Mg3FeO4 is Caswellsilverite-like structured and crystallizes in the triclinic P-1 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(3) and four equivalent O(4) atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedra are not tilted. In the second Mg site, Mg(2) is bonded to two equivalent O(4) and four equivalent O(3) atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedra are not tilted. In the third Mg site, Mg(3) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with three equivalent Fe(1)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, edges with two equivalent Mg(3)O6 octahedra, edges with three equivalent Fe(1)O6 octahedra, and edges with four equivalent Mg(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the fourth Mg site, Mg(4) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with three equivalent Mg(2)O6 octahedra, corners with three equivalent Fe(1)O6 octahedra,  an edgeedge with one Mg(2)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(4)O6 octahedra, edges with three equivalent Fe(1)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. Fe(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form FeO6 octahedra that share corners with three equivalent Mg(3)O6 octahedra, corners with three equivalent Mg(4)O6 octahedra, edges with three equivalent Mg(3)O6 octahedra, edges with three equivalent Mg(4)O6 octahedra, and edges with six equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 3-4°. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(3), two equivalent Mg(4), and three equivalent Fe(1) atoms to form OMg3Fe3 octahedra that share corners with three equivalent O(2)Mg3Fe3 octahedra, corners with three equivalent O(3)Mg6 octahedra,  an edgeedge with one O(3)Mg6 octahedra, edges with two equivalent O(4)Mg6 octahedra, edges with four equivalent O(1)Mg3Fe3 octahedra, and edges with five equivalent O(2)Mg3Fe3 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second O site, O(2) is bonded to one Mg(4), two equivalent Mg(3), and three equivalent Fe(1) atoms to form OMg3Fe3 octahedra that share corners with three equivalent O(1)Mg3Fe3 octahedra, corners with three equivalent O(4)Mg6 octahedra,  an edgeedge with one O(4)Mg6 octahedra, edges with two equivalent O(3)Mg6 octahedra, edges with four equivalent O(2)Mg3Fe3 octahedra, and edges with five equivalent O(1)Mg3Fe3 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the third O site, O(3) is bonded to one Mg(1), one Mg(3), two equivalent Mg(2), and two equivalent Mg(4) atoms to form OMg6 octahedra that share corners with three equivalent O(1)Mg3Fe3 octahedra, corners with three equivalent O(3)Mg6 octahedra,  an edgeedge with one O(1)Mg3Fe3 octahedra, edges with two equivalent O(2)Mg3Fe3 octahedra, edges with three equivalent O(3)Mg6 octahedra, and edges with six equivalent O(4)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the fourth O site, O(4) is bonded to one Mg(2), one Mg(4), two equivalent Mg(1), and two equivalent Mg(3) atoms to form OMg6 octahedra that share corners with three equivalent O(2)Mg3Fe3 octahedra, corners with three equivalent O(4)Mg6 octahedra,  an edgeedge with one O(2)Mg3Fe3 octahedra, edges with two equivalent O(1)Mg3Fe3 octahedra, edges with three equivalent O(4)Mg6 octahedra, and edges with six equivalent O(3)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°.
Mg3FeO4 is Caswellsilverite-like structured and crystallizes in the triclinic P-1 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(3) and four equivalent O(4) atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedra are not tilted. Both Mg(1)-O(3) bond lengths are 2.12 Å. There are two shorter (2.14 Å) and two longer (2.15 Å) Mg(1)-O(4) bond lengths. In the second Mg site, Mg(2) is bonded to two equivalent O(4) and four equivalent O(3) atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedra are not tilted. Both Mg(2)-O(4) bond lengths are 2.12 Å. There are two shorter (2.14 Å) and two longer (2.15 Å) Mg(2)-O(3) bond lengths. In the third Mg site, Mg(3) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with three equivalent Fe(1)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, edges with two equivalent Mg(3)O6 octahedra, edges with three equivalent Fe(1)O6 octahedra, and edges with four equivalent Mg(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. The Mg(3)-O(1) bond length is 2.13 Å. The Mg(3)-O(3) bond length is 2.12 Å. Both Mg(3)-O(2) bond lengths are 2.12 Å. There is one shorter (2.14 Å) and one longer (2.15 Å) Mg(3)-O(4) bond length. In the fourth Mg site, Mg(4) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with three equivalent Mg(2)O6 octahedra, corners with three equivalent Fe(1)O6 octahedra,  an edgeedge with one Mg(2)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(4)O6 octahedra, edges with three equivalent Fe(1)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. The Mg(4)-O(2) bond length is 2.13 Å. The Mg(4)-O(4) bond length is 2.12 Å. Both Mg(4)-O(1) bond lengths are 2.12 Å. Both Mg(4)-O(3) bond lengths are 2.15 Å. Fe(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form FeO6 octahedra that share corners with three equivalent Mg(3)O6 octahedra, corners with three equivalent Mg(4)O6 octahedra, edges with three equivalent Mg(3)O6 octahedra, edges with three equivalent Mg(4)O6 octahedra, and edges with six equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 3-4°. There is one shorter (2.14 Å) and two longer (2.23 Å) Fe(1)-O(1) bond lengths. There are a spread of Fe(1)-O(2) bond distances ranging from 2.13-2.23 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(3), two equivalent Mg(4), and three equivalent Fe(1) atoms to form OMg3Fe3 octahedra that share corners with three equivalent O(2)Mg3Fe3 octahedra, corners with three equivalent O(3)Mg6 octahedra,  an edgeedge with one O(3)Mg6 octahedra, edges with two equivalent O(4)Mg6 octahedra, edges with four equivalent O(1)Mg3Fe3 octahedra, and edges with five equivalent O(2)Mg3Fe3 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second O site, O(2) is bonded to one Mg(4), two equivalent Mg(3), and three equivalent Fe(1) atoms to form OMg3Fe3 octahedra that share corners with three equivalent O(1)Mg3Fe3 octahedra, corners with three equivalent O(4)Mg6 octahedra,  an edgeedge with one O(4)Mg6 octahedra, edges with two equivalent O(3)Mg6 octahedra, edges with four equivalent O(2)Mg3Fe3 octahedra, and edges with five equivalent O(1)Mg3Fe3 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the third O site, O(3) is bonded to one Mg(1), one Mg(3), two equivalent Mg(2), and two equivalent Mg(4) atoms to form OMg6 octahedra that share corners with three equivalent O(1)Mg3Fe3 octahedra, corners with three equivalent O(3)Mg6 octahedra,  an edgeedge with one O(1)Mg3Fe3 octahedra, edges with two equivalent O(2)Mg3Fe3 octahedra, edges with three equivalent O(3)Mg6 octahedra, and edges with six equivalent O(4)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the fourth O site, O(4) is bonded to one Mg(2), one Mg(4), two equivalent Mg(1), and two equivalent Mg(3) atoms to form OMg6 octahedra that share corners with three equivalent O(2)Mg3Fe3 octahedra, corners with three equivalent O(4)Mg6 octahedra,  an edgeedge with one O(2)Mg3Fe3 octahedra, edges with two equivalent O(1)Mg3Fe3 octahedra, edges with three equivalent O(4)Mg6 octahedra, and edges with six equivalent O(3)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°.