Record details

Title
    Refinement of the crystal structure of cyrilovite from Cyrilov, Western Moravia, Czech Republic
Statement of responsibility
    Mark A. Cooper, Frank C. Hawthorne, Petr Černý
Other titles
    Krystalová struktura cyrilovitu z Cyrilova na západní Moravě v České republice
Author
    Cooper, Mark A.
    Černý, Petr
    Hawthorne, Frank C.
Language
    anglicky
Source title - serial
    Journal of the Czech Geological Society
Vol./nr.
    Vol. 45, no. 1-2
Pages
    p. 95-100
Year
    2000
Notes
    1 obr., 6 tab.
    České resumé
    il.
    Obsahuje bibliografické odkazy
    Zkr. název ser.: J. Czech geol. Soc.
Subject group
    cyrilovit
    dvojčatění
    fosforečnany
    krystalová struktura
    lokalita mineralogická
    mineralogie topografická
    moldanubikum strážecké
    složení
    štěpnost krystalová
Geographical name
    Cyrilov (Žďár nad Sázavou)
    ČR-Morava
Keyword
    Crystal
    Cyrilov
    Cyrilovite
    Czech
    Moravia
    Refinement
    Republic
    Structure
    Western
Abstract (in english)
   he crystal structure of cyrilovite from Cyrilov, western Moravia, Czech Republic, ideally Na [Fe3+ 3(PO4)2 (OH)4 (H2O)2], tetragonal, a 7.3255(4), c 19.328(2) A, V 1037.2(2) A3, Z=4, was refined to an R-index of 1.4 % for 1532 unique reflections measured with Mo K X-radiation on an automated four-circle diffractometer. Cyrilovite crystallizes in the enantiomorphic space group P41 2 1 2 and refinement of a twin model shows that both enantiomers, P4 1 2 1 2, are present as a 1:1 mixture; thus cyrilovite is racemically twinned. The structure consists of intersecting corner-sharing chains of Fe 3+Ý6 (Ý=unspecified anion) octahedra that form sheets parallel to (001). These sheets are linked into a framework of octahedra and tetrahedra by PO4 tetrahedra, with [8]-coordinated Na and H2O in the interstices of the framework.
   Consideration of local bond-valence requirements suggests that a small amount of Ca is incorporated into the cyrilovite structure via the substitution NaCa + M(1)Fe2+ NaNa + M(1)Fe3+. Cyrilovite is isostructural with wardite, Na [Al3 (PO4)2 (OH)4 (H2O)2]. Cyrilovite has no clevage, as suggested by the pattern of bond valence throughout the structure. However, wardite is listed in standard reference works as having perfect [001] cleavage. Examination of wardite shows is to have no cleavage, as suggested by its structural arrangement
Contributor
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
    U
Entered date
    16. 4. 2008
Import date
    8. 8. 2012