Rare earth elements power everything from electric vehicle motors and wind turbines to MRI scanners and smartphones. A layered manganese oxide whose nanoscale channels separate rare earth elements based on the size of the water shells surrounding them. Why rare earths are so difficult to separate For decades, separating rare earth elements has remained one of the biggest bottlenecks in the global supply chain. The 17 rare earth elements—including the 15 lanthanides, plus scandium and yttrium—are almost always found together in nature. Although rare earth elements behave almost identically chemically, each dissolved ion carries a shell of water molecules around it.