Large Chunks Of Sharp, Glassy Rocks!
Map data: 2013 Google, 2013 DigitalGlobe
Location of Obsidian Field
southern tip of Salton Sea, CA.
Black, Volcanic Glass
Obsidian is produced when magma cools very suddenly so that there is no time for mineral crystals to form. The resulting rock has a structure similar to glass. In ancient and modern times obsidian has been honed into ultra-sharp arrowheads, knives, and cutting tools, so be careful when handling the stuff!