MgFe2O5 crystallizes in the monoclinic Cc space group. Mg(1) is bonded to one O(1), one O(2), one O(3), one O(4), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with three equivalent Fe(1)O6 octahedra, corners with three equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(1)O6 octahedra, and edges with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 43-64°. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(3), one O(4), one O(5), and two equivalent O(1) atoms to form distorted FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with three equivalent Mg(1)O6 octahedra,  an edgeedge with one Fe(2)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, and  a faceface with one Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-52°. In the second Fe site, Fe(2) is bonded to one O(1), one O(2), one O(3), one O(5), and two equivalent O(4) atoms to form distorted FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with three equivalent Mg(1)O6 octahedra,  an edgeedge with one Fe(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, and  a faceface with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 43-56°. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Fe(2), and two equivalent Fe(1) atoms to form OMgFe3 trigonal pyramids that share  a cornercorner with one O(5)Mg2Fe2 trigonal pyramid,  a cornercorner with one O(4)MgFe3 trigonal pyramid, corners with two equivalent O(1)MgFe3 trigonal pyramids, edges with two equivalent O(5)Mg2Fe2 trigonal pyramids, and edges with two equivalent O(4)MgFe3 trigonal pyramids. In the second O site, O(2) is bonded in a trigonal planar geometry to one Mg(1), one Fe(1), and one Fe(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Fe(1), and one Fe(2) atom. In the fourth O site, O(4) is bonded to one Mg(1), one Fe(1), and two equivalent Fe(2) atoms to form OMgFe3 trigonal pyramids that share  a cornercorner with one O(5)Mg2Fe2 trigonal pyramid,  a cornercorner with one O(1)MgFe3 trigonal pyramid, corners with two equivalent O(4)MgFe3 trigonal pyramids, edges with two equivalent O(5)Mg2Fe2 trigonal pyramids, and edges with two equivalent O(1)MgFe3 trigonal pyramids. In the fifth O site, O(5) is bonded to two equivalent Mg(1), one Fe(1), and one Fe(2) atom to form distorted OMg2Fe2 trigonal pyramids that share  a cornercorner with one O(1)MgFe3 trigonal pyramid,  a cornercorner with one O(4)MgFe3 trigonal pyramid, corners with two equivalent O(5)Mg2Fe2 trigonal pyramids, edges with two equivalent O(1)MgFe3 trigonal pyramids, and edges with two equivalent O(4)MgFe3 trigonal pyramids.
MgFe2O5 crystallizes in the monoclinic Cc space group. Mg(1) is bonded to one O(1), one O(2), one O(3), one O(4), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with three equivalent Fe(1)O6 octahedra, corners with three equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(1)O6 octahedra, and edges with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 43-64°. The Mg(1)-O(1) bond length is 2.10 Å. The Mg(1)-O(2) bond length is 2.09 Å. The Mg(1)-O(3) bond length is 2.10 Å. The Mg(1)-O(4) bond length is 2.08 Å. Both Mg(1)-O(5) bond lengths are 2.12 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(3), one O(4), one O(5), and two equivalent O(1) atoms to form distorted FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with three equivalent Mg(1)O6 octahedra,  an edgeedge with one Fe(2)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, and  a faceface with one Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-52°. The Fe(1)-O(2) bond length is 1.88 Å. The Fe(1)-O(3) bond length is 1.85 Å. The Fe(1)-O(4) bond length is 2.06 Å. The Fe(1)-O(5) bond length is 1.96 Å. There is one shorter (1.99 Å) and one longer (2.00 Å) Fe(1)-O(1) bond length. In the second Fe site, Fe(2) is bonded to one O(1), one O(2), one O(3), one O(5), and two equivalent O(4) atoms to form distorted FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with three equivalent Mg(1)O6 octahedra,  an edgeedge with one Fe(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, and  a faceface with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 43-56°. The Fe(2)-O(1) bond length is 2.16 Å. The Fe(2)-O(2) bond length is 1.89 Å. The Fe(2)-O(3) bond length is 1.94 Å. The Fe(2)-O(5) bond length is 2.06 Å. There is one shorter (2.01 Å) and one longer (2.02 Å) Fe(2)-O(4) bond length. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Fe(2), and two equivalent Fe(1) atoms to form OMgFe3 trigonal pyramids that share  a cornercorner with one O(5)Mg2Fe2 trigonal pyramid,  a cornercorner with one O(4)MgFe3 trigonal pyramid, corners with two equivalent O(1)MgFe3 trigonal pyramids, edges with two equivalent O(5)Mg2Fe2 trigonal pyramids, and edges with two equivalent O(4)MgFe3 trigonal pyramids. In the second O site, O(2) is bonded in a trigonal planar geometry to one Mg(1), one Fe(1), and one Fe(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Fe(1), and one Fe(2) atom. In the fourth O site, O(4) is bonded to one Mg(1), one Fe(1), and two equivalent Fe(2) atoms to form OMgFe3 trigonal pyramids that share  a cornercorner with one O(5)Mg2Fe2 trigonal pyramid,  a cornercorner with one O(1)MgFe3 trigonal pyramid, corners with two equivalent O(4)MgFe3 trigonal pyramids, edges with two equivalent O(5)Mg2Fe2 trigonal pyramids, and edges with two equivalent O(1)MgFe3 trigonal pyramids. In the fifth O site, O(5) is bonded to two equivalent Mg(1), one Fe(1), and one Fe(2) atom to form distorted OMg2Fe2 trigonal pyramids that share  a cornercorner with one O(1)MgFe3 trigonal pyramid,  a cornercorner with one O(4)MgFe3 trigonal pyramid, corners with two equivalent O(5)Mg2Fe2 trigonal pyramids, edges with two equivalent O(1)MgFe3 trigonal pyramids, and edges with two equivalent O(4)MgFe3 trigonal pyramids.