2. brass—that is, copper; for brass is a mixed metal of copper and zinc, of modern invention. Iron is less easily discovered, and wrought, than copper; therefore copper was in common use long before iron. Copper-stone is called "cadmium" by Pliny [Natural History, 34:1; 36:21]. Iron is fitly said to be taken out of the "earth" (dust), for ore looks like mere earth.