Bastnäsite

The mineral bastnäsite is one of a family of three carbonate-fluoride minerals. There is bastnäsite-(Ce) with a formula of (Ce, La)CO3F. There is bastnäsite-(La) with a formula of (La, Ce)CO3F. There is also bastnäsite-(Y) with a formula of (Y, Ce)CO3F. Most bastnäsite is bastnäsite-(Ce), and cerium is by far the most common of the rare earths in this class of minerals. Bastnäsite and the phosphate mineral monazite are the two largest sources of cerium and other rare earth elements.

Bastnäsite was first described in 1841 from and named for the Bastnas Mine in the Riddarhyttan district, Vastermanland, Sweden.

Bastnäsite occurs in alkali granite and syenite and in associated pegmatites. It also occurs in carbonatites and in associated fenites and other metasomatites.