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Gneiss - Definition and Overview |
| Related Words: Basalt, Bedrock, Breccia, Conglomerate, Crag, Granite, Lava, Limestone, Magma, Monolith, Pahoehoe, Porphyry, Regolith, Rock |
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Banded gneiss with dike of granite orthogneiss Gneiss is a common and widely distributed type of rock formed by high grade regional metamorphic processes from preexisting formations that were originally either igneous or sedimentary rocks. Gneissic rocks are coarsely laminated and largely recrystallized but do not carry large quantities of micas, chlorite or other platy minerals. Gneisses that are metamorphosed igneous rocks or their equivalent are termed granite gneisses, diorite gneisses, etc. However, depending on their composition, they may also be called garnet gneiss, biotite gneiss, albite gneiss, etc. Orthogneiss designates a gneiss derived from an igneous rock, and paragneiss is one from a sedimentary rock.
The word "gneiss" is from an old Saxon mining term that seems to have meant decayed, rotten, or possibly worthless material.
See also
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Example Usage of Gneiss |
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_TDG_: @dotdothash Gneiss |
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mr_suh: i still enjoy that geological pun: "baby, you're so Gneiss i'll never take you for granite" |
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BCcorbit: Naturally, my first thought was of banded Gneiss but now I'm thinking along the lines of something more poetic like Tachylyte. |
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