Redetermination of despujolsite, Ca3Mn4+(SO4)2(OH)6·3H2O

The crystal structure of despujolsite [tricalcium manganese bis­(sulfate) hexahydroxide tri­hydrate], the Ca/Mn member of the fleischerite group, ideally Ca3Mn4+(SO4)2(OH)6·3H2O, 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 CaO8 polyhedra (m.. symmetry) inter­connected by Mn(OH)6 octa­hedra (32. symmetry) and SO4 tetra­hedra (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

Schaurteite, Ca3Ge(SO4)2(OH)6·3H2O

This report presents the first crystal structure determination of the mineral schaurteite, ideally Ca3Ge(SO4)2(OH)6·3H2O, tricalcium germanium bis(sulfate) hexahydroxide trihydrate. This single-crystal X-ray diffraction study investigated a natural sample from the type locality at Tsumeb, Namibia. Schaurteite is a member of the fleischerite group of minerals, which also includes fleischerite, despujolsite, and mallestigite. The structure of schaurteite consists of slabs of Ca(O,OH,H2O)8 polyhedra (site symmetry mm2) interleaved with a mixed layer of Ge(OH)6 octahedra (-3m.) and SO4 tetrahedra (3m.). There are two H atoms in the asymmetric unit, both located by full-matrix refinement, and both forming O—H...O hydrogen bonds

Agardite-(Y), Cu2+6Y(AsO4)3(OH)6·3H2O

Agardite-(Y), with a refined formula of Cu2+5.70(Y0.69Ca0.31)[(As0.83P0.17)O4]3(OH)6·3H2O [ideally Cu2+6Y(AsO4)3(OH)6·3H2O, hexacopper(II) yttrium tris(arsenate) hexahydroxide trihydrate], belongs to the mixite mineral group which is characterized by the general formula Cu2+6A(TO4)3(OH)6·3H2O, where nine-coordinated cations in the A-site include rare earth elements along with Al, Ca, Pb, or Bi, and the T-site contains P or As. This study presents the first structure determination of agardite-(Y). It is based on the single-crystal X-ray diffraction of a natural sample from Jote West mine, Pampa Larga Mining District, Copiapo, Chile. The general structural feature of agardite-(Y) is characterized by infinite chains of edge-sharing CuO5 square pyramids (site symmetry 1) extending down the c axis, connected in the ab plane by edge-sharing YO9 polyhedra (site symmetry -6..) and corner-sharing AsO4 tetrahedra (site symmetry m..). Hydroxyl groups occupy each corner of the CuO5-square pyramids not shared by a neighboring As or Y atom. Each YO9 polyhedron is surrounded by three tubular channels. The walls of the channels, parallel to the c axis, are six-membered hexagonal rings comprised of CuO5 and AsO4 polyhedra in a 2:1 ratio, and contain free molecules of lattice water