BGS Rock Classification Scheme

Dacite, lava, porphyritic

Code	DALVP
Description	Dacite, lava, porphyritic
Qualifiers	porphyritic   lava
Definition	Fine-grained, av.<0.25mm normal crystalline extrusive/intrusive rock; quartz 20-60% of QAPF, feldspar >65% plag, TAS SiO2 63-77wt%, Na2O+K2O <8wt%. Extruded in molten state & solidified. Contains undefined phenocrysts, larger crystals in finer matrix.
Linked data	http://data.bgs.ac.uk/id/EarthMaterialClass/RockName/DALVP

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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.