Fe3BO5 crystallizes in the monoclinic P2/m space group. There are five inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(4), two equivalent O(3), 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 60-62°. In the second Fe site, Fe(2) is bonded to two equivalent O(3) 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 third Fe site, Fe(3) is bonded to two equivalent O(5) 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 fourth Fe site, Fe(4) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 60°. In the fifth Fe site, Fe(5) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 62°. B(1) is bonded in a trigonal planar geometry to one O(1), one O(3), and one O(5) atom. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Fe(5), two equivalent Fe(4), and one B(1) atom. In the second O site, O(2) is bonded to one Fe(1), one Fe(4), and two equivalent Fe(5) atoms to form distorted OFe4 tetrahedra that share  a cornercorner with one O(4)Fe5 square pyramid, corners with five equivalent O(2)Fe4 tetrahedra, and  an edgeedge with one O(2)Fe4 tetrahedra. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Fe(2), two equivalent Fe(1), and one B(1) atom. In the fourth O site, O(4) is bonded to one Fe(1), two equivalent Fe(2), and two equivalent Fe(3) atoms to form OFe5 square pyramids that share corners with four equivalent O(4)Fe5 square pyramids,  a cornercorner with one O(2)Fe4 tetrahedra, and edges with four equivalent O(4)Fe5 square pyramids. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Fe(3), two equivalent Fe(1), and one B(1) atom.
Fe3BO5 crystallizes in the monoclinic P2/m space group. There are five inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(4), two equivalent O(3), 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 60-62°. The Fe(1)-O(2) bond length is 1.93 Å. The Fe(1)-O(4) bond length is 2.06 Å. Both Fe(1)-O(3) bond lengths are 2.18 Å. Both Fe(1)-O(5) bond lengths are 2.18 Å. In the second Fe site, Fe(2) is bonded to two equivalent O(3) 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(2)-O(3) bond lengths are 2.10 Å. All Fe(2)-O(4) bond lengths are 2.08 Å. In the third Fe site, Fe(3) is bonded to two equivalent O(5) 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(3)-O(5) bond lengths are 2.11 Å. All Fe(3)-O(4) bond lengths are 2.08 Å. In the fourth Fe site, Fe(4) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 60°. Both Fe(4)-O(2) bond lengths are 2.01 Å. All Fe(4)-O(1) bond lengths are 2.15 Å. In the fifth Fe site, Fe(5) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 62°. Both Fe(5)-O(1) bond lengths are 2.15 Å. All Fe(5)-O(2) bond lengths are 2.06 Å. B(1) is bonded in a trigonal planar geometry to one O(1), one O(3), and one O(5) atom. The B(1)-O(1) bond length is 1.38 Å. The B(1)-O(3) 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 4-coordinate geometry to one Fe(5), two equivalent Fe(4), and one B(1) atom. In the second O site, O(2) is bonded to one Fe(1), one Fe(4), and two equivalent Fe(5) atoms to form distorted OFe4 tetrahedra that share  a cornercorner with one O(4)Fe5 square pyramid, corners with five equivalent O(2)Fe4 tetrahedra, and  an edgeedge with one O(2)Fe4 tetrahedra. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Fe(2), two equivalent Fe(1), and one B(1) atom. In the fourth O site, O(4) is bonded to one Fe(1), two equivalent Fe(2), and two equivalent Fe(3) atoms to form OFe5 square pyramids that share corners with four equivalent O(4)Fe5 square pyramids,  a cornercorner with one O(2)Fe4 tetrahedra, and edges with four equivalent O(4)Fe5 square pyramids. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Fe(3), two equivalent Fe(1), and one B(1) atom.