‘Geodes’ that detect lithium underfoot – with the help of some satellites

As electrification accelerates and the world lets go of fossil fuels, minerals like lithium and copper are becoming ever more critical.

Finding them hasn’t changed much in decades: dig a hole, analyse the soil, and maybe dig another.

But new technologies are changing this. It turns out maybe the best way to look down might be to look up – using sensors and satellites.

Or, at least, that’s what South Australian company, Fleet Space Technologies, is seeing some success with.

Their “geodes” – nine-kilogram devices, each about the size of a shoebox – are designed to spot critical minerals, like lithium, in hard-to-reach places.

“They’re high sensitivity seismic nodes,” explains Matt Pearson, co-founder and chief exploration officer at Fleet.

“We put them out in big arrays, usually anywhere from 40 to 100 geodes, which might cover 10 to 100 square kilometres. Then we can generate images of structures in the subsurface based on seismic velocity, usually down to about two kilometres depth – which is around the range of what is commercially viable to extract.”

Mining companies rent the geodes out, then drive, walk, or helicopter them into an area of interest.

Once planted, they use a non-invasive technique called ambient noise tomography to get a sense of the different densities in the ground below. Then, they send that data to satellites, which ping it back to Earth for analysis.

“Most of this stuff is in really hard-to-reach places,” says Pearson. The more populated and well-connected an area is, the less desirable it is to mine there.

“What’s happened in the past is people would run around with hard drives and USB sticks, and they would download the data off the device, drive the truck back to base camp, sometimes put all the hard drives on a plane and cross the world, have all the data downloaded, and then analysed,” says Pearson.

“You get a result back in three to six months, sometimes as long as 12 months. By the time you get the results, the team that was in the field has usually moved on and is exploring elsewhere.”

The geodes, and their satellite connections, turn this into a near-instantaneous task – and it also means that survey areas can be adjusted to get more detail, if something interesting shows up on the corners of the maps.

“It means that an area can be explored so much more quickly, without trying to get permits and drilling the hell out of everything,” says Pearson.

So far, the geodes have been used to spot lithium, copper and gold, and Fleet is working on iron, titanium, uranium, and some rare earth minerals.

They’re not, according to Pearson, “silver bullets” – but useful additional datasets.

“If something’s too small or too narrow, then it’s hard for us to see. But we can still see underlying rock strata. So that can help you make decisions like: ‘Oh, there’s a fault line here. If there’s going to be gold, for instance, that’s probably where it’s going to be’.

“In Australia we’ve had quite a lot of success with direct detection of pegmatite dikes [a primary source of lithium] in the surrounding sandstone quite clearly. Which is very exciting, because no other geophysical technique actually works – they don’t show up as gravity anomalies or magnetic anomalies, but we can see them as seismic anomalies, quite clearly.”

It’s a new technique for metals, but seismic science has been known to the wider extractive industry for some time.

“This is kind of the way that oil and gas exploration has been done for decades, which is very highly geophysics-dependent. When they drill a hole in the oil and gas sector, they pretty much know they’re going to hit oil,” says Pearson.

“In the mining industry at the moment, it’s been operating the same way for many, many decades: they drill almost at random until they’ve hit something, then they keep drilling at random until they hit it again. So it’s very geology-based.”

Recent advances in sensory equipment and computing power have made it possible to take geophysics to mining. But the industry’s still new. Fleet’s geodes have already been through four iterations, with an even lighter version on the way.

“They started out with giant car batteries attached to them,” says Pearson.

“We’ve shrunk them down a lot, but the idea is to make them much smaller, and lighter-weight to deploy. Some of the some of the places that customers go can only be accessed by helicopter, so you need things that are small and lightweight.”

People have also walked geodes out to put them on mountains, or remote deserts.

With $50 million just raised in its most recent round of investor funding, Fleet has even more remote locations in mind, which will need even lighter equipment – and better preparation before you drill.

“The geode is also an early version of an instrument that we’re developing for the Moon,” says Pearson.

“If we want to find water on the Moon, or Mars, and lava tubes and caves to live in, this type of geophysical technique is really awesome for that type of work.”