Record details

    Scandium substitution in columbite-group minerals and ixiolite
Statement of responsibility
    Michael A. Wise, Petr Černý, Alexander U. Falster
Other titles
    Granitic pegmatites: The Černý - Foord volume (Variant.)
    Černý, Petr
    Falster, Alexander U.
    Wise, Michael A.
Source title - serial
    Canadian mineralogist
    Vol. 36, no. 2
    p. 673-680
    4 obr., 5 tab., 26 bibl.
    Francouzské resumé
    Zkr. název ser.: Canad. Mineralogist
Subject group
    chemismus minerálů
    frakcionace chemická
    skupina columbitu
Geographical name
    Bradlo (Jihlava)
    Cínovec (Teplice)
    Cyrilov (Žďár nad Sázavou)
    Česká republika
    Kosov (Jihlava)
    Maršíkov (Šumperk)
    Velká Británie-England
    Věžná (Žďár nad Sázavou)
Abstract (in english)
   Columbite-group minerals and ixiolite with extremely variable concentrations of scandium are widespread in moderately to highly fractionated rare-element granitic pegmatites. Columbite-group minerals with 1-3 wt. per cent Sc2O, are referred to as scandian columbite - tantalite and show degrees of structural order similar to columbite - tantalite lacking Sc. Disordered structures remain orthorhombic and become ordered upon heating. Pseudo-orthorhombic stannian (Sn-rich), titanian (Ti) and wolframian (W) variants of ixiolite may contain as much as 3.7 wt. per cent Sc2O3 and revert to monoclinic phases upon heating. Similarly, scandian ixiolite that contains Sc in excess of 3.0 and up to 18.8 wt. per cent Sc2O3 converts from orthorhombic to monoclinic symmetry upon heating and has a stoichiometry that approaches Sc(Nb,Ta)O4. Scandium-bearing columbite -tantalite and ixiolite show similar ranges in Mn/(Mn + Fe) and Ta/(Ta + Nb) values, but noticeably different Sn, Ti and Sc contents.
   Scandium is incorporated into the columbite and ixiolite structures via the coupled substitution Sc3+ + (Ti,Sn)4+ = (Fe,Mn)2+ + (Nb,Ta)5+; it is strongly partitioned into the (Fe,Mn) site, whereas the Ti and Sn prefer the (Nb.Ta) site. Within the (Fe,Mn) site, the substitution of Sc for Fe is more prevalent. In most pegmatites, Sc fractionation in columbite - tantalite, stannian ixiolite, titanian ixiolite and wolframian ixiolite is erratic, unlike scandian ixiolite, which shows strong enrichment in Sc with increasing Mn, Ta and Sn
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
Entered date
    26. 9. 2007
Import date
    8. 8. 2012