Deep-sea mud is a highly promising giant resource for rare-earth elements and the metal yttrium, according to a study published online in Nature Geoscience this week.World demand for rare-earth elements and yttrium — crucial for electronic equipment and green energy technologies — is rapidly increasing. Yasuhiro Kato and colleagues analysed the composition of more than 2,000 samples of seafloor sediments in the Pacific Ocean. The sediments contained high concentrations of rare-earth elements and yttrium. The researchers estimate that an area of just one square kilometre, surrounding one of the sampling sites, could provide one-fifth of the current annual world consumption of these elements.