lesslemming you are right about there is alot to consider when it come to stones when i think of hardness i try to keep it simple and think of density most of the time but not all of the time the harder the stone the slower it cuts but hardness has nothing to do with speed of cutting its what the stone is made of the "cutting agent" (and speaking of only natural stones because synthetic's are a different animal) take the ark stones their made of microcrystalline quartz once you start honing on the stone the quartz wears down flat it doesnt break apart it gets smooth and flat jnats are the completely different you could have two jnats from the same mine same hardness one having su and one w/o the one with su will cut faster like you said its alot to think about