This is the offering which you shall take from them: gold, silver, brass,
Referenced Verses
Deut 8:9 : 9 a land in which you shall eat bread without scarceness, you shall not lack anything in it; a land whose stones are iron, and out of whose hills you may dig copper.
Job 28:2 : 2 Iron is taken out of the earth, and copper is smelted out of the ore.