When I visited Rio Tinto in 1952 it was still being run by the British
company of that name which had taken over the operations in 1875.
Old dumps of "waste" rock which nevertheless carried some copper
values were sprayed with water, the run-off being channelled through
a series of concrete troughs into which scrap iron was dropped. One
channel at a time was dammed off from the water flow while the
precipitated copper was dug out.
I think it was only later that it was realised that bacterial leaching was
playing a key role in the process whereby the copper from the low
grade ore passed into solution in the water.