My best thought is a very large concretion originally made from several types of materials, that's why the softer materials have already weathered away.
Yes. It's stone. A little rusty looking but not iron. Looks perhaps it's spent some time in running water and softer minerals have eroded away. I'm tempted to try and cut it in half but won't.
my two cents... maybe sedimentary from an environment like a river or a beach where depending on conditions sand or mud were deposited which became sandstone and shale, the sandstone is weathering faster than the shale.
I can't imagine it being native to the area I found it. There's absolutely nothing that resembles it at all. My guess there's a story to this thing that I wish I knew.
Other than being a cool looking rock of some sort( everyone has great ideas). I'm gonna call it a flux capacitor out of the back to the Future delorian. Thanks everyone.