I’m not sure of heart of diamond can be found in loot chests, but as far as I know you must kill stonelings
I think it would be a good idea for there to be an alternate way to get HoDs without killing the cute little guys, not because they’re cute, but because some players like to roleplay as having a code of ethics when they play, and while saying goodbye to pickarangs is a valid sacrifice for their play style, it’s such a cool item that it’s a shame they couldn’t utilize it 😃
I would recommend perhaps a crafting recipe (expensive, to suggest that there is an easy way and a nice way) and/or a loot table in dungeon chests.
Fishing loot is another option but as it still involves killing it may not serve everyone’s needs.