Introduction
Periodicals
Bulletin mineralogicko-petrologického oddělení Národního muzea v Praze
2011/19/2
Walpurgin z uranového ložiska Medvědín, Krkonoše (Česká republika)
Walpurgin z uranového ložiska Medvědín, Krkonoše (Česká republika)
Radek Škoda, Pavel Škácha, Ivana Jebavá, Josef Plecháček, Jiří Sejkora, Jakub Plášil, Karla Fejfarová
| Pages | 171-181 |
|---|---|
| Citation | ŠKODA, Radek, ŠKÁCHA, Pavel, JEBAVÁ, Ivana, PLECHÁČEK, Josef, SEJKORA, Jiří, PLÁŠIL, Jakub a FEJFAROVÁ, Karla. Walpurgin z uranového ložiska Medvědín, Krkonoše (Česká republika). Bulletin mineralogicko-petrologického oddělení Národního muzea v Praze. Prague: National Museum, 2011, 19(2), 171-181. ISSN 1211-0329 (print), 1804-6495 (online). Also available from: https://publikace.nm.cz/en/periodicals/bmpholnrhmvp/19-2/walpurgin-z-uranoveho-loziska-medvedin-krkonose-ceska-republika |
Rare supergene Bi-uranyl arsenate, walpurgite, was found in material from the vein No. 18 at the abandoned adit No. 1 at the Medvědín uranium deposit, Krkonoše Mountains, northern Bohemia, Czech Republic. Walpurgite occurs there as bright yellow tabular crystals with characteristic greasy to vitreous lustre which form isolated aggregates up to 5 mm in size or rich crusts with area up to some cm2 at fissures and cavities of quartz gangue. Eulytite, bismutite, zeunerite and unnamed (BiO)8(UO2)(PO4)3(OH).nH2O were found in the association. Walpurgite is triclinic, space group P-1, the unit-cell parameters refined from single-crystal X-ray data are: a = 7.1199(9), b = 10.389(1), c = 5.4935(8) Å, α = 101.48(1), β = 110.63(1), γ = 88.04(1)o and V = 372.41(9) Å3. The crystal structure of walpurgite has been refined to R1 = 9.79% on the basis of 1637 unique reflections [Iobs.>3σ(I)] collected on a Oxford Diffraction Gemini diffractometer with a CCD detector and MoKα radiation. Chemical analyses of walpurgite yielded the average composition CaO 0.07, ZnO 0.07, Al2O3 0.05, Bi2O3 58.26, SiO2 0.10, As2O5 10.87, P2O5 1.78, V2O5 0.14, UO3 18.23, H2Ocalc. 2.21, total 91.78 wt. % corresponding to the empirical formula (Bi4.07Ca0.02Al0.02Zn0.01)Σ4.12 (UO2)1.04O4(AsO4)1.54(PO4)0.41(SiO4)0.03(VO4)0.02]Σ2.00 . 2H2O on the basis (As+P+Si+V) = 2 apfu.
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