Minerals

17 pages, 6772 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Achieving Zero Waste and CO₂ Reduction in Saline Water Treatment—Sustainable Salt and Ice Recovery Using Pipe Freeze Crystallization

by Kagiso S. More and Johannes P. Maree

Minerals 2025, 15(1), 51; https://doi.org/10.3390/min15010051 - 4 Jan 2025

Viewed by 915

Abstract

This study investigates the application of pipe freeze crystallization (PFC) as a sustainable, zero-waste technology for treating high-salinity industrial wastewater, enabling the simultaneous recovery of salts and clean water. PFC addresses the limitations of traditional brine treatment methods such as evaporation ponds and [...] Read more.

This study investigates the application of pipe freeze crystallization (PFC) as a sustainable, zero-waste technology for treating high-salinity industrial wastewater, enabling the simultaneous recovery of salts and clean water. PFC addresses the limitations of traditional brine treatment methods such as evaporation ponds and distillation, which are energy-intensive, produce concentrated brine requiring disposal, and emit significant CO₂. A pilot demonstration plant in Olifantsfontein, South Africa, served as the basis for this research. The plant operates at an energy consumption rate of 330 kJ/kg, significantly lower than distillation’s 2200 kJ/kg. It efficiently recovers high-purity Na₂SO₄ and clean ice, which can be reused as water, with plans underway to incorporate NaCl recovery. Comparative analyses highlight PFC’s energy efficiency and reduced CO₂ emissions, achieving an 82% reduction in greenhouse gas emissions compared to evaporation-based methods. This study evaluates the operational parameters and scalability of PFC for broader industrial applications. X-ray Diffraction analysis confirmed that the Na₂SO₄ recovered from the pilot plant achieved a purity level of 84.9%, demonstrating the process’s capability to produce valuable, market-ready by-products. These findings reinforce PFC’s potential as a cost-effective and environmentally sustainable alternative to conventional methods. PFC offers a transformative solution for managing saline effluents, aligning with zero-waste objectives and contributing to reduced environmental impact. This technology provides industries with an economically viable solution for resource recovery while supporting compliance with stringent environmental regulations. Full article

(This article belongs to the Section Mineral Processing and Extractive Metallurgy)

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17 pages, 5743 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Geochemical Discrimination of Agate in Diverse Volcanic Host Rocks Through Machine Learning Methods

by Peng Zhang, Bo-Chao Wang, Xiao-Wen Huang and Xi Xi

Minerals 2025, 15(1), 32; https://doi.org/10.3390/min15010032 - 30 Dec 2024

Cited by 1 | Viewed by 731

Abstract

The formation of agate is related to syngenetic or epigenetic magmatic hydrothermal fluids. Trace elements incorporated during the alteration of host rocks caused by hydrothermal magmatic fluids precipitate during their crystallization, reflecting the characteristics of the host rocks. While prior research has yielded [...] Read more.

The formation of agate is related to syngenetic or epigenetic magmatic hydrothermal fluids. Trace elements incorporated during the alteration of host rocks caused by hydrothermal magmatic fluids precipitate during their crystallization, reflecting the characteristics of the host rocks. While prior research has yielded extensive trace element data to differentiate agate types found in volcanic rocks, there remains a need for a more efficient method to identify the host volcanic rock of alluvial agate. In this study, a two-stage Random Forest approach was employed to classify the chemical compositions of agate originating from rhyolite, andesite, and basalt, with the aim of facilitating the determination of the host volcanic rock for unknown alluvial agate samples. A dataset comprising 203 agate compositional analyses, sourced from 16 distinct locations, was compiled and labeled for the purpose of training the Random Forest model. The classification results indicate that the developed models exhibit high accuracy (0.9524) and an F1 score of 0.9512, demonstrating their superior performance and efficiency. The feature importance analysis of these models reveals that U, Sb, and Sr contents are particularly crucial for discriminating between different types of volcanic rocks hosting agate. Furthermore, this study introduces a novel discriminant plot utilizing linear discriminant analysis (LDA) to evaluate the host volcanic rock of agate based on trace element data. Verifying the trace element data of agate samples related to basalt based on actual measurements shows that both the Random Forest (with accuracy of 0.813) and LDA plot underscore the effectiveness of using the trace elements found in alluvial agate for the identification of the host volcanic rock. Full article

(This article belongs to the Section Mineral Geochemistry and Geochronology)

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22 pages, 2762 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

On the Question of Finding Relationship Between Structural Features of Smectites and Adsorption and Surface Properties of Bentonites

by Victoria Krupskaya, Sergey Zakusin, Olga Zakusina, Petr Belousov, Boris Pokidko, Ivan Morozov, Tatiana Zaitseva, Ekaterina Tyupina and Tatiana Koroleva

Minerals 2025, 15(1), 30; https://doi.org/10.3390/min15010030 - 29 Dec 2024

Viewed by 1029

Abstract

During the development of the disposal concept in a crystalline massif of the Russian Federation, a question arose regarding the selection of the most suitable types of bentonite for a buffer layer. Data on the composition, structure, surface, and adsorption properties of four [...] Read more.

During the development of the disposal concept in a crystalline massif of the Russian Federation, a question arose regarding the selection of the most suitable types of bentonite for a buffer layer. Data on the composition, structure, surface, and adsorption properties of four promising deposits have been obtained. The correlations between genesis and specific surface area (SSA) revealed in this study indicate that bentonites of volcanogenic-sedimentary origin have lower SSA in comparison with those of sedimentary and hydrothermal origin. The main contribution to the charge of the 2:1 layer is made by isomorphic substitutions in the tetrahedral sheet, which directly affects the sorption properties of bentonites. The influence of smectite structure on adsorption properties have been described. In particular, the dependencies between the layer charge and cation exchange capacity (CEC) have been analyzed. At the same time, the research indicates that, unlike the CEC, the specific surface area of a deposit is determined by its geological history. Special attention is being paid to refining methodological approaches for deriving crystal chemical formulae of smectites, which will be needed in the future for modelling changes in bentonite over a long-term perspective. Full article

(This article belongs to the Special Issue Role of Clay Mineralogy in Geotechnical Engineering Behavior of Clay Soils)

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22 pages, 9989 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Microscopic, Spectroscopic and Chemical Analysis of Emeralds from Habachtal, Austria

by Maria Nikopoulou, Stefanos Karampelas, Ugo Hennebois, Pierre Gruss, Eloïse Gaillou, Emmanuel Fritsch, Annabelle Herreweghe, Lambrini Papadopoulou, Vasilios Melfos, Nikolaos Kantiranis and Aurélien Delaunay

Minerals 2025, 15(1), 22; https://doi.org/10.3390/min15010022 - 27 Dec 2024

Viewed by 1373

Abstract

Studies on emeralds from Habachtal (Austria) are scarce and non-exhaustive. However, they represent a significant interest to the community, as they have been assumed to be present in historical pieces of jewelry. Along with Egypt, Habachtal is suggested to be one of the [...] Read more.

Studies on emeralds from Habachtal (Austria) are scarce and non-exhaustive. However, they represent a significant interest to the community, as they have been assumed to be present in historical pieces of jewelry. Along with Egypt, Habachtal is suggested to be one of the main sources of gem-quality emeralds of archaeological significance. In this regard and due to their similar macroscopic look and geological context, it has always been challenging to distinguish Austrian and Egyptian emeralds set in historic jewelry. In this paper, a first comprehensive study of several Habchtal emeralds is presented based on a combination of classic gemology, chemistry and spectroscopy, using non-destructive to micro-destructive methods. Spectroscopic analyses, such as via Raman, FTIR and UV-Vis–NIR spectroscopies, showed that emeralds from Habachtal (Austria) contain Type II H₂O molecules with alkalis and they are colored by chromium and iron, similarly to emeralds from Egypt. Under an optical microscope (and identified by Raman spectroscopy), actinolite needle-like inclusions are frequently observed in Austrian emeralds. Other inclusions, such as quartz, plagioclase, albite, phlogopite and pyrite, can also be observed in Austrian samples. Chemical analysis of Austrian emeralds’ trace elements by LA–ICP–MS show similar results to those from Egypt, with the exception of V, K and Rb, which show a lesser content in Austrian emeralds. Thanks to the determination of inclusions combined with a careful examination of specific chemistry, this study shows that Austrian emeralds can be distinguished from their Egyptian counterpart. Full article

(This article belongs to the Special Issue Gem Deposits: Mineralogical and Gemological Aspects, 2nd Edition)

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14 pages, 2299 KiB

Open AccessEditor’s ChoiceArticle

Berthierine-2H₁ from Lovozero Alkaline Massif, Kola Peninsula, Russia: First Structure Model for Berthierine and Complexity-Stability Relations

by Sergey V. Krivovichev, Victor N. Yakovenchuk, Olga F. Goychuk, Yakov A. Pakhomovskii and Vladimir G. Krivovichev

Minerals 2025, 15(1), 13; https://doi.org/10.3390/min15010013 - 26 Dec 2024

Viewed by 943

Abstract

Berthierine was found in a natrolite vein intersecting volcanogenic-sedimentary rocks on the slope of Mt. Quamdespakh in the upper reaches of the Suolwai River, Lovozero alkaline massif, Kola peninsula, Russian Arctic. The mineral occurs as well-formed translucent pyramidal crystals up to 250 μm [...] Read more.

Berthierine was found in a natrolite vein intersecting volcanogenic-sedimentary rocks on the slope of Mt. Quamdespakh in the upper reaches of the Suolwai River, Lovozero alkaline massif, Kola peninsula, Russian Arctic. The mineral occurs as well-formed translucent pyramidal crystals up to 250 μm in size. The chemical composition determined by electron microprobe analysis corresponds to the empirical formula ^VI(Fe²⁺_1.99Al_0.94Mg_0.03Mn_0.04)_Σ3.00[^IV(Si_1.15Al_0.85)_Σ2.00O₅] [(OH)_3.92O_0.08]_Σ4.00; the idealized formula is ^VI(Fe²⁺₂Al)[^IV(SiAl)O₅](OH)₄. The crystal-structure determination (the first detailed crystal-structure characterization of berthierine) shows that the Lovozero mineral is hexagonal, P6₃cm (a = 5.3903(4), c = 14.0146(10) Å, V = 352.64(6) Å³, R₁ = 0.053 for 338 unique observed reflections), and corresponds to the 2H₁ polytype of serpentine-group minerals with 1:1 tetrahedral-octahedral layers. The unit cell contains two M₃[T₂O₅](OH)₄ layers (M = Fe²⁺,Al; T = Si,Al) stacked along the c axis. The calculations of information-based structural and topological complexity parameters indicate that berthierine is structurally and topologically simpler than its chlorite-group polymorph chamosite. Since berthierine usually crystallizes metastably in the stability field of chamosite, the complexity analysis is agreement with the Goldsmith rule that states that, in Ostwald sequences of crystallization, metastable phases are simpler and more disordered than their stable counterparts. This observation can be applied to a general case of the metastable formation of serpentine-group minerals prior to the crystallization of chlorites. Full article

(This article belongs to the Special Issue Isomorphism, Chemical Variability, and Solid Solutions of Minerals and Related Compounds, 2nd Edition)

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37 pages, 28889 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Pyrochlore-Supergroup Minerals and Their Relation to Columbite-Group Minerals in Peralkaline to Subaluminous A-Type Rare-Metal Granites with Special Emphasis on the Madeira Pluton, Amazonas, Brazil

by Karel Breiter, Hilton Tulio Costi and Zuzana Korbelová

Minerals 2024, 14(12), 1302; https://doi.org/10.3390/min14121302 - 23 Dec 2024

Viewed by 859

Abstract

Niobium (Nb) and tantalum (Ta) are quoted as “strategic” or “critical” elements for contemporaneous society. The main sources of Nb and Ta are minerals of the pyrochlore supergroup (PSGM) and the columbite group (CGM) mined from different magmatic lithologies. Textures and chemical compositions [...] Read more.

Niobium (Nb) and tantalum (Ta) are quoted as “strategic” or “critical” elements for contemporaneous society. The main sources of Nb and Ta are minerals of the pyrochlore supergroup (PSGM) and the columbite group (CGM) mined from different magmatic lithologies. Textures and chemical compositions of PSGM and CGM often provide key information about the origin of NbTa mineralization. Therefore, we decided to carry out a detailed study of the relations between the PSGM and CGM and their post-magmatic transformations, and the Madeira peralkaline pluton (Brazil) is an ideal object for such a study. Textures of the PSGM and CGM were studied using BSE imaging and SEM mapping, and their chemical compositions were determined using 325 electron microprobe analyses. Pyrochlore from the Madeira granite can be chemically characterized as Na, Ca-poor, U- and Pb-dominant, and Sn- and Zn-enriched; REE are enriched only during alteration. Two stages of alteration are present: (i) introduction of Fe + Mn, with the majority of them consumed by columbitization; (ii) introduction of Si and Fe, and in lesser amounts also Pb and U: Si, Pb, and U incorporated into pyrochlore, iron forming Fe-oxide halos around pyrochlore. During both stages, F and Na decreased. In the case of a (nearly) complete pyrochlore columbitization, U and Th were exsolved to form inclusions of a thorite/coffinite-like phase. In contrast to altered pyrochlores from other localities, pyrochlore from Madeira shows a relatively high occupancy of the A-site. Although Madeira melt was Na-, F-rich, contemporaneous crystallization of cryolite consumed both elements and pyrochlore was, from the beginning, relatively Na-, F-poor. Full article

(This article belongs to the Special Issue Rare-Metal Granites)

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40 pages, 20569 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

An Archean Porphyry-Type Deposit: Cu-Au Mineralization Associated with the Chibougamau Tonalite–Diorite Pluton, Abitibi Greenstone Belt, Canada

by Alexandre Crépon, Lucie Mathieu, Daniel J. Kontak, Jeffrey Marsh and Michael A. Hamilton

Minerals 2024, 14(12), 1293; https://doi.org/10.3390/min14121293 - 20 Dec 2024

Cited by 1 | Viewed by 1478

Abstract

The Neoarchean diorite- and tonalite-dominated Chibougamau pluton (Canada) is ideal for case studies dedicated to the petrogenesis and timing of emplacement of fertile magmatic systems and associated Cu-Au porphyry systems. Using whole-rock analyses, geochronology, and zircon chemistry, it is determined that an early [...] Read more.

The Neoarchean diorite- and tonalite-dominated Chibougamau pluton (Canada) is ideal for case studies dedicated to the petrogenesis and timing of emplacement of fertile magmatic systems and associated Cu-Au porphyry systems. Using whole-rock analyses, geochronology, and zircon chemistry, it is determined that an early magmatic phase (pre-2714 Ma) is derived from a dioritic magma with a moderate ƒO₂ (ΔFMQ 0 to +1), which is optimal for transporting Au and Cu, and that diorite is a potentially fertile magma. Field descriptions indicate that the main mineralizing style consists of sulfide-filled hairline fractures and quartz–carbonate veins. This is likely the consequence of fluid circulation facilitated by a well-developed diaclase network formed following the intrusion of magma at about 4–7 km depth in a competent hosting material. The petrographic features of fluid inclusions (FIs), considered with their microthermometric data and evaporate mound chemistry, suggest the exsolution of early CO₂-rich fluids followed by the unmixing of later aqueous saline fluids characterized by a magmatic signature (i.e., Na-, Ca-, Fe-, Mn-, Ba-, and Cl-F). The type of magmatism and its oxidation state, age relationships, the nature of mineralization, and fluid chemistry together support a model whereby metalliferous fluids are derived from an intermediate hydrous magma. This therefore enforces a porphyry-type metallogenic model for this Archean setting. Full article

(This article belongs to the Special Issue New Discovery and Exploration Methods of Porphyry and Epithermal Mineral Deposits)

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19 pages, 24243 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Water Redistribution in Vein Quartz Under Progressive Deformation (During Plastic Deformation): μFTIR and EBSD Study (Western Transbaikalia, Russia)

by Elvira N. Kungulova, Artem A. Bibko, Roman Y. Shendrik, Evgeny N. Moskvichev, Dmitry V. Lychagin and Platon A. Tishin

Minerals 2024, 14(12), 1289; https://doi.org/10.3390/min14121289 - 19 Dec 2024

Viewed by 928

Abstract

Water distribution in the structure of vein quartz formed as a result of successive plastic deformations associated with dislocation slip and subsequent recrystallization was estimated using infrared microspectroscopic (μFTIR) mapping. Water contained in quartz demonstrates a broad absorption band in the IR range [...] Read more.

Water distribution in the structure of vein quartz formed as a result of successive plastic deformations associated with dislocation slip and subsequent recrystallization was estimated using infrared microspectroscopic (μFTIR) mapping. Water contained in quartz demonstrates a broad absorption band in the IR range at 2800–3750 cm⁻¹, which indicates its molecular state and suggests the presence of water bearing water inclusions. In addition to water, the presence of an absorption band located at 2341 cm⁻¹ seems to be due to the presence of carbon dioxide in a molecular state. A necessary step before assessing the distribution of volatile components in the quartz structure was to calibrate the boundaries obtained by calculating the intensity ratios of the peaks at 1118 and 1160 cm⁻¹ in the reflectance spectrum and using electron back scatter diffraction (EBSD). A variety of fluid distributions in different elements of the structure was observed. At medium temperatures and medium strain rates, dislocation mass transfer is effective during dislocation slip. At low strain rates and elevated temperatures, the contribution of diffusion creep gradually increases, which facilitates the interaction of volatile components with migrating boundaries. It was found that in the process of successive rearrangements, migration of fluid components occurs within the main elements of the structure due to the redistribution of dislocations between defects of different scale levels. Redistribution of fluid from fluid inclusions as a result of plastic deformations in the quartz structure is one of the ways of relaxing intracrystalline stresses during strengthening of the structure. Full article

(This article belongs to the Special Issue Physicochemical Properties and Purification of Quartz Minerals)

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16 pages, 665 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Methods for Estimating the Bond Work Index for Ball Mills

by Vladimir Nikolić, Paula Sanchez Ferradal, Jesús Medina Pierres, Juan M. Menéndez-Aguado and Milan Trumić

Minerals 2024, 14(12), 1264; https://doi.org/10.3390/min14121264 - 12 Dec 2024

Cited by 4 | Viewed by 2031

Abstract

Mining is a crucial sector in the global economy, providing essential materials for various industries, including construction, electronics, and energy. However, traditional mining practices often have significant negative impacts on the environment. Therefore, integrating sustainable practices into mining has become vital. Grinding is [...] Read more.

Mining is a crucial sector in the global economy, providing essential materials for various industries, including construction, electronics, and energy. However, traditional mining practices often have significant negative impacts on the environment. Therefore, integrating sustainable practices into mining has become vital. Grinding is a crucial stage in the mineral processing industry, essential in liberating valuable minerals from ore. However, it is also one of the most energy-intensive processes in mining operations, consuming a substantial amount of electricity. Understanding and optimising electricity consumption in the grinding process is essential for enhancing energy efficiency and reducing operational costs. The relationship between electricity consumption in the grinding process and the Bond Work Index (BWI) is a crucial aspect of mineral processing and energy management in the mining industry. Understanding this relationship helps optimise grinding operations and improve energy efficiency. This review paper continues a previous work, where possible alternative modified methods for estimating the BWI in a Bond ball mill are presented. An analysis of selected methods is also provided to assess and obtain an accurate value of the BWI, which is essential in the grinding process. The methods for estimating the BWI using the wet method are presented. It is shown how the BWI can be estimated using dynamic elastic parameters and how changes in the Bond ball mill affect the BWI value. New equations for calculating the BWI and alternative procedures for evaluating the BWI in samples of non-standard size are proposed. The paper presents a comparative analysis of all presented methods. Full article

(This article belongs to the Special Issue Recent Advances in Ore Comminution)

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33 pages, 15331 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Analysis of Long-Term Thermo–Hydro–Mechanical Behavior in the Near-Field of a Deep Geological Repository System

by Mahsa Shafaei Bajestani, Othman Nasir and Caleb Coulson

Minerals 2024, 14(12), 1262; https://doi.org/10.3390/min14121262 - 11 Dec 2024

Cited by 3 | Viewed by 687

Abstract

The deep geological repository (DGR) system has been selected by most of the world’s nuclear waste management organizations for the long-term disposal of radioactive wastes. The DGR mainly consists of a multi-barrier system—comprising the natural host rock and an engineered barrier system—to contain [...] Read more.

The deep geological repository (DGR) system has been selected by most of the world’s nuclear waste management organizations for the long-term disposal of radioactive wastes. The DGR mainly consists of a multi-barrier system—comprising the natural host rock and an engineered barrier system—to contain and isolate high-level radioactive waste, including used fuel containers (UFCs), to protect humans and the environment. Bentonite materials and host rock are the main components of the DGR’s engineered and natural barrier system, respectively. It is crucial to understand the coupled behavior of bentonite and rock materials under various in situ conditions over long-term durations, as it supports safety assessments and enhances the overall safety level of DGR systems. This study presents a methodology for the numerical modeling of a hypothetical DGR using developed coupled models. The developed model was used to investigate the hydromechanical (HM) and thermomechanical (TM) response within the near-field (the area within a radius of 50 m near the UFC and multiple-barrier system) of a simplified hypothetical DGR, based on the proposed design concept of the Nuclear Waste Management Organization (NWMO) of Canada. The analysis results included the evolution of temperature, thermal stresses, saturation, and swelling pressure at different stages of the DGR system’s lifetime. The results indicated that it could take up to 10,000 years to fully saturate the bentonite materials with a corresponding swelling pressure of 2.7 MPa associated with a decrease in the rock’s strength/stress ratio near the placement room; however, the ratio did not indicate a significant system failure. Sensitivity analysis was also conducted to assess the impact of various parameters on the saturation time and the strength/stress ratio in a DGR. The results highlighted that saturation time was highly influenced by the permeability of both the rock formation and the bentonite, resulting in saturation times ranging from 500 to 20,000 years. Moreover, the strength/stress ratio was found to be sensitive to the model’s parameters, particularly the maximum swelling pressure. The results of the TM analysis show that temperature development around the placement of rooms in a DGR is highly influenced by room spacing, with a lower factor of safety (FOS) as time and temperature progressed due to elevated temperature, while the rock remained stable over the 150-year analysis period. The inclusion of temperature-dependent mechanical properties produced negligible changes to the overall stability of the rock around the placement rooms of the DGR. Full article

(This article belongs to the Special Issue Implications of THMC Processes on Long-Term Safety of Geological Disposal of Radioactive Waste)

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22 pages, 9320 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Targeting High-Grade Mineralization via a Synthesis of Compositional Profiles of Alluvial Gold with Structural and Paragenetic Models

by Robert John Chapman, Taija Marianne Torvela, Carl Peter Spence-Jones, Richard David Walshaw and Graham William McLeod

Minerals 2024, 14(12), 1236; https://doi.org/10.3390/min14121236 - 4 Dec 2024

Viewed by 1244

Abstract

Gold compositional studies have been advocated to resolve genetic relationships between alluvial and in situ occurrences based on the assumption that the P-T-X conditions at the sites of mineral deposition are reflected in common compositional signatures of gold. Here, we explore two refinements [...] Read more.

Gold compositional studies have been advocated to resolve genetic relationships between alluvial and in situ occurrences based on the assumption that the P-T-X conditions at the sites of mineral deposition are reflected in common compositional signatures of gold. Here, we explore two refinements to a simple ‘same or different’ approach, namely (i) in situ gold sources at different localities may correspond to multiple stages of mineralization and, therefore, different gold grade, and (ii) any duplication of gold signatures between localities requires fluid conduits compatible with the prevailing structural framework. The high-grade gold paragenetic stage at the Cononish Mine, Scotland, is characterized by relatively low Ag alloy associated with Ag-Au and Ag tellurides. This signature is replicated in the inclusion signature of alluvial gold from the adjacent drainage and is also present in two other drainages for which there are no known in situ sources. There is a strong correlation between the spatial extent of this signature and the fault linkage zone, but outside this zone, gold exhibits other compositional signatures. The study shows how structural considerations provide an independent and robust framework to evaluate genetic relationships suggested by compositional studies of alluvial gold in areas where the source location and economic potential are unknown. Full article

(This article belongs to the Special Issue Native Gold as a Specific Indicator Mineral for Gold Deposits, 2nd Edition)

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17 pages, 3748 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Iron Oxide-Bearing Wastes as Media for Supporting Biodegradation of BTEX

by Safaa A. Al-Obaidi, Pallavee Srivastava, Gordon Webster, Andrew J. Weightman and Devin Sapsford

Minerals 2024, 14(12), 1231; https://doi.org/10.3390/min14121231 - 3 Dec 2024

Viewed by 944

Abstract

Two common iron oxide-bearing wastes—a drinking water treatment residual and a passive mine water treatment sludge (MWTS)—were utilised with and without modification as media in microcosm experiments to treat artificial benzene, toluene, ethylbenzene, and xylene (BTEX)-contaminated wastewater. In all cases, the removal of [...] Read more.

Two common iron oxide-bearing wastes—a drinking water treatment residual and a passive mine water treatment sludge (MWTS)—were utilised with and without modification as media in microcosm experiments to treat artificial benzene, toluene, ethylbenzene, and xylene (BTEX)-contaminated wastewater. In all cases, the removal of BTEX was observed over the 160-day experiments, with benzene being the most recalcitrant. The solubilisation of iron was observed, which, alongside the syntropic relationship between the methanogens and firmicutes, allowed several anaerobic processes to occur, including iron reduction in concert with the biodegradation of BTEX. Nitrogen sparging prior to microcosm establishment, compared to aeration, was seen to lead to the greater subsequent removal of BTEX, indicating that anaerobic conditions favoured removal. The rates of BTEX removal indicated that these iron oxide-bearing wastes, an abundant waste stream, may be an interesting candidate for cost-effective media for BTEX remediation in applications such as permeable reactive barriers. Full article

(This article belongs to the Special Issue Recycling of Mining and Solid Wastes)

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17 pages, 16160 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Repainting and Authentic—Mineral Pigments in the Color Palettes Used in Three Old Romanian Royal Icons

by Zizi Balta, Daniela Cristea-Stan, Paul Mereuta, Dragos Mirea, Daniela Filimon, Alina Buterez and Ioana Stanculescu

Minerals 2024, 14(12), 1218; https://doi.org/10.3390/min14121218 - 29 Nov 2024

Viewed by 848

Abstract

The interior of Orthodox churches is entirely decorated with paintings, icons, and frescoes, to help create a special environment for the prayers and visitors. The paintings have religious, esthetic, and historical value, being created in the Byzantine tradition and following recommendations on style [...] Read more.

The interior of Orthodox churches is entirely decorated with paintings, icons, and frescoes, to help create a special environment for the prayers and visitors. The paintings have religious, esthetic, and historical value, being created in the Byzantine tradition and following recommendations on style and materials according to old church canons. Particular importance is attributed to the Iconostasis decorated with icons on several registers, as well as to polychrome wooden ornaments and imperial doors. This work presents the scientific investigation results of three royal icons, theoretically dating to the 19th century, from the Iconostasis of the Runcu church, an important 19th-century Romanian historical monument, aiming to answer questions regarding their age and constituent materials, especially what were the mineral pigments used in the color palettes for their painting and if there were any old repainting interventions, in order to assist their restoration and conservation. Methods of characterization employed were optical microscopy, SEM-EDX spectrometry, ATR/FTIR spectroscopy, and X-ray fluorescence spectrometry. Results obtained allowed us to date, attribute, and evaluate the conservation state of the Royal icons; to our knowledge, this study is among the very few research studies carried out so far on the religious heritage conservation field in Romania. Full article

(This article belongs to the Special Issue Historical Mineral Pigments, Volume II)

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17 pages, 2713 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Mineral Deposition on the Rough Walls of a Fracture

by Nathann Teixeira Rodrigues, Ismael S. S. Carrasco, Vaughan R. Voller and Fábio D. A. Aarão Reis

Minerals 2024, 14(12), 1213; https://doi.org/10.3390/min14121213 - 28 Nov 2024

Viewed by 744

Abstract

Modeling carbonate growth in fractures and pores is important for understanding carbon sequestration in the environment or when supersaturated solutions are injected into rocks. Here, we study the simple but nontrivial problem of calcite growth on fractures with rough walls of the same [...] Read more.

Modeling carbonate growth in fractures and pores is important for understanding carbon sequestration in the environment or when supersaturated solutions are injected into rocks. Here, we study the simple but nontrivial problem of calcite growth on fractures with rough walls of the same mineral using kinetic Monte Carlo simulations of attachment and detachment of molecules and scaling approaches. First, we consider wedge-shaped fracture walls whose upper terraces are in the same low-energy planes and show that the valleys are slowly filled by the propagation of parallel monolayer steps in the wedge sides. The growth ceases when the walls reach these low-energy configurations so that a gap between the walls may not be filled. Second, we consider fracture walls with equally separated monolayer steps (vicinal surfaces with roughness below 1 nm) and show that growth by step propagation will eventually clog the fracture gap. In both cases, scaling approaches predict the times to attain the final configurations as a function of the initial geometry and the step-propagation velocity, which is set by the saturation index. The same reasoning applied to a random wall geometry shows that step propagation leads to lateral filling of surface valleys until the wall reaches the low-energy crystalline plane that has the smallest initial density of molecules. Thus, the final configurations of the fracture walls are much more sensitive to the crystallography than to the roughness or the local curvature. The framework developed here may be used to determine those configurations, the times to reach them, and the mass of deposited mineral. Effects of transport limitations are discussed when the fracture gap is significantly narrowed. Full article

(This article belongs to the Special Issue Mineral Dissolution and Precipitation in Geologic Porous Media)

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30 pages, 13140 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Transformation of Mackinawite to Interlayered Greigite-Pyrrhotite and Pyrite in the Gaoping Submarine Canyon Sediments off Southwestern Taiwan

by Ko-Chun Huang and Wei-Teh Jiang

Minerals 2024, 14(12), 1206; https://doi.org/10.3390/min14121206 - 26 Nov 2024

Viewed by 2138

Abstract

Iron monosulfides and neoformed pyrite below the sulfate–methane transition zone (SMTZ) of rapidly accumulating turbiditic sediments from the Gaoping submarine canyon off southwestern Taiwan were examined by SEM-EDS-EBSD, HRTEM, and HAADF STEM to investigate their microstructural characteristics and processes of formation and transformation. [...] Read more.

Iron monosulfides and neoformed pyrite below the sulfate–methane transition zone (SMTZ) of rapidly accumulating turbiditic sediments from the Gaoping submarine canyon off southwestern Taiwan were examined by SEM-EDS-EBSD, HRTEM, and HAADF STEM to investigate their microstructural characteristics and processes of formation and transformation. Within a few meters below the SMTZ, mackinawite (Mkw) is largely replaced by interlayered greigite-pyrrhotite (Grg-Po) with {111}_Grg//{001}_Po and ⟨110⟩_Grg//⟨110⟩_Po, followed by pyrite neoformation in clusters of disseminated matrix grains consisting of coalescing pyrite microcrystals, arrays of polycrystalline interlayer pyrite grains between the cleavage planes of layer silicates, with each grain’s core having inclusions of interlayered Grg-Po locally containing relict Mkw, and amassed pyrite microcrystals on the surface of porous interlayered Grg-Po micronodules. In the deeper sediments, neoformed pyrite is absent and Mkw is largely preserved, with partial replacement by interlayered Grg-Po having an overall topotactic relationship of ⟨110⟩_Grg//⟨110 ⟩_Po//⟨100⟩_Mkw and {111}_Grg//(001)_Po//~{011}_Mkw and a sharp reaction front without transitional profiles. The mineral grain boundaries and structural discontinuities with Mkw resulting from extensive interlayering between Grg {111} cubic close-packed segments and Po {001} hexagonal close-packed layers could serve as conduits for fluid flow and mass transport to drive the replacement reaction. The conversion of Mkw to metastable interlayered Grg-Po is inferred to occur through interface-coupled dissolution–reprecipitation processes associated with partial oxidation while the partial replacement of interlayered Grg-Po ± minor relict Mkw by pyrite microcrystals with irregular grain boundaries and orientations probably occurred via a dissolution–precipitation mechanism. Mkw could be initially formed by sulfate reduction driven by anaerobic oxidation of methane in reactive iron-rich sediments in paleo-SMTZs and subsequently transformed into interlayered Grg-Po followed by pyrite neoformation in the sulfidization front below the SMTZ or recent SMTZs in the Gaoping submarine canyon sediments. Full article

(This article belongs to the Section Crystallography and Physical Chemistry of Minerals & Nanominerals)

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24 pages, 6690 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Advanced Trends in Shale Mechanical Inhibitors for Enhanced Wellbore Stability in Water-Based Drilling Fluids

by Erxin Ai, Qi Li, Zhikun Liu, Bo Zhang, Liupeng Wang and Chengyun Ma

Minerals 2024, 14(12), 1197; https://doi.org/10.3390/min14121197 - 25 Nov 2024

Viewed by 1707

Abstract

Wellbore instability, particularly in shale formations, presents a great challenge to modern drilling operations. Although conventional chemical inhibitors are frequently employed in water-based drilling fluids, they may not always function in highly reactive or naturally fractured shale formations. In recent years, mechanical inhibitors [...] Read more.

Wellbore instability, particularly in shale formations, presents a great challenge to modern drilling operations. Although conventional chemical inhibitors are frequently employed in water-based drilling fluids, they may not always function in highly reactive or naturally fractured shale formations. In recent years, mechanical inhibitors have attracted attention as a complementary solution to chemical methods. These inhibitors, which include carbon-based, silicon-based, metal-based, and mineral-based particle materials, provide structural support to the wellbore by physically plugging fractures and sealing microfractures. This paper presents a comprehensive review of the mineral types associated with shale wellbore instability as well as a critical analysis of the mechanisms, categories, and effectiveness of mechanical inhibitors in enhancing wellbore stability. The development challenges and prospects of mechanical inhibitors in water-based drilling fluids are also discussed. This review emphasizes the potential of mechanical inhibitors in reducing fluid invasion, preventing wellbore collapse, and improving overall drilling efficiency, which will help facilitate the development and large-scale application of mechanical inhibitors in drilling fluids. Full article

(This article belongs to the Special Issue Clay Minerals: Roles in Oil and Gas Generation, Drilling, and Enhanced Recovery)

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17 pages, 3229 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Application of Machine Learning for Generic Mill Liner Wear Prediction in Semi-Autogenous Grinding (SAG) Mills

by Yusuf Enes Pural, Tania Ledezma, Marko Hilden, Gordon Forbes, Feridun Boylu and Mohsen Yahyaei

Minerals 2024, 14(12), 1200; https://doi.org/10.3390/min14121200 - 25 Nov 2024

Viewed by 1170

Abstract

This study explores the application of machine learning techniques for predicting generic mill liner wear in semi-autogenous grinding (SAG) mills used in mineral processing. Various models were developed and compared using data from 143 liner measurements across 36 liner cycles from ten different [...] Read more.

This study explores the application of machine learning techniques for predicting generic mill liner wear in semi-autogenous grinding (SAG) mills used in mineral processing. Various models were developed and compared using data from 143 liner measurements across 36 liner cycles from ten different SAG mills. The research initially focused on individual mill modeling, employing simple linear regression, first-order kinetic approach, Multiple Linear Regression (MLR), tree-based methods (Decision Trees, Random Forests, XGBoost), and Multilayer Perceptron (MLP). Results showed that simple linear regression provided sufficient accuracy, with other methods only slightly improving performance. This study then developed a combined model using data from multiple mills. MLR and advanced machine learning techniques were applied for this generic model, with XGBoost emerging as the most successful. In the interpolation scenario involving a mill similar to those in the training data, the XGBoost model achieved a mean absolute percentage error (MAPE) of 5.27%. For the extrapolation scenario, with a mill larger than those in the training set, the MAPE increased slightly to 6.12%. These results demonstrate the potential of machine learning approaches in creating effective generic models for mill liner wear prediction. However, this study also highlights the potential for improving predictive models by incorporating additional key parameters such as liner and ball material properties. Full article

(This article belongs to the Section Mineral Processing and Extractive Metallurgy)

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12 pages, 2138 KiB

Open AccessFeature PaperEditor’s ChoiceCommunication

First Optically Stimulated Luminescence and Radiocarbon Dating of the Late Quaternary Eruptions in the Xilinhot Volcanic Field, China

by Zhiwei Shi, Furong Cui, Zhidan Zhao, Zhida Bai, Zeguang Chang and Junxiang Zhao

Minerals 2024, 14(11), 1181; https://doi.org/10.3390/min14111181 - 20 Nov 2024

Viewed by 912

Abstract

Precise dating of prehistoric volcanic eruptions is essential for reconstructing eruption sequences and assessing volcanic hazards. The timing of the onset and termination of volcanic activity in the Xilinhot volcanic field (XVF) has been a topic of debate for years. Volcanic eruptions in [...] Read more.

Precise dating of prehistoric volcanic eruptions is essential for reconstructing eruption sequences and assessing volcanic hazards. The timing of the onset and termination of volcanic activity in the Xilinhot volcanic field (XVF) has been a topic of debate for years. Volcanic eruptions in this area began during the Pliocene, with the K-Ar (Ar-Ar) method providing reliable ages for early formed volcanic rocks; however, this method is less effective for dating younger volcanic events that occurred since the Late Pleistocene. For younger volcanoes, sediments baked by volcanic materials, organic sediments, and silty mudstones entrapped in lava serve as excellent geological carriers for dating. In this study, suitable samples collected from the XVF were dated using ¹⁴C and optically stimulated luminescence (OSL) methods. The ¹⁴C ages obtained for the Gezishan volcano are ~6.8 cal. ka BP, while its OSL age is ~7.8 ka. The ages dated by these two methods, combined with volcano–sedimentary stratigraphic relationships and volcanic topography, confirm the Holocene eruptions of the Gezishan volcano, categorizing it as a broadly active volcano. The upper boundary age of the sandy loam layer beneath the Gezishan lava flow is ~15.5 ka, indicating that the south lava of the Gezishan effusion occurred later than the late stage of the Late Pleistocene. Additionally, the OSL ages of baked sediments at the bottom of the base surge deposits from a Maar-type volcano and aeolian sand interlayers within a Strombolian-type scoria cone in the study area are ~50 ka and ~60 ka, respectively, representing eruptions in the middle Late Pleistocene. These findings demonstrate that volcanic activity in the XVF remained vigorous during the Late Pleistocene to Holocene. This study provides significant insights for reconstructing the evolutionary history of Xilinhot volcanic activity and assessing regional volcanic hazards. Full article

(This article belongs to the Special Issue Magmatic Evolution through Time of Volcanic Zones: Evidence from Isotopic, Geochemical and Geochronological Data of Eruption Products)

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23 pages, 5951 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Core Story: Intertwined Maternal and Progeny Signatures Enclosed in the Otolith

by Clara Anne Lord, Sophie Berland, Vincent Haÿ and Philippe Keith

Minerals 2024, 14(11), 1176; https://doi.org/10.3390/min14111176 - 20 Nov 2024

Viewed by 775

Abstract

Analytical imaging via synchrotron analysis was used to study sagittal otoliths of four freshwater pipefish species exhibiting amphidromous or freshwater resident lifestyles. We undertook a hyperfine elemental scanning of a 25 μm diameter length area centred on the core, namely the pre-hatch zone, [...] Read more.

Analytical imaging via synchrotron analysis was used to study sagittal otoliths of four freshwater pipefish species exhibiting amphidromous or freshwater resident lifestyles. We undertook a hyperfine elemental scanning of a 25 μm diameter length area centred on the core, namely the pre-hatch zone, corresponding to the sagitta formed during embryogenesis. We analysed calcium (Ca), strontium (Sr), manganese (Mn), chromium (Cr), cobalt (Co), nickel (Ni) and sulphur (S), with the latter serving to count growth increments. Whatever the species, a Ca pit consistently marked the core; the amphidromous species exhibited Mn enrichment at the core and the sagitta formed a week before hatching. These results illustrate common otolith formation mechanistic processes. Sr and heavy metals’ signals in the pre-hatch zone were compared to their signal in the edge of the otolith, an area encompassing the adult freshwater (adFW) environmental signature. We found that Co and Ni otolith signals had no relation to environmental conditions, but it is worth looking into Cr as a marker of early-life environment. While we caution against the use of a Sr:Ca ratio for life history interpretations at the core because of the Ca pit, the Sr signal analysis uncovered possible variations in the parental behaviour that potentially trigger newly-hatched juvenile migration to sea or residency. Finally, our results demonstrate that the microchemistry of otolith formation during early development is a melting of maternal signal during egg yolk elaboration, of the environmental signal during egg incubation, and of individual physiology during early growth. Full article

(This article belongs to the Section Biomineralization and Biominerals)

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12 pages, 4933 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Mineral Liberation and Concentration Characteristics of Apatite Comminuted by High-Pressure GRU

by Yongbo Fan, Genghao Zhang, Shihai Li, Li Zhang, Jianqiang Guo and Chun Feng

Minerals 2024, 14(11), 1148; https://doi.org/10.3390/min14111148 - 13 Nov 2024

Cited by 1 | Viewed by 921

Abstract

Mineral liberation and concentration have always been the core issues in ore processing. The goal of multi-stage crushing and ball milling is liberation because mineral liberation is the foundation of beneficiation. High energy consumption and environmental pollution have always been unavoidable topics. We [...] Read more.

Mineral liberation and concentration have always been the core issues in ore processing. The goal of multi-stage crushing and ball milling is liberation because mineral liberation is the foundation of beneficiation. High energy consumption and environmental pollution have always been unavoidable topics. We put forward the method of high-pressure gas rapid unloading (GRU). Particle size followed MR-R distribution. The scanning electron microscopy data showed that the liberation of apatite particles smaller than 4 mm was sufficient by high-pressure GRU methods, and high-grade apatite concentrated in the particle size range of 0.5 to 4 mm. The average grade of the preferred particle size interval was 3%–5% higher than the original ore. Liberation degrees of apatite less than 4 mm are above 88%, which was beneficial for mineral processing. Compared to the traditional crushing method, the GRU method had a higher liberation and concentration in the particle size range of 0.5 to 4 mm. The total energy consumption was about 1.76 kW·h/t, less than that of the traditional crushing method. Full article

(This article belongs to the Special Issue Selected Papers from the 7th International Conference of Young Scholars in Mineral Processing)

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11 pages, 217 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Further Results on the Effects of the Grinding Environment on the Flotation of Copper Sulphides

by Warren J. Bruckard and Graham J. Sparrow

Minerals 2024, 14(11), 1140; https://doi.org/10.3390/min14111140 - 11 Nov 2024

Viewed by 1210

Abstract

Grinding conditions affect the flotation of copper sulphide minerals as changes in the properties of the grinding media and their interactions with the sulphide minerals, and between sulphide minerals themselves, affect the chemical environment in the flotation pulp. Galvanic interactions between steel grinding [...] Read more.

Grinding conditions affect the flotation of copper sulphide minerals as changes in the properties of the grinding media and their interactions with the sulphide minerals, and between sulphide minerals themselves, affect the chemical environment in the flotation pulp. Galvanic interactions between steel grinding media and sulphide minerals, and between sulphide minerals, can lower the pulp potential, decrease the dissolved oxygen concentration in the mineral slurry, and lead to the dissolution of iron and copper from the media and the minerals. As a result, the formation of hydrophilic iron hydroxides and their adsorption on the copper sulphide minerals can be deleterious to copper flotation while pyrite (when present) can be activated to flotation by dissolved copper lowering the grade of the copper concentrate. Electrochemically less active grinding media (e.g., chrome alloy balls rather than mild steel media) can have beneficial effects on flotation performance due to the lower oxidation of the grinding media and consequently the lower production of oxidised iron species in the pulp. Copper activation of pyrite can be decreased by chemical additions to the pulp. In this paper, relevant experimental data published in the last 15 years are discussed. Full article

(This article belongs to the Special Issue Grinding Chemistry and Its Impact on Downstream Processing)

17 pages, 7671 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

High-Resolution Reconstruction of Oxidation–Reduction Conditions: Raman Spectroscopy and μ-XRF Analysis of Manganese Nodule and Crust on Tabletop of Western Pacific Magellan Seamounts

by Jinsub Park, Huijeong Hwang, Hyeonho An and Kiho Yang

Minerals 2024, 14(11), 1135; https://doi.org/10.3390/min14111135 - 10 Nov 2024

Viewed by 1093

Abstract

Ferromanganese (Fe-Mn) deposits are widely used in paleoenvironmental reconstructions owing to their mineralogical and geochemical properties. We analyzed Fe-Mn deposits using micro-X-ray fluorescence and Raman spectroscopy to study the paleo-ocean environment. Samples were collected from the OSM-XX seamount in the western Pacific. The [...] Read more.

Ferromanganese (Fe-Mn) deposits are widely used in paleoenvironmental reconstructions owing to their mineralogical and geochemical properties. We analyzed Fe-Mn deposits using micro-X-ray fluorescence and Raman spectroscopy to study the paleo-ocean environment. Samples were collected from the OSM-XX seamount in the western Pacific. The Fe-Mn crust was divided into three parts: phosphatized, massive non-phosphatized, and porous non-phosphatized. Vernadite was identified in all layers. Furthermore, in the nodule, high values of Mn, Ni, and Cu were observed near the nucleus, with vernadite and todorokite, and these values decreased outward. A high Mn/Fe ratio near the nucleus indicates early diagenetic processes. Formation of Fe-Mn nodules began around 19–16 Ma, and this period corresponded to a minor phosphatization event and persistent reducing conditions. From 11–10 Ma, the Mn/Fe and Co/Mn ratios decreased due to the formation of a western Pacific warm pool during this period. Subsequently, with the opening of the Indonesian seaway and global cooling, the Mn/Fe and Co/Mn ratios in the Fe-Mn deposits increased again. The comparative analysis of variations in Mn/Fe ratio and vernadite crystallinity in the Fe-Mn deposits confirmed that it is possible to reconstruct paleo-productivity and redox condition changes in the western Pacific Magellan Seamount. Full article

(This article belongs to the Section Mineral Deposits)

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21 pages, 4160 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Investigating the Timing of Carbonate Precipitations and Their Potential Impact on Fossil Preservation in the Hell Creek Formation

by Daigo Yamamura

Minerals 2024, 14(11), 1133; https://doi.org/10.3390/min14111133 - 9 Nov 2024

Viewed by 1122

Abstract

Because fossilized skeletal remains and enclosing sedimentary rocks experience similar diagenetic conditions (i.e., temperature, pressure, and pore fluid interaction,) enclosing sedimentary rocks may provide insight into bone diagenesis. A fossil assemblage, including in situ dinosaur fossils, was discovered in Makoshika State Park near [...] Read more.

Because fossilized skeletal remains and enclosing sedimentary rocks experience similar diagenetic conditions (i.e., temperature, pressure, and pore fluid interaction,) enclosing sedimentary rocks may provide insight into bone diagenesis. A fossil assemblage, including in situ dinosaur fossils, was discovered in Makoshika State Park near Glendive, MT. Fossil-bearing sandstone is a crevasse splay deposit, and fossils show no sorting or preferred orientation. Bone-bearing sandstone exhibits evidence for intense diagenesis, suggesting a maximum temperature of ~90 °C. Concretion associated with fossils includes two distinctive matrices: dark- and light-colored matrices. Another concretion was found in channel sandstone near the base of the outcrop. These carbonate phases have distinctive isotopic compositions; δ¹³C values for dark-colored matrices, light-colored matrices, and spheroidal concretion are −7.5, 2.1, and −22.4‰ (VPDB), respectively, and their δ¹⁸O values are 16.4, 25.9, and 17.8‰ (VSMOW), respectively. In contrast, fossilized bone δ¹³C and δ¹⁸O values were −4.4‰ (VPDB) and 20.6‰ (VSMOW), respectively, suggesting fractionation with pore fluid was limited. Early carbonate precipitation evidenced by grain coating may have reduced interaction between pore fluids and fossils. Although concretion formation and permineralization do not appear to directly aid in fossil preservation, concretions preserve valuable evidence for diagenetic history. Full article

(This article belongs to the Special Issue Recent Advances in Bone Diagenesis)

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18 pages, 19629 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Local Crystallographic Texture of Alpha Quartz in Silicified Wood (Late Triassic, Madagascar)

by Alexey Pakhnevich, Tatiana Lychagina, Sancia Morris and Dmitry Nikolayev

Minerals 2024, 14(11), 1128; https://doi.org/10.3390/min14111128 - 8 Nov 2024

Viewed by 1454

Abstract

Compositional and anatomical studies of silicified wood have been carried out extensively all around the world. The classification of silicified wood as such deals with all the forms and phases of silica that come under its umbrella. One such class of silicified wood [...] Read more.

Compositional and anatomical studies of silicified wood have been carried out extensively all around the world. The classification of silicified wood as such deals with all the forms and phases of silica that come under its umbrella. One such class of silicified wood is fossil wood with a high content of quartz, and there are very limited mentions of this category of fossilized wood. The examined wood belongs to gymnosperm and comes from the Upper Triassic deposits of Madagascar. A fresh approach to such samples is adopted by studying the crystallographic texture of the fossil wood to understand the orientation of the crystals replacing the organic matter within the sample. This work focuses on crystallographic texture analysis based on pole figures measured by X-ray diffraction. The intensity of the pole density maxima on the pole figures measured on the heartwood surface part of the analyzed samples is higher than that on the sapwood. This affirms that the crystallographic texture is sharper at the heartwood part compared to the sapwood. The X-ray tomography study, conducted to understand the difference in mineral distribution within the sample, reveals a greater X-ray absorbing phase on the sapwood of both samples. This is due to the concentration of iron compounds, which both replace the remaining conductive structures of the wood and fill the cavities inside them. We believe that this research on silicified wood is the first research work that encompasses crystallographic texture analysis with pole figures, an approach not previously undertaken in similar studies. We hope that our research can be useful in understanding the processes of replacement of organic matter by minerals. Full article

(This article belongs to the Section Biomineralization and Biominerals)

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16 pages, 3757 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Preconcentrating Ultrafine Ilmenite Tailings Using a Laboratory-Scale Reflux Classifier

by Zhenqiang Liu, Zhenhua Su, Bing Liu, Yuhua Wang, Yuxin Zhang, Xuqun Zhong, Kangkang Chen, Xiaoxing Hu and Dongfang Lu

Minerals 2024, 14(11), 1125; https://doi.org/10.3390/min14111125 - 7 Nov 2024

Cited by 1 | Viewed by 956

Abstract

China is rich in reserves of titanium, but a large amount of titanium resources is lost in the ultrafine tailings, and it is challenging to treat the ilmenite contained in ultrafine ore. The reflux classifier (RC), a novel gravity concentration technology, has been [...] Read more.

China is rich in reserves of titanium, but a large amount of titanium resources is lost in the ultrafine tailings, and it is challenging to treat the ilmenite contained in ultrafine ore. The reflux classifier (RC), a novel gravity concentration technology, has been applied in the preconcentration of ultrafine ilmenite in this study. During this process, the feasibility of using RC for preconcentration of ultrafine ilmenite was explored through theory and conditional experiments. After one-stage preconcentration using RC, the ultrafine ilmenite ore with a TiO₂ grade of 8.77% can be concentrated into a product with a TiO₂ grade of 20.3% and a recovery rate of 82.8%. The tailings grade is as low as 2.44%, and the yield reaches 62.6%. The separation efficiency achieves 50.0%. Experimental results demonstrate that utilizing RC for the preconcentration of ultrafine ilmenite can avoid the influence of weakly magnetic gangue and achieve better results compared to a magnetic separator. Therefore, RC offers a more effective and affordable method for preconcentrating ultrafine ilmenite ore. Full article

(This article belongs to the Special Issue Advances in the Theory and Technology of Physical Separation)

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15 pages, 3187 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Raman Quantitative Measurement on the Cl⁻ Molarity of H₂O-NaCl-CO₂ System: Application to Fluid Inclusions

by Xian He, Wei-Qi Wang, Yu-Zhen Liu and Qiang Sun

Minerals 2024, 14(11), 1121; https://doi.org/10.3390/min14111121 - 6 Nov 2024

Viewed by 945

Abstract

In this study, Raman spectroscopy is applied to determine the salinity of fluid inclusions in the H₂O-NaCl-CO₂ system. In the work, various systems are prepared, such as H₂O-NaCl, H₂O-CO₂, and H₂O-NaCl-CO₂ [...] Read more.

In this study, Raman spectroscopy is applied to determine the salinity of fluid inclusions in the H₂O-NaCl-CO₂ system. In the work, various systems are prepared, such as H₂O-NaCl, H₂O-CO₂, and H₂O-NaCl-CO₂. For the H₂O-NaCl system, the addition of NaCl salts decreases the intensity of the sub-band below 3330 cm⁻¹ but increases the intensity of the sub-band above 3330 cm⁻¹. According to the structural analysis of the H₂O-NaCl system, the spectral changes are mainly related to the interactions between Cl⁻ and water. After the Raman OH stretching bands are fitted into two sub-bands, the intensity ratio between them is used to calculate the Cl⁻ concentrations (molarity scale) of NaCl solutions. Additionally, based on the measured Raman spectra, the effects of CO₂ on water structure may be weak. It is reasonable to ignore the impact of dissolved CO₂ on Raman OH stretching bands. The procedure above can be extended to quantitatively determine the Cl⁻ molarity of the H₂O-NaCl-CO₂ system. To demonstrate its reliability, this method is applied to determine the salinity of synthetic and natural fluid inclusions containing CO₂. Full article

(This article belongs to the Section Crystallography and Physical Chemistry of Minerals & Nanominerals)

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13 pages, 3557 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Preparation and Performance Evaluation of Small-Molecule Ammonium as a Shale Hydration Inhibitor

by Quande Wang, Huifeng He, Yarui Zhao, Jing Rui, Ruichen Jiang, Michal Slaný, Gang Chen and Xuefan Gu

Minerals 2024, 14(11), 1117; https://doi.org/10.3390/min14111117 - 3 Nov 2024

Cited by 1 | Viewed by 1138

Abstract

In this paper, small-molecule quaternary ammonium salts were synthesized by N-alkylation to inhibit hydration swelling and hydration dispersion. The prepared small-molecule quaternary ammonium salt was characterized by Fourier transform infrared (FTIR) spectroscopy, Thermogravimetric analysis (TGA), particle size analysis and Scanning electron microscopy (SEM), [...] Read more.

In this paper, small-molecule quaternary ammonium salts were synthesized by N-alkylation to inhibit hydration swelling and hydration dispersion. The prepared small-molecule quaternary ammonium salt was characterized by Fourier transform infrared (FTIR) spectroscopy, Thermogravimetric analysis (TGA), particle size analysis and Scanning electron microscopy (SEM), and its performance as an inhibitor in clay was evaluated by an anti-swelling test and a linear swelling test. The results show that small-molecule quaternary ammonium salt (TEE-2) synthesized by triethanolamine and epichlorohydrin in ethanol with a molar ratio of 1:1.5 can successfully inhibit the hydration swelling and dispersion of clay. The anti-swelling rate of TEE-2 was 84.94%, the linear swelling rate was 36.42%, and the linear swelling rate of 0.5% TEE-2 was only 29.34%. The hydration swelling of clay in 0.5% TEE-2 solution was significantly inhibited. The hydration inhibition mechanism of the small-molecule quaternary ammonium salt inhibitor 0.5% TEE-2 was analyzed by FTIR, SEM and TGA. It was considered that 0.5% TEE-2 has strong hydration inhibition, which was realized by infiltration and adsorption on the clay surface. Small-molecule quaternary ammonium salts were beneficial for maintaining wellbore stability and reducing the risk of wellbore instability. Full article

(This article belongs to the Special Issue Clay Minerals: Roles in Oil and Gas Generation, Drilling, and Enhanced Recovery)

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18 pages, 5748 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Investigating Physicochemical Methods to Recover Rare-Earth Elements from Appalachian Coals

by Rachel Yesenchak, Scott Montross and Shikha Sharma

Minerals 2024, 14(11), 1106; https://doi.org/10.3390/min14111106 - 30 Oct 2024

Viewed by 1239

Abstract

The demand for rare-earth elements is expected to grow due to their use in critical technologies, including those used for clean energy generation. There is growing interest in developing unconventional rare-earth element resources, such as coal and coal byproducts, to help secure domestic [...] Read more.

The demand for rare-earth elements is expected to grow due to their use in critical technologies, including those used for clean energy generation. There is growing interest in developing unconventional rare-earth element resources, such as coal and coal byproducts, to help secure domestic supplies of these elements. Within the U.S., Appalachian Basin coals are particularly enriched in rare-earth elements, but recovery of the elements is often impeded by a resistant aluminosilicate matrix. This study explores the use of calcination and sodium carbonate roasting pre-treatments combined with dilute acid leaching to recover rare-earth elements from Appalachian Basin coals and underclay. The results suggest that rare-earth element recovery after calcination is dependent on the original mineralogy of samples and that light rare-earth minerals may be more easily decomposed than heavy rare-earth minerals. Sodium carbonate roasting can enhance the recovery of both light and heavy rare-earth elements. Maximum recovery in this study, ranging from 70% to 84% of total rare-earth elements, was achieved using a combination of calcination and sodium carbonate roasting, followed by 0.25 M citric acid leaching. Full article

(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)

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16 pages, 819 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Approximation of the Role of Mineralized Collagen Fibril Orientation in the Mechanical Properties of Bone: A Computational Study on Dehydrated Osteonal Lamellar Bone

by Onur Cem Namli and Feride Sermin Utku

Minerals 2024, 14(11), 1107; https://doi.org/10.3390/min14111107 - 30 Oct 2024

Viewed by 970

Abstract

Bone is a natural composite of the hierarchical arrangement of mineralized collagen fibrils in various orientations. This study aims to understand how the orientation of the bone mineral, guiding the removal of water contained in the humidity-responsive layers during dehydration, affects its mechanical [...] Read more.

Bone is a natural composite of the hierarchical arrangement of mineralized collagen fibrils in various orientations. This study aims to understand how the orientation of the bone mineral, guiding the removal of water contained in the humidity-responsive layers during dehydration, affects its mechanical properties. A sublamellar pattern with mineralized collagen fibrils oriented between 0° to 150° at 5° angles was the model studied. Using basic transformational computational methods, dimensional change was calculated in the transverse and oblique planes of osteonal lamellar bone while considering bone components sensitive to dehydration in radial, tangential, and axial orientations. The anisotropy ratios of the change in the dimension of the variable mineralized collagen fibril orientations calculated using the computed model displayed values ranging between 0.847 to 2.092 for the transverse plane and 0.9856 to 1.0207 for the oblique plane. A comparison of the anisotropy results of the suggested model indicated that they approach the experimental results of both transversely and obliquely cut samples. As collagen fibril and mineral orientation take place both temporally and spatially in relationship with the static and dynamic loads placed on the different volumes of bone, the results may imply that the mechanical demands involved in bone resorption and deposition contribute to the formation of this multi-faceted and hierarchically structured natural composite. Full article

(This article belongs to the Special Issue Skeletal Tissues Mineralization)

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19 pages, 3360 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Enhancing Mineral Exploration Programs Through Quantitative XRD: A Case Study from the Gumsberg Polymetallic Sulphide Deposits, Sweden

by Sheida Makvandi, Evelien Rost, Thomas Witzke, Matteo Pernechele and Hein Raat

Minerals 2024, 14(11), 1100; https://doi.org/10.3390/min14111100 - 29 Oct 2024

Cited by 1 | Viewed by 1268

Abstract

As challenges in precious and base metal exploration intensify due to the diminishing availability of high-grade ore deposits, rising demand, energy costs, and stricter regulations towards net-zero carbon activities, advanced techniques to enhance exploration efficiency are becoming increasingly critical. This study demonstrates the [...] Read more.

As challenges in precious and base metal exploration intensify due to the diminishing availability of high-grade ore deposits, rising demand, energy costs, and stricter regulations towards net-zero carbon activities, advanced techniques to enhance exploration efficiency are becoming increasingly critical. This study demonstrates the effectiveness of quantitative X-ray diffraction (QXRD) with Rietveld refinement, coupled with multivariate statistical analysis (including agglomerative hierarchical clustering, principal component analysis, and fuzzy analysis), in characterizing the complex mineralogy of strata-bound volcanic-associated limestone-skarn Zn-Pb-Ag-(Cu-Au)-type sulphide deposits (SVALS). Focusing on 113 coarse rejects from the Gumsberg project located in the Bergslagen mining district in central Sweden, the research identified five distinct mineralogical clusters corresponding to polymetallic base metal sulphide mineralization, its proximal alteration zones, and variably metamorphosed host rocks. The results reveal significant sulphide mineralization, ranging from disseminated to massive occurrences of sphalerite, pyrrhotite, pyrite, and galena, with trace amounts of secondary minerals like anglesite in certain samples indicating weathering processes. The study also identifies rare minerals such as armenite, often overlooked in traditional geological logging. These findings underscore the potential of QXRD to enhance resource estimation, optimize exploration strategies, and contribute to more efficient and sustainable mineral exploration programs. The accuracy of QXRD was cross-validated with geological logs and geochemical data, confirming its reliability as a mineralogical discrimination tool. Full article

(This article belongs to the Special Issue Mineralogical and Geochemical Characterization of Geological Materials)

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19 pages, 5921 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Geochemical Dynamics and Evolutionary Implications of Sediments at the Xingu–Amazon Rivers’ Confluence: Proxies for Mixing, Mobility and Weathering

by Lucio Cardoso Medeiros Filho, Nils Edvin Asp, Jean Michel Lafon, Thiago Pereira Souza, José Francisco Berredo and Gabriel Negreiros Salomão

Minerals 2024, 14(11), 1101; https://doi.org/10.3390/min14111101 - 29 Oct 2024

Cited by 1 | Viewed by 1275

Abstract

This study investigates the geochemical characteristics and evolutionary implications of sediments at the confluence of the Xingu and Amazon Rivers. The main objective is to understand sediment mixing, mobility, and weathering processes through geochemical proxies. Samples were collected from various sections of the [...] Read more.

This study investigates the geochemical characteristics and evolutionary implications of sediments at the confluence of the Xingu and Amazon Rivers. The main objective is to understand sediment mixing, mobility, and weathering processes through geochemical proxies. Samples were collected from various sections of the lower Xingu River, focusing on its interaction with the Amazon River. Analytical techniques such as X-ray diffraction (XRD), X-ray fluorescence (XRF), and inductively coupled plasma mass spectrometry (ICP-MS) were employed to analyze major and trace elements. The results reveal significant spatial variations in mineralogical and textural patterns, with sediments forming distinct groupings based on their location. The data suggest that the lower Xingu River is strongly influenced by sediment inputs from the Amazon River, particularly affecting sediment composition and chemical weathering processes. This research highlights the critical interactions between river systems and their implications for the evolution of the Amazon basin, especially regarding sediment contributions from various geological sources. Even though the Xingu River drains cratonic regions at higher elevations, the geochemistry of the bottom sediments confirms that the bedload is derived from heterogeneous sources with primarily intermediate igneous compositions and has undergone substantial recycling during river transport. Full article

(This article belongs to the Special Issue Potentially Toxic Elements: Source, Distribution, Risk Assessment and Remediation)

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26 pages, 11780 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Peridotite Weathering and Ni Redistribution in New Caledonian Laterite Profiles: Influence of Climate, Hydrology, and Structure

by Michel Cathelineau, Yoram Teitler, Jean-Louis Grimaud, Sylvain Favier, Fabrice Golfier, Erick Ramanaidou, Sylvain Grangeon, Yohann Kerreveur, Julie Jeanpert, Samuel Étienne, Manuel Muñoz and Marc Ulrich

Minerals 2024, 14(11), 1082; https://doi.org/10.3390/min14111082 - 27 Oct 2024

Viewed by 1197

Abstract

The peridotite massifs of New Caledonia are characterised by complex hydrodynamics influenced by intense inherited fracturing, uplift, and erosion. Following the formation of the erosion surfaces and alteration processes, these processes drive chemical redistribution during weathering; particularly lateritisation and saprolitisation. Magnesium, silica, and [...] Read more.

The peridotite massifs of New Caledonia are characterised by complex hydrodynamics influenced by intense inherited fracturing, uplift, and erosion. Following the formation of the erosion surfaces and alteration processes, these processes drive chemical redistribution during weathering; particularly lateritisation and saprolitisation. Magnesium, silica, and trace elements such as nickel and cobalt—released as the dissolution front advances—are redistributed through the system. New observations and interpretations reveal how lateritic paleo-land surfaces evolved, and their temporal relationship with alteration processes since the Oligocene. Considering the geometry of discontinuity networks ranging from micro-fractures to faults, the transfers occur in dual-permeability environments. Olivine dissolution rates are heterogeneously due to differential solution renewal caused by erosion and valley deepening. Differential mass transfer occurs between mobile regions of highly transmissive faults, while immobile areas correspond to the rock matrix and the secondary fracture network. The progression of alteration fronts controls the formation of boulders and the distribution of nickel across multiple scales. In the saprolite, nickel reprecipitates mostly in talc-like phases, as well as minor nontronite and goethite with partial diffusion in inherited serpentine. The current nickel distribution results from a complex interplay of climatic, hydrological and structural factors integrated into a model across different scales and times. Full article

(This article belongs to the Special Issue Chemical Weathering Studies)

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8 pages, 1837 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Gypsum Crystals Formed by the Anhydrite–Gypsum Transformation at Low Temperatures: Implications for the Formation of the Geode of Pulpí

by Andrea Cotellucci, Juan-Manuel Garcia-Ruiz, Fermín Otálora, Àngels Canals, Marco Bruno, Quentin Wehrung, Luca Pellegrino, Dino Aquilano and Linda Pastero

Minerals 2024, 14(11), 1074; https://doi.org/10.3390/min14111074 - 25 Oct 2024

Viewed by 1345

Abstract

Determining the mechanisms of the formation of giant crystals is a challenging subject. Gypsum, calcium sulfate dihydrate (CaSO₄·2H₂O), is known to form crystals larger than one meter in several locations worldwide. These selenite crystals grow at different temperatures, either [...] Read more.

Determining the mechanisms of the formation of giant crystals is a challenging subject. Gypsum, calcium sulfate dihydrate (CaSO₄·2H₂O), is known to form crystals larger than one meter in several locations worldwide. These selenite crystals grow at different temperatures, either in sedimentary or hydrothermal systems. The famous selenite crystals of the geode of Pulpí (Almería, Spain) are known to have grown at a temperature T = 20 ± 5 °C and have been proposed to form in a subaqueous environment by a self-feeding mechanism triggered by anhydrite dissolution and the ripening of microcrystalline gypsum, enhanced by oscillations in temperature. This paper reports the monitored crystallization of gypsum crystals, from anhydrite powder dissolution, inside airtight evaporation-free reactors under oscillating low temperatures (15 °C < T < 25 °C). These crystals are clearly smaller than the ones in the Pulpí mine but exhibit similar habits (i.e., single blocky crystals and twins following the 100 twinning law). The growth rate of gypsum single crystals has been measured to be between 3.8 and 35.3 µm/day. Noteworthy, we document the occurrence of the 100 contact twinning law of gypsum, which is the most widespread twinning law in natural environments but never univocally reported in laboratory experiments. The selection of the 100 contact twinning law has been correlated to the low supersaturation values obtained in the experiment, where the concentration in these long-duration experiments can be safely assumed to be the equilibrium concentration, i.e., 0.3 (at 25 °C) ≤ SI ≤ 0.4 (at 15 °C). We discuss the relevance of our experiment for forming the gypsum crystals of Pulpí in the framework of the geological history of Pulpí mineralization. These laboratory model experiments contribute to a deeper understanding of mineral nucleation and growth processes in natural environments. Full article

(This article belongs to the Special Issue Gypsum Crystals: The Importance and the Role of Calcium Sulphate in Past and Modern Environments)

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16 pages, 5730 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Modeling and Hybrid Inversion of Mineral Deposits Using the Dipping Dike Model with Finite Depth Extent

by Saulo Pomponet Oliveira, Juarez dos Santos Azevedo, Joelson da Conceição Batista and Diego Menezes Novais

Minerals 2024, 14(10), 1054; https://doi.org/10.3390/min14101054 - 21 Oct 2024

Cited by 1 | Viewed by 1017

Abstract

The dipping dike model has shown to be a useful approximation for mineral deposits. To make this model more realistic, we include the thickness, which yields the depth to the bottom, as an additional parameter. The magnetic anomaly is obtained by combining the [...] Read more.

The dipping dike model has shown to be a useful approximation for mineral deposits. To make this model more realistic, we include the thickness, which yields the depth to the bottom, as an additional parameter. The magnetic anomaly is obtained by combining the anomalies of two infinite dikes, so that the resulting expression is simpler than the classical prismatic models with polygonal cross section. We employ a Metropolis-Hasting (MH) algorithm coupled with the Levenberg-Marquardt (LM) method to invert magnetic profiles assuming a model of multiple dike-like sources. We use a few iterations of the LM method to improve the candidate solutions at the end of each random walk generated by MH. The following parameters are obtained: depth to the top, thickness, half-width, horizontal location of the top center, geological dip, in addition to two effective parameters that depend on the intensity of magnetization and the directions of the induced and remanent fields. For synthetic anomalies, both noise-free and noisy magnetic data are considered, with examples presented for each scenario. These examples highlight the discrepancy between models with finite and infinite sources. They also illustrate the higher accuracy of the hybrid MH-LM method over the pure MH approach. Moreover, two field examples related to mineral exploration have been considered: the Pima copper mine, United States, where the relative differences between the parameters obtained by our algorithm and those known from drilling are not higher than 10%, and a magnetic profile over iron ore deposits located in Laje, northeast Brazil, where the inverted parameters were useful for detailing previous studies. Full article

(This article belongs to the Section Mineral Exploration Methods and Applications)

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14 pages, 4268 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

‘Rhythmite’, Ca₂₉(SiO₄)₈Cl₂₆, an Anthropogenic Phase from the Chelyabinsk Coal Basin (Ural, Russia) with a Complex Modular Structure Related to α-Ca₃SiO₄Cl₂ (‘Albovite’): Crystal Structure, Raman Spectra, and Thermal Expansion

by Margarita S. Avdontceva, Andrey A. Zolotarev, Anastasia S. Brazhnikova, Vladimir N. Bocharov, Natalia S. Vlasenko, Mikhail A. Rassomakhin and Sergey V. Krivovichev

Minerals 2024, 14(10), 1048; https://doi.org/10.3390/min14101048 - 18 Oct 2024

Viewed by 992

Abstract

‘Rhythmite’, Ca₂₉(SiO₄)₈Cl₂₆, an anthropogenic calcium chloride silicate from the Chelyabinsk coal basin (South Ural, Russia), was investigated using chemical microprobe analysis, in situ single-crystal X-ray diffraction analysis (27–727 °C), and Raman spectroscopy. ‘Rhythmite’ is orthorhombic, [...] Read more.

‘Rhythmite’, Ca₂₉(SiO₄)₈Cl₂₆, an anthropogenic calcium chloride silicate from the Chelyabinsk coal basin (South Ural, Russia), was investigated using chemical microprobe analysis, in situ single-crystal X-ray diffraction analysis (27–727 °C), and Raman spectroscopy. ‘Rhythmite’ is orthorhombic, Pnma: a = 17.0749(6), b = 15.1029(5), c = 13.2907(4) Å, and V = 3427.42(18) Å³ (R₁ = 0.045). The crystal structure of ‘rhythmite’ consists of a porous framework formed by Ca-O bonds and SiO₄ tetrahedra with additional Ca²⁺ cations and Cl⁻ anions in the structure interstices. The framework is built up from multinuclear [Ca₁₅(SiO₄)₄]¹⁴⁺ fundamental building blocks (FBBs) cut from the crystal structure of α-Ca₃SiO₄Cl₂ (‘albovite’). The FBBs are linked by sharing common Ca atoms to form a network with an overall pcu topology. The empirical chemical formula was calculated as Ca_29.02(Si_7.89Al_0.05P_0.05)_Ʃ7.99O₃₂Cl₂₆ (on the basis of Cl + O = 58). ‘Rhythmite’ is stable up to 627 °C and expands slightly anisotropically (α_max/α_min = 1.40) in the ab and bc planes and almost isotropically in the ac plane (α₃₃/α₁₁ = 1.02) with the following thermal expansion coefficients (×10⁶ °C⁻¹): α₁₁ = 14.6(1), α₂₂ = 20.5(4), α₃₃ = 15.0(3), and α_V = 50.1(6) (room temperature). During expansion, the silicate tetrahedra remain relatively rigid with average bond length changes of less than 0.5%. A structural complexity analysis indicates that ‘rhythmite’ is complex, with I_G,total = 920.313 (bits/u.c.), which significantly exceeds the average value of structural complexity for silicates and is caused by the modular framework construction and the presence of a large number of independent positions in the crystal structure. Full article

(This article belongs to the Section Crystallography and Physical Chemistry of Minerals & Nanominerals)

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19 pages, 15038 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Enhancing Iron Ore Grindability through Hybrid Thermal-Mechanical Pretreatment

by Sefiu O. Adewuyi, Hussin A. M. Ahmed, Angelina Anani, Abdu Saeed, Haitham M. Ahmed, Reem Alwafi and Kray Luxbacher

Minerals 2024, 14(10), 1027; https://doi.org/10.3390/min14101027 - 14 Oct 2024

Viewed by 1207

Abstract

Grinding is an important process of ore beneficiation that consumes a significant amount of energy. Pretreating ore before grinding has been proposed to improve ore grindability, reduce comminution energy, and enhance downstream operations. This paper investigates hybrid thermal mechanical pretreatment to improve iron [...] Read more.

Grinding is an important process of ore beneficiation that consumes a significant amount of energy. Pretreating ore before grinding has been proposed to improve ore grindability, reduce comminution energy, and enhance downstream operations. This paper investigates hybrid thermal mechanical pretreatment to improve iron ore grinding behavior. Thermal pretreatment was performed using conventional and microwave approaches, while mechanical pretreatment was conducted with a pressure device using a piston die. Results indicate that conventional (heating rate: 10 °C; maximum temperature: 400 °C), microwave (2.45 GHz, 1.7 kW, 60 s), and mechanical (14.86 MPa, zero delay time) pretreatments improved the studied iron ore grindability by 4.6, 19.8, and 15.4%, respectively. Meanwhile, conventional-mechanical and microwave-mechanical pretreatments enhanced the studied iron ore grindability by 19.2% and 22.6%, respectively. These results suggest that stand-alone mechanical pretreatment or microwave pretreatment may be more beneficial in improving the grinding behavior of the studied fine-grain iron ore sample. The results of the mechanical pretreatment obtained in this study may be used in a simulation of the HPGR system for grinding operations of similar iron ore Full article

(This article belongs to the Special Issue Comminution and Comminution Circuits Optimisation: 3rd Edition)

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18 pages, 11767 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Aeschynite Group Minerals Are a Potential Recovery Target for Niobium Resources at the Giant Bayan Obo Nb–REE–Fe Deposit in China

by Bo Yang, Li Yang, Yong-Gang Zhao, Guo-Ying Yan, Jian-Yong Liu, Wen-Xiang Meng, Jun-Fang Yu, Lei Chen, Xiao-Chun Li and Xian-Hua Li

Minerals 2024, 14(10), 1029; https://doi.org/10.3390/min14101029 - 14 Oct 2024

Cited by 1 | Viewed by 1496

Abstract

With the development of the steel industry, China’s demand for niobium is increasing. However, domestic niobium resources are not yet stably supplied and are heavily dependent on imports from abroad (nearly 100%). It is urgent to develop domestic niobium resources. The Bayan Obo [...] Read more.

With the development of the steel industry, China’s demand for niobium is increasing. However, domestic niobium resources are not yet stably supplied and are heavily dependent on imports from abroad (nearly 100%). It is urgent to develop domestic niobium resources. The Bayan Obo deposit is the largest rare earth element deposit in the world and contains a huge amount of niobium resources. However, the niobium resource has not been exploited due to the fine-grained size and heterogeneous and scattered occurrences of Nb minerals. To promote the utilization of niobium resources in the Bayan Obo deposit, we focused on the mineralogical and geochemical characterization of six types of ores and mineral processing samples from the Bayan Obo deposit, using optical microscopes, EPMA, TIMA, and LA–ICP–MS. Our results show that: (1) the niobium mineral compositions are complex, with the main Nb minerals including aeschynite group minerals, columbite–(Fe), fluorcalciopyrochlore, Nb–bearing rutile, baotite, fergusonite–(Y), fersmite, and a small amount of samarskite–(Y). Aeschynite group minerals, columbite–(Fe), and fluorcalciopyrochlore are the main niobium-carrying minerals and should be the primary focus of industrial recycling and utilization. Based on mineralogical and geochemical investigation, the size of the aeschynite group minerals is large enough for mineral processing. Aeschynite group minerals are thus a significant potential recovery target for niobium, as well as for medium–heavy REE resources. The Nb–rich aegirine-type ores with aeschynite group mineral megacrysts are suggested to be the most significant niobium resource for mineral processing and prospecting. Combined with geological features, mining, and mineral processing, niobium beneficiation efforts of aeschynite group minerals are crucial for making breakthroughs in the utilization of niobium resources at the Bayan Obo. Full article

(This article belongs to the Special Issue Mineral Resources in North China Craton)

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15 pages, 9591 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Influence of Steel and Poly Vinyl Alcohol Fibers on the Development of High-Strength Geopolymer Concrete

by Shaik Hussain, John Matthews, Sudhir Amritphale, Richard Edwards, Elizabeth Matthews, Niloy Paul and John Kraft

Minerals 2024, 14(10), 1007; https://doi.org/10.3390/min14101007 - 5 Oct 2024

Cited by 2 | Viewed by 1102

Abstract

The present study focuses on the mechanical performance of steel and polyvinyl alcohol fibers embedded in the geopolymer matrix. A high-strength geopolymer concrete with fly ash, slag and silica fume as precursors and sodium hydroxide and sodium silicate solutions as activators has been [...] Read more.

The present study focuses on the mechanical performance of steel and polyvinyl alcohol fibers embedded in the geopolymer matrix. A high-strength geopolymer concrete with fly ash, slag and silica fume as precursors and sodium hydroxide and sodium silicate solutions as activators has been tested for its strength in compression and flexure. The influence of fibers on flowability, long-term shrinkage and sulphuric acid attack on the geopolymer concrete has also been studied. The dosage of fibers was maintained at 1%, 2% and 3% by volume, and fibers of length 13 mm have been used in the study. Results indicate that slag with 3% steel fibers by volume had a predominant influence on the strength development of steel fiber-reinforced geopolymer concrete, yielding a compressive strength of 107 MPa after 28 days. Blast furnace slag resulted in increasing the shrinkage of concrete due to rapid gel formation owing to the presence of calcium ions, although the fibers helped reduce the shrinkage to some extent. The strength of steel fiber geopolymer concrete was superior to PVA fiber geopolymer concrete; however, after an acid attack, the strength of steel fiber geopolymer concrete was reduced more than PVA fiber geopolymer concrete due to the enhanced corrosion resistance of PVA fibers. Full article

(This article belongs to the Special Issue Geopolymers: Synthesis, Characterization and Application)

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31 pages, 15724 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Mineralogy and Geochemistry of Listvenite-Hosted Ni–Fe Sulfide Paragenesis—A Case Study from Janjevo and Melenica Listvenite Occurrences (Kosovo)

by Konrad Kluza, Jaroslav Pršek and Sławomir Mederski

Minerals 2024, 14(10), 1008; https://doi.org/10.3390/min14101008 - 5 Oct 2024

Cited by 1 | Viewed by 1915

Abstract

The main goal of this paper is to determine the order of the paragenetic sequence and phase transitions of the Ni–Fe sulfide association hosted in listvenites. Listvenites are hydrothermally altered mafic and ultramafic rocks that are often associated with active tectonic settings, such [...] Read more.

The main goal of this paper is to determine the order of the paragenetic sequence and phase transitions of the Ni–Fe sulfide association hosted in listvenites. Listvenites are hydrothermally altered mafic and ultramafic rocks that are often associated with active tectonic settings, such as transform faults, suture zones, and regional extensional faults, usually in contact with volcanic or carbonate rocks. Listvenitization is displayed by a carbonation process when the original olivine, pyroxene, and serpentine group minerals are altered to Mg–Fe–Ca carbonates (magnesite, calcite, dolomite, and siderite), talc, quartz, and accessory Cr spinel, fuchsite, and Ni–Fe sulfides. The formed rocks are highly reactive; therefore, very often, younger hydrothermal processes are observed, overprinting the mineralogy and geochemistry of the original listvenitization products, including accessory Ni–Fe sulfide paragenesis. The studied samples of listvenites were collected from two locations in Kosovo (Vardar Zone): Janjevo and Melenica. The Ni–Fe sulfide textures and relationships with the surrounding listvenite-hosted minerals were obtained using reflected and transmitted light microscopy, while their chemical composition was determined using an electron microprobe. They form accessory mono-or polymetallic aggregates that usually do not exceed 100 μm in size disseminated in the studied listvenites. Generally, the paragenetic sequence of Ni–Fe sulfides is divided into three stages. The first pre-listvenite magmatic phase is represented by pentlandite and millerite. The second listvenite stage consists of Ni–Co bearing pyrite I (Ni content up to 11.57 wt.% [0.24 apfu], and Co content up to 6.54 wt.% [0.14 apfu]) and differentiated thiospinels (violarite + siegenite ± polydymite). The last, late listvenite stage is represented by younger gersdorffite−ullmannite and base metal mineralization: pyrite + marcasite + sphalerite + galena ± chalcopyrite ± sulfosalts. The findings obtained should help in the interpretation of many disseminated accessory Ni–Fe–Co mineralizations associated with mafic and ultramafic rocks worldwide. Full article

(This article belongs to the Special Issue Sulfide Mineralogy and Geochemistry)

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24 pages, 6021 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Analytical Techniques for Detecting Rare Earth Elements in Geological Ores: Laser-Induced Breakdown Spectroscopy (LIBS), MFA-LIBS, Thermal LIBS, Laser Ablation Time-of-Flight Mass Spectrometry, Energy-Dispersive X-ray Spectroscopy, Energy-Dispersive X-ray Fluorescence Spectrometer, and Inductively Coupled Plasma Optical Emission Spectroscopy

by Amir Fayyaz, Muhammad Aslam Baig, Muhammad Waqas and Usman Liaqat

Minerals 2024, 14(10), 1004; https://doi.org/10.3390/min14101004 - 2 Oct 2024

Cited by 3 | Viewed by 2583

Abstract

Rare earth elements (REEs) hold significant industrial, scientific, and modern technological worth. This study focused on detecting and quantifying REEs in various geological ore samples. These samples were collected from different REE-bearing locations recommended by geological experts. The analysis was conducted using laser-induced [...] Read more.

Rare earth elements (REEs) hold significant industrial, scientific, and modern technological worth. This study focused on detecting and quantifying REEs in various geological ore samples. These samples were collected from different REE-bearing locations recommended by geological experts. The analysis was conducted using laser-induced breakdown spectroscopy (LIBS) and laser ablation time-of-flight mass spectrometry (LA-TOF-MS). In this work, LIBS methodology was employed using three different configurations: standard LIBS, LIBS with an applied magnetic field, and LIBS with both an applied magnetic field and target sample heating within an optimal temperature range. Elements from the REE group, specifically lanthanum (La), cerium (Ce), and neodymium (Nd), were identified and quantified. To detect, quantify, and validate the results from LIBS and LA-TOF-MS, we utilized an array of analytical techniques—Energy-Dispersive X-ray Spectroscopy (EDX), Energy-Dispersive X-ray Fluorescence Spectrometer (ED-XRF), and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Interestingly, the quantitative results for REEs (La, Ce, and Nd) in the ore samples obtained using the LIBS technique with various configurations were found to be in agreement with those from LA-TOF-MS, EDX, XRF, and ICP-OES. In addition, LIBS enables detailed microchemical imaging, allowing the map of the spatial distribution of elements within the mineral–ore matrix. The high-resolution microscale elemental mapping of REEs was accomplished using the emission lines Ce (II) at 446.0 nm, La (II) at 492.1 nm, and Nd (II) at 388.8 nm. By integrating multiple analytical techniques, our study enabled the construction of a complete elemental distribution map, providing new insights into the geochemical processes and mineral composition of rare earth ores, while advancing geochemistry and contributing valuable data for rare earth resource exploration. Full article

(This article belongs to the Special Issue Laser-Induced Breakdown Spectroscopy (LIBS) Applied to Determination of Rare Earth Elements and Critical Minerals)

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21 pages, 1691 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Ultrasonic Enhancement for Mineral Flotation: Technology, Device, and Engineering Applications

by Xiaoou Zhang, Huaigang Cheng, Kai Xu, Danjing Ding, Xin Wang, Bo Wang and Zhuohui Ma

Minerals 2024, 14(10), 986; https://doi.org/10.3390/min14100986 - 30 Sep 2024

Cited by 4 | Viewed by 1733

Abstract

In the past five years, the number of articles related to ultrasonic mineral flotation has increased by about 50 per year, and the overall trend is on the rise. The most recent developments in ultrasonics for flotation process intensification are reviewed herein, including [...] Read more.

In the past five years, the number of articles related to ultrasonic mineral flotation has increased by about 50 per year, and the overall trend is on the rise. The most recent developments in ultrasonics for flotation process intensification are reviewed herein, including effects of ultrasound treatment on an aqueous slurry, improvement in flotation methods and technological processes, device development tracking, and application effects in mineral process engineering. At this point in time, there are pilot-scale flotation tests to evaluate the feasibility of ultrasonic pretreatment technology for industrial use to enhance residue flotation separation, and the results showed that the recovery rate of concentrate is increased by about 10%. Four aspects of ultrasonic flotation process improvement are summarized, namely, changing the ultrasonic parameters, the synergistic effect of ultrasound and reagents, the ultrasonic effect of particles with different-sized fractions, and application to new systems. In addition, the effect of ultrasonic flotation mechanisms is explored through a quadratic model and numerical simulation. The combination of ultrasonic flotation with other fields, such as magnetic fields, to enhance the separation efficiency and recovery of minerals is also a future trend. It is also proposed that ultrasonic flotation technology will be used with big data, industrial Internet of Things, and automatic control technology to achieve deep bundling, optimizing the flotation process by implementing remote monitoring and control of the flotation process. Full article

(This article belongs to the Special Issue Industrial Minerals Flotation—Fundamentals and Applications)

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42 pages, 852 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Chiral Minerals

by David Avnir

Minerals 2024, 14(10), 995; https://doi.org/10.3390/min14100995 - 30 Sep 2024

Cited by 2 | Viewed by 1804

Abstract

Hundreds of minerals are chiral, that is, they appear in nature in two forms—left-handed and right-handed. Yet except for quartz, this key structural property has remained, by and large, in shadow in the world of minerals in research, in museum displays and for [...] Read more.

Hundreds of minerals are chiral, that is, they appear in nature in two forms—left-handed and right-handed. Yet except for quartz, this key structural property has remained, by and large, in shadow in the world of minerals in research, in museum displays and for collectors. This review is devoted to providing a full picture of chiral minerals in nature. It starts with a general outline of the crystallographic background needed for the characterization of chiral minerals, continues with a detailed description of the many chemical and physical processes leading to their formation and follows with their chemical reactivities and transformations, with their physical properties and with the ways to analyze and identify them. Many tables with listings of various types of chiral minerals are provided. The “missing-glove” situation, in which the recognition that a chiral mineral appears in nature in two distinctly forms is, by and large, missing, is described, and it is hoped that this review will spark interest in this aspect of nature’s crystals. Full article

(This article belongs to the Section Crystallography and Physical Chemistry of Minerals & Nanominerals)

22 pages, 9844 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Numerical Investigation of Heterogeneous Calcite Distributions in MICP Processes

by Lingxiang Wang, Yajie Chu, Xuerui Wang, Pengzhi Pan and Dianlei Feng

Minerals 2024, 14(10), 999; https://doi.org/10.3390/min14100999 - 30 Sep 2024

Cited by 2 | Viewed by 982

Abstract

Microbially induced calcite precipitation (MICP) is a sustainable and environmentally friendly technology with applications in soil stabilization, concrete crack repair, and wastewater treatment. This study presents an improved Darcy-scale numerical model to simulate the MICP processes in heterogeneous porous media. It focuses on [...] Read more.

Microbially induced calcite precipitation (MICP) is a sustainable and environmentally friendly technology with applications in soil stabilization, concrete crack repair, and wastewater treatment. This study presents an improved Darcy-scale numerical model to simulate the MICP processes in heterogeneous porous media. It focuses on the effects of porosity heterogeneity, characterized by average porosity and correlation length, as well as injection strategies. Both average porosity and correlation length are critical factors influencing mass transport and calcite distribution during MICP treatment. An increase in average porosity leads to significant reductions in transport distance and total calcite mass. Notably, in the case of low averaged porosity, a larger correlation length results in more heterogeneous calcite distributions. However, there exists an upper threshold value of the initial averaged porosity (

ϕ_{0} = 0.45

) above which the heterogeneity of the calcite does not present clear dependence on the correlation length. Additionally, injection strategies significantly impact the consolidation effects. Compared to continuous injection, using the phased injection strategy can greatly improve the precipitated calcite area and mass due to its high utility and the efficiency of reactants. Full article

(This article belongs to the Special Issue Mineral Dissolution and Precipitation in Geologic Porous Media)

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20 pages, 6163 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Review on the Challenges of Magnesium Removal in Nickel Sulfide Ore Flotation and Advances in Serpentinite Depressor

by Fengxiang Yin, Chengxu Zhang, Yao Yu, Chenyang Lv, Zhengbo Gao, Bingang Lu, Xiaohui Su, Chunhua Luo, Xiangan Peng, Belinda McFadzean and Jian Cao

Minerals 2024, 14(10), 965; https://doi.org/10.3390/min14100965 - 25 Sep 2024

Viewed by 1193

Abstract

Nickel is an important raw metal material in industry, which has been identified as a strategic mineral resource by the Chinese Ministry of Land and Resources. Nickel sulfide ore accounts for 40% of all nickel ores worldwide. However, magnesium silicate gangue minerals in [...] Read more.

Nickel is an important raw metal material in industry, which has been identified as a strategic mineral resource by the Chinese Ministry of Land and Resources. Nickel sulfide ore accounts for 40% of all nickel ores worldwide. However, magnesium silicate gangue minerals in sulfide nickel ores, particularly serpentine, pose significant challenges to the flotation of nickel sulfide ores. The presence of magnesium silicate gangue leads to a series of issues, including increased energy consumption in subsequent smelting processes, accelerated equipment wastage, and increased SO₂ emissions, which severely impact the comprehensive utilization of nickel resources in sulfide nickel ores. In this regard, flotation depressants are the most direct and effective method to reduce adverse influences caused by magnesium silicate gangue in the flotation of nickel sulfide ore concentrate. Based on the characteristics of the typical magnesium-containing nickel sulfide ore, this review illustrates the difficulties of the depression of magnesium silicate gangue during the flotation of nickel sulfide ore and gives an overview of the common depressants from six aspects (chelation depressants, dispersion depressants, flocculation depressants, depressants for grinding, depressants for slurry adjustment and combination depressants). Each section summarizes the relevant depression mechanisms and analyzes the advantages and disadvantages of various reagents, providing a reference for designing depressants specifically targeting serpentine. Full article

(This article belongs to the Special Issue Selected Papers from the 7th International Conference of Young Scholars in Mineral Processing)

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18 pages, 3488 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Adsorption of Ciprofloxacin and Lidocaine by Non-Fibrous Raw Mg-Clays: The Role of Composition and Texture

by Maria Eugenia Roca-Jalil, Telma Musso, Vanina Rodriguez-Ameijide, Micaela Sanchez, Andrea Maggio, Miria Teresita Baschini, Gisela Pettinari, Luis Villa, Manuel Pozo and Alejandro Pérez-Abad

Minerals 2024, 14(10), 966; https://doi.org/10.3390/min14100966 - 25 Sep 2024

Viewed by 933

Abstract

This study evaluated non-fibrous Mg-clays as potential adsorbents of emerging contaminants (ECs) from water. The materials were characterized, and their textural and structural properties were related to their ability to remove two model EC molecules: ciprofloxacin (CPX) and lidocaine (LID). The results showed [...] Read more.

This study evaluated non-fibrous Mg-clays as potential adsorbents of emerging contaminants (ECs) from water. The materials were characterized, and their textural and structural properties were related to their ability to remove two model EC molecules: ciprofloxacin (CPX) and lidocaine (LID). The results showed that Ad-6 and Ad-7 are mixed-layer kerolite/stevensite, while Ad-5 and Ad-8 are mainly composed of smectite minerals like stevensite and saponite, respectively. Ad-8 exhibited the highest CPX-adsorption capacity (0.91 mmol·g⁻¹ clay), likely due to its saponite content. Mixed-layer materials also performed well, with Ad-6 and Ad-7 achieving an adsorption capacity of 0.8 and 0.55 mmol·g⁻¹ clay, respectively. Adsorption studies suggested that CPX is adsorbed through ion exchange in materials with high smectite content (Ad-8 and Ad-5), while interstratified materials showed enhanced retention due to kerolite presence, which improves their porous structures. Similar findings were observed for LID, indicating a cationic-exchange mechanism for LID adsorption in all the materials and suggesting that the molecular size of the EC could regulate the removal capacity of these materials. This work showed that the studied Mg-clays could be effectively used for the removal of pharmaceutical pollutants, expanding their commercial possibilities. Full article

(This article belongs to the Special Issue Mineralogical and Geochemical Characterization of Geological Materials)

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15 pages, 4732 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

About the Origin of Carbonado

by Valentin Afanasiev, Vladimir Kovalevsky, Alexander Yelisseyev, Rudolf Mashkovtsev, Sergey Gromilov, Sargylana Ugapeva, Ekaterina Barabash, Oksana Ivanova and Anton Pavlushin

Minerals 2024, 14(9), 927; https://doi.org/10.3390/min14090927 - 11 Sep 2024

Viewed by 1963

Abstract

Carbonado is a specific variety of diamonds, typical representatives of which are distributed in the diamond placers of Central Africa, Brazil, and Venezuela. Carbonado consists of the microcrystalline aggregates of diamonds, with inclusions of mineral matter. These aggregates appear as fragments that are [...] Read more.

Carbonado is a specific variety of diamonds, typical representatives of which are distributed in the diamond placers of Central Africa, Brazil, and Venezuela. Carbonado consists of the microcrystalline aggregates of diamonds, with inclusions of mineral matter. These aggregates appear as fragments that are rounded to varying degrees. Carbonado has been known for a long time, but its primary sources have not been found and its genesis remains unclear. We have substantiated the hypothesis that the most probable precursor of carbonado is shungite. Shungite is a specific form of non-crystalline, non-graphitic, fullerene-like carbon. Shungite rocks, currently known in Karelia (Russia), are natural microdispersed composite materials containing shungite—carbonaceous matter and mineral components of different compositions. The content of carbonaceous matter in shungite rocks is from less than 10% to 98%. The carbon isotopic composition of shungite is light ẟ¹³C from −25‰ to −40‰. The age of shungite rock is more than 2 billion years old, but earlier shungite was probably much more widespread. Known shungite rocks are more than 2 billion years old, but earlier shungite was probably much more widespread. Shungite rocks could recrystallize into diamond rock upon subduction to high pressure and temperature. The diamond rocks could then be exhumed to the Earth’s surface, where they could undergo disruption and reworking with formation of those very fragments that are known as “carbonado”. Full article

(This article belongs to the Section Mineral Geochemistry and Geochronology)

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20 pages, 12039 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Innovative Seismic Imaging of the Platinum Deposits, Maseve Mine: Surface and In-Mine

by Moyagabo Rapetsoa, Musa Manzi, Ian James, Mpofana Sihoyiya, Raymond Durrheim and Michelle Pienaar

Minerals 2024, 14(9), 913; https://doi.org/10.3390/min14090913 - 6 Sep 2024

Cited by 1 | Viewed by 3999

Abstract

Maseve Mine is located in the western limb of the Bushveld Complex, recognized as the largest layered igneous intrusion in the world. The study shows results from surface (SP1, SP2, and SP3) and tunnel (T3a, T3b, and TP4b) reflection seismic profiles, totaling 4150 [...] Read more.

Maseve Mine is located in the western limb of the Bushveld Complex, recognized as the largest layered igneous intrusion in the world. The study shows results from surface (SP1, SP2, and SP3) and tunnel (T3a, T3b, and TP4b) reflection seismic profiles, totaling 4150 m. Tunnel seismic data were acquired using a seismic landstreamer and spiked geophones with 5 m receiver and shot spacing, as well as a sledgehammer for shots due to space constraints and safety. The profiles, 10–50 m above mineral deposits, crossed major geological structures. Surface seismic profiles used cabled systems and wireless sensors with 5 m and 10 m receiver spacing, respectively, and a 500 kg drop hammer as a source with 10 m shot spacing. Despite high noise levels from mine infrastructure and power cables, a careful processing workflow enhanced target reflections. Interpretation was constrained using borehole data, geological models, and 2D/3D seismic modeling. The processed data exhibit gently dipping reflections associated with faults and dykes, imaging the target mineralization (Merensky Reef and Upper Group 2) and a possible extension. Tunnel seismic experiments demonstrated the application of seismic methods using in-mine infrastructure, while surface experiments proved efficient, illustrating small-scale seismic surveys’ capability to image the subsurface, adding value in active mining environments for exploration with cost-effective seismic equipment. Full article

(This article belongs to the Section Mineral Exploration Methods and Applications)

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22 pages, 7448 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Dissolution Mechanisms and Surface Charge of Clay Mineral Nanoparticles: Insights from Kinetic Monte Carlo Simulations

by Inna Kurganskaya

Minerals 2024, 14(9), 900; https://doi.org/10.3390/min14090900 - 2 Sep 2024

Viewed by 1146

Abstract

The widespread use of clay minerals and clays in environmental engineering, industry, medicine, and cosmetics largely stems from their adsorption properties and surface charge, as well as their ability to react with water. The dissolution and growth of minerals as a function of [...] Read more.

The widespread use of clay minerals and clays in environmental engineering, industry, medicine, and cosmetics largely stems from their adsorption properties and surface charge, as well as their ability to react with water. The dissolution and growth of minerals as a function of pH are closely related to acid–base reactions at their surface sites and their surface charge. The vivid tapestry of different types of surface sites across different types of clay minerals generates difficulties in experimental studies of structure–property relationships. The aim of this paper is to demonstrate how a mesoscale stochastic kinetic Monte Carlo (kMC) approach altogether with atomistic acid-base models and empirical data can be used for understanding the mechanisms of dissolution and surface charge behavior of clay minerals. The surface charge is modeled based on equilibrium equations for de/protonated site populations, which are defined by the pH and site-specific acidity constants (pK_as). Lowered activation energy barriers for these sites in de/protonated states introduce pH-dependent effects into the dissolution kinetics. The V-shaped curve observed in laboratory experiments is reproduced with the new kMC model. A generic rate law for clay mineral dissolution as a function of pH is derived from this study. Thus, the kMC approach can be used as a hypothesis-testing tool for the verification of acid–base models for clay and other minerals and their influence on the kinetics of mineral dissolution and growth. Full article

(This article belongs to the Special Issue Feature Papers in Clays and Engineered Mineral Materials)

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21 pages, 5593 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Moment Estimation from Time Domain Electromagnetic Data

by Marc A. Vallée and Mouhamed Moussaoui

Minerals 2024, 14(9), 888; https://doi.org/10.3390/min14090888 - 30 Aug 2024

Viewed by 1082

Abstract

Moment representations have been proposed to facilitate the interpretation of geophysical time domain electromagnetic responses. We present a new methodology for estimating these moments from field data for different system waveforms when on-time and off-time measurements are available. Quadrature impulse response moments are [...] Read more.

Moment representations have been proposed to facilitate the interpretation of geophysical time domain electromagnetic responses. We present a new methodology for estimating these moments from field data for different system waveforms when on-time and off-time measurements are available. Quadrature impulse response moments are estimated by a recursive relation involving moments of the input waveform and moments of the observed response. After adapting this method to time domain electromagnetic applications—in particular, MEGATEM and AeroTEM (AirTEM) airborne electromagnetic systems—we present the results from applying this method on synthetic and real data collected over the Reid–Mahaffy test site in northern Ontario, Canada. Full article

(This article belongs to the Special Issue Advances in Magnetic and Electromagnetic Techniques for Mineral Exploration: Enhancing Resource Discovery)

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32 pages, 7574 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Source Rock Assessment of the Permian to Jurassic Strata in the Northern Highlands, Northwestern Jordan: Insights from Organic Geochemistry and 1D Basin Modeling

by Dina Hamdy, Sherif Farouk, Abdelrahman Qteishat, Fayez Ahmad, Khaled Al-Kahtany, Thomas Gentzis, Luigi Jovane and Amr S. Zaky

Minerals 2024, 14(9), 863; https://doi.org/10.3390/min14090863 - 25 Aug 2024

Cited by 1 | Viewed by 1508

Abstract

The present study focused on the Permian to Jurassic sequence in the Northern Highlands area, NW Jordan. The Permian to Jurassic sequence in this area is thick and deeply buried, consisting mainly of carbonate intercalated with clastic shale. This study integrated various datasets, [...] Read more.

The present study focused on the Permian to Jurassic sequence in the Northern Highlands area, NW Jordan. The Permian to Jurassic sequence in this area is thick and deeply buried, consisting mainly of carbonate intercalated with clastic shale. This study integrated various datasets, including total organic carbon (TOC, wt%), Rock-Eval pyrolysis, visual kerogen examination, gross composition, lipid biomarkers, vitrinite reflectance (VRo%), and bottom-hole temperature measurements. The main aim was to investigate the source rock characteristics of these strata regarding organic richness, kerogen type, depositional setting, thermal maturity, and hydrocarbon generation timing. The Permian strata are poor to fair source rocks, primarily containing kerogen type (KT) III. They are immature in the AJ-1 well and over-mature in the NH-2 well. The Upper Triassic strata are poor source rocks in the NH-1 well and fair to marginally good source rocks in the NH-2 well, containing highly mature terrestrial KT III. These strata are immature to early mature in the AJ-1 well and at the peak oil window stage in the NH-2 well. The Jurassic strata are poor source rocks, dominated by KT III and KT II-III. They are immature to early mature in the AJ-1 well and have reached the oil window in the NH-2 well. Biomarker-related ratios indicate that the Upper Triassic oils and Jurassic samples are source rocks that received mainly terrestrial organic input accumulated in shallow marine environments under highly reducing conditions. These strata are composed mostly of clay-rich lithologies with evidence of deposition in hypersaline and/or stratified water columns. 1D basin models revealed that the Upper Triassic strata reached the peak oil window from the Early Cretaceous (~80 Ma) to the present day in the NH-1 well and from ~130 Ma (Early Cretaceous) to ~90 Ma (Late Cretaceous) in the NH-2 well, with the late stage of hydrocarbon generation continuing from ~90 Ma to the present time. The present-day transformation ratio equals 77% in the Upper Triassic source rocks, suggesting that these rocks have expelled substantial volumes of hydrocarbons in the NH-2 well. To achieve future successful hydrocarbon discoveries in NW Jordan, accurate seismic studies and further geochemical analyses are recommended to precisely define the migration pathways. Full article

(This article belongs to the Special Issue Environmental Geochemistry and Mineralogy: Application for Hydrocarbon Exploration and Ore Deposits)

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