January 1999

Harvest of Gold

By David Graham

Gold miners aren't going to want to throw away their drills and explosives-at least, not right away. But in New Zealand, researchers have come up with another way to mine gold. It's a plant, Brassica juncea, that is in the same family as cabbage.

No one is likely to strike it rich using this floral method, says Robert R. Brooks, a geochemist at New Zealand's Massey University who trained the plant in gold mining. But it could provide an effective way to glean gold from the "tailings," or spent earth, around old mines.

The New Zealand scientists added to the soil the compound ammonium thiocyanate, which binds to gold particles, forming a water-soluble complex that is transported through the roots and gathered in the shoots and leaves. The dried plants can be incinerated, leaving small flecks of ore in the ash.

Brooks is prospecting for other plants that can absorb gold even more efficiently. He speculates that the technology of induced accumulation might also be applied to collect silver, platinum, palladium and other precious metals.

With the price of platinum even higher than that of gold, it just might be time to get out the rototiller and expand that garden this spring.