gneiss

[ nahys ]

noun

1. 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.

gneiss

/ naɪs /

noun

1. any coarse-grained metamorphic rock that is banded and foliated: represents the last stage in the metamorphism of rocks before melting

gneiss

/ nīs /

1. 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.

Derived Forms

• ˈgneissic, adjective

Other Words From

• gneissic adjective

Word History and Origins

Origin of gneiss¹

Borrowed into English from German around 1750–60

Word History and Origins

Origin of gneiss¹

C18: from German Gneis, probably from Middle High German ganeist spark; related to Old Norse gneista to give off sparks

Example Sentences

Gneiss is a similar mixture, but characterised by the predominance of mica, and by its banded structure.

From Project Gutenberg

A course gneiss is the predominant rock, but is associated with garnetiferous mica-schists and much intrusive granite.

From Project Gutenberg

The former—mostly gneiss—is far more rugged and interesting, and there is infinitely more of the latter.

From Project Gutenberg

The tertiary formation is followed by an azoic formation of gneiss, mica slate, and phylada with large intrusions of granite.

From Project Gutenberg

Hannam operated the forge, and picks and drills were sent along for pointing; an outcrop of gneiss serving as an anvil.

From Project Gutenberg