Ca2Al2(SiO4)3 crystallizes in the orthorhombic Pma2 space group. Ca(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form AlO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. In the second Al site, Al(2) is bonded to one O(6), one O(7), two equivalent O(4), and two equivalent O(5) atoms to form AlO6 octahedra that share corners with four equivalent Si(2)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form SiO4 tetrahedra that share corners with two equivalent Al(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form SiO4 tetrahedra that share 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 47-52°. There are seven inequivalent O sites. In the first O site, O(6) is bonded in a trigonal non-coplanar geometry to two equivalent Ca(1) and one Al(2) atom. In the second O site, O(7) is bonded in a trigonal non-coplanar geometry to two equivalent Ca(1) and one Al(2) atom. In the third O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Al(1), and one Si(1) atom. In the fourth O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Ca(1), one Si(1), and one Si(2) atom. In the fifth O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Al(1), and one Si(2) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(2), and one Si(2) atom. In the seventh O site, O(5) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(2), and one Si(2) atom.
Ca2Al2(SiO4)3 crystallizes in the orthorhombic Pma2 space group. Ca(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom. The Ca(1)-O(1) bond length is 2.42 Å. The Ca(1)-O(2) bond length is 2.79 Å. The Ca(1)-O(3) bond length is 2.58 Å. The Ca(1)-O(4) bond length is 2.41 Å. The Ca(1)-O(5) bond length is 2.41 Å. The Ca(1)-O(6) bond length is 2.33 Å. The Ca(1)-O(7) bond length is 2.33 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form AlO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. Both Al(1)-O(1) bond lengths are 1.76 Å. Both Al(1)-O(3) bond lengths are 1.75 Å. In the second Al site, Al(2) is bonded to one O(6), one O(7), two equivalent O(4), and two equivalent O(5) atoms to form AlO6 octahedra that share corners with four equivalent Si(2)O4 tetrahedra. The Al(2)-O(6) bond length is 1.90 Å. The Al(2)-O(7) bond length is 1.89 Å. Both Al(2)-O(4) bond lengths are 1.94 Å. Both Al(2)-O(5) bond lengths are 1.93 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form SiO4 tetrahedra that share corners with two equivalent Al(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. Both Si(1)-O(1) bond lengths are 1.62 Å. Both Si(1)-O(2) bond lengths are 1.65 Å. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form SiO4 tetrahedra that share 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 47-52°. The Si(2)-O(2) bond length is 1.69 Å. The Si(2)-O(3) bond length is 1.65 Å. The Si(2)-O(4) bond length is 1.63 Å. The Si(2)-O(5) bond length is 1.63 Å. There are seven inequivalent O sites. In the first O site, O(6) is bonded in a trigonal non-coplanar geometry to two equivalent Ca(1) and one Al(2) atom. In the second O site, O(7) is bonded in a trigonal non-coplanar geometry to two equivalent Ca(1) and one Al(2) atom. In the third O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Al(1), and one Si(1) atom. In the fourth O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Ca(1), one Si(1), and one Si(2) atom. In the fifth O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Al(1), and one Si(2) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(2), and one Si(2) atom. In the seventh O site, O(5) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(2), and one Si(2) atom.