Redetermination of despujolsite, Ca(3)Mn(SO(4))(2)(OH)(6)·3H(2)O.

The crystal structure of despujolsite [tricalcium manganese bis-(sulfate) hexahydroxide tri-hydrate], the Ca/Mn member of the fleischerite group, ideally Ca(3)Mn(4+)(SO(4))(2)(OH)(6)·3H(2)O, was previously determined based on X-ray diffraction intensity data from photographs, without H-atom positions located [Gaudefroy et al. (1968 ▶). Bull. Soc. Fr. Minéral. Crystallogr.91, 43-50]. The current study redetermines the structure of despujolsite from a natural specimen, with all H atoms located and with higher precision. The structure of despujolsite is characterized by layers of CaO(8) polyhedra (m.. symmetry) inter-connected by Mn(OH)(6) octa-hedra (32. symmetry) and SO(4) tetra-hedra (3.. symmetry) along [001]. The average Ca-O, Mn-O and S-O bond lengths are 2.489, 1.915, and 1.472 Å, respectively. There are two distinct hydrogen bonds that stabilize the structural set-up. This work represents the first description of hydrogen bonds in the fleischerite group of minerals.