• journal_title：The Canadian Mineralogist
• Contributor：Jakub Plášil ; Stuart J. Mills ; Karla Fejfarová ; Michal Dušek ; Milan Novák ; Radek Škoda ; Jiří Čejka ; Jiří Sejkora
• Publisher：Mineralogical Association of Canada
• Date：2011-
• Format：text/html
• Language：en
• Identifier：10.3749/canmin.49.4.1089
• journal_abbrev：Can Mineral
• issn：0008-4476
• volume：49
• issue：4
• firstpage：1089
• section：Articles

The crystal structure of natural zippeite, K_1.85H⁺_0.15[(UO₂)₄O₂(SO₄)₂OH₂](H₂O)₄, from Jáchymov, Czech Republic, has been determined by single-crystal X-ray diffraction and refined to R₁ = 0.0367. Zippeite is monoclinic, space group C2/m, with a 8.7802(6), b 13.9903(12), c 8.8630(6) Å, β 104.524(7)°, V 1053.92(12) ų and Z = 2. The structure consists of structural sheets of the zippeite uranyl anion topology and an interlayer, in which split K⁺ atoms and disordered O atoms (of the H₂O groups) are located. The structure unit [(UO₂)₄O₂(SO₄)₂OH₂]²⁻ is novel for both natural and synthetic compounds, but generally consistent with the known zippeite-type structures. The structural formula is in agreement with bond-valence analysis and the results of an electron-microprobe study. The composition of the zippeite specimen studied is assessed from the point of view of the bond-valence approach. Further, we comment on morphology of zippeite, its optical properties, and its relationship to the crystal structure.