Scientists have created a global “treasure map” for rare earth elements by uncovering where the strange volcanic rocks that contain them are most likely to form. By combining thousands of rock samples with seismic images of Earth’s deep interior, the team discovered that these metal-rich rocks tend to appear along the ancient, thick roots of continents. These unusual rocks, once seen as geological oddities, are now incredibly important because they hold many of the materials used in smartphones, electric vehicles, and wind turbines.