title: Redetermination of despujolsite, Ca(3)Mn(SO(4))(2)(OH)(6)·3H(2)O.
abstract: 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.
authors: Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721-0077,  USA.
authors: Madison C
authors: MC
authors: Barkley
authors: Hexiong
authors: H
authors: Yang
authors: Stanley H
authors: SH
authors: Evans
authors: Robert T
authors: RT
authors: Downs
authors: Marcus J
authors: MJ
authors: Origlieri