It’s not exactly 24-carat, but you could say some Australian eucalyptus trees are decorated with gold leaf. Trees growing above gold deposits 40 metres under ground incorporate the precious metal into their leaves.
Studying the leaves could point the way to gold deposits in remote areas difficult to assess using conventional tools.
“The fact that these trees were able to take up gold from such depths was a big surprise for us,” says Mel Lintern of Australian science agency, the CSIRO.
In two locations in Western Australia, Lintern and his colleagues demonstrated that gold was absorbed through the plant’s vasculature, and stored in the leaves and bark in concentrations as high as 100 parts per billion.
Lab experiments showed how: some of the gold dissolves as ions in water, which is sucked up by the roots. Gold is toxic to plants, so they trap it in calcium oxalate crystals that cannot affect cell function, Lintern says.
The results show that trees can be used to find gold deposits in rugged terrain, where exploratory drilling can be difficult. Lintern says the method is so effective that some companies may already be aware of it, but have kept it quiet.