The iron-rich variety of zanazziite Ca₂[Mg_0.65Fe_0.35□_1.0][Mg_1.90Fe_1.25Al_0.5Mn_0.35]_Σ4Be₄(PO₄)₆(OH)₄(H₂O,OH)₂ · 4H₂O, which is a heteropolyhedral framework roscherite-group beryllophos-phate from the Sapucaia pegmatite (Minas Gerais, Brazil), was studied by X-ray diffraction. The refinement was carried out in the triclinic and monoclinic systems. It was found that the cation distribution on octahedral sites in the crystal structure is in better agreement with the monoclinic symmetry (a = 15.876 Å, b = 11.860 Å, c = 6.607 Å, β = 95.49°, sp. gr. C2/c). In the sample under study, no ordering of Mg or Fe atoms in octahedral sites is observed in sp. gr. P $ \bar 1 $ \bar 1 , unlike the more iron-rich member of the roscherite group (atencioite).