The mineral bastnäsite (or bastnaesite) is one of a family of three carbonate-fluoride minerals, which includes bastnäsite-(Ce) with a formula of (Ce, La)CO₃F, bastnäsite-(La) with a formula of (La, Ce)CO₃F, and 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.