By JOSIE CLARKE
A New Zealand scientist has discovered how vegetables and other common plants can be used to "mine" gold.
Chris Anderson of Massey University is attracting international attention for finding a chemical that makes gold soluble, allowing plants to "grab" the precious metal as they grow.
Scientists had already discovered "phyto-mining" of other minerals such as nickel. But nobody had been able to get plants to take up gold until Dr Anderson found that ammonium thiocyanate could dissolve gold.
Dr Anderson's experiments involved planting a range of plants, including carrots and chicory, in soil containing traces of gold from the Martha Mine in Waihi.
Once the plants had grown, he added a solution including the ammonium thiocyanate to the soil to dissolve the gold. After about 10 days of soaking up the solution, the plants were harvested, dried and burned, leaving the gold.
Dr Anderson said trials showed that an average yield of 100g of gold from a tonne of dried plant material was enough to make the process economic, when carried out over treated mine tailings. Profits were similar to returns on a crop of wheat.
He said the chemical used in the process sounded "nasty," but existed naturally in a lot of soils and did not harm the environment.
"In parts of Brazil, people are trying to extract gold using mercury. Mercury is dangerous to human health and leaves the soil contaminated. It's a huge problem in developing countries, where people are poor and try to get gold at any cost."
The research has attracted the interest of Dutch chemicals company Akzo Nobel, one of the world's biggest producers of ammonium thiocyanate, which has funded a $100,000 research contract based on the project.
The Brazilian Government is sending a doctoral student to Massey this year to help to investigate the development.
Scientist puts gold's glitter into carrots
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