BGS Rock Classification Scheme

Basalt, porphyritic

Code	PHBA
Description	Basalt, porphyritic
Qualifiers	porphyritic
Definition	Fine-grained, av. <0.25mm porphyritic textured extrusive/intrusive normal crystalline rock; TAS SiO2 45-52wt%, Na2O+K2O <5wt%, phenocryst type not defined
Linked data	http://data.bgs.ac.uk/id/EarthMaterialClass/RockName/PHBA

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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.