Mg2W3O8 crystallizes in the hexagonal P6_3mc space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent W(1)O6 octahedra, corners with three equivalent Mg(2)O4 trigonal pyramids, and edges with three equivalent W(1)O6 octahedra. The corner-sharing octahedral tilt angles are 51°. In the second Mg site, Mg(2) is bonded to one O(4) and three equivalent O(2) atoms to form MgO4 trigonal pyramids that share corners with three equivalent Mg(1)O6 octahedra and corners with nine equivalent W(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-65°. W(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form WO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with three equivalent Mg(2)O4 trigonal pyramids,  an edgeedge with one Mg(1)O6 octahedra, and edges with four equivalent W(1)O6 octahedra. The corner-sharing octahedral tilt angles are 51°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Mg(1) and two equivalent W(1) atoms. In the second O site, O(2) is bonded to one Mg(1), one Mg(2), and two equivalent W(1) atoms to form a mixture of distorted corner and edge-sharing OMg2W2 tetrahedra. In the third O site, O(3) is bonded in a distorted T-shaped geometry to three equivalent W(1) atoms. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Mg(2) and three equivalent W(1) atoms.
Mg2W3O8 crystallizes in the hexagonal P6_3mc space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent W(1)O6 octahedra, corners with three equivalent Mg(2)O4 trigonal pyramids, and edges with three equivalent W(1)O6 octahedra. The corner-sharing octahedral tilt angles are 51°. All Mg(1)-O(1) bond lengths are 2.11 Å. All Mg(1)-O(2) bond lengths are 2.17 Å. In the second Mg site, Mg(2) is bonded to one O(4) and three equivalent O(2) atoms to form MgO4 trigonal pyramids that share corners with three equivalent Mg(1)O6 octahedra and corners with nine equivalent W(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-65°. The Mg(2)-O(4) bond length is 2.03 Å. All Mg(2)-O(2) bond lengths are 2.03 Å. W(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form WO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with three equivalent Mg(2)O4 trigonal pyramids,  an edgeedge with one Mg(1)O6 octahedra, and edges with four equivalent W(1)O6 octahedra. The corner-sharing octahedral tilt angles are 51°. The W(1)-O(3) bond length is 2.10 Å. The W(1)-O(4) bond length is 2.14 Å. Both W(1)-O(1) bond lengths are 2.04 Å. Both W(1)-O(2) bond lengths are 2.14 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Mg(1) and two equivalent W(1) atoms. In the second O site, O(2) is bonded to one Mg(1), one Mg(2), and two equivalent W(1) atoms to form a mixture of distorted corner and edge-sharing OMg2W2 tetrahedra. In the third O site, O(3) is bonded in a distorted T-shaped geometry to three equivalent W(1) atoms. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Mg(2) and three equivalent W(1) atoms.