i just got through laping a new one i got it is a natural stone uncut sides top and bottom has been flatend so i laped the topside and rounded one side , it took 5 sheets of norton 150 w/d sand paper and still had marks on hone so i got 325 dmt and 30 min. later it was flat , as far as your ark. hard it willbe around 4 to 6k , the soft will be around 1k they work well but are slow cuters,