ZnCr2O4 crystallizes in the orthorhombic Cmcm space group. Cr(1) is bonded to one O(2), two equivalent O(3), and three equivalent O(1) atoms to form a mixture of corner and edge-sharing CrO6 octahedra. The corner-sharing octahedral tilt angles range from 0-55°. Zn(1) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(1) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Cr(1) and two equivalent Zn(1) atoms to form distorted OZn2Cr3 trigonal bipyramids that share corners with five equivalent O(2)Zn2Cr2 tetrahedra, corners with two equivalent O(1)Zn2Cr3 trigonal bipyramids,  an edgeedge with one O(2)Zn2Cr2 tetrahedra, and edges with five equivalent O(1)Zn2Cr3 trigonal bipyramids. In the second O site, O(2) is bonded to two equivalent Cr(1) and two equivalent Zn(1) atoms to form OZn2Cr2 tetrahedra that share corners with two equivalent O(2)Zn2Cr2 tetrahedra, corners with ten equivalent O(1)Zn2Cr3 trigonal bipyramids, and edges with two equivalent O(1)Zn2Cr3 trigonal bipyramids. In the third O site, O(3) is bonded in a square co-planar geometry to four equivalent Cr(1) atoms.
ZnCr2O4 crystallizes in the orthorhombic Cmcm space group. Cr(1) is bonded to one O(2), two equivalent O(3), and three equivalent O(1) atoms to form a mixture of corner and edge-sharing CrO6 octahedra. The corner-sharing octahedral tilt angles range from 0-55°. The Cr(1)-O(2) bond length is 2.01 Å. Both Cr(1)-O(3) bond lengths are 2.07 Å. There are two shorter (2.01 Å) and one longer (2.04 Å) Cr(1)-O(1) bond length. Zn(1) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(1) atoms. Both Zn(1)-O(2) bond lengths are 2.03 Å. All Zn(1)-O(1) bond lengths are 2.34 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Cr(1) and two equivalent Zn(1) atoms to form distorted OZn2Cr3 trigonal bipyramids that share corners with five equivalent O(2)Zn2Cr2 tetrahedra, corners with two equivalent O(1)Zn2Cr3 trigonal bipyramids,  an edgeedge with one O(2)Zn2Cr2 tetrahedra, and edges with five equivalent O(1)Zn2Cr3 trigonal bipyramids. In the second O site, O(2) is bonded to two equivalent Cr(1) and two equivalent Zn(1) atoms to form OZn2Cr2 tetrahedra that share corners with two equivalent O(2)Zn2Cr2 tetrahedra, corners with ten equivalent O(1)Zn2Cr3 trigonal bipyramids, and edges with two equivalent O(1)Zn2Cr3 trigonal bipyramids. In the third O site, O(3) is bonded in a square co-planar geometry to four equivalent Cr(1) atoms.