CaCoSi2O6 is Esseneite structured and crystallizes in the monoclinic C2/c space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. Co(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form CoO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra and edges with two equivalent Co(1)O6 octahedra. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with three equivalent Co(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 35-58°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to two equivalent Ca(1) and two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ca(1), one Co(1), and one Si(1) atom. In the third O site, O(3) is bonded to one Ca(1), two equivalent Co(1), and one Si(1) atom to form a mixture of distorted edge and corner-sharing OCaCo2Si trigonal pyramids.
CaCoSi2O6 is Esseneite structured and crystallizes in the monoclinic C2/c space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. Both Ca(1)-O(2) bond lengths are 2.35 Å. Both Ca(1)-O(3) bond lengths are 2.35 Å. There are two shorter (2.64 Å) and two longer (2.79 Å) Ca(1)-O(1) bond lengths. Co(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form CoO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra and edges with two equivalent Co(1)O6 octahedra. Both Co(1)-O(2) bond lengths are 2.09 Å. There are two shorter (2.11 Å) and two longer (2.18 Å) Co(1)-O(3) bond lengths. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with three equivalent Co(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 35-58°. The Si(1)-O(2) bond length is 1.61 Å. The Si(1)-O(3) bond length is 1.62 Å. There is one shorter (1.68 Å) and one longer (1.70 Å) Si(1)-O(1) bond length. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to two equivalent Ca(1) and two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ca(1), one Co(1), and one Si(1) atom. In the third O site, O(3) is bonded to one Ca(1), two equivalent Co(1), and one Si(1) atom to form a mixture of distorted edge and corner-sharing OCaCo2Si trigonal pyramids.