MgCrO4 crystallizes in the monoclinic C2/m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Cr(1)O4 tetrahedra, corners with four equivalent Cr(2)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and edges with two equivalent Mg(2)O6 octahedra. In the second Mg site, Mg(2) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with two equivalent Cr(2)O4 tetrahedra, corners with four equivalent Cr(1)O4 tetrahedra, and edges with two equivalent Mg(1)O6 octahedra. There are two 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 two equivalent Mg(1)O6 octahedra and corners with four equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 19-55°. In the second Cr site, Cr(2) is bonded to one O(1), one O(2), and two equivalent O(5) atoms to form CrO4 tetrahedra that share corners with two equivalent Mg(2)O6 octahedra and corners with four equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 15-63°. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Mg(2), two equivalent Mg(1), and one Cr(2) atom to form distorted edge-sharing OMg3Cr tetrahedra. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Mg(2) and one Cr(2) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Mg(2) and one Cr(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one Cr(1) atom. In the fifth O site, O(5) is bonded in a linear geometry to one Mg(1) and one Cr(2) atom.
MgCrO4 crystallizes in the monoclinic C2/m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Cr(1)O4 tetrahedra, corners with four equivalent Cr(2)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and edges with two equivalent Mg(2)O6 octahedra. Both Mg(1)-O(1) bond lengths are 2.19 Å. Both Mg(1)-O(4) bond lengths are 2.12 Å. Both Mg(1)-O(5) bond lengths are 2.08 Å. In the second Mg site, Mg(2) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with two equivalent Cr(2)O4 tetrahedra, corners with four equivalent Cr(1)O4 tetrahedra, and edges with two equivalent Mg(1)O6 octahedra. The Mg(2)-O(1) bond length is 2.17 Å. The Mg(2)-O(2) bond length is 2.04 Å. Both Mg(2)-O(3) bond lengths are 2.10 Å. Both Mg(2)-O(4) bond lengths are 2.13 Å. There are two 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 two equivalent Mg(1)O6 octahedra and corners with four equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 19-55°. Both Cr(1)-O(3) bond lengths are 1.64 Å. Both Cr(1)-O(4) bond lengths are 1.70 Å. In the second Cr site, Cr(2) is bonded to one O(1), one O(2), and two equivalent O(5) atoms to form CrO4 tetrahedra that share corners with two equivalent Mg(2)O6 octahedra and corners with four equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 15-63°. The Cr(2)-O(1) bond length is 1.76 Å. The Cr(2)-O(2) bond length is 1.64 Å. Both Cr(2)-O(5) bond lengths are 1.64 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Mg(2), two equivalent Mg(1), and one Cr(2) atom to form distorted edge-sharing OMg3Cr tetrahedra. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Mg(2) and one Cr(2) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Mg(2) and one Cr(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one Cr(1) atom. In the fifth O site, O(5) is bonded in a linear geometry to one Mg(1) and one Cr(2) atom.