gneiss
/nʌɪs
/noun [mass noun]
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.
Derivatives
gneissic
- Scattered throughout the Pena Negra migmatites there are small bodies of Upper Proterozoic gneissic granodiorite and granite.
- The Cenozoic melanges, widely distributed in central and eastern Sabah, exclusively contain mixed mafic-ultramafic, chert, and Cenozoic sandstone blocks, and lack any granitic, gneissic, or otherwise ‘continental’ clasts.
- The tonalite is gneissic, banded on a decimetre scale, and loaded with discrete mafic enclaves, metasedimentary xenoliths and garnet, feldspar and rutile xenocrysts, such that the body has a migmatitic appearance.
gneissose
- A large pebble with a gneissose appearance is a retrograded orthogneiss, consisting of quartz, plagioclase, feldspar and muscovite, with relics of biotite, mostly chloritized, and a weakly folded tectonic foliation.
- The generally gneissose, NW-trending margin of the Mpuluzi batholith of the western domain shows a characteristic swing to more easterly trends at and close to the termination of the Welverdiend shear zone.
- The base of the Grampian Group beneath the oldest lithostratigraphical unit (Glen Shirra Subgroup) is nowhere exposed and its relationship to gneissose metasedimentary rocks that may constitute basement is unknown.
gneissoid
Origin
Mid 18th century: from German, from Old High German gneisto 'spark' (because of the rock's sheen).
Rhymes
- phenoxide
- phenoxy
- phenoxyacetic
- phenoxymethylpenicillin
- phentermine
- phentolamine
- phenyl
- phenylacetamide
- phenylacetate
- phenylacetic
- phenylacetylene
- phenylalanine
- phenylamide
- phenylamine
- phenylarsonic
- phenyl blue
- phenylbutazone
- phenylene
- phenylene blue
- phenylene brown
- phenylenediamine
- phenylephrine
- phenyl ether
- phenylethylamine
- phenylglycol