I appreciate all of your comments and input. And yes, the rock has an outer layer of sorts, there are a couple spots where the outer layer is missing. There are cracks all around the whole rock that seem to be that outer layer that is cracked. Two geology professors at a local college said they really didn't know what it is. One of them said it was extremely dense and heavy... my Mom said she thought she said something that sounded like "barium". As a kid I wondered if it was a geode... but they aren't shaped like that. Because of the way it looked, I also wondered if it started out as something more like a liquid or melted form and then hardened. (But how would something be loose inside of it if that was the case?) The shape of it always intrigued me.... But I'm someone who is clueless about rock formation. Merely a guess on my part. (I used to joke that maybe it was a prehistoric cow paddy that petrified) LOL
The college said if they got it x-rayed, maybe it would reveal what was inside. I don't think that my parents would be wanting to cut into it.