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2013-10-23 10:17:38
By Rebecca Morelle Science reporter, BBC World Service
Money might not grow on trees, but scientists have confirmed that gold is found in the leaves of some plants.
Researchers from Australia say that the presence of the particles in a eucalyptus tree's foliage indicates that deposits are buried many metres below.
They believe that the discovery offers a new way to locate the sought-after metal in difficult-to-reach locations.
The research is published in the journal Nature Communications.
Dr Mel Lintern, a geochemist from Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO), said: "We've found a lot of the easy deposits in Australia and elsewhere in the world as well.
"Now we are trying to tackle finding these more difficult ones that are buried beneath tens of metres of river sediments and sand dunes.
"And the trees are providing us with a method to be able to do this."
Buried treasure
Gold particles have been found around the soils of eucalyptus trees, but the researchers confirmed that the plants were taking in the element.
Using the Australian synchrotron - a vast machine that uses X-rays to probe matter in remarkable detail - they found traces of gold in the leaves, twigs and bark of some trees.
The amounts of the precious metal were tiny.
Eucalyptus tree The trees were taking in the gold particles as they drew in water from deep within the soil
"We've done a calculation, and found that we need 500 trees growing over a gold deposit to have enough gold in the trees themselves to make a gold ring," said Dr Lintern.
However, the presence of the particles pointed to greater riches buried more than 30m (100ft) below.
Dr Lintern said: "We believe that the trees are acting like a hydraulic pump. They are bringing life-giving water from their roots, and in so doing, they are taking smaller dissolved gold particles up through the vascular system into the foliage."
Currently, the metal is found in outcrops, where the ore appears at the surface, or it is detected through exploratory drilling.
But the researchers said that analysing vegetation could offer a better method to find untapped gold deposits.
Dr Lintern said: "Not only do we believe it is a way of stretching the exploration dollar further, because exploring for these deposits can be quite expensive, it also minimises the damage to the environment because we are taking a very small sample from the trees themselves, as well as the leaves and twigs on the ground."
The researchers said the technique could also be used to find other minerals such as iron, copper and lead in other parts of the world.