You do have a point. How hard is this stone? Mine, the one I was saying it looks like this one, is the hardest stone I have ever seen. The back side of the stone was rough, and it looked more like this one, not like big broken pieces of flake. I can't remember it clearly, with their black glue etc, but that's the impression I have. And, on this one, you can see the flakes near the corners.