Melanie, could you post the other rock, too. Also, we could gain some helpful data if you told us where you found these rocks...something like in Tempe, Arizona, in a dry river gulch. Geographically specific with some information. If we know where you found it, it will help us narrow the focus. For example, if found outside of Houghton, Michigan, this stone might be a copper mineral....Thanks and please re-post with that information.