MgMn4(FeO4)2 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with six equivalent Mn(4)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, edges with two equivalent Mn(2)O6 octahedra, and edges with two equivalent Mn(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 6-8°. There are four inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MnO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(2)O6 octahedra, edges with two equivalent Mn(3)O6 octahedra, and edges with two equivalent Mn(4)O6 octahedra. In the second Mn site, Mn(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form MnO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, edges with two equivalent Mn(3)O6 octahedra, and edges with two equivalent Mn(4)O6 octahedra. In the third Mn site, Mn(3) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form MnO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, edges with two equivalent Mn(2)O6 octahedra, and edges with two equivalent Mn(4)O6 octahedra. In the fourth Mn site, Mn(4) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form MnO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, edges with two equivalent Mn(2)O6 octahedra, and edges with two equivalent Mn(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 6-8°. Fe(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mn(1), one Mn(2), one Mn(3), and one Fe(1) atom to form distorted OMn3Fe trigonal pyramids that share corners with three equivalent O(2)MgMn3Fe trigonal bipyramids, corners with three equivalent O(3)MgMn3Fe trigonal bipyramids, corners with three equivalent O(4)MgMn3Fe trigonal bipyramids, corners with three equivalent O(1)Mn3Fe trigonal pyramids,  an edgeedge with one O(2)MgMn3Fe trigonal bipyramid,  an edgeedge with one O(3)MgMn3Fe trigonal bipyramid, and  an edgeedge with one O(4)MgMn3Fe trigonal bipyramid. In the second O site, O(2) is bonded to one Mg(1), one Mn(1), one Mn(2), one Mn(4), and one Fe(1) atom to form OMgMn3Fe trigonal bipyramids that share  a cornercorner with one O(3)MgMn3Fe trigonal bipyramid,  a cornercorner with one O(4)MgMn3Fe trigonal bipyramid, corners with four equivalent O(2)MgMn3Fe trigonal bipyramids, corners with three equivalent O(1)Mn3Fe trigonal pyramids, edges with three equivalent O(3)MgMn3Fe trigonal bipyramids, edges with three equivalent O(4)MgMn3Fe trigonal bipyramids, and  an edgeedge with one O(1)Mn3Fe trigonal pyramid. In the third O site, O(3) is bonded to one Mg(1), one Mn(1), one Mn(3), one Mn(4), and one Fe(1) atom to form OMgMn3Fe trigonal bipyramids that share  a cornercorner with one O(2)MgMn3Fe trigonal bipyramid,  a cornercorner with one O(4)MgMn3Fe trigonal bipyramid, corners with four equivalent O(3)MgMn3Fe trigonal bipyramids, corners with three equivalent O(1)Mn3Fe trigonal pyramids, edges with three equivalent O(2)MgMn3Fe trigonal bipyramids, edges with three equivalent O(4)MgMn3Fe trigonal bipyramids, and  an edgeedge with one O(1)Mn3Fe trigonal pyramid. In the fourth O site, O(4) is bonded to one Mg(1), one Mn(2), one Mn(3), one Mn(4), and one Fe(1) atom to form distorted OMgMn3Fe trigonal bipyramids that share  a cornercorner with one O(2)MgMn3Fe trigonal bipyramid,  a cornercorner with one O(3)MgMn3Fe trigonal bipyramid, corners with four equivalent O(4)MgMn3Fe trigonal bipyramids, corners with three equivalent O(1)Mn3Fe trigonal pyramids, edges with three equivalent O(2)MgMn3Fe trigonal bipyramids, edges with three equivalent O(3)MgMn3Fe trigonal bipyramids, and  an edgeedge with one O(1)Mn3Fe trigonal pyramid.
MgMn4(FeO4)2 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with six equivalent Mn(4)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, edges with two equivalent Mn(2)O6 octahedra, and edges with two equivalent Mn(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 6-8°. Both Mg(1)-O(2) bond lengths are 2.10 Å. Both Mg(1)-O(3) bond lengths are 2.16 Å. Both Mg(1)-O(4) bond lengths are 2.18 Å. There are four inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MnO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(2)O6 octahedra, edges with two equivalent Mn(3)O6 octahedra, and edges with two equivalent Mn(4)O6 octahedra. Both Mn(1)-O(1) bond lengths are 1.96 Å. Both Mn(1)-O(2) bond lengths are 2.34 Å. Both Mn(1)-O(3) bond lengths are 2.00 Å. In the second Mn site, Mn(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form MnO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, edges with two equivalent Mn(3)O6 octahedra, and edges with two equivalent Mn(4)O6 octahedra. Both Mn(2)-O(1) bond lengths are 1.96 Å. Both Mn(2)-O(2) bond lengths are 2.34 Å. Both Mn(2)-O(4) bond lengths are 2.00 Å. In the third Mn site, Mn(3) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form MnO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, edges with two equivalent Mn(2)O6 octahedra, and edges with two equivalent Mn(4)O6 octahedra. Both Mn(3)-O(1) bond lengths are 2.10 Å. Both Mn(3)-O(3) bond lengths are 2.24 Å. Both Mn(3)-O(4) bond lengths are 2.23 Å. In the fourth Mn site, Mn(4) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form MnO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, edges with two equivalent Mn(2)O6 octahedra, and edges with two equivalent Mn(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 6-8°. Both Mn(4)-O(2) bond lengths are 2.21 Å. Both Mn(4)-O(3) bond lengths are 2.33 Å. Both Mn(4)-O(4) bond lengths are 2.40 Å. Fe(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. The Fe(1)-O(1) bond length is 1.95 Å. The Fe(1)-O(2) bond length is 2.02 Å. The Fe(1)-O(3) bond length is 2.21 Å. The Fe(1)-O(4) bond length is 2.19 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mn(1), one Mn(2), one Mn(3), and one Fe(1) atom to form distorted OMn3Fe trigonal pyramids that share corners with three equivalent O(2)MgMn3Fe trigonal bipyramids, corners with three equivalent O(3)MgMn3Fe trigonal bipyramids, corners with three equivalent O(4)MgMn3Fe trigonal bipyramids, corners with three equivalent O(1)Mn3Fe trigonal pyramids,  an edgeedge with one O(2)MgMn3Fe trigonal bipyramid,  an edgeedge with one O(3)MgMn3Fe trigonal bipyramid, and  an edgeedge with one O(4)MgMn3Fe trigonal bipyramid. In the second O site, O(2) is bonded to one Mg(1), one Mn(1), one Mn(2), one Mn(4), and one Fe(1) atom to form OMgMn3Fe trigonal bipyramids that share  a cornercorner with one O(3)MgMn3Fe trigonal bipyramid,  a cornercorner with one O(4)MgMn3Fe trigonal bipyramid, corners with four equivalent O(2)MgMn3Fe trigonal bipyramids, corners with three equivalent O(1)Mn3Fe trigonal pyramids, edges with three equivalent O(3)MgMn3Fe trigonal bipyramids, edges with three equivalent O(4)MgMn3Fe trigonal bipyramids, and  an edgeedge with one O(1)Mn3Fe trigonal pyramid. In the third O site, O(3) is bonded to one Mg(1), one Mn(1), one Mn(3), one Mn(4), and one Fe(1) atom to form OMgMn3Fe trigonal bipyramids that share  a cornercorner with one O(2)MgMn3Fe trigonal bipyramid,  a cornercorner with one O(4)MgMn3Fe trigonal bipyramid, corners with four equivalent O(3)MgMn3Fe trigonal bipyramids, corners with three equivalent O(1)Mn3Fe trigonal pyramids, edges with three equivalent O(2)MgMn3Fe trigonal bipyramids, edges with three equivalent O(4)MgMn3Fe trigonal bipyramids, and  an edgeedge with one O(1)Mn3Fe trigonal pyramid. In the fourth O site, O(4) is bonded to one Mg(1), one Mn(2), one Mn(3), one Mn(4), and one Fe(1) atom to form distorted OMgMn3Fe trigonal bipyramids that share  a cornercorner with one O(2)MgMn3Fe trigonal bipyramid,  a cornercorner with one O(3)MgMn3Fe trigonal bipyramid, corners with four equivalent O(4)MgMn3Fe trigonal bipyramids, corners with three equivalent O(1)Mn3Fe trigonal pyramids, edges with three equivalent O(2)MgMn3Fe trigonal bipyramids, edges with three equivalent O(3)MgMn3Fe trigonal bipyramids, and  an edgeedge with one O(1)Mn3Fe trigonal pyramid.