The structure of charoite, (K,Sr,Ba,Mn)15-16(Ca,Na)32[(Si70(O,OH)180)](OH,F)4.0·nH2O, (a = 31.96(6), b = 19.64(4), c = 7.09(1) Å, b = 90.0(1)°, V = 4450(24) Å3, space group P21/m) can be visualized as being composed of three different dreier silicate chains, which occur between ribbons of edge-sharing octahedra. From  SAED patterns on various single fibres it was found that charoite can form four different polytypes. Different polytypes are form by the shift on c/2 of tetrahedral chains along the octahedral bands in the neighbour unit cells. Charoite polytypism can be explained on the base of the OD-theory as a sequence of layers with parameters b, c, a/2 connected by a screw axis 2½ parallel to c.
Keywords: charoite, polytype