Mg3SiO6 is beta indium sulfide-derived structured and crystallizes in the orthorhombic Pnma space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form MgO6 octahedra that share corners with eight equivalent Mg(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent Mg(2)O6 octahedra, and  an edgeedge with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-57°. In the second Mg site, Mg(2) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, and  an edgeedge with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-60°. Si(1) is bonded to one O(3), one O(4), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra, and edges with two equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 56-60°. There are four inequivalent O sites. In the first O site, O(3) is bonded in a 4-coordinate geometry to one Mg(1), two equivalent Mg(2), and one Si(1) atom. In the second O site, O(4) is bonded in a rectangular see-saw-like geometry to one Mg(1), two equivalent Mg(2), and one Si(1) atom. In the third O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Mg(2), and one Si(1) atom. In the fourth O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1) and two equivalent Mg(2) atoms.
Mg3SiO6 is beta indium sulfide-derived structured and crystallizes in the orthorhombic Pnma space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form MgO6 octahedra that share corners with eight equivalent Mg(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent Mg(2)O6 octahedra, and  an edgeedge with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-57°. The Mg(1)-O(3) bond length is 2.25 Å. The Mg(1)-O(4) bond length is 2.08 Å. Both Mg(1)-O(1) bond lengths are 2.20 Å. Both Mg(1)-O(2) bond lengths are 2.06 Å. In the second Mg site, Mg(2) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, and  an edgeedge with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-60°. The Mg(2)-O(3) bond length is 2.14 Å. The Mg(2)-O(4) bond length is 2.21 Å. There is one shorter (2.03 Å) and one longer (2.17 Å) Mg(2)-O(1) bond length. There is one shorter (2.07 Å) and one longer (2.09 Å) Mg(2)-O(2) bond length. Si(1) is bonded to one O(3), one O(4), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra, and edges with two equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 56-60°. The Si(1)-O(3) bond length is 1.63 Å. The Si(1)-O(4) bond length is 1.66 Å. Both Si(1)-O(1) bond lengths are 1.66 Å. There are four inequivalent O sites. In the first O site, O(3) is bonded in a 4-coordinate geometry to one Mg(1), two equivalent Mg(2), and one Si(1) atom. In the second O site, O(4) is bonded in a rectangular see-saw-like geometry to one Mg(1), two equivalent Mg(2), and one Si(1) atom. In the third O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Mg(2), and one Si(1) atom. In the fourth O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1) and two equivalent Mg(2) atoms.