- 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.
Origin of gneiss
Examples from the Web for gneiss
Everywhere granite, gneiss, or other primitive rocks, show themselves.The Young Voyageurs
Here and there are mixtures of schist, gneiss, and porphyry.The Rocky Mountain Wonderland
Enos A. Mills
The southern parts of this range of mountains are composed of gneiss and granite.The Central Eskimo
My ground was on the gneiss side of the geological division.
Come,” I said, “let us go back till we find the joining of the gneiss and granite.
- any coarse-grained metamorphic rock that is banded and foliated: represents the last stage in the metamorphism of rocks before melting
Word Origin and History for gneiss
1757, from German Gneiss "type of metamorphic rock," probably from Middle High German gneist "spark" (so called because the rock glitters), from Old High German gneisto "spark" (cf. Old English gnast "spark," Old Norse gneisti).
- A highly foliated, coarse-grained metamorphic rock consisting of light-colored layers, usually of quartz and feldspar, alternating with dark-colored layers of other minerals, usually hornblende and biotite. Individual grains are often visible between layers. Gneiss forms as the result of the regional metamorphism of igneous, sedimentary, or other metamorphic rocks.