Well, I don't know much about rocks, but I know this one is pretty unusual. It is quite heavy. We ran a metal detector over it but it didn't seem to register. It has a sort of rusty look in some areas. It has a sort of rude shape - sorry about that! The surface is quite bumpy. It was lodged in a rock wall of a new property I just bought here in Iowa, but of course I don't know what its original source was. I have never seen a rock like this. I have 3 photos I will post. Any help on identifying it would be much appreciated.