The quest to replace fossil fuels is hampered by shortages of some of the minerals used for batteries and dynamos. Scientists at Australia's CSIRO are seeking ways to make it easier to find minerals like cobalt and nickel, and are getting help from termites.
Vast deserts in places like Western Australia are pocketed with termite mounds. Termites sometimes bring up mineral particles from extraordinary depths for such small creatures – hundreds of meters in some cases. In doing so they can give humans an indication of what lies beneath, allowing mineral explorers to focus their searches. Miners have been using this fact to search for gold for some time, but new research could extend this to metals sought for environmental technologies, rather than mostly desired for aesthetics.
The lithium-ion batteries used in everything from our phones to electric cars currently use cobalt in their cathodes. This creates a major roadblock to the expansion of pollution-free transport because half the world's cobalt is currently mined in the war-torn Democratic Republic of Congo, accompanied by appalling human rights abuses and environmental damage. Electric car manufacturers have succeeded in replacing more and more of the cobalt they use with nickel, and hope at some point to do without it altogether. So far, however, increases in battery production are outstripping the reduced amount of cobalt per battery.
In many locations “Manganese is mobilized in floodwaters,” Dr Sam Spinks told IFLScience, “Before precipitating out on surface features such as soil and rocks.” It bonds particularly well to termite mounds, forming a layer of manganese oxide, which Spinks calls super-absorbent of many other metals, including zinc, cobalt, and nickel.
Unfortunately, this can create “false anomalies” where the manganese oxide soaks up so much of a particular metal explorers think they have hit the jackpot, only to find little underground. In Chemical Geology Spinks describes a more sophisticated approach.
Zinc is much more abundant than other “base metals” in the Earth's crust, and is usually found along with them. Zinc is fairly cheap and seldom worth mining on its own, but can guide us to more valuable metals.
"Zinc from hydrothermal ore deposits can be uniquely isotopically light,” Spinks told IFLScience. Consequently, finding zinc with an unusual ratio of light isotopes, particularly in basaltic rocks, can be a sign of an ancient hydrothermal vent, around which nickel and cobalt are also likely to have been deposited. Spinks stressed the situation is more complex than this, because the manganese oxide on the termite mounds preferentially captures heavier zinc.
Nevertheless, "This new research shows we can now measure zinc variations, or isotopes, so accurately that we can identify what metal deposit lies deep underground," he said.
