MgNb3SiO10 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 6-coordinate geometry to one O(3), one O(4), one O(5), one O(7), one O(8), and one O(9) atom. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(3), one O(4), one O(5), one O(6), and one O(8) atom to form NbO6 octahedra that share corners with three equivalent Nb(3)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, and  an edgeedge with one Si(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 32-65°. In the second Nb site, Nb(2) is bonded to one O(10), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form NbO6 octahedra that share corners with three equivalent Si(1)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, and  an edgeedge with one Nb(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 32-61°. In the third Nb site, Nb(3) is bonded to one O(1), one O(10), one O(2), one O(4), one O(8), and one O(9) atom to form distorted NbO6 octahedra that share corners with three equivalent Nb(1)O6 octahedra, corners with four equivalent Si(1)O6 octahedra, and  an edgeedge with one Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 26-65°. Si(1) is bonded to one O(1), one O(10), one O(2), one O(6), one O(7), and one O(9) atom to form SiO6 octahedra that share corners with three equivalent Nb(2)O6 octahedra, corners with four equivalent Nb(3)O6 octahedra, and  an edgeedge with one Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 26-48°. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Nb(1), one Nb(3), and one Si(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Nb(3) and one Si(1) atom. In the third O site, O(3) is bonded in a T-shaped geometry to one Mg(1), one Nb(1), and one Nb(2) atom. In the fourth O site, O(4) is bonded in a distorted see-saw-like geometry to one Mg(1), one Nb(1), one Nb(2), and one Nb(3) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Mg(1), one Nb(1), and one Nb(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Nb(1), one Nb(2), and one Si(1) atom. In the seventh O site, O(7) is bonded in a T-shaped geometry to one Mg(1), one Nb(2), and one Si(1) atom. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Mg(1), one Nb(1), and one Nb(3) atom. In the ninth O site, O(9) is bonded in a distorted T-shaped geometry to one Mg(1), one Nb(3), and one Si(1) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Nb(2), one Nb(3), and one Si(1) atom.
MgNb3SiO10 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 6-coordinate geometry to one O(3), one O(4), one O(5), one O(7), one O(8), and one O(9) atom. The Mg(1)-O(3) bond length is 2.16 Å. The Mg(1)-O(4) bond length is 2.32 Å. The Mg(1)-O(5) bond length is 2.00 Å. The Mg(1)-O(7) bond length is 2.06 Å. The Mg(1)-O(8) bond length is 1.98 Å. The Mg(1)-O(9) bond length is 1.98 Å. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(3), one O(4), one O(5), one O(6), and one O(8) atom to form NbO6 octahedra that share corners with three equivalent Nb(3)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, and  an edgeedge with one Si(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 32-65°. The Nb(1)-O(1) bond length is 2.09 Å. The Nb(1)-O(3) bond length is 1.90 Å. The Nb(1)-O(4) bond length is 2.03 Å. The Nb(1)-O(5) bond length is 2.06 Å. The Nb(1)-O(6) bond length is 2.09 Å. The Nb(1)-O(8) bond length is 2.03 Å. In the second Nb site, Nb(2) is bonded to one O(10), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form NbO6 octahedra that share corners with three equivalent Si(1)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, and  an edgeedge with one Nb(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 32-61°. The Nb(2)-O(10) bond length is 2.04 Å. The Nb(2)-O(3) bond length is 2.02 Å. The Nb(2)-O(4) bond length is 2.19 Å. The Nb(2)-O(5) bond length is 1.91 Å. The Nb(2)-O(6) bond length is 2.08 Å. The Nb(2)-O(7) bond length is 2.07 Å. In the third Nb site, Nb(3) is bonded to one O(1), one O(10), one O(2), one O(4), one O(8), and one O(9) atom to form distorted NbO6 octahedra that share corners with three equivalent Nb(1)O6 octahedra, corners with four equivalent Si(1)O6 octahedra, and  an edgeedge with one Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 26-65°. The Nb(3)-O(1) bond length is 2.10 Å. The Nb(3)-O(10) bond length is 2.48 Å. The Nb(3)-O(2) bond length is 1.83 Å. The Nb(3)-O(4) bond length is 2.13 Å. The Nb(3)-O(8) bond length is 1.96 Å. The Nb(3)-O(9) bond length is 2.03 Å. Si(1) is bonded to one O(1), one O(10), one O(2), one O(6), one O(7), and one O(9) atom to form SiO6 octahedra that share corners with three equivalent Nb(2)O6 octahedra, corners with four equivalent Nb(3)O6 octahedra, and  an edgeedge with one Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 26-48°. The Si(1)-O(1) bond length is 1.88 Å. The Si(1)-O(10) bond length is 1.86 Å. The Si(1)-O(2) bond length is 1.91 Å. The Si(1)-O(6) bond length is 1.86 Å. The Si(1)-O(7) bond length is 1.78 Å. The Si(1)-O(9) bond length is 1.78 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Nb(1), one Nb(3), and one Si(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Nb(3) and one Si(1) atom. In the third O site, O(3) is bonded in a T-shaped geometry to one Mg(1), one Nb(1), and one Nb(2) atom. In the fourth O site, O(4) is bonded in a distorted see-saw-like geometry to one Mg(1), one Nb(1), one Nb(2), and one Nb(3) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Mg(1), one Nb(1), and one Nb(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Nb(1), one Nb(2), and one Si(1) atom. In the seventh O site, O(7) is bonded in a T-shaped geometry to one Mg(1), one Nb(2), and one Si(1) atom. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Mg(1), one Nb(1), and one Nb(3) atom. In the ninth O site, O(9) is bonded in a distorted T-shaped geometry to one Mg(1), one Nb(3), and one Si(1) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Nb(2), one Nb(3), and one Si(1) atom.