CaMg2Al4SiO12 crystallizes in the triclinic P1 space group. Ca(1) is bonded to one O(11), one O(12), one O(5), one O(6), one O(7), and one O(8) atom to form CaO6 octahedra that share corners with three equivalent Al(2)O4 tetrahedra, corners with three equivalent Al(3)O4 tetrahedra, corners with three equivalent Al(4)O4 tetrahedra, and corners with three equivalent Si(1)O4 tetrahedra. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(10), one O(2), one O(3), one O(4), and one O(9) atom to form MgO6 octahedra that share  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Al(3)O4 tetrahedra,  a cornercorner with one Al(4)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, edges with three equivalent Mg(2)O6 octahedra, and edges with three equivalent Al(1)O6 octahedra. In the second Mg site, Mg(2) is bonded to one O(1), one O(10), one O(2), one O(3), one O(4), and one O(9) atom to form MgO6 octahedra that share  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Al(3)O4 tetrahedra,  a cornercorner with one Al(4)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, edges with three equivalent Mg(1)O6 octahedra, and edges with three equivalent Al(1)O6 octahedra. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(10), one O(2), one O(3), one O(4), and one O(9) atom to form AlO6 octahedra that share  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Al(3)O4 tetrahedra,  a cornercorner with one Al(4)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, edges with three equivalent Mg(1)O6 octahedra, and edges with three equivalent Mg(2)O6 octahedra. In the second Al site, Al(2) is bonded to one O(11), one O(2), one O(5), and one O(6) atom to form AlO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Al(1)O6 octahedra, corners with three equivalent Ca(1)O6 octahedra, and corners with three equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 54-67°. In the third Al site, Al(3) is bonded to one O(12), one O(3), one O(7), and one O(8) atom to form AlO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Al(1)O6 octahedra, corners with three equivalent Ca(1)O6 octahedra, and corners with three equivalent Al(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 55-62°. In the fourth Al site, Al(4) is bonded to one O(12), one O(4), one O(7), and one O(8) atom to form AlO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Al(1)O6 octahedra, corners with three equivalent Ca(1)O6 octahedra, and corners with three equivalent Al(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 55-63°. Si(1) is bonded to one O(1), one O(11), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Al(1)O6 octahedra, corners with three equivalent Ca(1)O6 octahedra, and corners with three equivalent Al(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-61°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mg(2), one Al(1), and one Si(1) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mg(2), one Al(1), and one Al(2) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Mg(2), one Al(1), and one Al(3) atom. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Mg(2), one Al(1), and one Al(4) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(2), and one Si(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(2), and one Si(1) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Ca(1), one Al(3), and one Al(4) atom. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Ca(1), one Al(3), and one Al(4) atom. In the ninth O site, O(9) is bonded in a trigonal non-coplanar geometry to one Mg(1), one Mg(2), and one Al(1) atom. In the tenth O site, O(10) is bonded in a trigonal non-coplanar geometry to one Mg(1), one Mg(2), and one Al(1) atom. In the eleventh O site, O(11) is bonded in a trigonal planar geometry to one Ca(1), one Al(2), and one Si(1) atom. In the twelfth O site, O(12) is bonded in a trigonal planar geometry to one Ca(1), one Al(3), and one Al(4) atom.
CaMg2Al4SiO12 crystallizes in the triclinic P1 space group. Ca(1) is bonded to one O(11), one O(12), one O(5), one O(6), one O(7), and one O(8) atom to form CaO6 octahedra that share corners with three equivalent Al(2)O4 tetrahedra, corners with three equivalent Al(3)O4 tetrahedra, corners with three equivalent Al(4)O4 tetrahedra, and corners with three equivalent Si(1)O4 tetrahedra. The Ca(1)-O(11) bond length is 2.57 Å. The Ca(1)-O(12) bond length is 2.31 Å. The Ca(1)-O(5) bond length is 2.63 Å. The Ca(1)-O(6) bond length is 2.65 Å. The Ca(1)-O(7) bond length is 2.34 Å. The Ca(1)-O(8) bond length is 2.36 Å. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(10), one O(2), one O(3), one O(4), and one O(9) atom to form MgO6 octahedra that share  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Al(3)O4 tetrahedra,  a cornercorner with one Al(4)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, edges with three equivalent Mg(2)O6 octahedra, and edges with three equivalent Al(1)O6 octahedra. The Mg(1)-O(1) bond length is 2.10 Å. The Mg(1)-O(10) bond length is 2.06 Å. The Mg(1)-O(2) bond length is 2.13 Å. The Mg(1)-O(3) bond length is 2.10 Å. The Mg(1)-O(4) bond length is 2.05 Å. The Mg(1)-O(9) bond length is 2.07 Å. In the second Mg site, Mg(2) is bonded to one O(1), one O(10), one O(2), one O(3), one O(4), and one O(9) atom to form MgO6 octahedra that share  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Al(3)O4 tetrahedra,  a cornercorner with one Al(4)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, edges with three equivalent Mg(1)O6 octahedra, and edges with three equivalent Al(1)O6 octahedra. The Mg(2)-O(1) bond length is 2.20 Å. The Mg(2)-O(10) bond length is 2.05 Å. The Mg(2)-O(2) bond length is 2.07 Å. The Mg(2)-O(3) bond length is 2.04 Å. The Mg(2)-O(4) bond length is 2.14 Å. The Mg(2)-O(9) bond length is 2.05 Å. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(10), one O(2), one O(3), one O(4), and one O(9) atom to form AlO6 octahedra that share  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Al(3)O4 tetrahedra,  a cornercorner with one Al(4)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, edges with three equivalent Mg(1)O6 octahedra, and edges with three equivalent Mg(2)O6 octahedra. The Al(1)-O(1) bond length is 2.07 Å. The Al(1)-O(10) bond length is 1.87 Å. The Al(1)-O(2) bond length is 1.92 Å. The Al(1)-O(3) bond length is 1.92 Å. The Al(1)-O(4) bond length is 1.90 Å. The Al(1)-O(9) bond length is 1.88 Å. In the second Al site, Al(2) is bonded to one O(11), one O(2), one O(5), and one O(6) atom to form AlO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Al(1)O6 octahedra, corners with three equivalent Ca(1)O6 octahedra, and corners with three equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 54-67°. The Al(2)-O(11) bond length is 1.78 Å. The Al(2)-O(2) bond length is 1.76 Å. The Al(2)-O(5) bond length is 1.79 Å. The Al(2)-O(6) bond length is 1.79 Å. In the third Al site, Al(3) is bonded to one O(12), one O(3), one O(7), and one O(8) atom to form AlO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Al(1)O6 octahedra, corners with three equivalent Ca(1)O6 octahedra, and corners with three equivalent Al(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 55-62°. The Al(3)-O(12) bond length is 1.77 Å. The Al(3)-O(3) bond length is 1.79 Å. The Al(3)-O(7) bond length is 1.77 Å. The Al(3)-O(8) bond length is 1.77 Å. In the fourth Al site, Al(4) is bonded to one O(12), one O(4), one O(7), and one O(8) atom to form AlO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Al(1)O6 octahedra, corners with three equivalent Ca(1)O6 octahedra, and corners with three equivalent Al(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 55-63°. The Al(4)-O(12) bond length is 1.77 Å. The Al(4)-O(4) bond length is 1.80 Å. The Al(4)-O(7) bond length is 1.77 Å. The Al(4)-O(8) bond length is 1.77 Å. Si(1) is bonded to one O(1), one O(11), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Al(1)O6 octahedra, corners with three equivalent Ca(1)O6 octahedra, and corners with three equivalent Al(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-61°. The Si(1)-O(1) bond length is 1.66 Å. The Si(1)-O(11) bond length is 1.66 Å. The Si(1)-O(5) bond length is 1.66 Å. The Si(1)-O(6) bond length is 1.65 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mg(2), one Al(1), and one Si(1) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mg(2), one Al(1), and one Al(2) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Mg(2), one Al(1), and one Al(3) atom. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Mg(2), one Al(1), and one Al(4) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(2), and one Si(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(2), and one Si(1) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Ca(1), one Al(3), and one Al(4) atom. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Ca(1), one Al(3), and one Al(4) atom. In the ninth O site, O(9) is bonded in a trigonal non-coplanar geometry to one Mg(1), one Mg(2), and one Al(1) atom. In the tenth O site, O(10) is bonded in a trigonal non-coplanar geometry to one Mg(1), one Mg(2), and one Al(1) atom. In the eleventh O site, O(11) is bonded in a trigonal planar geometry to one Ca(1), one Al(2), and one Si(1) atom. In the twelfth O site, O(12) is bonded in a trigonal planar geometry to one Ca(1), one Al(3), and one Al(4) atom.