MgHg(SbO3)2 crystallizes in the monoclinic Cm space group. Mg(1) is bonded in a 5-coordinate geometry to one Hg(1), one O(1), one O(2), and two equivalent O(4) atoms. Hg(1) is bonded to one Mg(1), one O(2), and two equivalent O(3) atoms to form distorted HgMgO3 tetrahedra that share corners with six equivalent Sb(1)O6 octahedra and  a cornercorner with one O(2)MgHgSb2 trigonal pyramid. The corner-sharing octahedral tilt angles range from 51-63°. Sb(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted SbO6 octahedra that share corners with three equivalent Hg(1)MgO3 tetrahedra and edges with three equivalent Sb(1)O6 octahedra. 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 Sb(1) atoms. In the second O site, O(2) is bonded to one Mg(1), one Hg(1), and two equivalent Sb(1) atoms to form distorted OMgHgSb2 trigonal pyramids that share  a cornercorner with one Hg(1)MgO3 tetrahedra. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Hg(1) and two equivalent Sb(1) atoms. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Mg(1) and two equivalent Sb(1) atoms.
MgHg(SbO3)2 crystallizes in the monoclinic Cm space group. Mg(1) is bonded in a 5-coordinate geometry to one Hg(1), one O(1), one O(2), and two equivalent O(4) atoms. The Mg(1)-Hg(1) bond length is 2.60 Å. The Mg(1)-O(1) bond length is 2.17 Å. The Mg(1)-O(2) bond length is 2.12 Å. Both Mg(1)-O(4) bond lengths are 2.09 Å. Hg(1) is bonded to one Mg(1), one O(2), and two equivalent O(3) atoms to form distorted HgMgO3 tetrahedra that share corners with six equivalent Sb(1)O6 octahedra and  a cornercorner with one O(2)MgHgSb2 trigonal pyramid. The corner-sharing octahedral tilt angles range from 51-63°. The Hg(1)-O(2) bond length is 2.64 Å. Both Hg(1)-O(3) bond lengths are 2.53 Å. Sb(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted SbO6 octahedra that share corners with three equivalent Hg(1)MgO3 tetrahedra and edges with three equivalent Sb(1)O6 octahedra. The Sb(1)-O(1) bond length is 2.08 Å. The Sb(1)-O(2) bond length is 2.05 Å. There is one shorter (2.00 Å) and one longer (2.03 Å) Sb(1)-O(3) bond length. There is one shorter (2.07 Å) and one longer (2.10 Å) Sb(1)-O(4) bond length. 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 Sb(1) atoms. In the second O site, O(2) is bonded to one Mg(1), one Hg(1), and two equivalent Sb(1) atoms to form distorted OMgHgSb2 trigonal pyramids that share  a cornercorner with one Hg(1)MgO3 tetrahedra. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Hg(1) and two equivalent Sb(1) atoms. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Mg(1) and two equivalent Sb(1) atoms.