A metamorphic rock with a banded or foliated structure, typically coarse-grained and consisting mainly of feldspar, quartz, and mica.‘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 Borve Series is dominated by varieties of quartzo-feldspathic schist and gneiss, composed mainly of plagioclase, quartz, and biotite.’
- ‘The sample is weakly banded amphibolite-facies gneiss consisting of quartz, plagioclase, biotite and hornblende.’
- ‘Quarzitic gneiss, low-grade metamorphic basic rocks, phyllites and dark chert can be abundant in some layers.’
Mid 18th century from German, from Old High German gneisto ‘spark’ (because of the rock's sheen).
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