Abstract The cerium fluorocarbonate minerals containing both calcium and barium have been studied by the lattice imaging technique. It has been found that the crystal structure of such minerals are formed by stacking at random along the direction c layers of various barium-Cerium as well as calcium-cerium fluorocarbonate minerals. The inter-growth of some calcium-cerium fluorocarbonate minerals with different composition has been observed in the range of several angstrons. A possible new polytype in Roentgenite has been proposed. The results show the advantage of the lattice imaging technique in direct observation of the crystal structure of such minerals.