Creepy Rock -- do I want to know what it is?

[LotsaRocks]

Here's the most interesting (in my opinion) of the rocks I'm trying to identify.  I have been told that they were all collected in or around North Dakota; and the collection is "many years" old.

[bilquest]

Looks like a severed eyeball... got nuthin'

[slabbercabber]

I'd call that prairie agate.  Some years ago we filled the truck with them for the rock garden.  Left them behind when I retired.

[tetonartgallery]

need a heart transplant?

[Yukon Jade]

  Could be Fairburn agate,I think they come from that part of the country