K3B3O10 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 10-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), two equivalent O(5), and two equivalent O(6) atoms. In the second K site, K(2) is bonded to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(6) atoms to form distorted KO8 hexagonal bipyramids that share corners with two equivalent B(1)O4 tetrahedra, edges with four equivalent K(2)O8 hexagonal bipyramids, and edges with two equivalent B(1)O4 tetrahedra. There are two inequivalent B sites. In the first B site, B(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form BO4 tetrahedra that share corners with two equivalent K(2)O8 hexagonal bipyramids,  a cornercorner with one B(1)O4 tetrahedra, and edges with two equivalent K(2)O8 hexagonal bipyramids. In the second B site, B(2) is bonded in a trigonal planar geometry to one O(5) and two equivalent O(1) atoms. There are six inequivalent O sites. In the first O site, O(3) is bonded in a distorted single-bond geometry to one K(1), two equivalent K(2), and one B(1) atom. In the second O site, O(4) is bonded in a distorted bent 120 degrees geometry to two equivalent K(1) and two equivalent B(1) atoms. In the third O site, O(5) is bonded in a distorted single-bond geometry to two equivalent K(1) and one B(2) atom. In the fourth O site, O(6) is bonded in a distorted T-shaped geometry to one K(1) and two equivalent K(2) atoms. In the fifth O site, O(1) is bonded in a distorted bent 120 degrees geometry to two equivalent K(2), one B(1), and one B(2) atom. In the sixth O site, O(2) is bonded in a distorted single-bond geometry to one K(1), two equivalent K(2), and one B(1) atom.
K3B3O10 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 10-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), two equivalent O(5), and two equivalent O(6) atoms. Both K(1)-O(2) bond lengths are 2.85 Å. Both K(1)-O(3) bond lengths are 2.93 Å. There is one shorter (2.64 Å) and one longer (2.66 Å) K(1)-O(4) bond length. There is one shorter (2.85 Å) and one longer (3.07 Å) K(1)-O(5) bond length. Both K(1)-O(6) bond lengths are 3.08 Å. In the second K site, K(2) is bonded to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(6) atoms to form distorted KO8 hexagonal bipyramids that share corners with two equivalent B(1)O4 tetrahedra, edges with four equivalent K(2)O8 hexagonal bipyramids, and edges with two equivalent B(1)O4 tetrahedra. There is one shorter (2.97 Å) and one longer (3.03 Å) K(2)-O(1) bond length. There is one shorter (2.71 Å) and one longer (2.77 Å) K(2)-O(2) bond length. There is one shorter (2.71 Å) and one longer (2.80 Å) K(2)-O(3) bond length. There is one shorter (3.08 Å) and one longer (3.24 Å) K(2)-O(6) bond length. There are two inequivalent B sites. In the first B site, B(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form BO4 tetrahedra that share corners with two equivalent K(2)O8 hexagonal bipyramids,  a cornercorner with one B(1)O4 tetrahedra, and edges with two equivalent K(2)O8 hexagonal bipyramids. The B(1)-O(1) bond length is 1.48 Å. The B(1)-O(2) bond length is 1.47 Å. The B(1)-O(3) bond length is 1.48 Å. The B(1)-O(4) bond length is 1.43 Å. In the second B site, B(2) is bonded in a trigonal planar geometry to one O(5) and two equivalent O(1) atoms. The B(2)-O(5) bond length is 1.37 Å. Both B(2)-O(1) bond lengths are 1.40 Å. There are six inequivalent O sites. In the first O site, O(3) is bonded in a distorted single-bond geometry to one K(1), two equivalent K(2), and one B(1) atom. In the second O site, O(4) is bonded in a distorted bent 120 degrees geometry to two equivalent K(1) and two equivalent B(1) atoms. In the third O site, O(5) is bonded in a distorted single-bond geometry to two equivalent K(1) and one B(2) atom. In the fourth O site, O(6) is bonded in a distorted T-shaped geometry to one K(1) and two equivalent K(2) atoms. In the fifth O site, O(1) is bonded in a distorted bent 120 degrees geometry to two equivalent K(2), one B(1), and one B(2) atom. In the sixth O site, O(2) is bonded in a distorted single-bond geometry to one K(1), two equivalent K(2), and one B(1) atom.