Optical and X-ray powder data are given for bastnasite from four localities in Norway. The indices of refraction and the birefringences are lower than those reported earlier. The crystallographic constants are in close agreement with the previously published values, except in one case where the mineral shows smaller a₀ and c₀ values. The variation in the unit cell and the optical properties are discussed, but lack of chemical data prevents any conclusive explanation. Bastnasite has been found as a secondary mineral, mostly as an alteration product of allanite. The mineral seems to be more widespread than supposed earlier, especially in pegmatites containing altered allanite.