MgCr2O4 crystallizes in the orthorhombic Amm2 space group. Mg(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted MgO4 tetrahedra that share corners with four equivalent Cr(2)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra, and  an edgeedge with one Cr(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 5-60°. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded in a 5-coordinate geometry to one O(2) and four equivalent O(3) atoms. In the second Cr site, Cr(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form CrO6 octahedra that share corners with four equivalent Mg(1)O4 tetrahedra, edges with two equivalent Cr(2)O6 octahedra, and  an edgeedge with one Mg(1)O4 tetrahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(1) and two equivalent Cr(2) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Cr(1) and two equivalent Cr(2) atoms. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Cr(2), and two equivalent Cr(1) atoms.
MgCr2O4 crystallizes in the orthorhombic Amm2 space group. Mg(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted MgO4 tetrahedra that share corners with four equivalent Cr(2)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra, and  an edgeedge with one Cr(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 5-60°. Both Mg(1)-O(1) bond lengths are 1.94 Å. Both Mg(1)-O(3) bond lengths are 2.05 Å. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded in a 5-coordinate geometry to one O(2) and four equivalent O(3) atoms. The Cr(1)-O(2) bond length is 1.91 Å. All Cr(1)-O(3) bond lengths are 2.05 Å. In the second Cr site, Cr(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form CrO6 octahedra that share corners with four equivalent Mg(1)O4 tetrahedra, edges with two equivalent Cr(2)O6 octahedra, and  an edgeedge with one Mg(1)O4 tetrahedra. Both Cr(2)-O(1) bond lengths are 2.09 Å. Both Cr(2)-O(2) bond lengths are 2.00 Å. Both Cr(2)-O(3) bond lengths are 2.03 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(1) and two equivalent Cr(2) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Cr(1) and two equivalent Cr(2) atoms. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Cr(2), and two equivalent Cr(1) atoms.