Copper Lumps.
 

are these things ever used in crafting anything or are they meant to be used as npc food? btw, i have stone and scroll craft.

Copper lumps are only good for selling to the NPCs. Thats how all lumps are, indcluding gold and silver lumps. Just NPC them. People who sell them in shops are just trying to earn more than there worth, so dont buy them in player shops either. THey are not used in any production skill