A review of the literature on calcium antimonates reveals numerous discrepancies among results of various investigators, particularly in reference to the composition and crystal structure of calcium fluoantimonate and calcium pyroantimonate. A study of the preparation of these two compounds has been made and it has been established that is orthorhombic. Calcium fluoantimonate has been synthesized for the first time and found to have the cubic structure of the mineral romeite. The probable formula is . Powder diffraction data are given for these two materials as well as for calcium metaantimonate. The behavior of antimony during the firing of calcium halophosphate phosphors is discussed briefly with special reference to the formation of calcium antimonates during the processing.