3.htm
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Gneiss is a medium to coarse-grained banded rock formed as a result of high grade regional metamorphism. It is characterised by a layered appearance caused by the segregation of ferromagnesian minerals from quartzo-feldspathic minerals in discontinuous layers.
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www.kabrna.com/cpgs/rocks/metamorphic/gneiss.htm
www.kabrna.com/cpgs/rocks/metamorphic/gneiss.htm
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How Rocks & Minerals Are Formed; RocksForKids.com ... Most of the earth's crystals were formed millions of years ago. Crystals form when the liquid rock from inside the earth cool and harden. Sometimes crystals form when liquids underground find their ... Gneiss has a streaky look because of alternating layers of minerals.
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www.rocksforkids.com/RFK/howrocks.html
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How are Rocks Formed? ... Learn to read to read rocks and identify those formed by wind and water (sedimentary rocks), volcanoes (igneous rocks), and pressure (metamorphic rocks). Your neighborhood is full of secrets just waiting for you to dig up, and before you know it, you will have one gem of a collection.
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cte.jhu.edu/techacademy/fellows/brannon/webquest/Rmform...
cte.jhu.edu/techacademy/fellows/brannon/webquest/Rmform.htm
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