Rhyolite is an igneous rock in the class designated as  felsic  rock. This class of rock crystallizes from silicate minerals at relatively low temperatures and with relatively a high percentage of silica.It is at the low temperature extreme of the Bowen reaction series.hyolite is much less common than granite, but there are large lava flows and deposits of rhyolite in Yellowstone Park, Wyoming, USA. These rhyolite formations are along the Snake River in Hell's Canyon on the Idaho-Oregon border.