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Extending the mineralogy of U6+ (I): Crystal structure of lepersonnite-(Gd) and a description of the new mineral lepersonnite-(Nd)

Published online by Cambridge University Press:  14 July 2025

Jakub Plášil Open the ORCID record for Jakub Plášil [Opens in a new window] ,
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] ,
Anthony R. Kampf Open the ORCID record for Anthony R. Kampf [Opens in a new window] ,
Pavel Uher ,
Martin Ondrejka Open the ORCID record for Martin Ondrejka [Opens in a new window] ,
Radek Škoda Open the ORCID record for Radek Škoda [Opens in a new window] ,
Zdeněk Dolníček ,
Simon Philippo  and
Mael Guennou Open the ORCID record for Mael Guennou [Opens in a new window]
...Show all authors
Jakub Plášil*
Affiliation:
Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic
Gwladys Steciuk
Affiliation:
Université de Lorraine, CNRS, Nancy, France
Jiří Sejkora
Affiliation:
Department of Mineralogy and Petrology, National Museum, Prague, Czech Republic
Anthony R. Kampf
Affiliation:
Mineral Sciences Department, Natural History Museum of Los Angeles County, Los Angeles, CA, USA
Pavel Uher
Affiliation:
Department of Mineralogy, Petrology and Economic Geology, Faculty of Natural Sciences, Comenius University, Mlynská dolina, Bratislava, Slovakia
Martin Ondrejka
Affiliation:
Department of Mineralogy, Petrology and Economic Geology, Faculty of Natural Sciences, Comenius University, Mlynská dolina, Bratislava, Slovakia
Radek Škoda
Affiliation:
Section Minéralogie, Musée d’Histoire Naturelle, Luxembourg
Zdeněk Dolníček
Affiliation:
Department of Mineralogy and Petrology, National Museum, Prague, Czech Republic
Simon Philippo
Affiliation:
Department of Physics and Materials Science, University of Luxembourg, Luxembourg
Mael Guennou
Affiliation:
Department of Geological Sciences, Masaryk University, Brno, Czech Republic
Nicolas Meisser
Affiliation:
Département de géologie, Muséum cantonal des sciences naturelles (Naturéum), Université de Lausanne (UNIL), Lausanne, Switzerland;
Jan Rohlíček
Affiliation:
Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic
Florias Mees
Affiliation:
Royal Museum for Central Africa, Tervuren, Belgium
*
Corresponding author: Jakub Plášil; Email: plasil@fzu.cz
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Abstract

Two uranyl carbonate silicate minerals have been studied in detail, lepersonnite-(Gd) and the new mineral lepersonnite-(Nd). Both minerals originate from Katanga province in the Democratic Republic of Congo (Africa): lepersonnite-(Gd) from the Shinkolobwe mine (type locality) and lepersonnite-(Nd) from the Swambo mine (type locality) and Shinkolobwe mine. Each occurs as radial to acicular aggregates composed of long prismatic, thin crystals, as the products of hydration–oxidation weathering of uraninite. A detailed description of the chemical and physical properties of lepersonnite-(Nd) is provided, including the thermal analysis of the -(Gd) member. Moreover, Raman and infrared spectroscopy data are provided for both minerals. The crystal structure of lepersonnite-(Gd) has been solved based on 3D electron diffraction data. According to the best dataset at 95 K, lepersonnite-(Gd) is orthorhombic, with a = 11.838(134) Å, b = 15.822(333) Å, c = 39.147(190) Å and V = 7353(282) Å3 (Z = 4). The dynamic refinement of the crystal structure (Robs/wRobs = 0.1204/0.1088 and Rall/wRall = 0.1204/0.1088 for 3090/50507 observed/all reflections and 247 refined parameters) revealed a large complex sheet structure with structural units defining a new lepersonnite topology. It contains infinite sheets of uranyl polyhedra, planar CO3 groups, protonated Si-tetrahedra, and Gd3+ polyhedra, and a thick interlayer hosted with H2O and partially occupied Ca2+ sites. Based on the structure refinement, bond-valence considerations, and new electron microprobe data, we infer that the ideal formula of lepersonnite-(Gd) is [Ca0.5Gd0.5(H2O)18(OH)1.5] [Gd(UO2)12(SiO3OH)2(CO3)4(OH)10O2(H2O)5]. On the basis of their closely related powder X-ray diffraction patterns and the similar behaviour of Nd and Gd, we expect the two minerals to adopt the same structures, apart from Ca, which was absent in lepersonnite-(Nd). The ideal formula for lepersonnite-(Nd) is [Nd(H2O)18(OH)2][Nd(UO2)12(SiO3OH)2(CO3)4(OH)10O2(H2O)5].

Keywords

lepersonnite-(Gd)lepersonnite-(Nd)rare-earth elementsnew mineralcrystal structure3D electron diffractioncomplexity

Information

Type
Article
Information
Mineralogical Magazine , Volume 89 , Issue 5 , October 2025 , pp. 549 - 565
Copyright
© 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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Footnotes

Associate Editor: Oleg I Siidra

We dedicate this paper to Michel Deliens, our dear friend and colleague, on the occasion of his 85th birthday.

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