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.
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- gneissic, adjective
- gneiss , nice
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
How to use gneiss in a sentence
gneiss is a similar mixture, but characterised by the predominance of mica, and by its banded structure.Elements of Agricultural Chemistry | Thomas Anderson
A course gneiss is the predominant rock, but is associated with garnetiferous mica-schists and much intrusive granite.
The former—mostly gneiss—is far more rugged and interesting, and there is infinitely more of the latter.Mount Everest the Reconnaissance, 1921 | Charles Kenneth Howard-Bury
The tertiary formation is followed by an azoic formation of gneiss, mica slate, and phylada with large intrusions of granite.Guatemala, the country of the future | Charles M. Pepper
Hannam operated the forge, and picks and drills were sent along for pointing; an outcrop of gneiss serving as an anvil.The Home of the Blizzard | Douglas Mawson
British Dictionary definitions for gneiss
any coarse-grained metamorphic rock that is banded and foliated: represents the last stage in the metamorphism of rocks before melting
- gneissic, gneissoid or gneissose, adjective
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Scientific definitions for gneiss
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.
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