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Redetermination of ruizite, Ca2Mn(3+) 2[Si4O11(OH)2](OH)2·2H2O.

ABSTRACT: The crystal structure of ruizite, ideally Ca2Mn(3+) 2[Si4O11(OH)2](OH)2·2H2O [dicalcium dimanganese(III) tetra-silicate tetra-hydroxide dihydrate] was first determined in space group A2 with an isotropic displacement parameter model (R = 5.6%) [Hawthorne (1984 ▸). Tschermaks Mineral. Petrogr. Mitt. 33, 135-146]. A subsequent refinement in space group C2/m with anisotropic displacement parameters for non-H atoms converged with R = 8.4% [Moore et al. (1985 ▸). Am. Mineral. 70, 171-181]. The current study reports a redetermination of the ruizite structure by means of single-crystal X-ray diffraction data of a natural sample from the Wessels mine, Kalahari Manganese Field, Northern Cape Province, South Africa. Our data (R 1 = 3.0%) confirm that the space group of ruizite is that of the first study rather than C2/m. This work improves upon the structure reported by Hawthorne (1984 ▸) in that all non-H atoms were refined with anisotropic displacement parameters and all hydrogen atoms were located. The crystal structure consists of [010] chains of edge-sharing MnO6 octa-hedra flanked by finite [Si4O11(OH)2] chains. The Ca(2+) cations are situated in the cavities of this arrangement and exhibit a coordination number of seven.

SUBMITTER: Fendrich KV

PROVIDER: S-EPMC4992915 | biostudies-literature | 2016 Jul

REPOSITORIES: biostudies-literature

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Redetermination of ruizite, Ca2Mn(3+) 2[Si4O11(OH)2](OH)2·2H2O.

Fendrich Kim V KV Downs Robert T RT Origlieri Marcus J MJ

Acta crystallographica. Section E, Crystallographic communications 20160614 Pt 7

The crystal structure of ruizite, ideally Ca2Mn(3+) 2[Si4O11(OH)2](OH)2·2H2O [dicalcium dimanganese(III) tetra-silicate tetra-hydroxide dihydrate] was first determined in space group A2 with an isotropic displacement parameter model (R = 5.6%) [Hawthorne (1984 ▸). Tschermaks Mineral. Petrogr. Mitt. 33, 135-146]. A subsequent refinement in space group C2/m with anisotropic displacement parameters for non-H atoms converged with R = 8.4% [Moore et al. (1985 ▸). Am. Mineral. 70, 171-181]. The curren ...[more]

PMID: 27555940

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Project description:The crystal structure of brackebuschite, ideally Pb2Mn(3+)(VO4)2(OH) [dilead(II) manganese(III) vanadate(V) hydroxide], was redetermined based on single-crystal X-ray diffraction data of a natural sample from the type locality Sierra de Cordoba, Argentina. Improving on previous results, anisotropic displacement parameters for all non-H atoms were refined and the H atom located, obtaining a significant improvement of accuracy and an unambiguous hydrogen-bonding scheme. Brackebuschite belongs to the brackebuschite group of minerals with general formula A 2 M(T1O4)(T2O4)(OH, H2O), with A = Pb(2+), Ba, Ca, Sr; M = Cu(2+), Zn, Fe(2+), Fe(3+), Mn(3+), Al; T1 = As(5+), P, V(5+); and T2 = As(5+), P, V(5+), S(6+). The crystal structure of brackebuschite is based on a cubic closest-packed array of O and Pb atoms with infinite chains of edge-sharing [Mn(3+)O6] octa-hedra located about inversion centres and decorated by two unique VO4 tetra-hedra (each located on a special position 2e, site symmetry m). One type of VO4 tetra-hedra is linked with the (1) ∞[MnO4/2O2/1] chain by one common vertex, alternating with H atoms along the chain, while the other type of VO4 tetra-hedra link two adjacent octa-hedra by sharing two vertices with them and thereby participating in the formation of a three-membered Mn2V ring between the central atoms. The (1) ∞[Mn(3+)(VO4)2OH] chains run parallel to [010] and are held together by two types of irregular [PbO x ] polyhedra (x = 8, 11), both located on special position 2e (site symmetry m). The magnitude of the libration component of the O atoms of the (1) ∞[Mn(3+)(VO4)2OH] chain increases linearly with the distance from the centerline of the chain, indicating a significant twisting to and fro of the chain along [010]. The hy-droxy group bridges one Pb(2+) cation with two Mn(3+) cations and forms an almost linear hydrogen bond with a vanadate group of a neighbouring chain. The O⋯O distance of this inter-action determined from the structure refinement agrees well with Raman spectroscopic data.

Dataset Information

Redetermination of ruizite, Ca2Mn(3+) 2[Si4O11(OH)2](OH)2·2H2O.

Publications

Redetermination of ruizite, Ca2Mn(3+) 2[Si4O11(OH)2](OH)2·2H2O.

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