Heres my code and thanks in advance:
del(/obj/mining/Copper)
del(/obj/mining/Tin)
Same reason your other code didn't work: These are type paths, not actual atoms in your contents. What you need is to del(locate(/obj/mining/Copper) in usr), and so on.
Same reason your other code didn't work: These are type paths, not actual atoms in your contents. What you need is to del(locate(/obj/mining/Copper) in usr), and so on.
Lummox JR