It is half a turquoise bead, that was in the same area!
I believe this slab was used more for it's abrasive properties. I found the pieces amongst a high bank deposit of alluvium river rocks, I believe it was being used to shape certain stones into cleats or axe heads? The type of rock this grinding slab is did not come from the area I found it. It is a form sedimentary stone, whereas the geology all around the area I did find it is all platonic granite mountains. The upper Arkansas River valley was visited by tribes that would come there from many regions from the North, South, East and West to hunt, fish and gather Pinõn nuts in the summer months. I myself was a gatherer of pinõn nuts during the years the trees would produce them.
