MgMn4O6 crystallizes in the orthorhombic Cmcm space group. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(3) atoms. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(3), two equivalent O(1), and three equivalent O(4) atoms to form a mixture of edge and corner-sharing MnO6 octahedra. The corner-sharing octahedral tilt angles range from 0-18°. In the second Mn site, Mn(2) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form a mixture of distorted edge and corner-sharing MnO6 octahedra. The corner-sharing octahedral tilt angles range from 0-69°. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mn(2) and four equivalent Mn(1) atoms to form OMn6 octahedra that share corners with four equivalent O(4)Mn5 square pyramids, corners with two equivalent O(2)Mg2Mn2 tetrahedra, edges with two equivalent O(1)Mn6 octahedra, edges with six equivalent O(4)Mn5 square pyramids, and edges with four equivalent O(3)Mg2Mn3 trigonal bipyramids. In the second O site, O(2) is bonded to two equivalent Mg(1) and two equivalent Mn(2) atoms to form OMg2Mn2 tetrahedra that share corners with two equivalent O(1)Mn6 octahedra, corners with four equivalent O(4)Mn5 square pyramids, corners with two equivalent O(2)Mg2Mn2 tetrahedra, corners with eight equivalent O(3)Mg2Mn3 trigonal bipyramids, and edges with two equivalent O(3)Mg2Mn3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 10°. In the third O site, O(3) is bonded to two equivalent Mg(1), one Mn(1), and two equivalent Mn(2) atoms to form distorted OMg2Mn3 trigonal bipyramids that share corners with five equivalent O(4)Mn5 square pyramids, corners with four equivalent O(2)Mg2Mn2 tetrahedra, corners with two equivalent O(3)Mg2Mn3 trigonal bipyramids, edges with two equivalent O(1)Mn6 octahedra,  an edgeedge with one O(4)Mn5 square pyramid,  an edgeedge with one O(2)Mg2Mn2 tetrahedra, and edges with three equivalent O(3)Mg2Mn3 trigonal bipyramids. In the fourth O site, O(4) is bonded to two equivalent Mn(2) and three equivalent Mn(1) atoms to form OMn5 square pyramids that share corners with two equivalent O(1)Mn6 octahedra, corners with two equivalent O(2)Mg2Mn2 tetrahedra, corners with five equivalent O(3)Mg2Mn3 trigonal bipyramids, edges with three equivalent O(1)Mn6 octahedra, edges with four equivalent O(4)Mn5 square pyramids, and  an edgeedge with one O(3)Mg2Mn3 trigonal bipyramid. The corner-sharing octahedral tilt angles are 8°.
MgMn4O6 crystallizes in the orthorhombic Cmcm space group. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(3) atoms. Both Mg(1)-O(2) bond lengths are 2.05 Å. All Mg(1)-O(3) bond lengths are 2.33 Å. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(3), two equivalent O(1), and three equivalent O(4) atoms to form a mixture of edge and corner-sharing MnO6 octahedra. The corner-sharing octahedral tilt angles range from 0-18°. The Mn(1)-O(3) bond length is 1.93 Å. Both Mn(1)-O(1) bond lengths are 2.18 Å. There is one shorter (2.00 Å) and two longer (2.16 Å) Mn(1)-O(4) bond lengths. In the second Mn site, Mn(2) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form a mixture of distorted edge and corner-sharing MnO6 octahedra. The corner-sharing octahedral tilt angles range from 0-69°. The Mn(2)-O(1) bond length is 2.40 Å. The Mn(2)-O(2) bond length is 2.02 Å. Both Mn(2)-O(3) bond lengths are 2.19 Å. Both Mn(2)-O(4) bond lengths are 2.26 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mn(2) and four equivalent Mn(1) atoms to form OMn6 octahedra that share corners with four equivalent O(4)Mn5 square pyramids, corners with two equivalent O(2)Mg2Mn2 tetrahedra, edges with two equivalent O(1)Mn6 octahedra, edges with six equivalent O(4)Mn5 square pyramids, and edges with four equivalent O(3)Mg2Mn3 trigonal bipyramids. In the second O site, O(2) is bonded to two equivalent Mg(1) and two equivalent Mn(2) atoms to form OMg2Mn2 tetrahedra that share corners with two equivalent O(1)Mn6 octahedra, corners with four equivalent O(4)Mn5 square pyramids, corners with two equivalent O(2)Mg2Mn2 tetrahedra, corners with eight equivalent O(3)Mg2Mn3 trigonal bipyramids, and edges with two equivalent O(3)Mg2Mn3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 10°. In the third O site, O(3) is bonded to two equivalent Mg(1), one Mn(1), and two equivalent Mn(2) atoms to form distorted OMg2Mn3 trigonal bipyramids that share corners with five equivalent O(4)Mn5 square pyramids, corners with four equivalent O(2)Mg2Mn2 tetrahedra, corners with two equivalent O(3)Mg2Mn3 trigonal bipyramids, edges with two equivalent O(1)Mn6 octahedra,  an edgeedge with one O(4)Mn5 square pyramid,  an edgeedge with one O(2)Mg2Mn2 tetrahedra, and edges with three equivalent O(3)Mg2Mn3 trigonal bipyramids. In the fourth O site, O(4) is bonded to two equivalent Mn(2) and three equivalent Mn(1) atoms to form OMn5 square pyramids that share corners with two equivalent O(1)Mn6 octahedra, corners with two equivalent O(2)Mg2Mn2 tetrahedra, corners with five equivalent O(3)Mg2Mn3 trigonal bipyramids, edges with three equivalent O(1)Mn6 octahedra, edges with four equivalent O(4)Mn5 square pyramids, and  an edgeedge with one O(3)Mg2Mn3 trigonal bipyramid. The corner-sharing octahedral tilt angles are 8°.