Fe3BO5 crystallizes in the orthorhombic Pbam space group. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 21°. In the second Fe site, Fe(2) is bonded to one O(1), one O(5), two equivalent O(3), and two equivalent O(4) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 21-62°. In the third Fe site, Fe(3) is bonded to one O(3), one O(4), two equivalent O(2), and two equivalent O(5) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 59-62°. In the fourth Fe site, Fe(4) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 59°. B(1) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(5) atom. There are five inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Fe(2), two equivalent Fe(4), and one B(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Fe(1), two equivalent Fe(3), and one B(1) atom. In the third O site, O(3) is bonded to one Fe(3), one Fe(4), and two equivalent Fe(2) atoms to form distorted OFe4 tetrahedra that share corners with three equivalent O(4)Fe5 square pyramids, corners with three equivalent O(3)Fe4 tetrahedra, and  an edgeedge with one O(4)Fe5 square pyramid. In the fourth O site, O(4) is bonded to one Fe(3), two equivalent Fe(1), and two equivalent Fe(2) atoms to form OFe5 square pyramids that share corners with two equivalent O(4)Fe5 square pyramids, corners with three equivalent O(3)Fe4 tetrahedra, edges with three equivalent O(4)Fe5 square pyramids, and  an edgeedge with one O(3)Fe4 tetrahedra. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Fe(2), two equivalent Fe(3), and one B(1) atom.
Fe3BO5 crystallizes in the orthorhombic Pbam space group. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 21°. Both Fe(1)-O(2) bond lengths are 2.11 Å. All Fe(1)-O(4) bond lengths are 2.08 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(5), two equivalent O(3), and two equivalent O(4) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 21-62°. The Fe(2)-O(1) bond length is 2.12 Å. The Fe(2)-O(5) bond length is 2.12 Å. Both Fe(2)-O(3) bond lengths are 2.05 Å. Both Fe(2)-O(4) bond lengths are 2.10 Å. In the third Fe site, Fe(3) is bonded to one O(3), one O(4), two equivalent O(2), and two equivalent O(5) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 59-62°. The Fe(3)-O(3) bond length is 1.93 Å. The Fe(3)-O(4) bond length is 2.04 Å. Both Fe(3)-O(2) bond lengths are 2.18 Å. Both Fe(3)-O(5) bond lengths are 2.17 Å. In the fourth Fe site, Fe(4) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 59°. Both Fe(4)-O(3) bond lengths are 2.00 Å. All Fe(4)-O(1) bond lengths are 2.16 Å. B(1) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(5) atom. The B(1)-O(1) bond length is 1.38 Å. The B(1)-O(2) bond length is 1.38 Å. The B(1)-O(5) bond length is 1.38 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Fe(2), two equivalent Fe(4), and one B(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Fe(1), two equivalent Fe(3), and one B(1) atom. In the third O site, O(3) is bonded to one Fe(3), one Fe(4), and two equivalent Fe(2) atoms to form distorted OFe4 tetrahedra that share corners with three equivalent O(4)Fe5 square pyramids, corners with three equivalent O(3)Fe4 tetrahedra, and  an edgeedge with one O(4)Fe5 square pyramid. In the fourth O site, O(4) is bonded to one Fe(3), two equivalent Fe(1), and two equivalent Fe(2) atoms to form OFe5 square pyramids that share corners with two equivalent O(4)Fe5 square pyramids, corners with three equivalent O(3)Fe4 tetrahedra, edges with three equivalent O(4)Fe5 square pyramids, and  an edgeedge with one O(3)Fe4 tetrahedra. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Fe(2), two equivalent Fe(3), and one B(1) atom.