BGS Rock Classification Scheme

Gneiss, microcline-porphyroblastic

Code	GNKPG
Description	Gneiss, microcline-porphyroblastic
Qualifiers	microcline   porphyroblastic
Definition	Med-coarse-grained (av. 0.25-16mm) crystalloblastic meta rock (protolith undefined) >5mm irreg/discont layers defined by contrasting text/grainsize/mineralogy, preferred min orientation common. 5-20% large metamorphic microcline crys in finer groundmass.
Linked data	http://data.bgs.ac.uk/id/EarthMaterialClass/RockName/GNKPG

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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.