gneiss(redirected from Lewisian gneiss)
Also found in: Thesaurus, Encyclopedia.
A banded or foliated metamorphic rock, usually of the same composition as granite.
[German Gneis, probably alteration of Middle High German ganeist, spark (from its appearance), from Old High German gneista.]
gneiss′ic (nī′sĭk), gneiss′oid′ (nī′soid′), gneiss′ose′ (nī′sōs′) adj.
(Geological Science) any coarse-grained metamorphic rock that is banded and foliated: represents the last stage in the metamorphism of rocks before melting
[C18: from German Gneis, probably from Middle High German ganeist spark; related to Old Norse gneista to give off sparks]
ˈgneissic, ˈgneissoid, ˈgneissose, gneiˈssitic adj
a metamorphic rock, generally made up of bands that differ in color and composition, some bands being rich in feldspar and quartz, others rich in hornblende or mica.
[1750–60; < German Gneis, ultimately derivative of Old High German gneisto spark]
gneiss′ic, gneiss′oid, adj.
A type of metamorphic rock consisting of light-colored layers, usually of quartz and feldspar, alternating with dark-colored layers of other minerals. The layers are often folded into curves. See Table at rock.
A coarse-grained metamorphic rock with minerals in wavy layers.