Record details

    Highly ordered, homogeneous ferrocolumbite from an anorogenic granitic pegmatite at Ivittuut (Ivigtut), SW Greenland
Statement of responsibility
    Milan Novák, Petr Černý
    Černý, Petr
    Novák, Milan, 1952-
Source title - serial
    Neues Jahrbuch für Mineralogie. Monatshefte
    H. 10
    p. 433-443
    2 obr., 4 tab.
    Obsahuje bibliografické odkazy
    Zkr. název ser.: Neu. Jb. Mineral., Mh.
Subject group
    ložisko kryolitu
    mřížkové parametry
    skupina columbitu
    stupeň uspořádanosti
Geographical name
Abstract (in english)
   Accessory but widespread ferrocolumbite occurs in a coarse-grained microcline+quartz pegmatite overlying the ivigtut cryolite deposit, SW greenland. Euhedral crystals, up to 2 cm in size, are enclosed in microcline, locally in quartz, and overgrown by late cryolite. The crystals are commonly found loose, very likely due to weathering of th matrix. Associated minor and accessory minerals include sulphides (galena, sphalerite, chalcopyrite, molybdenite) and Nb-rich cassiterite (with Nb/Ta wt.=17.2-7.5). All ferrocolumbite samples studied are extremely homogeneous and have remarkably similar chemical compositions; the ratio Mn/(Mn+Fe)at. varies from 0.22 to 0.27, whereas Ta/(Ta+Nb)at. ranges from 0.004 to 0.02, and Nb/Ta wt.=46.1-25.1. Minor elements include Ti and W up to 0.14 apfu, Zn up to 0.06 apfu and Sn up to 0.02 apfu. The unit-cell dimensions indicate highly to fully ordered structure.
   The very high Nb/Ta ratio and homogeneity of ferrocolumbite seem to be caused by very low activity of Ta relative to Nb in the parent (possibly mantle-derived) melt; and by near-equilibrium crystallization
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
Entered date
    11. 12. 2006
Import date
    8. 8. 2012