What Kind of Rock Is This?
ES0610  Igneous Rock: Obsidian
Matthew Nyman, TERC
Does your rock have a glassy texture, sharp edges, and curved fractured surfaces? If yes, your rock is obsidian. Obsidian can appear black, red, or greenish.

If you have identified your sample, return to the beginning of the rock identification key, select another rock sample, and begin the process over again.

If your rock sample does not have any of the features described on this page, reexamine the rock with a hand lens or magnifying glass. Look at the sample from all angles. Concentrate on fresh surfaces where you might be able to better determine the texture. Return to the beginning of the rock identification key and start over again.