Obsidian?

Blogroll Me!
My girlfriend was digging up the dirt to plant a garden and she started finding all sorts of metal. Today she found this rock which is not metal. It has a rainbow sheen to it. I am guessing it is volcanic. I am gonna take a stab and say Rainbow Sheen Obsidian. If anyone else out there knows please write me or contact me through the comments button. Here is a link to the album with more pictures of this rock and the other metal things that have been secretly waiting under the dirt.
http://picasaweb.google.com/skymetalsmith/Obsidian?feat=directlink