How trees drinking gold can help the mining industry
A paper published in Nature Communications reports that trees sip up gold deposits below, a find that could help prospectors pinpoint the location of buried reserves.
It’s not just the gods of antiquity who sloshed back cups of liquid gold. Trees drink gold, too.Skip to next paragraph
In Pictures Gold: A Test of Mettle
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A paper published this week in Nature Communications reports that gold crystals can be found in Eucalyptus trees growing above buried deposits of the mineral.
The report offers a tentative solution to a worldwide slump in new gold deposit discoveries, suggesting that, somewhat counterintuitively, an effective means of peering into the Earth is to look up – not to the gods, but to the trees.
Trees leaves filled with gold sapped up from below ground can help gold explorers “see what is buried beneath,” says Mel Lintern, a researcher at the Commonwealth Scientific and Industrial Research Organization in Australia and the lead author on the paper.
“The work will enable mineral explorers to cover more ground with a limited amount of funds,” he said.
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Prospectors have known for decades that aboveground brush and trees are at times proverbial X's marking the spots of brimming mineral deposits below – not just gold, but copper and silver, too. At times, mineral explorers had used this treasure-laced foliage to uncover buried reserves.
Still, the method, called biogeochemical analysis, had failed to become mainstream, in large part because it had been unclear if the auric leaves were reliable indicators of gold below or just red (or, rather, gold) herrings: sure, it was possible that the gold been sipped up from buried troves. But it was just as possible that it had been ferried there from elsewhere, settling in the trees’ leaves as glittering dupery.
Even over the last decade, as scientists had begun to proffer proof that trees do, in fact, drink gold, the exploration technique had not caught on in the prospecting world, says Dr. Lintern. Since most greenhouse and lab studies used higher quantities of gold than occur in the natural process, prospectors had lacked confidence that the method was applicable to the field, he said. And no previous research had identified gold crystals collecting in free-growing trees out in the field, he said.
“We need to build the technique up into a robust method so that explorers can use it confidently,” says Lintern.
Drinking gold for trees
In the latest research, the scientists directly sampled Eucalyptus and Acacia trees (also called thorntrees) in the Freddo Gold Prospect, in western Australia, and the Barns Gold Prospect, in southern Australia. At both sites, the gold is buried around 100 feet underground. The researchers also conducted supplemental greenhouse work using potted plants from the two sites.
The gold in the leaves is not visible to the eye (no, Australia is not bejeweled with giant gilded Eucalyptus trees). Instead, detecting it requires the help of a high-powered X-ray machine – a super, super high-powered machine.
If all the dimensions are scaled up by factor of 1,000, finding a gold crystal in a Eucalyptus leaf is like “finding a single minute particle of gold the size of a grain of sand in the area of a large football field searching the soil to a depth of 1 metre [3 feet],” said David Paterson, principle scientist at Australia Synchrotron, where the leaves were imaged, and an author on the paper, in an email.
After finding gold in the leaves, the researchers then ran tests for its origins, confirming that it was drawn up from the rock below. The team proposes that ionic gold is absorbed through the tree’s deep roots during periods of drought, when the trees roots reach down deeper and deeper for a drink. The ions are then distributed throughout the tree’s cells and precipitate into crystals.
Gold crystals are found in highest concentrations in the tree’s leaves, possibly because large quantities of gold are toxic to a plant, the researchers say. In order to keep concentrations to a minimum, trees must ferry the ions out to their furthest extremities, like King Midas’ daughter willing the spreading gold not to reach her heart.