Glass Buttes Fire Pit Obsidian

Glass Buttes Fire Pit Obsidian Slab

Glass Buttes are a group of volcanic mountains consisting of two prominent peaks and several smaller hills. They are located in the remote northeast corner of the Lake County between Bend and Burns in central Oregon, United States.  The buttes are an important landmark in an area once known as the Oregon’s Great Sandy Desert. They are named for the numerous large deposits of obsidian found on their slopes. Today, most of the mountains and surrounding land are administered by the Bureau of Land Management. The mountains offer a number of recreational opportunities including rock collecting, hiking, camping, and hunting.

Obsidian is an extrusive igneous rock which is formed naturally when felsic lava is extruded from a volcano and cools rapidly with minimal crystal growth. It is commonly found within the margins of rhyolitic lava flows known as obsidian flows, where the high silica content causes a high viscosity and is rapidly cooled.  This process forms a natural glass from the lava. The inhibition of atomic diffusion through this highly viscous lava explains the lack of crystal growth. Obsidian is hard, brittle, and amorphous and fractures with very sharp edges. In the past it was used to manufacture cutting and piercing tools and it has been used experimentally as surgical scalpel blades.