Gilding the Gum Tree: Scientists Strike Gold in Leaves

Eucalyptus trees in the Kalgoorlie region of Western Australia are drawing up gold particles from Earth via their root system and depositing it their leaves and branches.

"The eucalypt acts as a hydraulic pump -- its roots extend tens of metres into the ground and draw up water containing the gold. As the gold is likely to be toxic to the plant, it's moved to the leaves and branches where it can be released or shed to the ground," CSIRO geochemist Dr Mel Lintern said.

The discovery is unlikely to start an old-time gold rush -- the "nuggets" are about one-fifth the diameter of a human hair. However, it could provide a golden opportunity for mineral exploration, as the leaves or soil underneath the trees could indicate gold ore deposits buried up to tens of metres underground and under sediments that are up to 60 million years old.

"The leaves could be used in combination with other tools as a more cost effective and environmentally friendly exploration technique," Dr Lintern said. "By sampling and analysing vegetation for traces of minerals, we may get an idea of what's happening below the surface without the need to drill. It's a more targeted way of searching for minerals that reduces costs and impact on the environment. "Eucalyptus trees are so common that this technique could be widely applied across Australia. It could also be used to find other metals such as zinc and copper."