Terrestrial feldspars (orthoclase, anorthite, bytownite, labradorite, oligoclase, and albite) have been irradiated with252Cf-fission products as well as Kr and Xe ions of different energies in order to study track length and track diameter as a function of crystal orientation. Both track length and track diameter of heavy particle tracks in orthoclase depend on the angle of incidence as well as on the angle of azimuth with respect to a fixed direction in the crystal surface plane. As to the plagioclase feldspars, only the track diameters appear to vary with crystal orientation. The different bulk and track etch rates for the main cleavage planes {001} and {010} are given. Within the plagioclase group the track registration properties were found to vary distinctly with the Ca content. Possible explanations for this observation are discussed.