Rhyolite is an igneous rock which comes in the class of felsic rocks. Rhyolite forms of the lava with high silica content so the lava is very viscous. If rhyolitic magma is rich in gases, it can erupt explosively which will solidify quickly forming pumice. Certain times extremely porous rhyolite lava flows occur and such flow allow degassing and subsequent collapse of lava which forms obsidian.
Rhyolite has composition similar to that of granite but with much smaller grains. It is composed of light colour silicates. Generally composition is quartz and plagioclase with less amount of orthoclase, biotite, amphibole, pyroxene and glass.
Colour and texture
Colour of rhyolite is light grey and the texture of it is aphanitic.