Monazite
.
Monazite is a mineral and an ore of rare earth elements. Chemically, it is a mixture of phosphates of lanthanide elements and thorium.
Refining
Dissolving monazite with sodium hydroxide makes a slurry of metal oxides. Adding hydrochloric acid makes a solution of lanthanide chlorides and a residue containing thorium dioxide. The exact process can vary depending on specific properties of the mineral.[1]
References