Ca2MgAl2(SiO4)3 is Esseneite-derived structured and crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(3), one O(4), one O(5), one O(7), one O(8), and two equivalent O(6) atoms. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(11), one O(2), one O(7), one O(9), and two equivalent O(12) atoms. Mg(1) is bonded to one O(10), one O(2), one O(4), one O(5), and two equivalent O(3) atoms to form MgO6 octahedra that share  a cornercorner with one Si(3)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Al(2)O6 octahedra. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(12), one O(7), one O(8), and one O(9) atom to form AlO4 tetrahedra that share corners with three equivalent Al(2)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 33-62°. In the second Al site, Al(2) is bonded to one O(10), one O(11), one O(4), one O(8), and two equivalent O(9) atoms to form AlO6 octahedra that share  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, corners with three equivalent Al(1)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Al(2)O6 octahedra. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form SiO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 38-59°. In the second Si site, Si(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra,  a cornercorner with one Al(1)O4 tetrahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 41-60°. In the third Si site, Si(3) is bonded to one O(1), one O(10), one O(11), and one O(12) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent Al(2)O6 octahedra,  a cornercorner with one Al(1)O4 tetrahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 34-62°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Ca(1), one Ca(2), one Si(1), and one Si(3) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ca(2), one Mg(1), and one Si(1) atom. In the third O site, O(3) is bonded to one Ca(1), two equivalent Mg(1), and one Si(1) atom to form distorted edge-sharing OCaMg2Si tetrahedra. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(1), one Mg(1), one Al(2), and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ca(1), one Mg(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to two equivalent Ca(1), one Si(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(1), and one Si(2) atom. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Ca(1), one Al(1), and one Al(2) atom. In the ninth O site, O(9) is bonded to one Ca(2), one Al(1), and two equivalent Al(2) atoms to form distorted edge-sharing OCaAl3 tetrahedra. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Ca(2), one Mg(1), one Al(2), and one Si(3) atom. In the eleventh O site, O(11) is bonded in a distorted T-shaped geometry to one Ca(2), one Al(2), and one Si(3) atom. In the twelfth O site, O(12) is bonded in a 4-coordinate geometry to two equivalent Ca(2), one Al(1), and one Si(3) atom.
Ca2MgAl2(SiO4)3 is Esseneite-derived structured and crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(3), one O(4), one O(5), one O(7), one O(8), and two equivalent O(6) atoms. The Ca(1)-O(1) bond length is 2.63 Å. The Ca(1)-O(3) bond length is 2.36 Å. The Ca(1)-O(4) bond length is 2.42 Å. The Ca(1)-O(5) bond length is 2.37 Å. The Ca(1)-O(7) bond length is 2.49 Å. The Ca(1)-O(8) bond length is 2.36 Å. There is one shorter (2.59 Å) and one longer (2.76 Å) Ca(1)-O(6) bond length. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(11), one O(2), one O(7), one O(9), and two equivalent O(12) atoms. The Ca(2)-O(1) bond length is 2.63 Å. The Ca(2)-O(10) bond length is 2.41 Å. The Ca(2)-O(11) bond length is 2.41 Å. The Ca(2)-O(2) bond length is 2.34 Å. The Ca(2)-O(7) bond length is 2.70 Å. The Ca(2)-O(9) bond length is 2.42 Å. There is one shorter (2.47 Å) and one longer (2.61 Å) Ca(2)-O(12) bond length. Mg(1) is bonded to one O(10), one O(2), one O(4), one O(5), and two equivalent O(3) atoms to form MgO6 octahedra that share  a cornercorner with one Si(3)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Al(2)O6 octahedra. The Mg(1)-O(10) bond length is 2.09 Å. The Mg(1)-O(2) bond length is 2.06 Å. The Mg(1)-O(4) bond length is 2.16 Å. The Mg(1)-O(5) bond length is 2.06 Å. There is one shorter (2.06 Å) and one longer (2.14 Å) Mg(1)-O(3) bond length. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(12), one O(7), one O(8), and one O(9) atom to form AlO4 tetrahedra that share corners with three equivalent Al(2)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 33-62°. The Al(1)-O(12) bond length is 1.79 Å. The Al(1)-O(7) bond length is 1.81 Å. The Al(1)-O(8) bond length is 1.74 Å. The Al(1)-O(9) bond length is 1.77 Å. In the second Al site, Al(2) is bonded to one O(10), one O(11), one O(4), one O(8), and two equivalent O(9) atoms to form AlO6 octahedra that share  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, corners with three equivalent Al(1)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Al(2)O6 octahedra. The Al(2)-O(10) bond length is 2.10 Å. The Al(2)-O(11) bond length is 1.96 Å. The Al(2)-O(4) bond length is 1.97 Å. The Al(2)-O(8) bond length is 1.85 Å. There is one shorter (1.94 Å) and one longer (1.97 Å) Al(2)-O(9) bond length. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form SiO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 38-59°. The Si(1)-O(1) bond length is 1.70 Å. The Si(1)-O(2) bond length is 1.61 Å. The Si(1)-O(3) bond length is 1.62 Å. The Si(1)-O(6) bond length is 1.67 Å. In the second Si site, Si(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra,  a cornercorner with one Al(1)O4 tetrahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 41-60°. The Si(2)-O(4) bond length is 1.65 Å. The Si(2)-O(5) bond length is 1.61 Å. The Si(2)-O(6) bond length is 1.71 Å. The Si(2)-O(7) bond length is 1.65 Å. In the third Si site, Si(3) is bonded to one O(1), one O(10), one O(11), and one O(12) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent Al(2)O6 octahedra,  a cornercorner with one Al(1)O4 tetrahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 34-62°. The Si(3)-O(1) bond length is 1.68 Å. The Si(3)-O(10) bond length is 1.64 Å. The Si(3)-O(11) bond length is 1.63 Å. The Si(3)-O(12) bond length is 1.65 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Ca(1), one Ca(2), one Si(1), and one Si(3) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ca(2), one Mg(1), and one Si(1) atom. In the third O site, O(3) is bonded to one Ca(1), two equivalent Mg(1), and one Si(1) atom to form distorted edge-sharing OCaMg2Si tetrahedra. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(1), one Mg(1), one Al(2), and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ca(1), one Mg(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to two equivalent Ca(1), one Si(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(1), and one Si(2) atom. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Ca(1), one Al(1), and one Al(2) atom. In the ninth O site, O(9) is bonded to one Ca(2), one Al(1), and two equivalent Al(2) atoms to form distorted edge-sharing OCaAl3 tetrahedra. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Ca(2), one Mg(1), one Al(2), and one Si(3) atom. In the eleventh O site, O(11) is bonded in a distorted T-shaped geometry to one Ca(2), one Al(2), and one Si(3) atom. In the twelfth O site, O(12) is bonded in a 4-coordinate geometry to two equivalent Ca(2), one Al(1), and one Si(3) atom.