Rare earth elements (REE) are classified as critical minerals based on their international dependence, vulnerable supply chains, and vital uses in modern technologies. This study characterized the occurrences of the REE in a 28-ft kaolin-clay core through the Paleocene-Eocene Nanafalia Formation at Eufaula, Alabama. The core was divided into fourteen composite samples from 2-ft lengths. These composite samples contained kaolinite (96-98% by whole rock), iron minerals, and trace amounts of zircon, schorl, weathered ilmenite, and xenotime. Hematite, goethite, and siderite concretions occur in the upper, middle, and lower core, respectively. Total REE concentrations are highest in the 70-74 ft interval (507.5-536.6 ppm). Leaching efficiencies of the LREE were as high as 21.38% (66-68 ft). Leaching efficiencies of the HREE were as high as 6.86% (72-74 ft) by ion-exchange experiments. These results will inform the choice of extractive methods to recover the REE from these kaolins.
Drew Hooper (Thu,) studied this question.