Hey, welcome to the forum! You'll find a lot of great people here with a lot of knowledge. I'm pretty new myself, so here's a few things you could provide that would help some of these folks figure out what you have:
1 - where did you find it?
2 - underground? out in the open?
3 - did you find it with a metal detector? if so, what did it register as? If not, do you have access to a detector so you can see if it has metal?
4 - is it magnetic?
5 - if you scratch it on the underside of the toilet cover, what color streak does it make? (if it leaves one at all).
6 - follow these instructions to find out the specific gravity - that can really help narrow it down:
7 - can you scratch it with your fingernail? if not, can you scratch it with a penny? if not, how about a pocket knife?
Get as many of those as you can and that will help us a lot.