British scientists exploring an underwater mountain in the Atlantic Ocean have discovered a treasure trove of rare minerals.
Their investigation of a seamount more than 500km (300 miles) from the Canary Islands has revealed a crust of "astonishingly rich" rock.
Samples brought back to the surface contain the scarce substance tellurium in concentrations 50,000 times higher than in deposits on land.
Tellurium is used in a type of advanced solar panel, so the discovery raises a difficult question about whether the push for renewable energy may encourage mining of the seabed.
The rocks also contain what are called rare earth elements that are used in wind turbines and electronics.
Known as Tropic Seamount, the mountain stands about 3,000m tall – about the size of one of the middle-ranging Alpine summits – with a large plateau at its top, lying about 1,000m below the ocean surface.