MgCr4O8 crystallizes in the orthorhombic Imm2 space group. Mg(1) is bonded to two equivalent O(2) and two equivalent O(4) atoms to form distorted MgO4 trigonal pyramids that share corners with six equivalent Cr(3)O6 octahedra, corners with two equivalent Cr(1)O4 tetrahedra, and  an edgeedge with one Cr(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 61-79°. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form CrO4 tetrahedra that share corners with six equivalent Cr(3)O6 octahedra and corners with two equivalent Mg(1)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 42-60°. In the second Cr site, Cr(2) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form CrO4 tetrahedra that share corners with six equivalent Cr(3)O6 octahedra and  an edgeedge with one Mg(1)O4 trigonal pyramid. The corner-sharing octahedral tilt angles range from 55-61°. In the third Cr site, Cr(3) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form CrO6 octahedra that share corners with three equivalent Cr(1)O4 tetrahedra, corners with three equivalent Cr(2)O4 tetrahedra, corners with three equivalent Mg(1)O4 trigonal pyramids, and edges with two equivalent Cr(3)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Cr(2) and one Cr(3) atom. In the second O site, O(2) is bonded to one Mg(1), one Cr(2), and two equivalent Cr(3) atoms to form distorted edge-sharing OMgCr3 tetrahedra. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Cr(1) and two equivalent Cr(3) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cr(1), and one Cr(3) atom.
MgCr4O8 crystallizes in the orthorhombic Imm2 space group. Mg(1) is bonded to two equivalent O(2) and two equivalent O(4) atoms to form distorted MgO4 trigonal pyramids that share corners with six equivalent Cr(3)O6 octahedra, corners with two equivalent Cr(1)O4 tetrahedra, and  an edgeedge with one Cr(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 61-79°. Both Mg(1)-O(2) bond lengths are 2.06 Å. Both Mg(1)-O(4) bond lengths are 1.91 Å. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form CrO4 tetrahedra that share corners with six equivalent Cr(3)O6 octahedra and corners with two equivalent Mg(1)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 42-60°. Both Cr(1)-O(3) bond lengths are 1.82 Å. Both Cr(1)-O(4) bond lengths are 1.81 Å. In the second Cr site, Cr(2) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form CrO4 tetrahedra that share corners with six equivalent Cr(3)O6 octahedra and  an edgeedge with one Mg(1)O4 trigonal pyramid. The corner-sharing octahedral tilt angles range from 55-61°. Both Cr(2)-O(1) bond lengths are 1.74 Å. Both Cr(2)-O(2) bond lengths are 1.93 Å. In the third Cr site, Cr(3) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form CrO6 octahedra that share corners with three equivalent Cr(1)O4 tetrahedra, corners with three equivalent Cr(2)O4 tetrahedra, corners with three equivalent Mg(1)O4 trigonal pyramids, and edges with two equivalent Cr(3)O6 octahedra. The Cr(3)-O(1) bond length is 1.95 Å. The Cr(3)-O(4) bond length is 2.02 Å. Both Cr(3)-O(2) bond lengths are 2.08 Å. Both Cr(3)-O(3) bond lengths are 2.07 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Cr(2) and one Cr(3) atom. In the second O site, O(2) is bonded to one Mg(1), one Cr(2), and two equivalent Cr(3) atoms to form distorted edge-sharing OMgCr3 tetrahedra. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Cr(1) and two equivalent Cr(3) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cr(1), and one Cr(3) atom.