KMg6BO7 crystallizes in the tetragonal P4mm space group. K(1) is bonded to one O(1), one O(2), and four equivalent O(4) atoms to form KO6 octahedra that share corners with four equivalent K(1)O6 octahedra, edges with four equivalent Mg(4)O6 octahedra, and edges with four equivalent Mg(1)O5 square pyramids. The corner-sharing octahedral tilt angles are 1°. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(3) and four equivalent O(4) atoms to form MgO5 square pyramids that share  a cornercorner with one Mg(2)O5 square pyramid, corners with four equivalent Mg(1)O5 square pyramids, edges with four equivalent K(1)O6 octahedra, and edges with four equivalent Mg(4)O6 octahedra. In the second Mg site, Mg(2) is bonded to one O(3) and four equivalent O(5) atoms to form MgO5 square pyramids that share  a cornercorner with one Mg(1)O5 square pyramid, corners with four equivalent Mg(2)O5 square pyramids, and edges with four equivalent Mg(4)O6 octahedra. In the third Mg site, Mg(3) is bonded in a 4-coordinate geometry to one O(4), one O(5), and two equivalent O(1) atoms. In the fourth Mg site, Mg(4) is bonded to one O(4), one O(5), two equivalent O(2), and two equivalent O(3) atoms to form distorted MgO6 octahedra that share corners with four equivalent Mg(4)O6 octahedra, edges with two equivalent K(1)O6 octahedra, edges with four equivalent Mg(4)O6 octahedra, edges with two equivalent Mg(1)O5 square pyramids, and edges with two equivalent Mg(2)O5 square pyramids. The corner-sharing octahedral tilt angles range from 3-27°. B(1) is bonded in a linear geometry to one O(1) and one O(2) atom. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one K(1), four equivalent Mg(3), and one B(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one K(1), four equivalent Mg(4), and one B(1) atom. In the third O site, O(3) is bonded to one Mg(1), one Mg(2), and four equivalent Mg(4) atoms to form OMg6 octahedra that share corners with four equivalent O(3)Mg6 octahedra and edges with four equivalent O(4)K2Mg4 octahedra. The corner-sharing octahedral tilt angles are 3°. In the fourth O site, O(4) is bonded to two equivalent K(1), one Mg(3), one Mg(4), and two equivalent Mg(1) atoms to form OK2Mg4 octahedra that share corners with four equivalent O(4)K2Mg4 octahedra, edges with two equivalent O(3)Mg6 octahedra, and edges with four equivalent O(4)K2Mg4 octahedra. The corner-sharing octahedral tilt angles range from 1-2°. In the fifth O site, O(5) is bonded in a square co-planar geometry to one Mg(3), one Mg(4), and two equivalent Mg(2) atoms.
KMg6BO7 crystallizes in the tetragonal P4mm space group. K(1) is bonded to one O(1), one O(2), and four equivalent O(4) atoms to form KO6 octahedra that share corners with four equivalent K(1)O6 octahedra, edges with four equivalent Mg(4)O6 octahedra, and edges with four equivalent Mg(1)O5 square pyramids. The corner-sharing octahedral tilt angles are 1°. The K(1)-O(1) bond length is 2.59 Å. The K(1)-O(2) bond length is 2.59 Å. All K(1)-O(4) bond lengths are 2.39 Å. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(3) and four equivalent O(4) atoms to form MgO5 square pyramids that share  a cornercorner with one Mg(2)O5 square pyramid, corners with four equivalent Mg(1)O5 square pyramids, edges with four equivalent K(1)O6 octahedra, and edges with four equivalent Mg(4)O6 octahedra. The Mg(1)-O(3) bond length is 1.99 Å. All Mg(1)-O(4) bond lengths are 2.39 Å. In the second Mg site, Mg(2) is bonded to one O(3) and four equivalent O(5) atoms to form MgO5 square pyramids that share  a cornercorner with one Mg(1)O5 square pyramid, corners with four equivalent Mg(2)O5 square pyramids, and edges with four equivalent Mg(4)O6 octahedra. The Mg(2)-O(3) bond length is 2.00 Å. All Mg(2)-O(5) bond lengths are 2.39 Å. In the third Mg site, Mg(3) is bonded in a 4-coordinate geometry to one O(4), one O(5), and two equivalent O(1) atoms. The Mg(3)-O(4) bond length is 2.01 Å. The Mg(3)-O(5) bond length is 1.92 Å. Both Mg(3)-O(1) bond lengths are 2.46 Å. In the fourth Mg site, Mg(4) is bonded to one O(4), one O(5), two equivalent O(2), and two equivalent O(3) atoms to form distorted MgO6 octahedra that share corners with four equivalent Mg(4)O6 octahedra, edges with two equivalent K(1)O6 octahedra, edges with four equivalent Mg(4)O6 octahedra, edges with two equivalent Mg(1)O5 square pyramids, and edges with two equivalent Mg(2)O5 square pyramids. The corner-sharing octahedral tilt angles range from 3-27°. The Mg(4)-O(4) bond length is 2.01 Å. The Mg(4)-O(5) bond length is 1.92 Å. Both Mg(4)-O(2) bond lengths are 2.46 Å. Both Mg(4)-O(3) bond lengths are 2.39 Å. B(1) is bonded in a linear geometry to one O(1) and one O(2) atom. The B(1)-O(1) bond length is 1.34 Å. The B(1)-O(2) bond length is 1.34 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one K(1), four equivalent Mg(3), and one B(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one K(1), four equivalent Mg(4), and one B(1) atom. In the third O site, O(3) is bonded to one Mg(1), one Mg(2), and four equivalent Mg(4) atoms to form OMg6 octahedra that share corners with four equivalent O(3)Mg6 octahedra and edges with four equivalent O(4)K2Mg4 octahedra. The corner-sharing octahedral tilt angles are 3°. In the fourth O site, O(4) is bonded to two equivalent K(1), one Mg(3), one Mg(4), and two equivalent Mg(1) atoms to form OK2Mg4 octahedra that share corners with four equivalent O(4)K2Mg4 octahedra, edges with two equivalent O(3)Mg6 octahedra, and edges with four equivalent O(4)K2Mg4 octahedra. The corner-sharing octahedral tilt angles range from 1-2°. In the fifth O site, O(5) is bonded in a square co-planar geometry to one Mg(3), one Mg(4), and two equivalent Mg(2) atoms.