Rhyolite




Rhyolite is a fine grained extrusive volcanic rock that contains, quartz, biotite, mica, horneblende, pyroxene, and both alkali and plagioclase feldspar. It is closely related to granite, with the main difference being that its crystal structure cannot be seen with the naked eye. It is formed when molten lavas are ejected high into the air by explosive volcanic eruptions, as well as when lava flows cool down. The density of the resulting rock varies depending on the manner of formation. Rhyolite is generally a gray to purple color, sometimes red-brown or black, and is used for a variety of construction purposes in many different parts of the world.

Color:
Very variable, from light to red-brown, to gray, or black
Origin:
Extrusive
Grain Size:
Fine
Occurence:
Worldwide