The crystal structure of ganophyllite, a complex manganese aluminosilicate. I. Polytypism and strutural variation

The reciprocal-lattice geometry of ganophyllite has been investigated by X-ray diffraction, two distinct variants being noted. These structures, comprising a monoclinic form and a hitherto unreported triclinic variant, can both be interpreted in terms of structural columns which can be stacked in varying sequences along either of the {011} planes. Diffracted intensities from models of this type for both variants give good agreement with the distinctive pattern of intensities actually observed. With the structural column concept, it is also possible to explain instances of two-dimensionally disordered intergrowths of these structures.