Rhyolite is a felsic, extrusive igneous rock. It has the same chemistry & mineralogy as granite, but is very finely crystalline (aphanitic texture; crystals <1 mm in size) due to cooling of high-viscosity lava. Rhyolites are often light gray to pinkish to somewhat reddish in color. Rhyolite lavas are highly viscous (thick & slow-moving) when erupted and often appear as if they have flowed like oozing toothpaste. Sometimes the term felsite is applied to rhyolites. There does not seem to be a consistent definition of felsite, cf. rhyolite. However, felsite appears to be the broader term, applicable to all light-colored volcanic rocks.