This page's about a volcanic rock. For the ghost town see Rhyolite, Nevada, and for the satellite system, see Rhyolite/Aquacade. Rhyolite's an igneous, volcanic (extrusive) rock, of felsic (silicon-rich) composition (typically >69% SiO2 — see the TAS classification). It may have any texture from aphanitic to porphyritic. The mineral assemblage's usually quartz, alkali feldspar and plagioclase (in a ratio > 1:2 — see the QAPF diagram). Biotite and hornblende are common accessory miner… (More on Rhyolite)