A mineral, Ce(CO3)F; average density 4.97; hardness 4–5; hexagonal to ditrigonal dipyramidal; cleavage {1011} imperfect, {0001} indistinct; yellow or reddish brown, translucent to transparent; white streak; vitreous to greasy lustre; crystals prismatic but it can be massive; named for the Bastnäs mine, Västermanland, Sweden, it also occurs widely, but never in large concentrations, in karst bauxite deposits and carbonatites elsewhere in Europe, and in Mongolia, Malawi, California, and Canada.