Rare earth elements (REE) are important for technology and energy. Researchers studied underclay rock from Appalachian coal seams as a new source of REE. They used a special method to extract REE from the rock, producing a solution with high REE and low unwanted elements. The citrate solution used was better at extracting REE than other methods like hydrochloric acid. This study shows that underclay from coal seams could be a valuable source of REE.