Lotharmeyerite, Ca(Zn,Mn) 2(AsO 4)2-(H 2O,OH) 2

Yongbo W. Yang, Stanley H. Evans, Robert T. Downs, Hexiong Yang

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

Lotharmeyerite, calcium bis(zinc/manganese) bis(arsenate) bis(hydroxide/hydrate), Ca(Zn,Mn 3+) 2(AsO 4) 2(H 2O,OH) 2, is a member of the natrochalcite group of minerals, which are characterized by the general formula AM 2(XO 4) 2(H 2O,OH) 2, where A may be occupied by Pb 2+, Ca 2+, Na +, and Bi 3+, M by Fe 3+, Mn 3+, Cu 2+, Zn 2+, Co 2+, Ni 2+, Al 3+, and Mg 2+, and X by P V, As V, V V, and S VI. The minerals in the group display either monoclinic or triclinic symmetry, depending on the ordering of chemical components in the M site. Based on single-crystal X-ray diffraction data of a sample from the type locality, Mapimi, Durango, Mexico, this study presents the first structure determination of lotharmeyerite. Lotharmeyerite is isostructural with natrochalcite and tsumcorite. The structure is composed of rutile-type chains of edge-shared MO 6 octahedra (site symmetry 1̄) extending along [010], which are interconnected by XO 4 tetrahedra (site symmetry 2) and hydrogen bonds to form [M 2(XO 4) 2(OH,H 2O) 2] sheets parallel to (001). These sheets are linked by the larger A cations (site symmetry 2/m), as well as by hydrogen bonds. Bond-valence sums for the M cation, calculated with the parameters for Mn 3+ and Mn 2+ are 2.72 and 2.94 v.u., respectively, consistent with the occupation of the M site by Mn 3+. Two distinct hydrogen bonds are present, one with O···O = 2.610(4) Å and the other O···O = 2.595(3) Å. One of the H-atom positions is disordered over two sites with 50% occupancy, in agreement with observations for other natrochalcite-type minerals, such as natrochalcite and tsumcorite.

Original languageEnglish (US)
Pages (from-to)i9-i10
JournalActa Crystallographica Section E: Structure Reports Online
Volume68
Issue number1
DOIs
StatePublished - Jan 1 2012

Keywords

  • Data-to-parameter ratio = 15.1
  • Disorder in main residue
  • Mean σ(As-O) = 0.002 Å
  • R factor = 0.019
  • Single-crystal X-ray study
  • T = 293 K
  • wR factor = 0.045

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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