Rhyolite

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Rhyolite
Igneous rock
RhyoliteUSGOV.jpg
Composeetion
Felsic: igneous quartz an alkali feldspar (orthoclase, sanidine an sodic plagioclase), biotite an hornblende.

Rhyolite is an igneous, volcanic rock, o felsic (silica-rich) composeetion (teepically > 69% SiO2—see the TAS classification). It mey hae ony texture frae glassy tae aphanitic tae porphyritic. The mineral assemblage is uisually quartz, alkali feldspar an plagioclase (in a ratio > 1:2—see the QAPF diagram). Biotite an hornblende are common accessory minerals.