Mg(Fe2O3)2 crystallizes in the orthorhombic Cmcm space group. Mg(1) is bonded to two equivalent O(4) and four equivalent O(2) atoms to form distorted MgO6 pentagonal pyramids that share corners with four equivalent Fe(1)O6 octahedra, corners with eight equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, and faces with two equivalent Mg(1)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 24-75°. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), two equivalent O(1), and three equivalent O(3) atoms to form FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent Mg(1)O6 pentagonal pyramids, edges with five equivalent Fe(1)O6 octahedra, and edges with five equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-12°. In the second Fe site, Fe(2) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with four equivalent Mg(1)O6 pentagonal pyramids, edges with two equivalent Fe(2)O6 octahedra, edges with five equivalent Fe(1)O6 octahedra, and  an edgeedge with one Mg(1)O6 pentagonal pyramid. The corner-sharing octahedral tilt angles range from 0-62°. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Fe(2) and four equivalent Fe(1) atoms to form OFe6 octahedra that share corners with four equivalent O(3)Fe5 square pyramids, corners with two equivalent O(4)Mg2Fe2 tetrahedra, edges with two equivalent O(1)Fe6 octahedra, edges with six equivalent O(3)Fe5 square pyramids, and edges with four equivalent O(2)Mg2Fe3 trigonal bipyramids. In the second O site, O(2) is bonded to two equivalent Mg(1), one Fe(1), and two equivalent Fe(2) atoms to form distorted OMg2Fe3 trigonal bipyramids that share corners with five equivalent O(3)Fe5 square pyramids, corners with four equivalent O(4)Mg2Fe2 tetrahedra, corners with two equivalent O(2)Mg2Fe3 trigonal bipyramids, edges with two equivalent O(1)Fe6 octahedra,  an edgeedge with one O(3)Fe5 square pyramid,  an edgeedge with one O(4)Mg2Fe2 tetrahedra, and edges with three equivalent O(2)Mg2Fe3 trigonal bipyramids. In the third O site, O(3) is bonded to two equivalent Fe(2) and three equivalent Fe(1) atoms to form OFe5 square pyramids that share corners with two equivalent O(1)Fe6 octahedra, corners with two equivalent O(4)Mg2Fe2 tetrahedra, corners with five equivalent O(2)Mg2Fe3 trigonal bipyramids, edges with three equivalent O(1)Fe6 octahedra, edges with four equivalent O(3)Fe5 square pyramids, and  an edgeedge with one O(2)Mg2Fe3 trigonal bipyramid. The corner-sharing octahedral tilt angles are 5°. In the fourth O site, O(4) is bonded to two equivalent Mg(1) and two equivalent Fe(2) atoms to form OMg2Fe2 tetrahedra that share corners with two equivalent O(1)Fe6 octahedra, corners with four equivalent O(3)Fe5 square pyramids, corners with two equivalent O(4)Mg2Fe2 tetrahedra, corners with eight equivalent O(2)Mg2Fe3 trigonal bipyramids, and edges with two equivalent O(2)Mg2Fe3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 5°.
Mg(Fe2O3)2 crystallizes in the orthorhombic Cmcm space group. Mg(1) is bonded to two equivalent O(4) and four equivalent O(2) atoms to form distorted MgO6 pentagonal pyramids that share corners with four equivalent Fe(1)O6 octahedra, corners with eight equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, and faces with two equivalent Mg(1)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 24-75°. Both Mg(1)-O(4) bond lengths are 2.10 Å. All Mg(1)-O(2) bond lengths are 2.30 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), two equivalent O(1), and three equivalent O(3) atoms to form FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent Mg(1)O6 pentagonal pyramids, edges with five equivalent Fe(1)O6 octahedra, and edges with five equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-12°. The Fe(1)-O(2) bond length is 2.07 Å. Both Fe(1)-O(1) bond lengths are 2.14 Å. There is one shorter (2.15 Å) and two longer (2.22 Å) Fe(1)-O(3) bond lengths. In the second Fe site, Fe(2) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with four equivalent Mg(1)O6 pentagonal pyramids, edges with two equivalent Fe(2)O6 octahedra, edges with five equivalent Fe(1)O6 octahedra, and  an edgeedge with one Mg(1)O6 pentagonal pyramid. The corner-sharing octahedral tilt angles range from 0-62°. The Fe(2)-O(1) bond length is 2.34 Å. The Fe(2)-O(4) bond length is 2.01 Å. Both Fe(2)-O(2) bond lengths are 2.07 Å. Both Fe(2)-O(3) bond lengths are 2.05 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Fe(2) and four equivalent Fe(1) atoms to form OFe6 octahedra that share corners with four equivalent O(3)Fe5 square pyramids, corners with two equivalent O(4)Mg2Fe2 tetrahedra, edges with two equivalent O(1)Fe6 octahedra, edges with six equivalent O(3)Fe5 square pyramids, and edges with four equivalent O(2)Mg2Fe3 trigonal bipyramids. In the second O site, O(2) is bonded to two equivalent Mg(1), one Fe(1), and two equivalent Fe(2) atoms to form distorted OMg2Fe3 trigonal bipyramids that share corners with five equivalent O(3)Fe5 square pyramids, corners with four equivalent O(4)Mg2Fe2 tetrahedra, corners with two equivalent O(2)Mg2Fe3 trigonal bipyramids, edges with two equivalent O(1)Fe6 octahedra,  an edgeedge with one O(3)Fe5 square pyramid,  an edgeedge with one O(4)Mg2Fe2 tetrahedra, and edges with three equivalent O(2)Mg2Fe3 trigonal bipyramids. In the third O site, O(3) is bonded to two equivalent Fe(2) and three equivalent Fe(1) atoms to form OFe5 square pyramids that share corners with two equivalent O(1)Fe6 octahedra, corners with two equivalent O(4)Mg2Fe2 tetrahedra, corners with five equivalent O(2)Mg2Fe3 trigonal bipyramids, edges with three equivalent O(1)Fe6 octahedra, edges with four equivalent O(3)Fe5 square pyramids, and  an edgeedge with one O(2)Mg2Fe3 trigonal bipyramid. The corner-sharing octahedral tilt angles are 5°. In the fourth O site, O(4) is bonded to two equivalent Mg(1) and two equivalent Fe(2) atoms to form OMg2Fe2 tetrahedra that share corners with two equivalent O(1)Fe6 octahedra, corners with four equivalent O(3)Fe5 square pyramids, corners with two equivalent O(4)Mg2Fe2 tetrahedra, corners with eight equivalent O(2)Mg2Fe3 trigonal bipyramids, and edges with two equivalent O(2)Mg2Fe3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 5°.