Russian scientists made a great contribution to understanding how fine gold particles with time turned into large pieces of the yellow metal. The key factor in concentrating gold is microorganisms, which can concentrate up to several kilograms of this precious metal per year.

Researchers from the Institute of Geology and Natural Management and the Amur science centre (both institutions belong to the Russian academy of sciences) study microbes, which inhabit industrial gold-bearing placers. These microorganisms under favourable conditions are able to concentrate up to several kilograms of gold per year in their “bodies”.

Gold extraction at Far East of Russia usually takes place at shallow dipping placers, located in river valleys. Gold, found in these valleys, is finely grained – particles have 0.25-0.0005 millimeters in diameter. Such dust is very hard to extract, that is why heaps of placer gold are lost during exploration and mining at gold deposits of this type. However, several years are enough for gold dust to coarsen and to become available for further extraction.

Now we know that microorganisms are responsible for the process of gold accumulation and crystallization in gold placers, but how active are they? Scientists from Russian Far East have given evaluation for microbial gold concentration in Upper Amur region, where placers have stayed intact since 1965. Researchers have isolated from rock samples over 1500 microbial strains, which appeared to be perfectly adapted to extreme environmental conditions and could concentrate gold. The ability to accumulate gold was shown for 80% of microorganisms, isolated from samples of industrial placers. Most active gold “accumulators” were found among bacteria of Bacillus and Micrococcus genera, as well as fungi of Penicillum genus. Model experiments showed that gold in colloid form almost fully precipitated on microbial biomass within 5-10 minutes.

 

 

As for ore deposits, researchers have also detected microbes, able to absorb colloid gold on their cells, however, only 30% of total microbial population of mentioned habitats showed this wonderful ability, and it took gold much longer to precipitate – 18-20 hours.

The majority of golden ore deposits and gold placers of Russian Federation are located within permafrost zone of northern and central taiga of Siberia and Far East. Climatic conditions of these regions are favourable for intensive microbial proliferation only for 3-4 months every year – in spring and early autumn, when melt waters or heavy rainfalls saturate soil with oxygen and dissolved organic compounds. When the weather is warm and damp throughout the year, microorganisms concentrate from several hundred grams up to several kilograms of gold per one hectare, depending of initial concentration of this precious metal in soil. In other words, it takes tiny creatures several yeas to turn gold dust into gold ingots in placers.

Source: Science News

Kizilova Anna