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Redetermination of metarossite, CaV 5+ 2 O 6 · 2H 2 O

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ABSTRACT

6: The crystal structure of metarossite, ideally CaV2O6·2H2O [chemical name: calcium divanadium(V) hexa­oxide dihydrate], was first determined using precession photographs, with fixed isotropic displacement parameters and without locating the positions of the H atoms, leading to a reliability factor R = 0.11 [Kelsey & Barnes (1960 ▸). Can. Mineral., 448–466]. This communication reports a structure redetermination of this mineral on the basis of single-crystal X-ray diffraction data of a natural sample from the Blue Cap mine, San Juan County, Utah, USA (R1 = 0.036). Our study not only confirms the structural topology reported in the previous study, but also makes possible the refinement of all non-H atoms with anisotropic displacement parameters and all H atoms located. The metarossite structure is characterized by chains of edge-sharing [CaO8] polyhedra parallel to [100] that are themselves connected by chains of alternating [VO5] trigonal bipyramids parallel to [010]. The two H2O mol­ecules are bonded to Ca. Analysis of the displacement parameters show that the [VO5] chains librate around [010]. In addition, we measured the Raman spectrum of metarossite and compared it with IR and Raman data previously reported. Moreover, heating of metarossite led to a loss of water, which results in a transformation to the brannerite-type structure, CaV2O6, implying a possible dehydration pathway for the compounds M2+V2O6·xH2O, with M = Cu, Cd, Mg or Mn, and x = 2 or 4.

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Photograph of the metarossite specimen analyzed in this study.
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fig1: Photograph of the metarossite specimen analyzed in this study.

Mentions: This study reports the refinement of the structure of a metarossite sample (Fig. 1 ▸) from the Blue Cap mine, San Juan County, Utah, USA, with anisotropic displacement parameters for all non-hydrogen atoms, positions of hydrogen atoms determined, and improvement of the reliability factor to 0.036. Raman spectra were also recorded and compared with that reported in the two studies by Frost et al. (2004 ▸, 2005 ▸), on a sample from the Burro mine, San Miguel County of Colorado, USA.


Redetermination of metarossite, CaV 5+ 2 O 6 · 2H 2 O
Photograph of the metarossite specimen analyzed in this study.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120707&req=5

fig1: Photograph of the metarossite specimen analyzed in this study.
Mentions: This study reports the refinement of the structure of a metarossite sample (Fig. 1 ▸) from the Blue Cap mine, San Juan County, Utah, USA, with anisotropic displacement parameters for all non-hydrogen atoms, positions of hydrogen atoms determined, and improvement of the reliability factor to 0.036. Raman spectra were also recorded and compared with that reported in the two studies by Frost et al. (2004 ▸, 2005 ▸), on a sample from the Burro mine, San Miguel County of Colorado, USA.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

6: The crystal structure of metarossite, ideally CaV2O6·2H2O [chemical name: calcium divanadium(V) hexa­oxide dihydrate], was first determined using precession photographs, with fixed isotropic displacement parameters and without locating the positions of the H atoms, leading to a reliability factor R = 0.11 [Kelsey & Barnes (1960 ▸). Can. Mineral., 448–466]. This communication reports a structure redetermination of this mineral on the basis of single-crystal X-ray diffraction data of a natural sample from the Blue Cap mine, San Juan County, Utah, USA (R1 = 0.036). Our study not only confirms the structural topology reported in the previous study, but also makes possible the refinement of all non-H atoms with anisotropic displacement parameters and all H atoms located. The metarossite structure is characterized by chains of edge-sharing [CaO8] polyhedra parallel to [100] that are themselves connected by chains of alternating [VO5] trigonal bipyramids parallel to [010]. The two H2O mol­ecules are bonded to Ca. Analysis of the displacement parameters show that the [VO5] chains librate around [010]. In addition, we measured the Raman spectrum of metarossite and compared it with IR and Raman data previously reported. Moreover, heating of metarossite led to a loss of water, which results in a transformation to the brannerite-type structure, CaV2O6, implying a possible dehydration pathway for the compounds M2+V2O6·xH2O, with M = Cu, Cd, Mg or Mn, and x = 2 or 4.

No MeSH data available.