What is this?

My in-laws have had this for a door stop and they say it came from the civil war. Can anyone ID this thing and tell me something about it? Is it even an ordnance piece?
s348.photobucket.com/albums/q331 … on%20Shot/

That does not appear to be anything related to Civil War ordnance, or anything else military. No idea what is is, but pretty certain about what it is NOT.

I can say, without hestitation, one of the finest blivits I have ever seen. An excellent example of doorstoppery.

That’s a MK I Blivit.

Is it cast iron, stone, concrete?

Cast iron and heavy! OK so what’s a “blivit”? OK went to Google and I get it now, ;-) well it has to be something, maybe not something that went boom, but it’s gotta be something. It was cast in this shape for some reason. Thanks for the input so far!