The paper describes an analysis of the crystal structures of the minerals of the triphylite, alluaudite, zwieselite, and graftonite groups, from the perspective of the ubiquitous presence of 2-polyhedra-wide ribbons formed from corner linking of M₂(PO₄)₂Φ₈ cyclic tetramers. The study helps to unify the crystal chemistry of the four most dominant primary Fe and Mn phosphate mineral groups in granitic pegmatites.