Zn4Si2O9 crystallizes in the orthorhombic Imm2 space group. Zn(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form ZnO4 tetrahedra that share corners with three equivalent Si(1)O4 tetrahedra and corners with four equivalent Zn(1)O4 tetrahedra. Si(1) is bonded to one O(2), one O(4), and two equivalent O(1) atoms to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with six equivalent Zn(1)O4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to two equivalent Zn(1) and one Si(1) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to two equivalent Zn(1) and one Si(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to two equivalent Zn(1) atoms. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms.
Zn4Si2O9 crystallizes in the orthorhombic Imm2 space group. Zn(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form ZnO4 tetrahedra that share corners with three equivalent Si(1)O4 tetrahedra and corners with four equivalent Zn(1)O4 tetrahedra. The Zn(1)-O(2) bond length is 2.02 Å. The Zn(1)-O(3) bond length is 1.93 Å. There is one shorter (1.97 Å) and one longer (1.98 Å) Zn(1)-O(1) bond length. Si(1) is bonded to one O(2), one O(4), and two equivalent O(1) atoms to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with six equivalent Zn(1)O4 tetrahedra. The Si(1)-O(2) bond length is 1.64 Å. The Si(1)-O(4) bond length is 1.65 Å. Both Si(1)-O(1) bond lengths are 1.65 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to two equivalent Zn(1) and one Si(1) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to two equivalent Zn(1) and one Si(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to two equivalent Zn(1) atoms. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms.