The importance of accurate and reliable techniques for the chemical characterization of rare-earth materials at various stages of their extraction processing cannot be overemphasized. The analysis of rare-earth materials is carried out for (1) the determination of total rare earths in materials like minerals, concentrates, compounds, alloys, and metals as well as process solutions; (2) the determination of individual rare-earth contents in a mixture of various rare earths; and (3) the determination of non-rare-earth metallic and nonmetallic impurities in rare earths. Until the early 1940s, routine rare-earth analysis was essentially confined to category (1) above (Banks and Klingman 1961). The rare earths were isolated from materials that hosted them and determined as a group by gravimetric methods. Much of the developments in the analytical characterization of rare earths-as with many other branches of rare-earth extractive metallurgy-have occurred since the 1940s.