Priderite (M.M. 29-496) has been re-examined by electron microprobe and electron diffraction. The formula of (K0.97Ba0.33)(Fe1.17Ti6.60Mg0.23)O16 is in line with the observed superlattice periodicity of m = 5.88, there being intergrowths of m = 5 and m = 6 superstructures. A surprisingly high degree of lateral correlation between tunnel cations was noted. -R.A.H.