Volcanoes house more than molten rock. Alongside the magma sits a mysterious substance called magmatic brine, a mineral-rich soup that collects underneath both active and dormant volcanoes. Geologists are now exploring whether these deep subterranean pools can be tapped for dissolved treasure such as lithium, copper and cobalt. The extraction could be powered by geothermal energy, leading some scientists to call it “green mining”.

Drilling into volcanoes would be a technically challenging and potentially seismic twist on the net-zero minerals rush but, given the ethical and environmental concerns linked to mining on land and at sea, the prospect is justifiably attracting geological and commercial interest. Sub-volcanic brine mining could also be of strategic geopolitical importance, by expanding the supply of critical minerals and breaking the stranglehold enjoyed by China.