Science, Maths & Technology
Rhyolite
...Open University's Science courses and qualifications Rhyolite is a fine-grained extrusive igneous rock or volcanic rock. It is pale coloured, often light grey, tan or pinkish. Rhyolite is made up of quartz and feldspar crystals, and occasionally contains some mafic (dark coloured) minerals. Usually the crystals are too small to see without magnification, but occasionally...