Ca2MgSi2O7 is Esseneite-like structured and crystallizes in the monoclinic P2_1/c 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), two equivalent O(6), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(5), one O(7), and two equivalent O(4) atoms. Mg(1) is bonded to one O(1), one O(2), one O(5), and one O(6) atom to form MgO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra and corners with two equivalent Mg(1)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with two equivalent Mg(1)O4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(7) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one Si(1) atom. In the second O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), one Mg(1), and one Si(2) atom. In the third O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(2), one Mg(1), and one Si(2) atom. In the fourth O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Si(1), and one Si(2) atom. In the fifth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(1), two equivalent Ca(2), and one Si(2) atom. In the sixth O site, O(5) is bonded in a distorted tetrahedral geometry to one Ca(1), one Ca(2), one Mg(1), and one Si(1) atom. In the seventh O site, O(6) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Mg(1), and one Si(1) atom.
Ca2MgSi2O7 is Esseneite-like structured and crystallizes in the monoclinic P2_1/c 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), two equivalent O(6), and two equivalent O(7) atoms. The Ca(1)-O(1) bond length is 2.92 Å. The Ca(1)-O(3) bond length is 2.45 Å. The Ca(1)-O(4) bond length is 2.48 Å. The Ca(1)-O(5) bond length is 2.40 Å. There is one shorter (2.43 Å) and one longer (2.75 Å) Ca(1)-O(6) bond length. There is one shorter (2.44 Å) and one longer (2.83 Å) Ca(1)-O(7) bond length. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(5), one O(7), and two equivalent O(4) atoms. The Ca(2)-O(1) bond length is 2.38 Å. The Ca(2)-O(2) bond length is 2.31 Å. The Ca(2)-O(5) bond length is 2.40 Å. The Ca(2)-O(7) bond length is 2.64 Å. There is one shorter (2.46 Å) and one longer (2.50 Å) Ca(2)-O(4) bond length. Mg(1) is bonded to one O(1), one O(2), one O(5), and one O(6) atom to form MgO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. The Mg(1)-O(1) bond length is 1.97 Å. The Mg(1)-O(2) bond length is 1.93 Å. The Mg(1)-O(5) bond length is 1.99 Å. The Mg(1)-O(6) bond length is 1.96 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra and corners with two equivalent Mg(1)O4 tetrahedra. The Si(1)-O(3) bond length is 1.69 Å. The Si(1)-O(5) bond length is 1.65 Å. The Si(1)-O(6) bond length is 1.64 Å. The Si(1)-O(7) bond length is 1.62 Å. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with two equivalent Mg(1)O4 tetrahedra. The Si(2)-O(1) bond length is 1.63 Å. The Si(2)-O(2) bond length is 1.63 Å. The Si(2)-O(3) bond length is 1.69 Å. The Si(2)-O(4) bond length is 1.65 Å. There are seven inequivalent O sites. In the first O site, O(7) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one Si(1) atom. In the second O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), one Mg(1), and one Si(2) atom. In the third O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(2), one Mg(1), and one Si(2) atom. In the fourth O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Si(1), and one Si(2) atom. In the fifth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(1), two equivalent Ca(2), and one Si(2) atom. In the sixth O site, O(5) is bonded in a distorted tetrahedral geometry to one Ca(1), one Ca(2), one Mg(1), and one Si(1) atom. In the seventh O site, O(6) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Mg(1), and one Si(1) atom.