Pseudomalachite and descloizite in supergene mineral assemblage from Krucemburk (Czech Republic)
Article PDFPseudomalachite and descloizite in supergene mineral assemblage from Krucemburk (Czech Republic)
The locality Krucemburk (14 km N from Žďár nad Sázavou) is well known by its historical occurrence of secondary Cu-phosphate pseudomalachite Cu5(PO4)2(OH)4. A new revision of supergene minerals confirmed pseudomalachite while other polymorph (reichenbachite, ludjibaite) were not identified. Pseudomalachite is monoclinic with space group P21/c and with following unit-cell parameters refined from X-ray powder diffraction pattern: a 4.4781(2), b 5.7590(2), c 17.0278(8) Å, β 90.894(4)° and V 439.09(2) Å3. Average chemical composition of radial pseudomalachite correspond to the formula Cu4.98Zn0.12Pb0.02]Σ5.12 (P1.91As0.02Si0.01)Σ1.94 O8 (OH)4, only narrow rim has higher content of Zn (up to 2.89 wt. % ZnO; 0.21 apfu Zn). Sporadic grains of descloizite with composition [Pb0.97Zn0.78Cu0.12Fe0.12Na0.06Mn0.03]Σ2.08 (V0.93As0.03P0.01Si0.01)Σ0.98 O4 (OH) in the centre he misphe rical aggregates of pseudomalachite were found. Malachite, the dominant copper mineral of the supergene zone forms thin coatings on phylites. Unspecified Cu-S minerals of the chalcocite-digenite group, minute grains of acanthite, relics of galenite, chalcopyrite and supergene baryte only locally occur.
Jiří Toman, Department of Mineralogy and Petrography, Moravian Museum, Zelný trh 6, 659 37, Brno, Czech Republic. e-mail: jtoman@mzm.cz; Institute of Geological Sciences, Masaryk University, Kotlářská 2, 611 37, Brno, Czech Republic. e-mail: 211300@mail.muni.cz
Vladimír Hrazdil, Department of Mineralogy and Petrography, Moravian Museum, Zelný trh 6, 659 37, Brno, Czech Republic
Jiří Sejkora, Department of Mineralogy and Petrology, National Museum, Cirkusová 1740, 193 00, Praha 9, Czech Republic. e-mail: jiri_sejkora@nm.cz