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Rocks intermediate between rhyolite and dacite, containing >10% quartz and subequal amounts of plagioclase and alkali feldspar. The extrusive equivalent of granodiorite. The principal minerals, sodic plagioclase, K-feldspar, quartz, and biotite or hornblende, commonly occur as phenocrysts in a finely crystalline groundmass of feldspar and quartz. Accessory minerals are apatite and magnetite, and occasionally augite.
Classification of RhyodaciteHide
Sub-divisions of RhyodaciteHide
Mineralogy of RhyodaciteHide
Essential minerals - these are minerals that are required within the classification of this rock:
|Feldspar > Alkali Feldspar||Feldspar Group minerals rich in Potassium or Sodium.|
|Feldspar > Plagioclase||A petrological term for Albite-Anorthite Series.|
|Silica > Quartz||SiO2|
Non-essential minerals - these minerals are common, sometimes major components, but are not always present: