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Crystal structure of richetite revisited: Crystallographic evidence for the presence of pentavalent uranium

  • Jakub Plášil EMAIL logo
Published/Copyright: September 5, 2017
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American Mineralogist
From the journal American Mineralogist Volume 102 Issue 9

Abstract

Revision of crystal structure of the rare U-oxide mineral richetite provided crystallographic evidence for the presence of pentavalent U. The structure of richetite, space group P1, a = 12.0919(2), b = 16.3364(4), c = 20.2881(4) Å, α = 68.800(2), β = 78.679(2), γ = 76.118(2)°, with V = 3600.65(14) Å3 and Z = 1, was solved by charge-flipping algorithm and refined to an agreement index (R) of 5.6% for 9955 unique reflections collected using microfocus X-ray source. The refined structure, in line with the previous structure determination, contains U-O-OH sheets of the α-U3O8 type (protasite topology) and an interstitial complex comprising Pb2+, Fe2+, Mg2+ cations and molecular H2O. However, the polyhedral geometry, the bond-valence sum incident at one U site within the sheet (U17) together with charge-balance requirements, indicate that U17 site is occupied by U5+. The U17Φ7 (Φ: O, OH) polyhedra is distorted, with two shorter U–O bond-lengths (~2.01 Å), four longer U–O bond-lengths (~2.2 Å) and one, very long U–O bond (2.9 Å). The color of richetite also supports the presence of U5+ in the structure The current results show that α-U3O8 type of sheet can incorporate U5+. Richetite is the third mineral containing pentavalent uranium that occurs in nature.

Keywords: Richetite; uranyl oxide hydroxy-hydrate; crystal structure; pentavalent uranium; weathering

Special collection papers can be found online at http://www.minsocam.org/MSA/AmMin/special-collections.html.

Acknowledgments

Jean-Claude Leydet (Brest, France) is thanked for providing me a sample for single-crystal study. My thanks go to Jiří Čejka (Roudnice nad Labem, Czech Republic) for his encouragement for the study and critical reading of the manuscript and to Stephan Wolfsried (Waiblingen, Germany) for beautiful microphotography or richetite crystals. The manuscript benefited from the comprehensive thorough reviews of Sergey Krivovichev and an anonymous referee. The editorial handling of Peter Burns is highly acknowledged. This research was financially supported the Project No. LO1603 under the Ministry of Education, Youth and Sports National sustainability program I of Czech Republic.

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Received: 2017-1-31
Accepted: 2017-5-4
Published Online: 2017-9-5
Published in Print: 2017-9-26

© 2017 by Walter de Gruyter Berlin/Boston

Articles in the same Issue

  1. Highlights and Breakthroughs
  2. Looking for “missing” nitrogen in the deep Earth
  3. Actinides in Geology, Energy, and the Environment
  4. Crystal structure of richetite revisited: Crystallographic evidence for the presence of pentavalent uranium
  5. Actinides in Geology, Energy, and the Environment
  6. Mobilization and agglomeration of uraninite nanoparticles: A nano-mineralogical study of samples from the Matoush Uranium ore deposit
  7. Actinides in Geology, Energy, and the Environment
  8. Radiation damage in sulfides: Radioactive galena from burning heaps, after coal mining in the Lower Silesian basin (Czech Republic)
  9. Special Collection: Mechanisms, Rates, and Timescales of Geochemical Transport Processes in the Crust and Mantle
  10. Element mobility during regional metamorphism in crustal and subduction zone environments with a focus on the rare earth elements (REE)
  11. Special Collection: Water in Nominally Hydrous and Anhydrous Minerals
  12. Subsolidus hydrogen partitioning between nominally anhydrous minerals in garnet-bearing peridotite
  13. Special Collection: Water in Nominally Hydrous and Anhydrous Minerals
  14. OH defects in quartz as monitor for igneous, metamorphic, and sedimentary processes
  16. Quantitative electron backscatter diffraction (EBSD) data analyses using the dictionary indexing (DI) approach: Overcoming indexing difficulties on geological materials
  18. Trace element inventory of meteoritic Ca-phosphates
  20. Insights into solar nebula formation of pyrrhotite from nanoscale disequilibrium phases produced by H2S sulfidation of Fe metal
  22. Unraveling the presence of multiple plagioclase populations and identification of representative two-dimensional sections using a statistical and numerical approach
  24. Refractive indices of minerals and synthetic compounds
  26. Can we use pyroxene weathering textures to interpret aqueous alteration conditions? Yes and No
  28. Phase relations and formation of K-bearing Al-10 Å phase in the MORB+H2O system: Implications for H2O- and K-cycles in subduction zones
  30. Effect of alkalis on the reaction of clinopyroxene with Mg-carbonate at 6 GPa: Implications for partial melting of carbonated lherzolite
  32. Synthesis and crystal structure of LiNbO3-type Mg3Al2Si3O12: A possible indicator of shock conditions of meteorites
  34. Single crystal synthesis of δ-(Al,Fe)OOH
  35. Letter
  36. EosFit-Pinc: A simple GUI for host-inclusion elastic thermobarometry
  38. New Mineral Names
https://doi.org/10.2138/am-2017-6092
Keywords for this article
Richetite; uranyl oxide hydroxy-hydrate; crystal structure; pentavalent uranium; weathering

Articles in the same Issue

  1. Highlights and Breakthroughs
  2. Looking for “missing” nitrogen in the deep Earth
  3. Actinides in Geology, Energy, and the Environment
  4. Crystal structure of richetite revisited: Crystallographic evidence for the presence of pentavalent uranium
  5. Actinides in Geology, Energy, and the Environment
  6. Mobilization and agglomeration of uraninite nanoparticles: A nano-mineralogical study of samples from the Matoush Uranium ore deposit
  7. Actinides in Geology, Energy, and the Environment
  8. Radiation damage in sulfides: Radioactive galena from burning heaps, after coal mining in the Lower Silesian basin (Czech Republic)
  9. Special Collection: Mechanisms, Rates, and Timescales of Geochemical Transport Processes in the Crust and Mantle
  10. Element mobility during regional metamorphism in crustal and subduction zone environments with a focus on the rare earth elements (REE)
  11. Special Collection: Water in Nominally Hydrous and Anhydrous Minerals
  12. Subsolidus hydrogen partitioning between nominally anhydrous minerals in garnet-bearing peridotite
  13. Special Collection: Water in Nominally Hydrous and Anhydrous Minerals
  14. OH defects in quartz as monitor for igneous, metamorphic, and sedimentary processes
  16. Quantitative electron backscatter diffraction (EBSD) data analyses using the dictionary indexing (DI) approach: Overcoming indexing difficulties on geological materials
  18. Trace element inventory of meteoritic Ca-phosphates
  20. Insights into solar nebula formation of pyrrhotite from nanoscale disequilibrium phases produced by H2S sulfidation of Fe metal
  22. Unraveling the presence of multiple plagioclase populations and identification of representative two-dimensional sections using a statistical and numerical approach
  24. Refractive indices of minerals and synthetic compounds
  26. Can we use pyroxene weathering textures to interpret aqueous alteration conditions? Yes and No
  28. Phase relations and formation of K-bearing Al-10 Å phase in the MORB+H2O system: Implications for H2O- and K-cycles in subduction zones
  30. Effect of alkalis on the reaction of clinopyroxene with Mg-carbonate at 6 GPa: Implications for partial melting of carbonated lherzolite
  32. Synthesis and crystal structure of LiNbO3-type Mg3Al2Si3O12: A possible indicator of shock conditions of meteorites
  34. Single crystal synthesis of δ-(Al,Fe)OOH
  35. Letter
  36. EosFit-Pinc: A simple GUI for host-inclusion elastic thermobarometry
  38. New Mineral Names
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