How Is Obsidian Formed In The Rock Cycle?

How Is Obsidian Formed In The Rock Cycle? obsidian, igneous rock occurring as a natural glass formed by the rapid cooling of viscous lava from volcanoes. Obsidian is extremely rich in silica (about 65 to 80 percent), is low in water, and has a chemical composition similar to rhyolite. How is obsidian formed simple? Obsidian