Rhyolite is a volcanic rock. It is fine-grained because it forms by the rapid cooling of magma, usually when it erupts onto the Earth's surface. ... Rhyolite forms from magma that contains lots of silica (quartz) and is the fine-grained equivalent of granite.

How does rhyolitic magma form?

Rhyolitic magma forms as a result of wet melting of continental crust. Rhyolites are rocks that contain water and minerals that contain water, such as biotite. ... This crystallization releases the basaltic magma's heat, causing the temperature of the continental crust to rise and melt.

Where is rhyolite found?

The silica content of rhyolite is usually between 60% to 77%. Rhyolite has the mineralogical composition of granite. Rhyolite rocks can be found in many countries including New Zealand, Germany, Iceland, India, and China, and the deposits can be found near active or extinct volcanoes.