Scientists from Australia’s national science agency, the Commonwealth Scientific and Industrial Research Organisation (CSIRO), have proved that the leaves of certain eucalyptus trees contain minute amounts of the precious metal that have been naturally absorbed.
Eucalypts in the Kalgoorlie region of Western Australia and the Eyre Peninsula in South Australia are drawing up water containing gold particles from the earth via their roots and depositing it in their leaves and branches.
The scientists published their findings in the scientific journal Nature Communications this week.
One of the authors of the paper, the CSIRO geochemist Dr Mel Lintern, said some eucalyptus root systems dived down deeper than 30m, through much of the sediment that sits on top of solid ore-bearing rock. The tree acts “as a hydraulic pump … drawing up water containing the gold”, he said.
It is not economical to mine the gold stored in the trees. Actually, minute amounts of gold are present in lots of places but not easily retrievable. The value in this find is that the gold was not just deposited by dust in the air but brought from the sediments below meaning that they may be gold enriched. So, this is a new way to find gold prospects, by testing trees. Potentially. It remains to be seen if that will work.
Gold mining is highly destructive to the environment. All the easy to reach deposits have been exploited. Now, huge tonnages of material are excavated and processed for a small amount of gold.
Australia has extensive gold deposits:
Most gold mined in Australia today cannot be seen in the rock. It is very fine grained and mostly has a concentration of less than 5 grams in every tonne of rock mined. Primary gold deposits are formed from gold-bearing fluids at sites where the chemistry and physical characteristics permit gold deposition. Primary deposits are often modified by weathering, but secondary deposits are formed only after the complete breakdown of the host rock has occurred. Liberated gold is concentrated in alluvial (placer) deposits.
Examples of primary deposits include those mined at Kalgoorlie in the Super Pit, Granny Smith, St Ives, Norseman and Mount Magnet (WA), Gympie and Ravenswood (Qld), Callie (NT), Stawell (Vic), Cadia (NSW), Henty (Tas) and Challenger(SA). At Olympic Dam (SA) gold occurs and is mined with copper and uranium. Secondary (alluvial) deposits which sparked the rushes of the 1850s, are no longer major sources in Australia. Gold is found also as a minor component in many base metal deposits and is recovered as a by-product at some operations such as Rosebery (Tas).