Ho3GaO6 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent Ho sites. In the first Ho site, Ho(1) is bonded to one O(1), two equivalent O(4), and four equivalent O(3) atoms to form distorted HoO7 pentagonal bipyramids that share  a cornercorner with one Ga(1)O4 tetrahedra, edges with two equivalent Ho(1)O7 pentagonal bipyramids, and  an edgeedge with one Ga(1)O4 tetrahedra. In the second Ho site, Ho(2) is bonded in a 7-coordinate geometry to one O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. Ga(1) is bonded to one O(1), one O(2), and two equivalent O(4) atoms to form GaO4 tetrahedra that share  a cornercorner with one Ho(1)O7 pentagonal bipyramid and  an edgeedge with one Ho(1)O7 pentagonal bipyramid. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Ho(1), two equivalent Ho(2), and one Ga(1) atom to form distorted OHo3Ga tetrahedra that share corners with eight equivalent O(3)Ho4 tetrahedra,  a cornercorner with one O(2)Ho4Ga trigonal bipyramid, corners with four equivalent O(4)Ho3Ga trigonal pyramids, edges with two equivalent O(2)Ho4Ga trigonal bipyramids, and edges with two equivalent O(4)Ho3Ga trigonal pyramids. In the second O site, O(2) is bonded to four equivalent Ho(2) and one Ga(1) atom to form distorted OHo4Ga trigonal bipyramids that share  a cornercorner with one O(1)Ho3Ga tetrahedra, corners with four equivalent O(3)Ho4 tetrahedra, corners with six equivalent O(4)Ho3Ga trigonal pyramids, edges with two equivalent O(1)Ho3Ga tetrahedra, edges with two equivalent O(3)Ho4 tetrahedra, edges with two equivalent O(2)Ho4Ga trigonal bipyramids, and edges with two equivalent O(4)Ho3Ga trigonal pyramids. In the third O site, O(3) is bonded to two equivalent Ho(1) and two equivalent Ho(2) atoms to form OHo4 tetrahedra that share corners with two equivalent O(3)Ho4 tetrahedra, corners with four equivalent O(1)Ho3Ga tetrahedra, corners with two equivalent O(2)Ho4Ga trigonal bipyramids, corners with six equivalent O(4)Ho3Ga trigonal pyramids, edges with three equivalent O(3)Ho4 tetrahedra,  an edgeedge with one O(2)Ho4Ga trigonal bipyramid, and  an edgeedge with one O(4)Ho3Ga trigonal pyramid. In the fourth O site, O(4) is bonded to one Ho(1), two equivalent Ho(2), and one Ga(1) atom to form distorted OHo3Ga trigonal pyramids that share corners with two equivalent O(1)Ho3Ga tetrahedra, corners with six equivalent O(3)Ho4 tetrahedra, corners with three equivalent O(2)Ho4Ga trigonal bipyramids, corners with two equivalent O(4)Ho3Ga trigonal pyramids,  an edgeedge with one O(1)Ho3Ga tetrahedra,  an edgeedge with one O(3)Ho4 tetrahedra,  an edgeedge with one O(2)Ho4Ga trigonal bipyramid, and  an edgeedge with one O(4)Ho3Ga trigonal pyramid.
Ho3GaO6 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent Ho sites. In the first Ho site, Ho(1) is bonded to one O(1), two equivalent O(4), and four equivalent O(3) atoms to form distorted HoO7 pentagonal bipyramids that share  a cornercorner with one Ga(1)O4 tetrahedra, edges with two equivalent Ho(1)O7 pentagonal bipyramids, and  an edgeedge with one Ga(1)O4 tetrahedra. The Ho(1)-O(1) bond length is 2.38 Å. Both Ho(1)-O(4) bond lengths are 2.41 Å. There are two shorter (2.24 Å) and two longer (2.27 Å) Ho(1)-O(3) bond lengths. In the second Ho site, Ho(2) is bonded in a 7-coordinate geometry to one O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. The Ho(2)-O(1) bond length is 2.33 Å. There is one shorter (2.50 Å) and one longer (2.55 Å) Ho(2)-O(2) bond length. There is one shorter (2.18 Å) and one longer (2.22 Å) Ho(2)-O(3) bond length. There is one shorter (2.24 Å) and one longer (2.36 Å) Ho(2)-O(4) bond length. Ga(1) is bonded to one O(1), one O(2), and two equivalent O(4) atoms to form GaO4 tetrahedra that share  a cornercorner with one Ho(1)O7 pentagonal bipyramid and  an edgeedge with one Ho(1)O7 pentagonal bipyramid. The Ga(1)-O(1) bond length is 1.84 Å. The Ga(1)-O(2) bond length is 1.87 Å. Both Ga(1)-O(4) bond lengths are 1.87 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Ho(1), two equivalent Ho(2), and one Ga(1) atom to form distorted OHo3Ga tetrahedra that share corners with eight equivalent O(3)Ho4 tetrahedra,  a cornercorner with one O(2)Ho4Ga trigonal bipyramid, corners with four equivalent O(4)Ho3Ga trigonal pyramids, edges with two equivalent O(2)Ho4Ga trigonal bipyramids, and edges with two equivalent O(4)Ho3Ga trigonal pyramids. In the second O site, O(2) is bonded to four equivalent Ho(2) and one Ga(1) atom to form distorted OHo4Ga trigonal bipyramids that share  a cornercorner with one O(1)Ho3Ga tetrahedra, corners with four equivalent O(3)Ho4 tetrahedra, corners with six equivalent O(4)Ho3Ga trigonal pyramids, edges with two equivalent O(1)Ho3Ga tetrahedra, edges with two equivalent O(3)Ho4 tetrahedra, edges with two equivalent O(2)Ho4Ga trigonal bipyramids, and edges with two equivalent O(4)Ho3Ga trigonal pyramids. In the third O site, O(3) is bonded to two equivalent Ho(1) and two equivalent Ho(2) atoms to form OHo4 tetrahedra that share corners with two equivalent O(3)Ho4 tetrahedra, corners with four equivalent O(1)Ho3Ga tetrahedra, corners with two equivalent O(2)Ho4Ga trigonal bipyramids, corners with six equivalent O(4)Ho3Ga trigonal pyramids, edges with three equivalent O(3)Ho4 tetrahedra,  an edgeedge with one O(2)Ho4Ga trigonal bipyramid, and  an edgeedge with one O(4)Ho3Ga trigonal pyramid. In the fourth O site, O(4) is bonded to one Ho(1), two equivalent Ho(2), and one Ga(1) atom to form distorted OHo3Ga trigonal pyramids that share corners with two equivalent O(1)Ho3Ga tetrahedra, corners with six equivalent O(3)Ho4 tetrahedra, corners with three equivalent O(2)Ho4Ga trigonal bipyramids, corners with two equivalent O(4)Ho3Ga trigonal pyramids,  an edgeedge with one O(1)Ho3Ga tetrahedra,  an edgeedge with one O(3)Ho4 tetrahedra,  an edgeedge with one O(2)Ho4Ga trigonal bipyramid, and  an edgeedge with one O(4)Ho3Ga trigonal pyramid.