Money may not grow on trees but researchers have found that the next best thing does. Gold.
Giving gold leaf a more literal meaning, CSIRO scientists have established that Eucalyptus trees draw up gold particles from deep in the soil via water absorbed by their root system.
The gold, likely toxic to the plant, is deposited in leaves and bark before being shed as a way of getting rid of the unwanted element.
"If you had five hundred eucalypt trees growing over a gold deposit, they would only have enough gold in there to make a wedding ring": Dr Mel Lintern, CSIRO Geochemist. Photo: Wayne Taylor
However the findings, published in the journal Nature Communications on Wednesday, are not expected to spark a gold rush.
At about a fifth of the diameter of a human hair, the "nuggets" are invisible to the naked eye. They were only detected using the CSIRO's Maia detector for x-ray elemental imaging at the Australian Synchrotron in Melbourne, which found the precious metal in both the vascular system and cells of leaves.
"If you had 500 eucalypt trees growing over a gold deposit, they would only have enough gold in there to make a wedding ring," CSIRO geochemist and lead author of the study Mel Lintern said.
Precious discovery: Traces of minerals in Eucalyptus leaves. Photo: Leigh Henningham
But the study is likely to prove useful to the mining and exploration industries as the leaves and soil under the tree indicate if gold ore deposits are below, all without needing to drill.
Analysing the mineral content of leaves and bark, including searching for other minerals such as zinc and copper, may prove a more cost-effective and environmentally friendly way of locating and assessing mineral deposits.
Dr Lintern said it was the first time the precious metal had been detected in the tissue of a naturally occurring, living thing.
"It just happens to be a eucalypt leaf," he said.
The researchers studied Eucalyptus and Acacia trees in the Kalgoorlie region of Western Australia but Dr Lintern said the findings would apply to all Eucalyptus trees, given the right conditions.
The research was partially sponsored by the Australian Mineral Institute Research Association.