So how do you decide the problem knapping is the stone and not you?  Or your bopper is subpar?  And when is it just you ;-) ?  Tried last night to take another crack at doing stone and moose billet on a fresh piece of keokuk.  After 30 min of banging away I had made my salad plate piece of stone the size of maybe a baseball and it wan't meaningfully thinner than when i started...so frustrating.  Step fractures and crumbled edges everywhere...
I guess I know that the antler billets wear out but really don't know what that actually means/looks like.  Stone hammers don't wear out I guess but certainly some stones are better than others..?  And I guess the stone hammer hardness might depend on which stone you are banging on?
Last night my edges either didn't break at all or they simply crumbled... And I broke my "almost preform".... 

  Paul