(Ce,La,Y)CO₃(F,OH)

This sample of bastnaesite is displayed in the Smithsonian Museum of Natural History. Bastnaesite is a carbonate compound of cerium, lanthanum and yttrium with the composition (Ce,La,Y)CO₃(F,OH). The sample at left is about 10x30 cm and is from Ambatafangshana, Madagascar.

Another of bastnaesite has the stated composition (Ce,La)CO₃. This sample is from Trimouns talc mine, Luzenac, Ariege, France. Its size is about 3.5x3.5 cm.