Record details

    Contribution to the mineralogy of acid drainage of Uranium minerals: Marecottite and the zippeite-group
Statement of responsibility
    J. Brugger, Peter C. Burns, N. Meisser
    Brugger, J.
    Burns, Peter C.
    Meisser, N.
Source title - serial
    American mineralogist
    Vol. 88, no. 4
    p. 676-685
    2 obr., 1 fot., 8 tab., 37 bibl.
    Zkr. název ser.: Amer. Mineralogist
Subject group
    krystalová struktura
    kyselá důlní voda
    minerály supergenní
    minerály uranu
    nový minerál
    rudy U
Geographical name
    Jáchymov (Karlovy Vary)
Abstract (in english)
   Sulfate-rich acid waters produced by oxidation of sulfide minerals enhance U mobility around U ores and U-bearing radioactive waste. Upon evaporation, several secondary uranyl minerals, including many uranyl sulfates, precipitate from these waters. The zippeite-group of minerals is one of the most common and diverse in such settings. To decipher the nature and crystal chemistry of the zippeite-group, the crystal structure of a new natural hydrated Mg uranyl sulfate related to Mg-zippeite was determined. The mineral is named marecottite after the type locality, the La Creusaz U prospect near Les Marécottes, Western Swiss Alps. Marecottite is triclinic, P1, with a = 10.815(4), b = 11.249(4), c = 13.851(6) ?, ? = 66.224(7), ß= 72.412(7), and ?= 69.95(2)°. The ideal structural formula is Mg3(H2O)l8[(UO2)4O3(OH)(SO4)2]2(H2O)lo.
   The crystal structure of marecottite contains uranyl sulfate sheets composed of chains of edge-sharing uranyl pentagonal bipyramids that are linked by vertex-sharing with sulfate tetrahedra. The uranyl sulfate sheets are topologically identical to those in zippeite, K(UO2)2(SO4)O2.2H2O. The zippeite-type sheets alternate with layers containing isolated Mg(H2O)6 octahedra and uncoordinated H2O groups. The uranyl sulfate and Mg layers are linked by hydrogen bonding only.Magnesium-zippeite is redefined as Mg(H2O)3.5(UO2)2(SO4)O2, based on comparison of the powder X-ray diffraction pattern of micro-crystalline co-type material with the pattern of a synthetic phase. Magnesium-zippeite contains zippeite-type uranyl sulfate sheets with Mg located between the layers, where it is in octahedral coordination. In Mg-zippeite, distorted Mg octahedra are linked by sharing vertices, resulting in dimers.
   The apices of the Mg octahedra correspond to two O atoms of uranyl ions, and four H2O groups.Magnesium-zippeite and marecottite co-exist, sometimes in the same sample, at Lucky Strike no. 2 mine, Emery County, Utah (type locality of Mg-zippeite), at Jáchymov, Czech Republic, and at La Creusaz. This study provides insight into the complexity of the zippeite-group minerals containing divalent cations, where different arrangements in the interlayers result in different unit cells and space groups
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
Entered date
    21. 8. 2007
Import date
    8. 8. 2012