This is an extrusive rock with the same general composition as granite.
Like granite, rhyolite is often rich in quartz and alkali feldspar, but glass is usually one of the major components of rhyolite. Biotite mica is usually present.

TEXTURE A fine-grained felsic volcanic rock which may have phenocrysts, giving a porphyritic texture. The matrix crystals are too small to be seen with the naked eye, and the rapid cooling of the lava causes the magmatic liquid to quench as a glass. Rhyolite may also have vesicles and amygdules.

ORIGIN These rocks erupt from volcanoes with explosive violence and are the result of the cooling of viscous lava. Such lavas may plug the volcano’s vent, causing a buildup of gaseous pressure.

Group: IGNEOUS

Origin: Extrusive

Grain size: Fine

Crystal shape: Anhedral

Classification: Felsic

Occurrence: Volcano

Color: Light