SrCa3Mg4(SiO3)8 is Esseneite-derived structured and crystallizes in the monoclinic P2 space group. Sr(1) is bonded in a 8-coordinate geometry to two equivalent O(11), two equivalent O(3), two equivalent O(6), and two equivalent O(9) atoms. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(10), two equivalent O(12), two equivalent O(4), and two equivalent O(5) atoms. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(11), two equivalent O(8), and two equivalent O(9) atoms. In the third Ca site, Ca(3) is bonded in a 8-coordinate geometry to two equivalent O(10), two equivalent O(12), two equivalent O(2), and two equivalent O(7) atoms. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(6), and two equivalent O(8) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra, and edges with two equivalent Mg(3)O6 octahedra. In the second Mg site, Mg(2) is bonded to two equivalent O(2), two equivalent O(5), and two equivalent O(7) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, and edges with two equivalent Mg(4)O6 octahedra. In the third Mg site, Mg(3) is bonded to two equivalent O(3), two equivalent O(6), and two equivalent O(8) atoms to form MgO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra, and edges with two equivalent Mg(1)O6 octahedra. In the fourth Mg site, Mg(4) is bonded to two equivalent O(4), two equivalent O(5), and two equivalent O(7) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra, and edges with two equivalent Mg(2)O6 octahedra. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(11), one O(5), and one O(9) 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 Mg(4)O6 octahedra, and corners with two equivalent Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 34-59°. In the second Si site, Si(2) is bonded to one O(10), one O(12), one O(2), 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 Mg(3)O6 octahedra, and corners with two equivalent Si(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 34-58°. In the third Si site, Si(3) is bonded to one O(11), one O(3), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Mg(3)O6 octahedra,  a cornercorner with one Mg(4)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-59°. In the fourth Si site, Si(4) is bonded to one O(10), one O(12), one O(4), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Mg(3)O6 octahedra,  a cornercorner with one Mg(4)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 34-58°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Ca(2), one Mg(1), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ca(3), one Mg(2), and one Si(2) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Sr(1), one Mg(3), and one Si(3) atom. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Ca(1), one Mg(4), and one Si(4) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Ca(1), one Mg(2), one Mg(4), and one Si(1) atom. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Sr(1), one Mg(1), one Mg(3), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Ca(3), one Mg(2), one Mg(4), and one Si(3) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one Ca(2), one Mg(1), one Mg(3), and one Si(4) atom. In the ninth O site, O(9) is bonded in a 2-coordinate geometry to one Sr(1), one Ca(2), one Si(1), and one Si(3) atom. In the tenth O site, O(10) is bonded in a 2-coordinate geometry to one Ca(1), one Ca(3), one Si(2), and one Si(4) atom. In the eleventh O site, O(11) is bonded in a 2-coordinate geometry to one Sr(1), one Ca(2), one Si(1), and one Si(3) atom. In the twelfth O site, O(12) is bonded in a 2-coordinate geometry to one Ca(1), one Ca(3), one Si(2), and one Si(4) atom.
SrCa3Mg4(SiO3)8 is Esseneite-derived structured and crystallizes in the monoclinic P2 space group. Sr(1) is bonded in a 8-coordinate geometry to two equivalent O(11), two equivalent O(3), two equivalent O(6), and two equivalent O(9) atoms. Both Sr(1)-O(11) bond lengths are 2.77 Å. Both Sr(1)-O(3) bond lengths are 2.47 Å. Both Sr(1)-O(6) bond lengths are 2.50 Å. Both Sr(1)-O(9) bond lengths are 2.62 Å. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(10), two equivalent O(12), two equivalent O(4), and two equivalent O(5) atoms. Both Ca(1)-O(10) bond lengths are 2.62 Å. Both Ca(1)-O(12) bond lengths are 2.78 Å. Both Ca(1)-O(4) bond lengths are 2.37 Å. Both Ca(1)-O(5) bond lengths are 2.38 Å. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(11), two equivalent O(8), and two equivalent O(9) atoms. Both Ca(2)-O(1) bond lengths are 2.37 Å. Both Ca(2)-O(11) bond lengths are 2.62 Å. Both Ca(2)-O(8) bond lengths are 2.38 Å. Both Ca(2)-O(9) bond lengths are 2.78 Å. In the third Ca site, Ca(3) is bonded in a 8-coordinate geometry to two equivalent O(10), two equivalent O(12), two equivalent O(2), and two equivalent O(7) atoms. Both Ca(3)-O(10) bond lengths are 2.77 Å. Both Ca(3)-O(12) bond lengths are 2.62 Å. Both Ca(3)-O(2) bond lengths are 2.37 Å. Both Ca(3)-O(7) bond lengths are 2.39 Å. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(6), and two equivalent O(8) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra, and edges with two equivalent Mg(3)O6 octahedra. Both Mg(1)-O(1) bond lengths are 2.08 Å. Both Mg(1)-O(6) bond lengths are 2.14 Å. Both Mg(1)-O(8) bond lengths are 2.09 Å. In the second Mg site, Mg(2) is bonded to two equivalent O(2), two equivalent O(5), and two equivalent O(7) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, and edges with two equivalent Mg(4)O6 octahedra. Both Mg(2)-O(2) bond lengths are 2.10 Å. Both Mg(2)-O(5) bond lengths are 2.17 Å. Both Mg(2)-O(7) bond lengths are 2.08 Å. In the third Mg site, Mg(3) is bonded to two equivalent O(3), two equivalent O(6), and two equivalent O(8) atoms to form MgO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra, and edges with two equivalent Mg(1)O6 octahedra. Both Mg(3)-O(3) bond lengths are 2.10 Å. Both Mg(3)-O(6) bond lengths are 2.08 Å. Both Mg(3)-O(8) bond lengths are 2.15 Å. In the fourth Mg site, Mg(4) is bonded to two equivalent O(4), two equivalent O(5), and two equivalent O(7) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra, and edges with two equivalent Mg(2)O6 octahedra. Both Mg(4)-O(4) bond lengths are 2.08 Å. Both Mg(4)-O(5) bond lengths are 2.09 Å. Both Mg(4)-O(7) bond lengths are 2.16 Å. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(11), one O(5), and one O(9) 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 Mg(4)O6 octahedra, and corners with two equivalent Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 34-59°. The Si(1)-O(1) bond length is 1.60 Å. The Si(1)-O(11) bond length is 1.70 Å. The Si(1)-O(5) bond length is 1.62 Å. The Si(1)-O(9) bond length is 1.69 Å. In the second Si site, Si(2) is bonded to one O(10), one O(12), one O(2), 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 Mg(3)O6 octahedra, and corners with two equivalent Si(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 34-58°. The Si(2)-O(10) bond length is 1.69 Å. The Si(2)-O(12) bond length is 1.71 Å. The Si(2)-O(2) bond length is 1.61 Å. The Si(2)-O(6) bond length is 1.62 Å. In the third Si site, Si(3) is bonded to one O(11), one O(3), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Mg(3)O6 octahedra,  a cornercorner with one Mg(4)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-59°. The Si(3)-O(11) bond length is 1.69 Å. The Si(3)-O(3) bond length is 1.60 Å. The Si(3)-O(7) bond length is 1.62 Å. The Si(3)-O(9) bond length is 1.71 Å. In the fourth Si site, Si(4) is bonded to one O(10), one O(12), one O(4), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Mg(3)O6 octahedra,  a cornercorner with one Mg(4)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 34-58°. The Si(4)-O(10) bond length is 1.71 Å. The Si(4)-O(12) bond length is 1.69 Å. The Si(4)-O(4) bond length is 1.61 Å. The Si(4)-O(8) bond length is 1.63 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Ca(2), one Mg(1), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ca(3), one Mg(2), and one Si(2) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Sr(1), one Mg(3), and one Si(3) atom. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Ca(1), one Mg(4), and one Si(4) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Ca(1), one Mg(2), one Mg(4), and one Si(1) atom. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Sr(1), one Mg(1), one Mg(3), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Ca(3), one Mg(2), one Mg(4), and one Si(3) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one Ca(2), one Mg(1), one Mg(3), and one Si(4) atom. In the ninth O site, O(9) is bonded in a 2-coordinate geometry to one Sr(1), one Ca(2), one Si(1), and one Si(3) atom. In the tenth O site, O(10) is bonded in a 2-coordinate geometry to one Ca(1), one Ca(3), one Si(2), and one Si(4) atom. In the eleventh O site, O(11) is bonded in a 2-coordinate geometry to one Sr(1), one Ca(2), one Si(1), and one Si(3) atom. In the twelfth O site, O(12) is bonded in a 2-coordinate geometry to one Ca(1), one Ca(3), one Si(2), and one Si(4) atom.