I am running a campaign where my characters need to destroy a roughly cylindrical stone, about a foot in diameter and a couple feet tall, with a hardness of 7 and 28HP (14 before it is broken). Hardness seems to act like resistance in general, but I would have thought that stone would have even greater resistance to slashing or piercing damage, than to bludgeoning damage. Is there any support for this in the rules, or has anyone just done it anyway?
I think the closest thing to support I see in the rules is the “GM’s discretion” bit here:
It doesn’t directly address slashing/piercing/bludgeoning, but does mention poison at least.
I think it’d be entirely reasonable for GM’s discretion to add resistance or even immunity to certain damage types. Material Statistics lists paper as having 1 HP, but I’m not sure hitting a piece of paper with a hammer would actually break it.