BGS Rock Classification Scheme

Granitic-rock, gneissose

Code	GGNR
Description	Granitic-rock, gneissose
Qualifiers	gneissose
Definition	Medium-coarse grained av. 0.25-16mm crystalloblastic metamorphic rock, >5mm irregular layers of contrasting grain size/mineralogy, preferred mineral orientation common. Granitic-rock protolith; qtz 20-60%, feld 40-80% of QAPF, feld, +/- mica/amphib.
Linked data	http://data.bgs.ac.uk/id/EarthMaterialClass/RockName/GGNR

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CAVEAT

"Thumbnail" definitions attached to some of the table entries are an interim attempt to provide simple short descriptions of the "unqualified" rock types presented within the BGS Rock Classification Scheme. Every effort has been made to ensure accuracy and consistency but minor contradictions or omissions might be present. The BGS welcomes any feedback pointing out such minor imperfections and/or providing constructive comment and suggestions for improvement of the definitions. In the first instance such feedback should be directed to Dr Tim McCormick.