The Probert Encyclopaedia of Rocks & Minerals

RHYOLITE

Rhyolite is a fine grained extrusive igneous rock similar to granite. Rhyolite forms from particularly viscous molten lava and is grey, brown or reddish in colour, darkening with age. Rhyolite is essentially composed of feldspar, mica and quartz with numerous accessory minerals present.
Research Rhyolite