Definition of gneiss in English:



  • [mass noun] A metamorphic rock with a banded or foliated structure, typically coarse-grained and consisting mainly of feldspar, quartz, and mica.

    • ‘Quarzitic gneiss, low-grade metamorphic basic rocks, phyllites and dark chert can be abundant in some layers.’
    • ‘The Borve Series is dominated by varieties of quartzo-feldspathic schist and gneiss, composed mainly of plagioclase, quartz, and biotite.’
    • ‘Corundum occurs as an accessory mineral in some metamorphic rocks, such as mica schist, gneiss, and crystalline limestone.’
    • ‘Between the Dharwas leucogranite and Kilar there is a simple planar structure of interspersed pelitic gneiss and leucogranite bands with a regional foliation dipping to the south or southeast.’
    • ‘The sample is weakly banded amphibolite-facies gneiss consisting of quartz, plagioclase, biotite and hornblende.’


Mid 18th century: from German, from Old High German gneisto spark (because of the rock's sheen).