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Extending the mineralogy of U6+ (IV): Uranyl phosphate sheet of novel topology in the crystal structure of ranunculite

Published online by Cambridge University Press:  02 September 2025

Jakub Plášil Open the ORCID record for Jakub Plášil [Opens in a new window] ,
Nathan Steciuk ,
Gwladys Steciuk Open the ORCID record for Gwladys Steciuk [Opens in a new window] ,
Jiří Sejkora Open the ORCID record for Jiří Sejkora [Opens in a new window] ,
Markéta Jarošová Open the ORCID record for Markéta Jarošová [Opens in a new window] ,
Jan Rohlíček ,
Simon Philippo ,
Ivan Němec  and
Alexander Matthies
Jakub Plášil*
Affiliation:
Institute of Physics of the CAS, Prague, Czech Republic
Nathan Steciuk
Affiliation:
Independent Researcher, Nancy, France
Gwladys Steciuk
Affiliation:
Université de Lorraine, CNRS, Nancy, France
Jiří Sejkora
Affiliation:
Department of Mineralogy and Petrology, National Museum, Prague, Czech Republic
Markéta Jarošová
Affiliation:
Institute of Physics of the CAS, Prague, Czech Republic
Jan Rohlíček
Affiliation:
Institute of Physics of the CAS, Prague, Czech Republic
Simon Philippo
Affiliation:
Section Minéralogie, Musée d’Histoire Naturelle, Luxembourg
Ivan Němec
Affiliation:
Department of Inorganic Chemistry, Faculty of Science, Charles University, Prague, Czech Republic
Alexander Matthies
Affiliation:
Independent Researcher, Nancy, France Independent Researcher, Frieberg, Germany
*
Corresponding author: Jakub Plášil; Email: plasil@fzu.cz
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Abstract

Ranunculite is a rare supergene hydrated aluminium uranyl phosphate reliably reported only from the type locality – the Kobokobo pegmatite in the Sud-Kivu province, Democratic Republic of Congo; its structure has remained unknown until now. Based on 3D electron diffraction data, ranunculite is monoclinic, with a C-centred unit cell: a = 11.1812(7) Å, b = 17.9281(5) Å, c = 17.91548(16) Å, β = 98.350(4)°, and V = 3553.2(2) Å3 (Z = 4). The structure (C2/c) was refined kinematically to R1 = 0.4114 for 1697 unique observed reflections. The structure of ranunculite is based upon infinite uranyl-phosphate sheets of novel topology. The two-dimensional representation of the structural unit consists of hexagons (occupied by U6+), pentagons (occupied by U6+), squares (occupied by Al3+) and triangles (occupied by P5+). Those sheets are stacked perpendicular to c; the interplanar distance is ~9.5 Å. They result from the clusters of edge-sharing uranyl hexagonal and pentagonal bipyramids linked by Al-octahedra and PO4 tetrahedra. The decoration of the sheets is unique but somewhat resembles the arrangement (of U-clusters, squares and triangles) observed in bijvoetite and lepersonnite topologies; the ring symbol is 61514232. In the interlayer, there are two Al3+-hosting sites (one [6]- and [5]-coordinated; the pyramidal one is only partially occupied), as well as isolated H2O groups. There is an extensive network of hydrogen bonds; adjacent sheets are either held by hydrogen bonds only or by tetramers of Al-polyhedra when occupied (through shared O19). This arrangement most probably causes a poor crystallinity of ranunculite (which gives rise to stacking faults observed in the powder diffraction data).

Keywords

ranunculitealuminium uranyl phosphateelectron diffractioncrystal structuresheet topology

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Article
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Mineralogical Magazine , Volume 90 , Issue 1 , February 2026 , pp. 164 - 175
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© The Author(s), 2025. Published by Cambridge University Press on behalf of The Mineralogical Society of the United Kingdom and Ireland.

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References

Bach, A., Fischer, D., and Jansen, M. (2013) Metastable phase formation of indium monochloride from an amorphous feedstock. Zeitschrift für Anorganische und Allgemaine Chemie, 639, 465–467.CrossRefGoogle Scholar
Bartlett, J.R. and Cooney, R.P. (1989) On the determination of uranium-oxygen bond lengths in dioxouranium (VI) compounds by Raman spectroscopy. Journal of Molecular Structure, 193, 295–300.CrossRefGoogle Scholar
Blatov, V.A., Shevchenko, A.P. and Proserpio, D.M. (2014) Applied topological analysis of crystal structures with the program package ToposPro. Crystal Growth & Design, 14, 3576–3586.CrossRefGoogle Scholar
Brázda, P., Klementová, M., Krysiak, Y., and Palatinus, L. (2022) Accurate lattice parameters from 3D electron diffraction data. I. Optical distortions. International Union of Crystallography Journal, 9, 1–21.CrossRefGoogle ScholarPubMed
Burnham, C. W. (1962) Lattice constant refinement. Carnegie Institute Washington Yearbook, 61, 132–135.Google Scholar
Čejka, J. (1999) Infrared spectroscopy and thermal analysis of the uranyl minerals. Reviews in Mineralogy, 38, 521–622.Google Scholar
Chakoumakos, B.C., Abraham, M.M. and Boatner, L.A. (1994) Crystal structure refinements of zircon-type MVO4 (M = Sc, Y, Ce, Pr, Nd, Tb, Ho, Er, Tm, Yb, Lu). Journal of Solid State Chemistry, 109, 197–202.CrossRefGoogle Scholar
Dal Bo, F., Hatért, F. and Philippo, S. (2017a) A new uranyl phosphate sheet in the crystal structure of furongite. European Journal of Mineralogy, 29: 517–527.CrossRefGoogle Scholar
Dal Bo, F., Hatért, F., Philippo, S. (2017b) New crystallographic data and formula revision of phuralumite, Al2[(UO2)3(PO4)2O(OH)](OH)3(H2O)9. Journal of Geosciences, 62, 87–95.CrossRefGoogle Scholar
Deliens, M. and Piret, P. (1979a) Les phosphates d’ura nyle et d’aluminium de Kobokobo. II. La phuralumite Al2(UO2)3(PO4)2(OH)6·10H2O et l’upalite Al(UO2)3(PO4)2(OH)3, nouveaux minéraux. Bulletin de Minéralogie, 102: 333–337.CrossRefGoogle Scholar
Deliens, M. and Piret, P. (1979b) Les phosphates d’uranyle et d’aluminium de Kobokobo. IV. La threadgoldite, Al(UO2)2(PO4)2(OH)·8H2O, nouveau minéral. Bulletin de Minéralogie, 102, 338–341.CrossRefGoogle Scholar
Deliens, M. and Piret, P. (1979c) Ranunculite, AlH(UO2)(PO4)(OH)3·4H2O, a new mineral. Mineralogical Magazine, 43, 321–323.CrossRefGoogle Scholar
Deliens, M. and Piret, P. (1981) Les phosphates d’uranyle et d’aluminium de Kobokobo. V. La mundite, nouveau minéral. Bulletin de Minéralogie, 104, 669–671.CrossRefGoogle Scholar
Deliens, M. and Piret, P. (1982) Les phosphates d’uranyle et d’aluminium de Kobokobo. VI. La triangulite, Al3(UO2·PO4)4(OH)5·5H2O, nouveau minéral. Bulletin de Minéralogie, 105, 611–614.CrossRefGoogle Scholar
Deliens, M. and Piret, P. (1984) La kamitugaïte, PbAl(UO2)5[(P,As)O4]2(OH)9·9,5H2O, nouveau minéral de Kobokobo, Kivu, Zaïre. Bulletin de Minéralogie, 107: 15–19.CrossRefGoogle Scholar
Deliens, M. and Piret, P. (1985a) Les phosphates d’uranyle et d’aluminium de Kobokobo. VII. La moreauïte, Al3UO2(PO4)3(OH)2 ·13H2O, nouveau minéral. Bulletin de Minéralogie, 108, 9–13.CrossRefGoogle Scholar
Deliens, M. and Piret, P. (1985b) Les minéralisations secon daires d’uranium associées à la pegmatite de Kobokobo, Kivu, Zaire. Revue des phosphates d’uranium du groupe structural de la phosphuranylite–dumontite. Rapp a Dép Géol Minéral Mus roy Afr cent, Ann 1983–1984, pp 81–86.Google Scholar
Deliens, M. and Piret, P. (1986) La kusuïte devient la wakefïeldite-(Ce) plombifère. Bulletin de Minéralogie, 109 (3) 305.CrossRefGoogle Scholar
Fischer, D. and Jansen, M. (2002) Low-activation and solid-state syntheses by reducing transport lengths to atomic scales as demonstrated by case studies on AgNO3 and AgO. Journal of American Chemical Society, 124, 3488–3489.CrossRefGoogle ScholarPubMed
Gagné, O.C. and Hawthorne, F.C (2015) Comprehensive derivation of bond-valence parameters for ion pairs involving oxygen. Acta Crystallographica, B71, 562–578.Google Scholar
Gemmi, M. and Lanza, A.E. (2019) 3D electron diffraction techniques. Acta Crystallographica, B75, 495–504.Google Scholar
Gemmi, M., Mugnaioli, E., Gorelik, T.E., Kolb, U., Palatinus, L., Boullay, P., Hovmöller, S. and Abrahams, J.P. (2019) 3D electron diffraction: The nanocrystallography revolution. ACS Central Science, 5, 1315–1329.CrossRefGoogle ScholarPubMed
Hawthorne, F.C. and Schindler, M. (2009) Understanding the weakly bonded constituents in oxysalt minerals. Zeitschrift für Kristallographie - Crystalline Materials, 223, 41–68.CrossRefGoogle Scholar
Holleman, A.F., Wiberg, F. and Wiberg, N. (2001) Inorganic Chemistry. Academic Press, San Diego, CA, pp 1–507.Google Scholar
Hunan Team (1976) Furongite - a new uranium mineral found in China. Acta Geologica Sinica, 2, 203–204 [Human 230 Laboratory, Hunan 305 Geological Team and X-ray Laboratory, Wuhan Geological Institute].Google Scholar
Khosrawan-Sazedj, F. (1982) On the space group of threadgoldite. Tschermaks Mineralogische und Petrographische Mitteilungen, 30, 111–115.CrossRefGoogle Scholar
Klar, P.B., Krysiak, Y., Xu, H., Steciuk, G., Cho, J., Zou, X., Palatinus, L. (2023) Accurate structure models and absolute configuration determination using dynamical effects in continuous-rotation 3D ED data. Nature Chemistry, 15, 1–8.CrossRefGoogle Scholar
Kraus, W. and Nolze, G. (1996) POWDER CELL– a program for the representation and manipulation of crystal structures and calculation of the resulting X-ray powder patterns. Journal of Applied Crystallography, 29, 301–303. https://doi.org/10.1107/S0021889895014920CrossRefGoogle Scholar
Krivovichev, S.V. (2004) Combinatorial topology of salts of inorganic oxoacids: zero-, one- and two-dimensional units with corner-sharing between coordination polyhedra. Crystallography Reviews, 10, 185–232.CrossRefGoogle Scholar
Krivovichev, S.V. (2010) Actinyl compounds with hexavalent elements (S, Cr, Se, Mo)-structural diversity, nanoscale chemistry, and cellular automata modelling. European Journal of Inorganic Chemistry, 2010, 2594–2603.CrossRefGoogle Scholar
Krivovichev, S.V. (2012) Topological complexity of crystal structures: quantitative approach. Acta Crystallographica, A68, 393–398.CrossRefGoogle Scholar
Krivovichev, S.V. (2013) Structural complexity of minerals: information storage and processing in the mineral world. Mineralogical Magazine, 77, 275–326.CrossRefGoogle Scholar
Krivovichev, S.V. (2016) Structural complexity and configurational entropy of crystals. Acta Crystallographica, B72, 274–276.Google Scholar
Krivovichev, S.V. (2017) Hydrogen bonding and structural complexity of the Cu3(AsO4)(OH)3 polymorphs (clinoclase, gilmarite): a theoretical study. Journal of Geosciences, 62, 79–85.CrossRefGoogle Scholar
Krivovichev, S.V. and Plášil, J. (2013) Mineralogy and crystallography of uranium. in “Uranium, from cradle to grave”, Burns, P.C. and Sigmon, G.E., eds. MAC. Short Course, 43, pp. 15–119, Winnipeg MB, May 2013.Google Scholar
Li, Y., Burns, P.C. and Gault, R.A. (2000) A new rare-earth element uranyl carbonate sheet in the structure of bijvoetite-(Y). The Canadian Mineralogist, 38, 153–162.CrossRefGoogle Scholar
Lussier, A. J., Lopez, R. A. and Burns, P. C. (2016) A revised and expanded structure hierarchy of natural and synthetic hexavalent uranium compounds. The Canadian Mineralogist, 54, 177–283.CrossRefGoogle Scholar
Mills, S.J., Birch, W.D., Kampf, A.R. and van Wambeke, L. (2010) Kobokoboite, Al6(PO4)4(OH)6·11H2O, a new mineral from the Kobokobo pegmatite, Democratic Republic of the Congo. European Journal of Mineralogy, 22, 305–308.CrossRefGoogle Scholar
Momma, K. and Izumi, F. (2011) VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data. Journal of Applied Crystallography, 44, 1272–1276.CrossRefGoogle Scholar
Mugnaioli, E., Lanza, A.E., Bortolozzi, G., Righi, L., Merlini, M., Cappello, V., Marini, L., Athanassiou, A., and Gemmi, M. (2020) Electron Diffraction on Flash-Frozen Cowlesite Reveals the Structure of the First Two-Dimensional Natural Zeolite. ACS Central Science, 6, 1578–1586.CrossRefGoogle ScholarPubMed
Nakamoto, K. (2009) Infrared and Raman spectra of inorganic and coordination compounds Part A: Theory and applications in inorganic chemistry. John Wiley and Sons Inc. Hoboken, New Jersey.Google Scholar
Ohwada, K. (1976) Infrared spectroscopic studies of some uranyl nitrate complexes. Journal of Coordination Chemistry, 6, 75–80.CrossRefGoogle Scholar
Ondruš, P. (1993) A computer program for analysis of X-ray powder diffraction patterns. Materials Science Forum, EPDIC-2, Enchede, 133–136, 297–300.CrossRefGoogle Scholar
Orlandi, P., Biagioni, C., Bindi, L. and Merlino, S. (2015) Nuragheite, Th(MoO4)2·H2O, the second natural thorium molybdate and its relationships to ichnusaite and synthetic Th(MoO4)2. American Mineralogist, 100, 267–273.CrossRefGoogle Scholar
Orlandi, P., Biagioni, C., Bindi, L. and Nestola, F. (2014) Ichnusaite, Th(MoO4)2·3H2O, the first natural thorium molybdate: occurrence, description, and crystal structure. American Mineralogist, 99, 2089–2094.CrossRefGoogle Scholar
Orlandi, P., Biagioni, C. and Zaccarini, F. (2017) Cabvinite, Th2F7(OH)·3H2O, the first natural actinide halide. American Mineralogist, 102, 1384–1389.CrossRefGoogle Scholar
Palatinus, L., Brázda, P., Jelínek, M., Hrdá, J., Steciuk, G., and Klementová, M. (2019) Specifics of the data processing of precession electron diffraction tomography data and their implementation in the program PETS2.0. Acta Crystallographica, B75, 512–522.Google Scholar
Palatinus, L. and Chapuis, G. (2007) SUPERFLIP—a computer program for the solution of crystal structures by charge flipping in arbitrary dimensions. Journal of Applied Crystallography, 40, 786–790.CrossRefGoogle Scholar
Petříček, V., Dušek, M., Plášil, J. and Palatinus, L. (2023) Jana2020 - a new version of the crystallographic computing system Jana. Zeitschrift für Kristallographie, 229, 345–352.CrossRefGoogle Scholar
Piret, P. and Declercq, J. P. (1983) Structure cristalline de l’upalite Al[(UO2)3O(OH)(PO4)2]·7H2O. Un exemple de macle mimétique. Bulletin de Minéralogie, 106, 383–389.CrossRefGoogle Scholar
Piret, P. and Deliens, M. (1982) La vanmeerscheite U(UO2)3(PO4)2(OH)6·4(H2O) et la méta-vanmeerscheite U(UO2)3(PO4)2(OH)6·2(H2O), nouveaux minéraux. Bulletin de Minéralogie, 105, 125–128.CrossRefGoogle Scholar
Piret, P. and Deliens, M. (1987) Les phosphates d’uranyle et d’aluminium de Kobokobo IX. L’althupite AlTh(UO2)[(UO2)3O(OH)(PO4)2]2(OH)3·15H2O, nouveau minéral; propriétés et structure cristalline. Bulletin de Minéralogie, 110, 65–72.CrossRefGoogle Scholar
Plana-Ruiz, S., Portillo, J., Estradé, S., Peiró, F., Nicolopoulos, S. and Kolb, U. (2018) Quasi-parallel precession diffraction: Alignment method for scanning transmission electron microscopes. Ultramicroscopy, 193, 39–51.CrossRefGoogle ScholarPubMed
Plášil, J. (2014) Oxidation-hydration weathering of uraninite: The current state of knowledge. Journal of Geosciences, 59, 99–114.CrossRefGoogle Scholar
Plášil, J. (2017) A novel sheet topology in the structure of kamitugaite, PbAl[(UO2)5(PO4)2.38(AsO4)0.62O2(OH)2](H2O)11.5. Journal of Geosciences, 62, 253–260.Google Scholar
Plášil, J., Buixaderas, E., Čejka, J., Sejkora, J., Jehlička, J. and Novák, M. (2010) Raman spectroscopic study of the uranyl sulphate mineral zippeite: low wavenumber and U–O stretching regions. Analytical and Bioanalytical Chemistry, 397, 2703–2715.CrossRefGoogle ScholarPubMed
Plášil, J. and Petříček, V. (2017) Crystal structure of the (REE)-uranyl carbonate mineral kamotoite-(Y). Mineralogical Magazine, 81, 653–660.CrossRefGoogle Scholar
Plášil, J, Steciuk, G., Sejkora, J., Kampf, A.R., Uher, P., Ondrejka, M., Škoda, R., Dolníček, Z., Philippo, S., Guennou, M., Meisser, N., Rohlíček, J. and Mees, F. (2025) Extending the mineralogy of U6+ (I.): Crystal structure of lepersonnite-(Gd) and a description of the new mineral lepersonnite-(Nd). Mineralogical Magazine, (accepted manuscript).Google Scholar
Safiannikoff, A. and Van Wambeke, L. (1967) La pegmatite radioactive à béryl de Kobokobo et les autres venues pegmatitiques et filoniennes de la région de Kamituga – Kivu – Rép. du Congo. Mineralia Deposita, 2, 119–130.CrossRefGoogle Scholar
Sejkora, J., Kristek, J., Škácha, P. and Dolníček, Z. (2024) Uramphite from the Nová Ves pod Pleší (Czech Republic), the third world occurrence-description and vibrational spectroscopy. Journal of Geosciences, 69, 173–182.CrossRefGoogle Scholar
Siidra, O., Zenko, D.S. and Krivovichev, S.V. (2014) Structural complexity of lead silicates: crystal structure of Pb21[Si7O22]2[Si4O13] and its comparison to hyttsjöite. American Mineralogist, 99, 817–823.CrossRefGoogle Scholar
Steciuk, G., Majzlan, J., Rohlíček, J., Škoda, R., Sejkora, J. and Plášil, J. (2024) Znucalite, the only known zinc uranyl carbonate: its crystal structure and environmental implications. American Mineralogist, 109, 949–959.CrossRefGoogle Scholar
Steciuk, G., Sejkora, J., Čejka, J., Plášil, J. and Hloušek, J. (2021) Krupičkaite, Cu6[AsO3(OH)]6·8H2O, a new copper arsenate mineral from Jáchymov (Czech Republic). Journal of Geosciences, 66, 37–50.CrossRefGoogle Scholar
Van Wambeke, L. (1972) Eylettersite, un nouveau phosphate de thorium appartenant à la série de la crandallite. Bulletin de la Société Francaise de Minéralogie et de Cristallographie, 95, 98–105.Google Scholar
Van Wambeke, L. (1987) La minéralogie de la pegmatite de Kobokobo, Kivu, Zaïre. Bulletin de la Societe belge de Géologie, 96, 137–142.Google Scholar
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