Bastnasite

In geology, the mineral bastnasite is one of a family of three carbonate-fluoride minerals. There is bastnasite-(Ce) with a formula of (Ce, La)CO₃F. There is bastnasite-(La) with a formula of (La, Ce)CO₃F. There is also bastnasite-(Y) with a formula of (Y, Ce)CO₃F. Most bastnasite is bastnasite-(Ce), and cerium is by far the most common of the rare earths in this class of minerals. Bastnasite and the phosphate mineral monazite are the two largest sources of cerium. The hardness of bastnasite ranges from 4 to 4.5. The specific gravity ranges from 4.7 to 5.0, which is above average for a mineral.