Titre du document / Document title

Crystal structure and crystal chemistry of biehlite, Sb_1.79As_0.21MoO₆

Auteur(s) / Author(s)

ADIWIDJAJA G. ⁽¹⁾ ; FRIESE K. ⁽²⁾ ; KLASKA K.-H. ⁽¹⁾ ; SCHLÜTER J. ⁽¹⁾ ; CZANK M. ⁽³⁾ ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ Universität Hamburg, Mineralogisch-Petrographisches Institut, Grindelallee 48, 20146 Hamburg, ALLEMAGNE
⁽²⁾ Universidad del Pais Vasco, Facultad de Ciencias, Departmento de Fisica de la Materia Condensada, Apdo. 644, 48080 Bilbao, ESPAGNE
⁽³⁾ Christian Albrechts Universität zu Kiel, Institut für Geowissenschaften, Mineralogie/Kristallographie, Olshausenstr. 40, 24098 Kiel, ALLEMAGNE

Résumé / Abstract

The new mineral biehlite was found in the Tsumeb mine, Namibia and has the composition Sb_1.79As_0.21 MoO₆. It crystallizes monoclinic, space group C2/c with lattice parmeters a 18.076(5) A, b = 5.920(5) A. c = 5.083(5) A. β 96.97(1)Å. Refinement led to a final R(F) value of 0.065 for 679 symmetrically independent reflections. [MoO₆]^6- octahedra share common cdges and form zig-zag chains which run parallel to the c direction. The octahedra are flanked by a [Sb₂O₂]² group on each side and infinite ribbons of composition [Sb₄Mo₂O₁₂] are obtained. Neighbouring ribbons are only held together by weak Sb-O bonds in the directions of a and b. The [MoO₆]⁶ octahedra are strongly distorted with Mo-O distances ranging from 1.700(5) to 2.248(6) A and O-Mo-O angles bctween 72 1(2) and 105.3(4)Å. The common O-O edge (2.492(8) A) is shortened with respect to the remaining edges of the octahedra (2.704(8) A -2.899(8) A). The Sb-cation forms three short bonds with oxygen at distances slightly smaller than 2 A. Six further oxygen atoms are located at distances ranging from 2.910(6) to 3.470(6) A. Calculated distance for the lone-pair is 1.18 A. Part of the Sb^3- is substituted by the smaller As³⁺ ion. The relationship of the new mineral to similar structures - especially to the mineral stibivanite and the synthetic compound Sb₂MoO₆ - is discussed.

Revue / Journal Title

Zeitschrift für Kristallographie   ISSN 0044-2968   CODEN ZEKRDZ 

Source / Source

2000, vol. 215, n^o9, pp. 529-535 (27 ref.)

Langue / Language

Anglais
Revue : Allemand

Editeur / Publisher

Oldenbourg, München, ALLEMAGNE  (1921) (Revue)

Mots-clés anglais / English Keywords

molybdates ; arsenic ; antimony ; new minerals ; crystal chemistry ; crystal structure ; cell dimensions ; chemical composition ; structural formula ; space groups ; mines ; Namibia ; crystal systems ; X-ray diffraction ; coordination ; atomic packing ; distortion ; interatomic bond ; substitution ; Southern Africa ; Africa ;

Mots-clés français / French Keywords

Molybdate ; Arsenic ; Antimoine ; Minéral nouveau ; Cristallochimie ; Structure cristalline ; Constante réticulaire ; Composition chimique ; Formule structurale ; Groupe espace ; Mine ; Namibie ; Système cristallin ; Diffraction RX ; Coordinence ; Empilement atome ; Distorsion ; Liaison interatomique ; Substitution ; Biehlite ; Mine Tsumeb ; Afrique du Sud ; Afrique ;

Mots-clés espagnols / Spanish Keywords

Molibdato ; Arsénico ; Antimonio ; Mineral nuevo ; Cristaloquímica ; Estructura cristalina ; Constante reticular ; Grupo espacio ; Mina ; Namibia ; Sistema cristalino ; Difracción RX ; Coordinancia ; Estructura átomo ; Distorsión ; Enlace interatómico ; Substitución ; África Sur ; Africa ;

Localisation / Location

INIST-CNRS, Cote INIST : 915, 35400009210023.0060