Ho3GaS6 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 S(3), two equivalent S(1), two equivalent S(2), and two equivalent S(4) atoms to form distorted HoS7 pentagonal bipyramids that share corners with four equivalent Ho(1)S7 pentagonal bipyramids, corners with three equivalent Ga(1)S4 tetrahedra, edges with two equivalent Ho(1)S7 pentagonal bipyramids,  an edgeedge with one Ga(1)S4 tetrahedra, and  a faceface with one Ho(1)S7 pentagonal bipyramid. In the second Ho site, Ho(2) is bonded in a 7-coordinate geometry to one S(3), two equivalent S(1), and four equivalent S(2) atoms. Ga(1) is bonded to one S(3), one S(4), and two equivalent S(1) atoms to form GaS4 tetrahedra that share corners with six equivalent Ho(1)S7 pentagonal bipyramids and edges with two equivalent Ho(1)S7 pentagonal bipyramids. There are four inequivalent S sites. In the first S site, S(1) is bonded in a rectangular see-saw-like geometry to one Ho(2), two equivalent Ho(1), and one Ga(1) atom. In the second S site, S(2) is bonded to two equivalent Ho(1) and two equivalent Ho(2) atoms to form SHo4 tetrahedra that share corners with two equivalent S(2)Ho4 tetrahedra, corners with four equivalent S(3)Ho3Ga tetrahedra, corners with two equivalent S(4)Ho4Ga trigonal bipyramids, edges with three equivalent S(2)Ho4 tetrahedra, and  an edgeedge with one S(4)Ho4Ga trigonal bipyramid. In the third S site, S(3) is bonded to one Ho(2), two equivalent Ho(1), and one Ga(1) atom to form distorted SHo3Ga tetrahedra that share corners with eight equivalent S(2)Ho4 tetrahedra,  a cornercorner with one S(4)Ho4Ga trigonal bipyramid, and edges with two equivalent S(4)Ho4Ga trigonal bipyramids. In the fourth S site, S(4) is bonded to four equivalent Ho(1) and one Ga(1) atom to form distorted SHo4Ga trigonal bipyramids that share  a cornercorner with one S(3)Ho3Ga tetrahedra, corners with four equivalent S(2)Ho4 tetrahedra, edges with two equivalent S(3)Ho3Ga tetrahedra, edges with two equivalent S(2)Ho4 tetrahedra, and edges with two equivalent S(4)Ho4Ga trigonal bipyramids.
Ho3GaS6 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 S(3), two equivalent S(1), two equivalent S(2), and two equivalent S(4) atoms to form distorted HoS7 pentagonal bipyramids that share corners with four equivalent Ho(1)S7 pentagonal bipyramids, corners with three equivalent Ga(1)S4 tetrahedra, edges with two equivalent Ho(1)S7 pentagonal bipyramids,  an edgeedge with one Ga(1)S4 tetrahedra, and  a faceface with one Ho(1)S7 pentagonal bipyramid. The Ho(1)-S(3) bond length is 2.77 Å. There is one shorter (2.74 Å) and one longer (2.88 Å) Ho(1)-S(1) bond length. There is one shorter (2.65 Å) and one longer (2.70 Å) Ho(1)-S(2) bond length. Both Ho(1)-S(4) bond lengths are 2.94 Å. In the second Ho site, Ho(2) is bonded in a 7-coordinate geometry to one S(3), two equivalent S(1), and four equivalent S(2) atoms. The Ho(2)-S(3) bond length is 3.01 Å. Both Ho(2)-S(1) bond lengths are 2.80 Å. There are two shorter (2.71 Å) and two longer (2.76 Å) Ho(2)-S(2) bond lengths. Ga(1) is bonded to one S(3), one S(4), and two equivalent S(1) atoms to form GaS4 tetrahedra that share corners with six equivalent Ho(1)S7 pentagonal bipyramids and edges with two equivalent Ho(1)S7 pentagonal bipyramids. The Ga(1)-S(3) bond length is 2.26 Å. The Ga(1)-S(4) bond length is 2.31 Å. Both Ga(1)-S(1) bond lengths are 2.28 Å. There are four inequivalent S sites. In the first S site, S(1) is bonded in a rectangular see-saw-like geometry to one Ho(2), two equivalent Ho(1), and one Ga(1) atom. In the second S site, S(2) is bonded to two equivalent Ho(1) and two equivalent Ho(2) atoms to form SHo4 tetrahedra that share corners with two equivalent S(2)Ho4 tetrahedra, corners with four equivalent S(3)Ho3Ga tetrahedra, corners with two equivalent S(4)Ho4Ga trigonal bipyramids, edges with three equivalent S(2)Ho4 tetrahedra, and  an edgeedge with one S(4)Ho4Ga trigonal bipyramid. In the third S site, S(3) is bonded to one Ho(2), two equivalent Ho(1), and one Ga(1) atom to form distorted SHo3Ga tetrahedra that share corners with eight equivalent S(2)Ho4 tetrahedra,  a cornercorner with one S(4)Ho4Ga trigonal bipyramid, and edges with two equivalent S(4)Ho4Ga trigonal bipyramids. In the fourth S site, S(4) is bonded to four equivalent Ho(1) and one Ga(1) atom to form distorted SHo4Ga trigonal bipyramids that share  a cornercorner with one S(3)Ho3Ga tetrahedra, corners with four equivalent S(2)Ho4 tetrahedra, edges with two equivalent S(3)Ho3Ga tetrahedra, edges with two equivalent S(2)Ho4 tetrahedra, and edges with two equivalent S(4)Ho4Ga trigonal bipyramids.