Ca3Er3BGe2O13 crystallizes in the monoclinic C2 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted CaO7 pentagonal bipyramids that share  a cornercorner with one Ca(1)O7 pentagonal bipyramid,  a cornercorner with one Er(2)O7 pentagonal bipyramid, corners with two equivalent Er(1)O7 pentagonal bipyramids, corners with two equivalent Ge(1)O4 tetrahedra, corners with two equivalent Ge(2)O4 tetrahedra,  an edgeedge with one B(1)O4 tetrahedra,  a faceface with one Er(2)O7 pentagonal bipyramid, and faces with two equivalent Er(1)O7 pentagonal bipyramids. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to one O(1), two equivalent O(2), two equivalent O(4), and two equivalent O(7) atoms. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted ErO7 pentagonal bipyramids that share  a cornercorner with one Er(1)O7 pentagonal bipyramid,  a cornercorner with one Er(2)O7 pentagonal bipyramid, corners with two equivalent Ca(1)O7 pentagonal bipyramids, corners with two equivalent Ge(1)O4 tetrahedra, corners with two equivalent Ge(2)O4 tetrahedra,  an edgeedge with one B(1)O4 tetrahedra,  a faceface with one Er(2)O7 pentagonal bipyramid, and faces with two equivalent Ca(1)O7 pentagonal bipyramids. In the second Er site, Er(2) is bonded to one O(1), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms to form distorted ErO7 pentagonal bipyramids that share corners with two equivalent Ca(1)O7 pentagonal bipyramids, corners with two equivalent Er(1)O7 pentagonal bipyramids, corners with two equivalent Ge(1)O4 tetrahedra, corners with two equivalent Ge(2)O4 tetrahedra,  an edgeedge with one B(1)O4 tetrahedra, faces with two equivalent Ca(1)O7 pentagonal bipyramids, and faces with two equivalent Er(1)O7 pentagonal bipyramids. B(1) is bonded to two equivalent O(2) and two equivalent O(3) atoms to form BO4 tetrahedra that share  an edgeedge with one Er(2)O7 pentagonal bipyramid, edges with two equivalent Ca(1)O7 pentagonal bipyramids, and edges with two equivalent Er(1)O7 pentagonal bipyramids. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to two equivalent O(6) and two equivalent O(7) atoms to form GeO4 tetrahedra that share corners with two equivalent Er(2)O7 pentagonal bipyramids, corners with four equivalent Ca(1)O7 pentagonal bipyramids, and corners with four equivalent Er(1)O7 pentagonal bipyramids. In the second Ge site, Ge(2) is bonded to two equivalent O(4) and two equivalent O(5) atoms to form GeO4 tetrahedra that share corners with two equivalent Er(2)O7 pentagonal bipyramids, corners with four equivalent Ca(1)O7 pentagonal bipyramids, and corners with four equivalent Er(1)O7 pentagonal bipyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Ca(2), two equivalent Ca(1), one Er(2), and two equivalent Er(1) atoms to form OCa3Er3 octahedra that share corners with six equivalent O(2)Ca2ErB trigonal pyramids and corners with six equivalent O(3)CaEr2B trigonal pyramids. In the second O site, O(2) is bonded to one Ca(1), one Ca(2), one Er(1), and one B(1) atom to form distorted OCa2ErB trigonal pyramids that share corners with three equivalent O(1)Ca3Er3 octahedra,  an edgeedge with one O(2)Ca2ErB trigonal pyramid, and edges with two equivalent O(3)CaEr2B trigonal pyramids. The corner-sharing octahedral tilt angles range from 31-33°. In the third O site, O(3) is bonded to one Ca(1), one Er(1), one Er(2), and one B(1) atom to form distorted OCaEr2B trigonal pyramids that share corners with three equivalent O(1)Ca3Er3 octahedra,  an edgeedge with one O(3)CaEr2B trigonal pyramid, and edges with two equivalent O(2)Ca2ErB trigonal pyramids. The corner-sharing octahedral tilt angles range from 30-32°. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Ca(1), one Ca(2), one Er(1), and one Ge(2) atom. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Ca(1), one Er(1), one Er(2), and one Ge(2) atom. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Ca(1), one Er(1), one Er(2), and one Ge(1) atom. In the seventh O site, O(7) is bonded in a rectangular see-saw-like geometry to one Ca(1), one Ca(2), one Er(1), and one Ge(1) atom.
Ca3Er3BGe2O13 crystallizes in the monoclinic C2 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted CaO7 pentagonal bipyramids that share  a cornercorner with one Ca(1)O7 pentagonal bipyramid,  a cornercorner with one Er(2)O7 pentagonal bipyramid, corners with two equivalent Er(1)O7 pentagonal bipyramids, corners with two equivalent Ge(1)O4 tetrahedra, corners with two equivalent Ge(2)O4 tetrahedra,  an edgeedge with one B(1)O4 tetrahedra,  a faceface with one Er(2)O7 pentagonal bipyramid, and faces with two equivalent Er(1)O7 pentagonal bipyramids. The Ca(1)-O(1) bond length is 2.43 Å. The Ca(1)-O(2) bond length is 2.35 Å. The Ca(1)-O(3) bond length is 2.37 Å. The Ca(1)-O(4) bond length is 2.39 Å. The Ca(1)-O(5) bond length is 2.44 Å. The Ca(1)-O(6) bond length is 2.47 Å. The Ca(1)-O(7) bond length is 2.40 Å. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to one O(1), two equivalent O(2), two equivalent O(4), and two equivalent O(7) atoms. The Ca(2)-O(1) bond length is 2.51 Å. Both Ca(2)-O(2) bond lengths are 2.36 Å. Both Ca(2)-O(4) bond lengths are 2.41 Å. Both Ca(2)-O(7) bond lengths are 2.43 Å. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted ErO7 pentagonal bipyramids that share  a cornercorner with one Er(1)O7 pentagonal bipyramid,  a cornercorner with one Er(2)O7 pentagonal bipyramid, corners with two equivalent Ca(1)O7 pentagonal bipyramids, corners with two equivalent Ge(1)O4 tetrahedra, corners with two equivalent Ge(2)O4 tetrahedra,  an edgeedge with one B(1)O4 tetrahedra,  a faceface with one Er(2)O7 pentagonal bipyramid, and faces with two equivalent Ca(1)O7 pentagonal bipyramids. The Er(1)-O(1) bond length is 2.36 Å. The Er(1)-O(2) bond length is 2.28 Å. The Er(1)-O(3) bond length is 2.32 Å. The Er(1)-O(4) bond length is 2.31 Å. The Er(1)-O(5) bond length is 2.38 Å. The Er(1)-O(6) bond length is 2.40 Å. The Er(1)-O(7) bond length is 2.30 Å. In the second Er site, Er(2) is bonded to one O(1), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms to form distorted ErO7 pentagonal bipyramids that share corners with two equivalent Ca(1)O7 pentagonal bipyramids, corners with two equivalent Er(1)O7 pentagonal bipyramids, corners with two equivalent Ge(1)O4 tetrahedra, corners with two equivalent Ge(2)O4 tetrahedra,  an edgeedge with one B(1)O4 tetrahedra, faces with two equivalent Ca(1)O7 pentagonal bipyramids, and faces with two equivalent Er(1)O7 pentagonal bipyramids. The Er(2)-O(1) bond length is 2.29 Å. Both Er(2)-O(3) bond lengths are 2.29 Å. Both Er(2)-O(5) bond lengths are 2.35 Å. Both Er(2)-O(6) bond lengths are 2.36 Å. B(1) is bonded to two equivalent O(2) and two equivalent O(3) atoms to form BO4 tetrahedra that share  an edgeedge with one Er(2)O7 pentagonal bipyramid, edges with two equivalent Ca(1)O7 pentagonal bipyramids, and edges with two equivalent Er(1)O7 pentagonal bipyramids. Both B(1)-O(2) bond lengths are 1.48 Å. Both B(1)-O(3) bond lengths are 1.50 Å. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to two equivalent O(6) and two equivalent O(7) atoms to form GeO4 tetrahedra that share corners with two equivalent Er(2)O7 pentagonal bipyramids, corners with four equivalent Ca(1)O7 pentagonal bipyramids, and corners with four equivalent Er(1)O7 pentagonal bipyramids. Both Ge(1)-O(6) bond lengths are 1.78 Å. Both Ge(1)-O(7) bond lengths are 1.77 Å. In the second Ge site, Ge(2) is bonded to two equivalent O(4) and two equivalent O(5) atoms to form GeO4 tetrahedra that share corners with two equivalent Er(2)O7 pentagonal bipyramids, corners with four equivalent Ca(1)O7 pentagonal bipyramids, and corners with four equivalent Er(1)O7 pentagonal bipyramids. Both Ge(2)-O(4) bond lengths are 1.79 Å. Both Ge(2)-O(5) bond lengths are 1.81 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Ca(2), two equivalent Ca(1), one Er(2), and two equivalent Er(1) atoms to form OCa3Er3 octahedra that share corners with six equivalent O(2)Ca2ErB trigonal pyramids and corners with six equivalent O(3)CaEr2B trigonal pyramids. In the second O site, O(2) is bonded to one Ca(1), one Ca(2), one Er(1), and one B(1) atom to form distorted OCa2ErB trigonal pyramids that share corners with three equivalent O(1)Ca3Er3 octahedra,  an edgeedge with one O(2)Ca2ErB trigonal pyramid, and edges with two equivalent O(3)CaEr2B trigonal pyramids. The corner-sharing octahedral tilt angles range from 31-33°. In the third O site, O(3) is bonded to one Ca(1), one Er(1), one Er(2), and one B(1) atom to form distorted OCaEr2B trigonal pyramids that share corners with three equivalent O(1)Ca3Er3 octahedra,  an edgeedge with one O(3)CaEr2B trigonal pyramid, and edges with two equivalent O(2)Ca2ErB trigonal pyramids. The corner-sharing octahedral tilt angles range from 30-32°. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Ca(1), one Ca(2), one Er(1), and one Ge(2) atom. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Ca(1), one Er(1), one Er(2), and one Ge(2) atom. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Ca(1), one Er(1), one Er(2), and one Ge(1) atom. In the seventh O site, O(7) is bonded in a rectangular see-saw-like geometry to one Ca(1), one Ca(2), one Er(1), and one Ge(1) atom.