Quote Originally Posted by mainaman View Post
A stone that is good for planes is not hard enough for razors.
It is more correct to say that the very hardest stones, which are still good for razors, are not good for planes because of the "Ji wo Hiku" phenomenon. However, there are plenty of stones that are hard enough for razors that don't cause "Ji wo Hiku", so there are plenty of stones that are good for planes that are also good for razors. In addition, simply seeing the plane on the stone doesn't really tell us anything about that stone.