Three new isostructural open-framework sulfides, (NH4)(5)Ga4SbS10 (1), (NH4)(4)Ga4SbS9(OH) center dot H2O (2a), and (NH4)(3)Ga4SbS9(H2O) center dot 2H(2)O (2b), were synthesized under basic hydrothermal conditions using ammonium hydroxide as the structure-directing agent. The structures feature a three-dimensional open framework comprised of adamantane [Ga(4)Q(10)](8-) clusters linked with Sb(3+)centers. The compounds are wide gap semiconductors, crystallize in the chiral space group P2(1)3, and represent a new structure type. They exhibit nonlinear optical properties.