A careful study of cordylite-(Ce), a barium rare earth fluor-carbonate mineral, has yielded the following results: (1) The compatibility values (1-Kp/Kc) of cordylite-(Ce) are very low (-0.1896 and -0.2139 respectively for data given by Chen (1975) and ideal chemical composition). (2) The structure of cordylites (Ce) assumed by Oftedal (1931) is in contradiction with its optical properties and space group. (3) The mean occupied volume of a single large cation (unit cell volume/number of large cations per cell) of cordylite-(Ce) is unusual (86.2A3), i. e. it is much larger than the volume in similar minerals such as cebaite- (Ce)and huangheite-(Ce)(about 72 A3).(4) Cordylite-(Ce) has no coordination polyhedra similar to those in huangheite-(Ce) etc. (5) The struc-ture of cordylite-(Ce) can not be compared with that of similar minerals.The previously-given chemical composition and structure of cordylite-(Ce)is therefore incorrect, and the formula of cordylite-(Ce) should be expressedas (Na1-x, Ca0.5x) BaCe2, (CO3)4F.