The crystal structure of legrandite -- Zn2(AsO4)(OH)(H2O), monoclinic, a 12.8052(3), b 7.9249(2), c 10.2173(2) Å, β 104.4329(3)°, V 1004.13(6) Å3, space group P21/c, Z = 2 -- has been refined to an R1 value of 1.2% based on 2844 unique [|Fo| > 4σF] reflections measured with a Bruker D8 three-circle diffractometer equipped with a rotating-anode generator (MoKα X-radiation), multilayer optics, and an APEX-II detector. The legrandite structure is a heteropolyhedral framework of (AsO4) tetrahedra, (Znφ5) square pyramids, and (Znφ6) octahedra [φ = O, (OH), (H2O)] with extensive hydrogen bonding across its interstices. All hydrogen positions were located, all hydrogen bonds were assigned, and the H...O distances are in reasonable accord with the published relation between O–H stretching frequency and H...O bond-length.
