Rareearth element Minerals and ores | Britannica
The clays at Xunwu have a most unusual distribution of rare earths, being rich in lanthanum and neodymium with a reasonably high yttrium content. The low concentrations of cerium and praseodymium in both clays, especially in the Xunwu clay, compared with the normal rareearth distribution in the other minerals, is also remarkable.