TSK · Numbers 31:22

Zillah also gave birth to Tubal Cain, the forger of every cutting instrument of brass and iron. Tubal Cain's sister was Naamah.

But all the silver, and gold, and vessels of brass and iron, are holy to Yahweh. They shall come into Yahweh's treasury."

Iron is taken out of the earth, and copper is smelted out of the ore.