Microorganisms release metals from minerals and help in the mining of copper and gold, and now also rare earths.
For centuries, Rome's power was based on a silver and copper mine in Andalusia; it was the largest mine in the empire; 150 meter deep tunnels and sophisticated ventilation and drainage systems are testimony to this. The environment, too, was doubly ruined by the smoke from the roasting of metals from the extracted rock and the water pumped from the mine. It was a smelly and extremely acidic broth, partly blue, partly red, from the latter the nearby river and the mine received the name: “Rio Tinto”.
The blue sewer was more interesting to the Romans; its color came from copper – the red of iron – and which could also be extracted in addition to what was mined. How it got there was only clarified more than 2,000 years later by Arthur Colmer (West Virginia State University): The color or copper was provided by bacteria, especially two, Thiobacillus ferrooxidans and Th. thiooxidans (Science 106, p. 253). They gain energy by oxidizing sulfides – of iron and copper: pyrite (FeS2) and chalcopyrite (CuFeS2) – and metals are dissolved from their matrix by this and the resulting sulfuric acid (Science 106, p. 253).
This 1947 publication had a huge influence on mining, and soon low-copper deposits and tailings piles were exploited with the bacteria – it's called “bioleaching” or “bioming” – it began in 1950 near Salt Lake City and today contributes for The world's largest deposits in Chile contribute ten percent to income (Minerals 6010023).
Bacteria get real gold from fool's gold
Copper remained the pioneer, but the process is also used to extract other metals (and to desulfurize coal), producing nickel, cobelt, zinc, uranium – and gold, which is a little more complicated: it is often embedded in the gold of fool – pyrite, looks like real gold – which has to be broken, Thiobacillus is used for this again. This began in South Africa in the 1990s (Science 264, p. 778).
But first there has to be gold, and of course there has been since the Earth was formed. But on the one hand, it was not concentrated, and on the other hand, there were long environmental conditions under which it only dissolved in water. This only changed when oxygen arrived, three billion years ago, produced by cyanobacteria photosynthesis. Gold was fixed in its wakes in coastal waters by oxygen, collected in sediments, especially in South Africa, where it formed the largest deposits on the planet: bacteria We have to thank gold, at least that is how Hartwig Frimmel, a geologist at the University of Würzburg , saw him (Mineralium Deposita 50, p. 5).