On a quest for buried gold? Leave the compass behind and let the trees guide you. Scientists in Australia have found the first nanoparticulate proof that, unlike money, gold actually does grow on trees. And where it does, it could indicate the locations of underground gold deposits.
A team of researchers from the Commonwealth Scientific and Industrial Research Organization (CSIRO), Australia’s national scientific research body, found that eucalyptus trees in two separate locations contained particulate Au embedded in the cells of their leaves. The nanoparticles of gold measured up to 8 microns wide – about 10 times thinner than a human hair, Live Science noted.
Scientists believe the gold in the trees’ leaves indicates there are gold deposits underneath. As Science Mag noted, trees absorb whatever nutrients are in the earth beneath it. That means any bits of gold dissolved in underground water reserves could be sucked up by the vegetation above it.
“The tree is a conveyor belt bringing gold to the surface,” Clifford Stanley, a geochemist at Acadia University in Wolfville, Canada, told Science Mag.
Scientists chose eucalyptus trees, which are native to Australia, because their elongated roots can stretch to depths of up to 130 feet – the equivalent of a 10-story building. The trees they studied were roughly 30 feet tall.
"We were astounded at the capability of the eucalyptus trees to bring up gold” from that depth, Melvyn Lintern, a geochemist at CSIRO and the lead author of the study, told Live Science.
Lintern and his team collected foliage samples consisting of leaves and twigs from two sites – one in west Australia, the other in the south – where geologists believe gold deposits exist. They then used x-ray imaging to check for gold in the samples. They found that samples taken from the trees directly above the gold deposits contained as much as 80 parts per billion of gold. Trees growing 200 meters away from the ore site contained far less.
Researchers found that of all the samples, the leaves contained the highest amount of particulate gold.
"Gold is probably toxic to plants and is moved to its extremities (such as leaves)," the researchers wrote in the study, published in the journal Nature Communications.
In addition to the field studies of eucalyptus trees, Lintern and his team performed an experiment of their own. They grew seedlings in greenhouses meant to keep out airborne dust and watered them with solutions laced with gold. They found that the trees really did pick up the metal from the soil and transfer it to their leaves.
Mining eucalyptus leaves for gold won’t make anyone rich, however. "The amount of gold in the trees is extremely small,” Lintern said. “You would need 500 trees or more growing over a gold deposit to have enough gold to make a ring."
Gold particles have been observed in leaves before. But scientists weren’t sure whether they were there because they had been absorbed by the tree or simply blown by the wind, Phys.org reported.
There are still a number of untapped gold ore deposits in the world. According to the U.S. Geological Survey, there are an estimated 51,000 tons of gold still nesting underneath the Earth’s surface.
The finding could provide a new way to locate the locations of gold deposits without needing to dig first.
“If they’re able to sample the trees [for gold] instead of drilling, then they’re going to save some money,” Lintern told Courier Mail. “The other aspect about that, of course, is [that] sampling the vegetation is more environmentally benign than digging big holes or drilling.”
He says the non-invasive tree-sampling method could lower exploration costs and reduce environmental damage.