MgHo6WO12 crystallizes in the trigonal R3 space group. Mg(1) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form MgO6 octahedra that share  a faceface with one W(1)O6 octahedra. There are two inequivalent Ho sites. In the first Ho site, Ho(1) is bonded in a 7-coordinate geometry to one O(3), two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms. In the second Ho site, Ho(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. W(1) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form WO6 octahedra that share  a faceface with one Mg(1)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), two equivalent Ho(1), and two equivalent Ho(2) atoms to form distorted OHo4Mg square pyramids that share corners with two equivalent O(1)Ho4Mg square pyramids, corners with two equivalent O(2)Ho4 tetrahedra, corners with two equivalent O(3)Ho3W trigonal pyramids, edges with two equivalent O(1)Ho4Mg square pyramids, edges with three equivalent O(2)Ho4 tetrahedra, and edges with two equivalent O(3)Ho3W trigonal pyramids. In the second O site, O(2) is bonded to two equivalent Ho(1) and two equivalent Ho(2) atoms to form OHo4 tetrahedra that share corners with two equivalent O(1)Ho4Mg square pyramids, corners with four equivalent O(2)Ho4 tetrahedra, corners with six equivalent O(3)Ho3W trigonal pyramids, and edges with three equivalent O(1)Ho4Mg square pyramids. In the third O site, O(3) is bonded to one Ho(1), two equivalent Ho(2), and one W(1) atom to form distorted OHo3W trigonal pyramids that share corners with two equivalent O(1)Ho4Mg square pyramids, corners with six equivalent O(2)Ho4 tetrahedra, corners with four equivalent O(3)Ho3W trigonal pyramids, and edges with two equivalent O(1)Ho4Mg square pyramids. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), two equivalent Ho(1), and one W(1) atom.
MgHo6WO12 crystallizes in the trigonal R3 space group. Mg(1) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form MgO6 octahedra that share  a faceface with one W(1)O6 octahedra. All Mg(1)-O(1) bond lengths are 2.14 Å. All Mg(1)-O(4) bond lengths are 2.12 Å. There are two inequivalent Ho sites. In the first Ho site, Ho(1) is bonded in a 7-coordinate geometry to one O(3), two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms. The Ho(1)-O(3) bond length is 2.52 Å. There is one shorter (2.25 Å) and one longer (2.47 Å) Ho(1)-O(1) bond length. There is one shorter (2.21 Å) and one longer (2.33 Å) Ho(1)-O(2) bond length. There is one shorter (2.21 Å) and one longer (2.39 Å) Ho(1)-O(4) bond length. In the second Ho site, Ho(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. Both Ho(2)-O(1) bond lengths are 2.39 Å. There is one shorter (2.24 Å) and one longer (2.26 Å) Ho(2)-O(2) bond length. There is one shorter (2.30 Å) and one longer (2.33 Å) Ho(2)-O(3) bond length. W(1) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form WO6 octahedra that share  a faceface with one Mg(1)O6 octahedra. All W(1)-O(3) bond lengths are 2.08 Å. All W(1)-O(4) bond lengths are 2.12 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), two equivalent Ho(1), and two equivalent Ho(2) atoms to form distorted OHo4Mg square pyramids that share corners with two equivalent O(1)Ho4Mg square pyramids, corners with two equivalent O(2)Ho4 tetrahedra, corners with two equivalent O(3)Ho3W trigonal pyramids, edges with two equivalent O(1)Ho4Mg square pyramids, edges with three equivalent O(2)Ho4 tetrahedra, and edges with two equivalent O(3)Ho3W trigonal pyramids. In the second O site, O(2) is bonded to two equivalent Ho(1) and two equivalent Ho(2) atoms to form OHo4 tetrahedra that share corners with two equivalent O(1)Ho4Mg square pyramids, corners with four equivalent O(2)Ho4 tetrahedra, corners with six equivalent O(3)Ho3W trigonal pyramids, and edges with three equivalent O(1)Ho4Mg square pyramids. In the third O site, O(3) is bonded to one Ho(1), two equivalent Ho(2), and one W(1) atom to form distorted OHo3W trigonal pyramids that share corners with two equivalent O(1)Ho4Mg square pyramids, corners with six equivalent O(2)Ho4 tetrahedra, corners with four equivalent O(3)Ho3W trigonal pyramids, and edges with two equivalent O(1)Ho4Mg square pyramids. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), two equivalent Ho(1), and one W(1) atom.