From what I have been told, that is crude oil impregnated shale. I have also heard it called black Buffalo River. I don't know what the real name is. It can be knapped raw, if you heat it, it has a tendancy to blow up. The grey rip rap that gets put for erosion control has bands of that in it. I watched Claude make 6" Lost Lake out of a chunk that he got off some riprap at Moundville about 5 years ago. It is very bad about frost cracking. The diesel smell goes away after about ten minutes or so. Bill