Obsidian

Part of Hall of Planet Earth.

Obsidian AMNH/R.Mickens

Obsidian is a volcanic glass, a comparatively rare and crystal-poor form of rhyolite, the most silica-rich lava. It forms when lava is quenches, or rapidly cooled. Obsidian is a major component of Glass Mountain.

Provided by Jeff Dinnel, Tionesta, California