noun \ˈnīs\

Definition of GNEISS

:  a foliated metamorphic rock corresponding in composition to a feldspathic plutonic rock (as granite)
gneiss·ic \ˈnī-sik\ adjective
gneiss·oid \-ˌsid\ adjective
gneiss·ose \-ˌsōs\ adjective

Origin of GNEISS

German Gneis, alteration of Middle High German gneiste spark, from Old High German gneisto; akin to Old English fȳrgnāst spark
First Known Use: 1757

Rhymes with GNEISS


noun    (Concise Encyclopedia)

Medium- to coarse-grained metamorphic rock with parallel, somewhat irregular banding that has little tendency to split along planes. Gneiss is the principal rock over extensive metamorphic terrains. Orthogneiss is formed by the metamorphism of igneous rocks; paragneiss results from the metamorphism of original sedimentary rocks. Pencil gneiss contains rod-shaped individual minerals or segregations of minerals, and augen gneiss contains large lenticular mineral grains or mineral aggregates having the appearance of eyes scattered through the rock.


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