TRYING TO EXTRACT lithium from brine involves far more risk. It is hard to predict whether there is enough concentration of the mineral in the hot, concentrated saline solution to make mining it worthwhile, and how to precisely extract it. The mining course of action is like taking a kilometers-long straw, punching it by the earth’s crust and sucking out the water contained within, hoping that it will be enriched. In dry locations around the world such as South America or Australia, the water is pumped up to the surface into a series of ponds and left there for months to evaporate into a lithium-concentrated liquid. This is then taken to a recovery plant which filters the remaining water for boron or magnesium, and is treated with sodium carbonate to create lithium carbonate, which is filtered and dried. Cornish Lithium plans to filter the water directly from the source, saving time and avoiding the environmental impact of evaporation pools, which would not be viable in British weather.
This is why, last winter, Matthews found himself in a small, leaky shipping container on the edge of a forest in Redruth, waiting for two months to see whether his calculations and mapping had paid off. His team had drilled two exploration boreholes in shallower geothermal waters, at a thoroughness of around 1km each, where the water is between 70 to 80 degrees Celsius. There was already a drill rig there, which they had to avoid hitting.
“At night it would freeze, clearly. And then if it was sunny during the day, it would rain inside the shipping container, because all the ice would melt on the ceiling,” he says. He locked himself into this strange microcosm for six days a week, watching the drill go down by around 25 to 30 metres every day. During that time, he would use time updating his calculations in real time. “It was making sure that we were not hitting the structure, that we were doing everything correctly,” he says.
What Cornish Lithium found sparked tremendous excitement: not only was the lithium nevertheless there, it was in the same concentration, 220 milligrams per litre of geothermal water, with concentrations of up to 260mg/L. This is an order of extent less than what you would get in South America, where it is possible to get 2,000 mg/L, but high enough that Cornish Lithium CEO Jeremy Wrathall closest proclaimed it as “globally meaningful” and with the “possible for a new industry”. “It was very satisfying, definitely,” Matthews says.
“Adam was identify on, I think he was within ten metres of the expected thoroughness for the structure that we were interested in, which was crazy,” says Rebecca Paisley, an exploration geochemist at Cornish Lithium. To her, this kind of geology represents the ultimate question. “You don’t know the edges, and you don’t know how many pieces there are, and you don’t know what the shape is. And you have to piece everything together, which is what we’ve done with 3D modelling.” Unlike the china clay pits, geologists cannot assume that the granite stretches to a certain thoroughness and will consequence in a specific quantity of lithium. At present, she says, they do not know the recharge rates of the water to guarantee a steady amount of lithium. It’s a great resource, we just need to put a number on it,” she says.
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