MgFe(GeO3)2 is Esseneite structured and crystallizes in the monoclinic C2/c space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with eight equivalent Ge(1)O4 tetrahedra and edges with three equivalent Fe(1)O6 octahedra. Fe(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form FeO6 octahedra that share corners with six equivalent Ge(1)O4 tetrahedra, edges with two equivalent Fe(1)O6 octahedra, and edges with three equivalent Mg(1)O6 octahedra. Ge(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form GeO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, and corners with two equivalent Ge(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-61°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Mg(1) and two equivalent Ge(1) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Fe(1), and one Ge(1) atom. In the third O site, O(3) is bonded to one Mg(1), two equivalent Fe(1), and one Ge(1) atom to form a mixture of distorted corner and edge-sharing OMgFe2Ge trigonal pyramids.
MgFe(GeO3)2 is Esseneite structured and crystallizes in the monoclinic C2/c space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with eight equivalent Ge(1)O4 tetrahedra and edges with three equivalent Fe(1)O6 octahedra. Both Mg(1)-O(1) bond lengths are 2.26 Å. Both Mg(1)-O(2) bond lengths are 2.04 Å. Both Mg(1)-O(3) bond lengths are 2.13 Å. Fe(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form FeO6 octahedra that share corners with six equivalent Ge(1)O4 tetrahedra, edges with two equivalent Fe(1)O6 octahedra, and edges with three equivalent Mg(1)O6 octahedra. Both Fe(1)-O(2) bond lengths are 2.11 Å. There are two shorter (2.17 Å) and two longer (2.20 Å) Fe(1)-O(3) bond lengths. Ge(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form GeO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, and corners with two equivalent Ge(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-61°. The Ge(1)-O(2) bond length is 1.73 Å. The Ge(1)-O(3) bond length is 1.76 Å. Both Ge(1)-O(1) bond lengths are 1.83 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Mg(1) and two equivalent Ge(1) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Fe(1), and one Ge(1) atom. In the third O site, O(3) is bonded to one Mg(1), two equivalent Fe(1), and one Ge(1) atom to form a mixture of distorted corner and edge-sharing OMgFe2Ge trigonal pyramids.