Ca2CoNiSi4O12 is Esseneite-derived structured and crystallizes in the monoclinic C2 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(4), two equivalent O(5), and two equivalent O(6) atoms. Co(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form CoO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and edges with two equivalent Ni(1)O6 octahedra. Ni(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Si(2)O4 tetrahedra, and edges with two equivalent Co(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Co(1)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 36-58°. In the second Si site, Si(2) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Co(1)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 35-59°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Ca(2), one Co(1), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ca(1), one Ni(1), and one Si(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1), one Co(1), one Ni(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(2), one Co(1), one Ni(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one Ca(1), one Ca(2), one Si(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Ca(1), one Ca(2), one Si(1), and one Si(2) atom.
Ca2CoNiSi4O12 is Esseneite-derived structured and crystallizes in the monoclinic C2 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. Both Ca(1)-O(2) bond lengths are 2.34 Å. Both Ca(1)-O(3) bond lengths are 2.36 Å. Both Ca(1)-O(5) bond lengths are 2.62 Å. Both Ca(1)-O(6) bond lengths are 2.79 Å. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(4), two equivalent O(5), and two equivalent O(6) atoms. Both Ca(2)-O(1) bond lengths are 2.34 Å. Both Ca(2)-O(4) bond lengths are 2.37 Å. Both Ca(2)-O(5) bond lengths are 2.79 Å. Both Ca(2)-O(6) bond lengths are 2.62 Å. Co(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form CoO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and edges with two equivalent Ni(1)O6 octahedra. Both Co(1)-O(1) bond lengths are 2.10 Å. Both Co(1)-O(3) bond lengths are 2.17 Å. Both Co(1)-O(4) bond lengths are 2.09 Å. Ni(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Si(2)O4 tetrahedra, and edges with two equivalent Co(1)O6 octahedra. Both Ni(1)-O(2) bond lengths are 2.09 Å. Both Ni(1)-O(3) bond lengths are 2.07 Å. Both Ni(1)-O(4) bond lengths are 2.15 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Co(1)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 36-58°. The Si(1)-O(1) bond length is 1.61 Å. The Si(1)-O(3) bond length is 1.62 Å. The Si(1)-O(5) bond length is 1.68 Å. The Si(1)-O(6) bond length is 1.70 Å. In the second Si site, Si(2) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Co(1)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 35-59°. The Si(2)-O(2) bond length is 1.61 Å. The Si(2)-O(4) bond length is 1.63 Å. The Si(2)-O(5) bond length is 1.70 Å. The Si(2)-O(6) bond length is 1.68 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Ca(2), one Co(1), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ca(1), one Ni(1), and one Si(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1), one Co(1), one Ni(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(2), one Co(1), one Ni(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one Ca(1), one Ca(2), one Si(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Ca(1), one Ca(2), one Si(1), and one Si(2) atom.