Ever since humans realized the intrinsic value of gold, we’ve constantly searched for – and perfected – ways to find more.
From early methods like panning and trenching, to lode prospectors hunting for rock outcrops and veins, to the invention of drill bits…
In modern times, we use increasingly sophisticated tools and techniques, such as seismic sensors, magnetometry, and gravimetrics to help locate potential gold deposits.
But, after thousands of years of digging for gold, the low-hanging fruit’s already been picked. Most remaining deposits are becoming increasingly difficult to find, and increasingly low grade.
Now, a surprising, brand-new gold prospecting tool may be in the offing – one that’s far less technologically demanding, and much less invasive.
It seems nature itself has found a way to extract gold from the ground.
Take a look at this picture:
Money Does in Fact Grow on Trees
Resource-rich Kalgoorlie, Western Australia, was the site of a major gold rush in the 1890s. And it also happens to be where this recent discovery was made.
Scientists from the Commonwealth Scientific and Industrial Research Organization (CSIRO) found that tiny nuggets of gold were hiding in the leaves of eucalyptus trees, just like the one at left.
So, how did the gold get there?
It seems the roots, which extend down over a hundred feet, suck up ground water wherein the gold particles are suspended.
According to geochemist Mel Lintern, the gold is toxic to the tree, so the eucalyptus just naturally sends it on “to the leaves and branches where it can be released or shed to the ground.”
Now, before you set off to Australia to hunt for gold-dusted eucalyptus leaves… It turns out the gold particles are so tiny, they measure only a fifth as wide as a human hair, and require advanced X-ray imaging to be seen.
Put another way, the concentration is so low, that all the gold in 500 trees would scarcely make a wedding ring.
Even so, that gold has considerable worth.
You see, scientists can use a method called biogeochemical sampling to test for potential gold.
Lintern told Daily News Egypt, “By sampling and analyzing vegetation for traces of minerals, we may get an idea of what’s happening below the surface without the need to drill.” He continued, “It’s a more targeted way of searching for minerals that reduces costs and impact on the environment.”
He figures that this same method could prove valuable in finding other metals too, like copper and zinc.
Nigel Radford, a geochemist who has been involved in gold exploration for decades in Western Australia, told the Australian Broadcasting Corporation that the discovery was a world-first with major implications for prospectors. “A lot of this stuff has been speculated about for some time, but the identification of the gold particles in the leaf materials is completely convincing and very, very important for the future of mineral exploration.”
But this interaction between valuable metals and their natural neighbors is not new.
In fact, nature’s been making major contributions not just to finding metals, but extractingthem too.
Gold Bugs, Literally
Bioleaching is the use of bacterial microorganisms to extract metals from the ore where it’s embedded. By feeding on the nutrients in minerals, bacteria separate the metal from its surrounding ore.
The Rio Tinto River in Spain owes its name to copper-bearing waters, thanks to microbial leaching.
Using microbes to leach metals from ore has been traced back millennia. As far back as 150 BCE, the Chinese dipped iron ore into a blue vitriol solution in order to extract copper.
But it was only in 1947 that scientists figured out that bacteria were actually responsible..
Recognizing the massive potential of having bugs do the work, the process was fast-tracked to commercialization.
Within a decade, bacterial leaching began at the Kennecott Utah Copper Company’sBingham Canyon Mine, where naturally occurring bacteria were oxidizing iron sulfides in waste piles, producing blue copper-containing solutions.
Today, some of the largest mining companies have developed bio-oxidation processes to extract metal.
Instead of using smelting or roasting processes, bioleaching is more cost-effective when metals are found in lower concentrations.
About 20% of copper today is produced through bioleaching, which emits little air and water pollution overall.
And as newer deposits are increasingly low grade, we can expect these methods to gain popularity in base metals mining.
But with ever-advancing technology, the demand for rare earth metals is rocketing.
Another Little Bug with Big Potential
That’s why another ground-breaking discovery is so exciting; it could eventually lead to the extraction of these crucial metals through the use of microorganisms.
This time it’s Dutch scientists who’ve found evidence of a life form that actually depends on rare earths to survive.
It may sound like an episode of Star Trek, but it’s not.
Deep inside the mud of Italian volcanoes lives a bacterium that flourishes on lanthanides.
Those are metals employed all around us, used to reduce auto emissions, in fiber optic communications, and as the red in our televisions screens.
What’s interesting is that this methane-consuming bacterium flourished when scientists added the rare earth metals cerium, lanthanum, praseodymium, and neodymium under controlled conditions.
Before this no one had considered that such elements could be essential to particular living organisms.
Admittedly, it’s still early stage, so we could still be years away from using bacteria to mine rare earths.
But, with demand for all metals exploding alongside lightning-speed technological advances, the new “picks and shovels,” like trees and exotic bacteria, might become common tools for prospecting – and mining – sooner than anyone expects.