Plants can draw gold from earth

SCIENTISTS HAVE succeeded in mining gold by growing crops that gather the precious metal in their leaves. Experiments have shown that plants, such as chicory, can extract gold from soil treated with a chemical. It allows the plants to dissolve the metal into a form that they can absorb.

At a price of pounds 178 an ounce, scientists believe it is commercially feasible to extract gold deposits using the "phytomining" method.

The scientists, who reporttheir experiments in the journal Nature, said the crop of gold was improved by spraying the soil with ammonium thiocyanate. It is commonly used for making gold soluble in mining operations. "The possibility of turning base metals into gold has intrigued many scientists since the early alchemists, and the discovery of significant gold uptake by plants has long been a philosopher's stone," said Robert Brooks, head of the research team at Massey University in Palmerston North, New Zealand.

To be economically viable a plant would have to accumulate around 17 micrograms of gold. The scientists succeeded in harvesting one plant, Brassica juncea, with 57 micrograms. More typical values were between nine and 19 micrograms.