Rhyolite
| Igneous rock | |
 | |
| 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.