During the late 1970s and new theory was put forward about the formation of gold nuggets with this theory stated that they were formed by a pair of bacterium; one of these was named Cupriavidus metallidurans and the other was named Delftia acidovorans either of which was capable of fixing gold from a solution of gold tetrachloride that is a compound that is highly toxic to ordinary bacteria.
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| Bacteria under an electron microscope NASA |
Cupriavidus metallidurans and a similar bacterium Delftia acidovorans have the ability of precipitating gold from a solution of this chemical. The gold often aggregates as a nugget that is made from their waste products. No wonder the Aztecs used to call gold the excrement of the gods.
It is a well-known fact that there are some bacterium that get their endorsement from metals the most common is the iron fixing bacteria that produce bog iron ore or form a thin film on the surface of swampy areas that looks like an oil slick, but when you touch the film it breaks up into a rectangle shaped fragments. There are some metal fixing bacterium that are being used today for remediating contaminated industrial Sites. There are specific bacterium for all the heavy metals including one for copper that is now being used to produce about 25% of the copper being mined in the world using the heap leach process.
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| The large Mojave nugget weighing 156 ounces that may have been formed by bacterial action. Photo by Chris Ralph |
There is an Australian geologist claims he is found some convincing evidence of gold fixing bacteria colonies that are in better then gold nuggets. He is further convinced that he is seeing these bacteria structures under an electron microscope that were not the result of anything he did.
A geologist with the United States Geological Survey first postulated this idea in the 1970s, but he later claimed that many of the structures he saw were from his washing the gold samples with an acid solution before he observed them under an electron microscope.
It hasn't reached the proportions of a cottage industry yet although for many years it was felt that gold feeding bacteria in rivers and streams that fixed the gold ions in the water creating gold nuggets. To our knowledge there have been no enterprising souls that are they lately to start doing this yet although if it is true there are probably more than one that is at least thinking.