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Minerals
Special Issues
Structure and Crystallochemistry of Clay Minerals
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Structure and Crystallochemistry of Clay Minerals

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

Deadline for manuscript submissions: closed (30 April 2022) | Viewed by 13887

Special Issue Editors

Dr. Ana I. Ruiz

E-Mail Website
Guest Editor
Department of Geology and Geochemistry, Autonomous University of Madrid, 28049 Madrid, Spain
Interests: structural characterization; clay minerals; clays for pollution control in waste effluents; clays as mineral barriers in the design of waste management
Dr. Jaime Cuevas Rodríguez

E-Mail Website
Co-Guest Editor
Department of Geology and Geochemistry, Autonomous University of Madrid, 28049 Madrid, Spain
Interests: mineralogy and geochemistry of clay minerals focussed to their characterization in order to address the role of geochemistry of mineral barriers in the design of waste management and residual effluents controls

Special Issue Information

Dear Colleagues,

Identifying the best applications of clay minerals requires a thorough knowledge of their structure and crystallochemical properties. Clay minerals’ structure consists of aluminosilicate layers (or sheets) in which the fundamental building blocks are composed of tetrahedral and octahedral units. These materials present an enormous structural versatility and capacity to evolve due to interlayer cations, stacking of the layers’ isomorphic substitutions, polymorphous transformations by octahedral cation migration, and other features. These properties influence their behavior in various natural or technical processes.

This Special Issue will focus on the accurate determination of the structural and crystallochemical characteristics of clay minerals, with the aim of better understanding and predict their properties.

Dr. Ana I. Ruiz
Guest Editors
Dr. Jaime Cuevas Rodríguez
Co-Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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 2400 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

  • clay minerals
  • mixed layers
  • octahedral sheet
  • tetrahedral sheet
  • coupled substitutions
  • redox processes
  • defects and surface properties
  • structural formulae
  • diffraction techniques
  • x-ray fluorescence spectroscopy

Published Papers (4 papers)

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Research

13 pages, 2690 KiB  
Article
Bentonite Powder XRD Quantitative Analysis Using Rietveld Refinement: Revisiting and Updating Bulk Semiquantitative Mineralogical Compositions
by Jaime Cuevas, Miguel Ángel Cabrera, Carlos Fernández, Carlos Mota-Heredia, Raúl Fernández, Elena Torres, María Jesús Turrero and Ana Isabel Ruiz
Minerals 2022, 12(6), 772; https://0-doi-org.brum.beds.ac.uk/10.3390/min12060772 - 17 Jun 2022
Cited by 9 | Viewed by 4436
Abstract
Bentonite is a claystone formed by a complex mineralogical mixture, composed of montmorillonite, illite, and accessory minerals like quartz, cristobalite, feldspars, carbonates, and minor amounts of iron oxy-hydroxides. Bentonite presents complexity at various scales: (1): a single mineral may present different chemical composition [...] Read more.
Bentonite is a claystone formed by a complex mineralogical mixture, composed of montmorillonite, illite, and accessory minerals like quartz, cristobalite, feldspars, carbonates, and minor amounts of iron oxy-hydroxides. Bentonite presents complexity at various scales: (1): a single mineral may present different chemical composition within the same quarry (e.g., feldspars solid solutions); (2): montmorillonite presents variability in the cation-exchange distribution while illite may be presented as mixed-layer with smectite sheets; and (3): hardness and crystal size are larger in accessory minerals than in clay minerals, preventing uniform grinding of bentonite. The FEBEX bentonite used is originally from Almería (Spain), and it is a predominantly calcium, magnesium, and sodium bentonite. This Spanish FEBEX bentonite has been hydrothermally altered at laboratory scale for 7–14 years. A thermal gradient was generated by heating a disk of pressed iron powder, simulating the metal waste canister, in contact with the compacted bentonite sample. Hydration was forced from the opposite direction. XRD recorded patterns were very similar. In order to minimize the bias of XRD semi-quantitative determination methods, Rietveld refinement was performed using BGMN software and different structural models. Confidence in the quantification of the main phases allows us to convincingly detect other subtle changes such as the presence of calcite in the hydration front, right at the interface between the saturated and unsaturated bentonite, or the presence of goethite, and not hematite, in the saturated bentonite, near the source of hydration. Smectite component was 72 ± 3% and the refinement was consistent with the presence of ~10% illite, comparable with previous characterizations. Full article
(This article belongs to the Special Issue Structure and Crystallochemistry of Clay Minerals)
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15 pages, 11263 KiB  
Article
Micro- and Nanotexture and Genesis of Ball Clays in the Lower Cretaceous (SE Iberian Range, NE Spain)
by Blanca Bauluz, María José Mayayo, Elisa Laita and Alfonso Yuste
Minerals 2021, 11(12), 1339; https://0-doi-org.brum.beds.ac.uk/10.3390/min11121339 - 29 Nov 2021
Cited by 1 | Viewed by 1641
Abstract
Ball clay deposits in the SE of the Iberian Range (NE Iberian Peninsula) consist of Albian clays and siltstones with greyish and blackish colors, interbedded with subbituminous coals. The ball clays are nowadays mined for the manufacture of white color ceramics. The mineralogy [...] Read more.
Ball clay deposits in the SE of the Iberian Range (NE Iberian Peninsula) consist of Albian clays and siltstones with greyish and blackish colors, interbedded with subbituminous coals. The ball clays are nowadays mined for the manufacture of white color ceramics. The mineralogy of these deposits consists mainly of kaolinite, illitic phases, and quartz. The euhedral to sub-euhedral morphology of the kaolinites suggests their in-situ origin. The anhedral morphology of the illites and the presence of frayed illites suggest a detrital origin. At the micro-scale, authigenic kaolinite booklets are observed filling pores and forming mica/kaolinite intergrowths, in which the kaolinite grows between the cleavage sheets of pre-existing detrital mica. At nanometer scale, illite/smectite (IS) phases are detected forming interlayers with mica and kaolinite, and evidence of the replacement of mica by kaolinite is observed. The matrix consists of defective illite and kaolinite, and random mixed layers of kaolinite-I/S (Kln-IS), illite-I/S (Ilt-IS), and I/S-smectite (IS-S). The textures of illite and the presence of different types of mixed layers suggest that the expandable phases and kaolinite are products of mica alteration. The effectivity of the alteration was probably a consequence of the low pH that occurred in the environment due to the presence of abundant organic- and acidic- rich fluids. Full article
(This article belongs to the Special Issue Structure and Crystallochemistry of Clay Minerals)
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18 pages, 8488 KiB  
Article
Mineralogical and Crystal-Chemical Constraints on the Glauconite-Forming Process in Neogene Sediments of the Lower Guadalquivir Basin (SW Spain)
by Sandra Fernández-Landero and Juan Carlos Fernández-Caliani
Minerals 2021, 11(6), 578; https://0-doi-org.brum.beds.ac.uk/10.3390/min11060578 - 28 May 2021
Cited by 10 | Viewed by 4078
Abstract
Glaucony is a significant green marine facies in the northwestern passive margin of the Guadalquivir Basin (Spain), where glauconite formed authigenically on a sediment-starved continental shelf, with fecal pellets and benthic foraminiferal tests being the main glauconitized substrates. Results from a study using [...] Read more.
Glaucony is a significant green marine facies in the northwestern passive margin of the Guadalquivir Basin (Spain), where glauconite formed authigenically on a sediment-starved continental shelf, with fecal pellets and benthic foraminiferal tests being the main glauconitized substrates. Results from a study using XRD, TGA-DSC, SEM-EDS, and EPMA have revealed that glauconite is remarkably heterogeneous in mineral composition and chemical maturity, even in a single grain, reflecting a complex interaction of micro-environmental factors, substrate influences and post-depositional alterations. In its early stage, the glauconitization process is consistent with the slow precipitation of a Fe-rich smectite phase, most likely intergrade between nontronite and Fe-montmorillonite end-members, which evolved to a regularly interstratified glauconite-smectite (Gl/S). The Fe-smectite-to-Gl/S transformation is interpreted as a diffusion-controlled reaction, involving sufficient Fe availability in pore water and the constant diffusive transport of seawater K+ and Mg2+ ions towards the substrate. The pelletal glauconite is actually a highly evolved Gl/S consisting almost totally of mica layers, with 0.74 ± 0.05 apfu of K+ in the interlayer, while the Gl/S occurring as replacements of foraminiferal tests contains a mean of 7% of expandable layers in the walls and 16% in the chamber fillings, due to rate-limited ion diffusion. Full article
(This article belongs to the Special Issue Structure and Crystallochemistry of Clay Minerals)
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19 pages, 3332 KiB  
Article
Thermal Evolution of Natural Layered Double Hydroxides: Insight from Quintinite, Hydrotalcite, Stichtite, and Iowaite as Reference Samples for CO3- and Cl-Members of the Hydrotalcite Supergroup
by Elena S. Zhitova, H. Chris Greenwell, Mariya G. Krzhizhanovskaya, David C. Apperley, Igor V. Pekov and Victor N. Yakovenchuk
Minerals 2020, 10(11), 961; https://0-doi-org.brum.beds.ac.uk/10.3390/min10110961 - 28 Oct 2020
Cited by 10 | Viewed by 2740
Abstract
In Situ high-temperature powder X-ray diffraction experiments were undertaken for the coarse crystalline natural layered double hydroxides (LDHs) quintinite, hydrotalcite, stichtite, and iowaite in the temperature range 25–1000 °C, with thermal analyses of these minerals and their annealed forms carried out in parallel. [...] Read more.
In Situ high-temperature powder X-ray diffraction experiments were undertaken for the coarse crystalline natural layered double hydroxides (LDHs) quintinite, hydrotalcite, stichtite, and iowaite in the temperature range 25–1000 °C, with thermal analyses of these minerals and their annealed forms carried out in parallel. In the temperature range from 25 °C to 170–210 °C quintinite, hydrotalcite, and stichtite (carbonate members of the LDH family) demonstrated contraction of the basal d00n-value of 0.1–0.3 Å, followed by a sharp contraction of 1.0–1.1 Å at T > 170–210 °C. The high-temperature modified states were stable up to 380–420 °C, before decomposing to an amorphous phase. Iowaite (chloride member of the family) was stable up to 320 °C and transformed to an amorphous phase at higher temperature. Iowaite experiences continuous contraction of the d00n-value of up to 0.5 Å in the temperature range 25–200 °C, reaching a plateau at a temperature range of 200–320 °C. Assessing the reversibility of thermal transformation shows complete reconstruction of the crystal structure of the hydrotalcite and iowaite heated to 300 °C. Solid-state nuclear magnetic resonance analysis shows that some Al changes coordination from 6- to 4-fold, synchronously with quintinite transformation to the amorphous phase. All phases transform to periclase and a spinel-type compound upon further heating. Thermal analysis of samples annealed at 125 °C shows that carbonate members do not have a tendency to form dehydrated phases, whereas for iowaite, a dehydrated phase having 0.9 apfu lesser water content as in the initial sample has been obtained. Thermal evolution of LDHs is found to depend on the nature of the interaction of interlayer species and water molecules to H atoms of the metal-hydroxide layer. Full article
(This article belongs to the Special Issue Structure and Crystallochemistry of Clay Minerals)
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