About 80% of the world’s copper-from-ore originates in Cu-Fe-S ores, such as chalcopyrite (CuFeS2) and chalcocite (Cu2S). The concentration of these minerals in an ore body is low. Typical copper ores contain from 0.5% Cu (open pit mines) to 1 or 2% Cu (underground mines). Cu-Fe-S minerals are not easily dissolved by aqueous solutions, so the vast majority of copper extraction from these minerals is pyro-metallurgy.  (Excerpt from Extractive Metallurgy of Copper)