FeMn(SiO4) is Ilmenite-derived structured and crystallizes in the orthorhombic Pnma space group. Mn(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MnO6 octahedra that share corners with four equivalent Fe(1)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent Mn(1)O6 octahedra, edges with two equivalent Fe(1)O6 octahedra, and edges with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-67°. Fe(1) is bonded to one O(2), one O(3), and four equivalent O(1) atoms to form FeO6 octahedra that share corners with four equivalent Mn(1)O6 octahedra, corners with four equivalent Fe(1)O6 octahedra, corners with four equivalent Si(1)O4 tetrahedra, edges with two equivalent Mn(1)O6 octahedra, and  an edgeedge with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-67°. 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 two equivalent Mn(1)O6 octahedra, corners with four equivalent Fe(1)O6 octahedra,  an edgeedge with one Fe(1)O6 octahedra, and edges with two equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-62°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Mn(1), two equivalent Fe(1), and one Si(1) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to two equivalent Mn(1), one Fe(1), and one Si(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Mn(1), one Fe(1), and one Si(1) atom.
FeMn(SiO4) is Ilmenite-derived structured and crystallizes in the orthorhombic Pnma space group. Mn(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MnO6 octahedra that share corners with four equivalent Fe(1)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent Mn(1)O6 octahedra, edges with two equivalent Fe(1)O6 octahedra, and edges with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-67°. Both Mn(1)-O(1) bond lengths are 2.28 Å. Both Mn(1)-O(2) bond lengths are 2.19 Å. Both Mn(1)-O(3) bond lengths are 2.21 Å. Fe(1) is bonded to one O(2), one O(3), and four equivalent O(1) atoms to form FeO6 octahedra that share corners with four equivalent Mn(1)O6 octahedra, corners with four equivalent Fe(1)O6 octahedra, corners with four equivalent Si(1)O4 tetrahedra, edges with two equivalent Mn(1)O6 octahedra, and  an edgeedge with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-67°. The Fe(1)-O(2) bond length is 2.14 Å. The Fe(1)-O(3) bond length is 2.24 Å. There are two shorter (2.13 Å) and two longer (2.34 Å) Fe(1)-O(1) 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 two equivalent Mn(1)O6 octahedra, corners with four equivalent Fe(1)O6 octahedra,  an edgeedge with one Fe(1)O6 octahedra, and edges with two equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-62°. The Si(1)-O(2) bond length is 1.67 Å. The Si(1)-O(3) bond length is 1.63 Å. Both Si(1)-O(1) bond lengths are 1.66 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Mn(1), two equivalent Fe(1), and one Si(1) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to two equivalent Mn(1), one Fe(1), and one Si(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Mn(1), one Fe(1), and one Si(1) atom.