Special Issue "Actinide Mineralogy and Crystallography"

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Crystallography and Physical Chemistry of Minerals".

Deadline for manuscript submissions: closed (15 January 2019)

Special Issue Editors

Guest Editor
Dr. Jakub Plasil

Department of Structure Analysis, Academy of Sciences of the Czech Republic, Prague, Czech Republic
Website | E-Mail
Interests: uranium mineralogy; X-ray crystallography; spectroscopy
Guest Editor
Prof. Dr. Sergey V. Krivovichev

Kola Science Centre, Russian Academy of Sciences, Apatity, Russia
Department of Crystallography, Saint-Petersburg State University, Saint-Petersburg, Russia
Website | E-Mail
Interests: mineralogy; crystallography; structural complexity; uranium

Special Issue Information

Dear Colleagues,

Actinide minerals, and especially those containing the structure uranyl ion, (UO2)2+, have attracted the interest of mineralogists and crystallographers since the discovery of the first “uranium mica” by I. Born in 1772. Nowadays, actinide minerals and inorganic compounds are inspiring objects of investigations, not only for mineralogists, crystallographers, geochemists, or spectroscopists, but also for chemists, who synthesize a large number of compounds inspired by the structural features of minerals. The demand for U worldwide, as well as the problems connected with a spent nuclear fuel, in the forms of waste dumps and piles after U mining or planned final repositories, all make research focused on actinides and, in particular, uranium and uranyl minerals, important.

This Special Issue welcomes contributions on actinide mineralogy, geochemistry, crystallography of both minerals and synthetic compounds, problems of uranium deposits and environmental impacts, and nuclear forensics, as useful applications of actinide geochemistry and mineralogy.

Dr. Jakub Plasil
Prof. Sergey V. Krivovichev
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • actinides
  • uranium
  • crystal-chemistry
  • crystallography
  • geochemistry
  • economic geology
  • environmental impacts
  • nuclear forensics

Published Papers (6 papers)

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Research

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Open AccessArticle Structure Refinement and Thermal Stability Studies of the Uranyl Carbonate Mineral Andersonite, Na2Ca[(UO2)(CO3)3]·(5+x)H2O
Minerals 2018, 8(12), 586; https://doi.org/10.3390/min8120586
Received: 21 November 2018 / Revised: 4 December 2018 / Accepted: 10 December 2018 / Published: 11 December 2018
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Abstract
A sample of uranyl carbonate mineral andersonite, Na2Ca[(UO2)(CO3)3]·5−6H2O, originating from the Cane Springs Canyon, San Juan Co., UT, USA was studied using single-crystal and powder X-ray diffraction at various temperatures. Andersonite is trigonal, [...] Read more.
A sample of uranyl carbonate mineral andersonite, Na2Ca[(UO2)(CO3)3]·5−6H2O, originating from the Cane Springs Canyon, San Juan Co., UT, USA was studied using single-crystal and powder X-ray diffraction at various temperatures. Andersonite is trigonal, R−3m, a = 17.8448(4), c = 23.6688(6) Å, V = 6527.3(3) Å3, Z = 18, R1 = 0.018. Low-temperature SCXRD determined the positions of H atoms and disordered H2O molecules, arranged within the zeolite-like channels. The results of high-temperature PXRD experiments revealed that the structure of andersonite is stable up to 100 °C; afterwards, it loses crystallinity due to release of H2O molecules. Taking into account the well-defined presence of H2O molecules forming channels’ walls that to the total of five molecules p.f.u., we suggest that the formula of andersonite is Na2Ca[(UO2)(CO3)3]·(5+x)H2O, where x ≤ 1. The thermal behavior of andersonite is essentially anisotropic with the lowest values of the main thermal expansion coefficients in the direction perpendicular to the channels (plane (001)), while the maximal expansion is observed along the c axis—in the direction of channels. The thermal expansion around 80 °C within the (001) plane becomes negative due to the total release of “zeolitic” H2O molecules. The information-based structural complexity parameters of andersonite were calculated after the removal of all the disordered atoms, leaving only the predominantly occupied sites, and show that the crystal structure of the mineral should be described as complex, possessing 4.535 bits/atom and 961.477 bits/cell, which is comparative to the values for another very common natural uranyl carbonate, liebigite. Full article
(This article belongs to the Special Issue Actinide Mineralogy and Crystallography)
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Open AccessArticle Synchrotron Diffraction Study of the Crystal Structure of Ca(UO2)6(SO4)2O2(OH)6·12H2O, a Natural Phase Related to Uranopilite
Minerals 2018, 8(12), 569; https://doi.org/10.3390/min8120569
Received: 27 October 2018 / Revised: 30 November 2018 / Accepted: 1 December 2018 / Published: 4 December 2018
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Abstract
The crystal structure of a novel natural uranyl sulfate, Ca(UO2)6(SO4)2O2(OH)6·12H2O (CaUS), has been determined using data collected under ambient conditions at the Swiss–Norwegian beamline BM01 of the European Synchrotron [...] Read more.
The crystal structure of a novel natural uranyl sulfate, Ca(UO2)6(SO4)2O2(OH)6·12H2O (CaUS), has been determined using data collected under ambient conditions at the Swiss–Norwegian beamline BM01 of the European Synchrotron Research Facility (ESRF). The compound is monoclinic, P21/c, a = 11.931(2), b = 14.246(6), c = 20.873(4) Å, β = 102.768(15), V = 3460.1(18) Å3, and R1 = 0.172 for 3805 unique observed reflections. The crystal structure contains six symmetrically independent U6+ atoms forming (UO7) pentagonal bipyramids that share OO edges to form hexamers oriented parallel to the (010) plane and extended along [1–20]. The hexamers are linked via (SO4) groups to form [(UO2)6(SO4)2O2(OH)6(H2O)4]2− chains running along the c-axis. The adjacent chains are arranged into sheets parallel to (010). The Ca2+ ions are coordinated by seven O atoms, and are located in between the sheets, providing their linkage into a three-dimensional structure. The crystal structure of CaUS is closely related to that of uranopilite, (UO2)6(SO4)O2(OH)6·14H2O, which is also based upon uranyl sulfate chains consisting of hexameric units formed by the polymerization of six (UO7) pentagonal bipyramids. However, in uranopilite, each (SO4) tetrahedron shares its four O atoms with (UO7) bipyramids, whereas in CaUS, each sulfate group is linked to three uranyl ions only, and has one O atom (O16) linked to the Ca2+ cation. The chains are also different in the U:S ratio, which is equal to 6:1 for uranopilite and 3:1 for CaUS. The information-based structural complexity parameters for CaUS were calculated taking into account H atoms show that the crystal structure of this phase should be described as very complex, possessing 6.304 bits/atom and 1991.995 bits/cell. The high structural complexity of CaUS can be explained by the high topological complexity of the uranyl sulfate chain based upon uranyl hydroxo/oxo hexamers and the high hydration character of the phase. Full article
(This article belongs to the Special Issue Actinide Mineralogy and Crystallography)
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Open AccessArticle Paddlewheelite, a New Uranyl Carbonate from the Jáchymov District, Bohemia, Czech Republic
Minerals 2018, 8(11), 511; https://doi.org/10.3390/min8110511
Received: 10 October 2018 / Revised: 1 November 2018 / Accepted: 5 November 2018 / Published: 7 November 2018
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Abstract
Paddlewheelite, MgCa5Cu2[(UO2)(CO3)3]4·33H2O, is a new uranyl carbonate mineral found underground in the Svornost mine, Jáchymov District, Bohemia, Czech Republic, where it occurs as a secondary oxidation product of uraninite. [...] Read more.
Paddlewheelite, MgCa5Cu2[(UO2)(CO3)3]4·33H2O, is a new uranyl carbonate mineral found underground in the Svornost mine, Jáchymov District, Bohemia, Czech Republic, where it occurs as a secondary oxidation product of uraninite. The conditions leading to its crystallization are complex, likely requiring concomitant dissolution of uraninite, calcite, dolomite, chalcopyrite, and andersonite. Paddlewheelite is named after its distinctive structure, which consists of paddle-wheel clusters of uranyl tricarbonate units bound by square pyramidal copper “axles” and a cubic calcium cation “gearbox.” Paddle wheels share edges with calcium polyhedra to form open sheets that are held together solely by hydrogen bonding interactions. The new mineral is monoclinic, Pc, a = 22.052(4), b = 17.118(3), c = 19.354(3) Å, β = 90.474(2)°, V = 7306(2) Å3 and Z = 4. Paddlewheelite is the second-most structurally complex uranyl carbonate mineral known after ewingite and its structure may provide insights into the insufficiently described mineral voglite, as well as Cu–U–CO3 equilibrium in general. Full article
(This article belongs to the Special Issue Actinide Mineralogy and Crystallography)
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Open AccessArticle New Uranyl Open Framework and Sheet Compounds Formed via In-Situ Protonation of Piperazine by Phosphorous Acid
Minerals 2018, 8(11), 497; https://doi.org/10.3390/min8110497
Received: 12 September 2018 / Revised: 18 October 2018 / Accepted: 19 October 2018 / Published: 1 November 2018
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Abstract
Two new uranyl compounds were hydrothermally synthesized employing piperazine as an organic templating agent. The piperazine was protonated in-situ by phosphorous acid, forming the piperazinium dication featured in these compounds. The two new structures presented here are a uranyl phosphite 2D sheet and [...] Read more.
Two new uranyl compounds were hydrothermally synthesized employing piperazine as an organic templating agent. The piperazine was protonated in-situ by phosphorous acid, forming the piperazinium dication featured in these compounds. The two new structures presented here are a uranyl phosphite 2D sheet and a 3D uranyl mixed phosphite–phosphate network with cation occupied channels. Both included strong hydrogen bonding from the piperazinium cation to the uranyl phosphite or mixed phosphite–phosphate network. These two structures can be reliably formed through careful control of pH of the starting solution and the reaction duration. The piperazinium uranyl phosphite compound was the latest in a family of uranyl phosphites, and demonstrates the structural versatility of this combination. The mixed phosphite–phosphate compound builds on hydrothermal redox chemistry, illustrating the variety of compounds that can be isolated by exploiting in-situ redox processes to elucidate new uranium structure types. Full article
(This article belongs to the Special Issue Actinide Mineralogy and Crystallography)
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Open AccessArticle Supergene Uranyl Mineralization of the Rabejac Deposit, Lodève, France
Minerals 2018, 8(9), 414; https://doi.org/10.3390/min8090414
Received: 21 August 2018 / Revised: 8 September 2018 / Accepted: 11 September 2018 / Published: 18 September 2018
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Abstract
The Rabejac uranium deposit that is located in the Lodève region, France, is the type locality for three uranyl minerals species (fontanite, seelite, and rabejacite). In addition, this deposit shows an extraordinary supergene uranyl mineralization characterized by the presence of many rare secondary [...] Read more.
The Rabejac uranium deposit that is located in the Lodève region, France, is the type locality for three uranyl minerals species (fontanite, seelite, and rabejacite). In addition, this deposit shows an extraordinary supergene uranyl mineralization characterized by the presence of many rare secondary uranyl species. In the present study, a mineralogical description as well as new chemical and crystallographic data are reported on (meta)zeunerite, (meta)nováčekite, (meta)uranospinite, heinrichite, nováčekite-I, arsenuranospathite, umohoite, calcurmolite, becquerelite, billietite, and liebigite. The chemical data indicate that the arsenate members of the autunite/meta-autunite group incorporate a significant amount of phosphorus. Moreover, the uranospinite samples usually exhibit high Mg content, thus moving toward the nováčekite end-member composition. The refined unit-cell parameters for all of the investigated mineral species are in agreement with the previous data reported in the literature. Finally, a model describing the alteration of the primary uraninite and the formation of secondary uranyl minerals is proposed in agreement with the observed mineral assemblages. Full article
(This article belongs to the Special Issue Actinide Mineralogy and Crystallography)
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Review

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Open AccessReview Mineralogy, Crystallography and Structural Complexity of Natural Uranyl Silicates
Minerals 2018, 8(12), 551; https://doi.org/10.3390/min8120551
Received: 10 October 2018 / Revised: 19 November 2018 / Accepted: 19 November 2018 / Published: 27 November 2018
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Abstract
Naturally occurring uranyl silicates are common constituents of the oxidized parts (i.e., supergene zone) of various types of uranium deposits. Their abundance reflects the widespread distribution of Si4+ in the Earth’s crust and, therefore, in groundwaters. Up to date, 16 uranyl silicate [...] Read more.
Naturally occurring uranyl silicates are common constituents of the oxidized parts (i.e., supergene zone) of various types of uranium deposits. Their abundance reflects the widespread distribution of Si4+ in the Earth’s crust and, therefore, in groundwaters. Up to date, 16 uranyl silicate minerals are known. Noteworthy is that the natural uranyl silicates are not extremely diverse regarding their crystal structures; it is a result of possible concentrations (activity) of Si4+ in aqueous solutions derived from dissolution of primary Si minerals or the composition of late hydrothermal fluids. Therefore, in natural systems, we distinguish in fact among two groups of uranyl silicate minerals: uranophane and weeksite-group. They differ in U:Si ratio (uranophane, 1:1; weeksite, 2:5) and they form under different conditions, reflected in distinctive mineral associations. An overview of crystal-chemistry is provided in this paper, along with the new structure data for few members of the uranophane group. Calculations of the structural complexity parameters for natural uranyl silicates are commented about as well as other groups of uranyl minerals; these calculations are also presented from the point of view of the mineral paragenesis and associations. Full article
(This article belongs to the Special Issue Actinide Mineralogy and Crystallography)
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