Note that this is for copper, not metals in general. Iron ores are oxide ores, not sulfide ores, so they would not be as subject to this issue.
The world produces about 100x more iron than copper each year.
The world produces about 100x more iron than copper each year.
The sulfide tailings of some mining regions, as in Spain, may in the future become exploited as sources of sulfur. Today most sulfur comes from desulfurization of oil and natural gas, but in a post-fossil fuel age that source will not be available, so the large amounts of pyrite in these tailings could be exploited instead.