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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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20 pages, 5757 KiB  
Article
Mineral Chemistry of Li-Bearing Minerals at the Giant Tanco Pegmatite, Canada
by Paul Alexandre and Stefano Salvi
Minerals 2025, 15(3), 221; https://doi.org/10.3390/min15030221 - 24 Feb 2025
Cited by 1 | Viewed by 826
Abstract
The highly fractionated late Archean Tanco pegmatite (Bernic Lake, SE Manitoba, Canada) is a world-class producer of tantalum and cerium but is also a major source of lithium. In order to better understand the major Li hosts and the overall Li budget of [...] Read more.
The highly fractionated late Archean Tanco pegmatite (Bernic Lake, SE Manitoba, Canada) is a world-class producer of tantalum and cerium but is also a major source of lithium. In order to better understand the major Li hosts and the overall Li budget of the Tanco pegmatite, the lithium-bearing minerals present here were analyzed for major and trace elements by electron microprobe and laser ablation ICP-MS, respectively. The major Li-bearing minerals present in the Tanco pegmatite are eucryptite (approximately 11.0 wt% Li2O), montebrasite (~11.2 wt%), lithiophilite (9.1 wt%), spodumene (~8.8 wt%), petalite (5.45 wt%), lepidolite (4.36 wt%), and tancoite (5.2 wt%); Li is also present in lithiowodginite, tourmaline, muscovite, beryl, pollucite, and apatite (between 0.1 and 1.3 wt% Li2O). Most of the Li present in Tanco is contained in petalite (69.4% of all the Li present here), followed by spodumene (11.4%), montebrasite (11.1%), and eucryptite (4.0%); all remaining Li-bearing minerals contain 4.0% of the Li present in the Tanco pegmatite. Overall, the Tanco pegmatite contains approximately 0.71 wt% Li2O, on par with previous estimates. The major practical implications of these finding are that (1) all Li-bearing minerals have to be considered to properly estimate the Li endowment of any pegmatite; (2) the main Li-bearing mineral is not always spodumene; (3) the exact and detailed Li mineralogy of a pegmatite will directly affect extraction and processing; and (4) a significant proportion of Li in any pegmatite is contained in other minerals than the main one, be it spodumene of petalite. Full article
(This article belongs to the Section Mineral Deposits)
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29 pages, 7079 KiB  
Article
Comparison of Ferronickel Alloys Produced via Microwave and Conventional Thermal Concentration of Pyrrhotite Tailings
by Michael Jaansalu and Christopher Pickles
Minerals 2025, 15(3), 196; https://doi.org/10.3390/min15030196 - 20 Feb 2025
Viewed by 652
Abstract
In modern nickel mineral processing operations, the aim is to separate pentlandite from gangue minerals. One of these gangue minerals, pyrrhotite, contains up to 1 wt% Ni but is disposed of as waste, i.e., as tailings. Declining sulfide ore grades and increasing nickel [...] Read more.
In modern nickel mineral processing operations, the aim is to separate pentlandite from gangue minerals. One of these gangue minerals, pyrrhotite, contains up to 1 wt% Ni but is disposed of as waste, i.e., as tailings. Declining sulfide ore grades and increasing nickel demand have led to renewed interest in extracting nickel from pyrrhotite tails. One proposed process is thermal concentration, which aims to recover the nickel as a ferronickel alloy via thermal treatment at temperatures greater than 900 °C. Achieving these temperatures requires substantial energy input as the reactions involved are highly endothermic. In the present research, microwave radiation was used to process a reaction mixture consisting of a concentrate of pyrrhotite tails, iron ore, and metallurgical coke. The fundamental property that determines the interaction of microwaves with a material is complex permittivity. It was found that the reaction mixture had very high real and imaginary permittivities, making it a good candidate for microwave treatment. An input power of 800 W of microwave radiation (2450 MHz) was then employed to heat various reaction mixtures for thermal treatment times of 120, 300, and 600 s. The ferroalloy grades (6–7.5 wt% Ni) were comparable to those produced by conventional heating and to those obtained by other authors using conventional heating techniques. The microwaved samples had increased metallization of nickel, which was attributed to increased melting due to the higher internal temperatures. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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27 pages, 11125 KiB  
Article
Geochemical Insights and Mineral Resource Potential of Rare Earth Elements (REE) in the Croatian Karst Bauxites
by Erli Kovačević Galović, Nikolina Ilijanić, Nikola Gizdavec, Slobodan Miko and Zoran Peh
Minerals 2025, 15(2), 192; https://doi.org/10.3390/min15020192 - 19 Feb 2025
Viewed by 988
Abstract
Karst bauxites are valuable terrestrial records of paleoclimate and tectonic evolution formed under tropical to subtropical conditions during the subaerial exposure of carbonate platforms. This study explores Croatian bauxite deposits within the Adriatic–Dinaric Carbonate Platform (ADCP), with a focus on the distribution and [...] Read more.
Karst bauxites are valuable terrestrial records of paleoclimate and tectonic evolution formed under tropical to subtropical conditions during the subaerial exposure of carbonate platforms. This study explores Croatian bauxite deposits within the Adriatic–Dinaric Carbonate Platform (ADCP), with a focus on the distribution and enrichment of rare earth elements (REE) across eight bauxite horizons from the Triassic to Neogene periods. The research applies statistical analyses of geochemical data, as well as developed models, to assess the factors influencing REE distribution and fractionation. The study found that variations in parent material, along with changes in paleogeographical and paleotectonic settings, significantly affected the REE content. The median REE concentrations in the analyzed bauxite horizons range from approximately 250 to 570 mg/kg. Notable REE enrichment was observed in the Late Paleogene, particularly in the Middle and Upper Eocene horizons. The analysis highlights the importance of physicochemical conditions, such as Eh and pH, during the weathering processes that lead to bauxite formation. The results suggest that the presence of REE-bearing minerals, rather than clay minerals, could possibly contribute to elevated concentrations of heavy REE (HREE). These findings indicate that Croatian bauxites, enriched in REE and associated trace elements, are significant not only as geological markers of past climatic and tectonic events but also as potential sources of critical raw materials. This study underscores the potential for the economic exploitation of these deposits in the context of modern technological demands. Full article
(This article belongs to the Special Issue Trace Elements in Bauxite Deposits: Critical Georesource and Significant Indicators of Paleoenvironmental Conditions)
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17 pages, 3450 KiB  
Article
Research on Optimization of Lifter of an SAG Mill Based on DEM Simulation and Orthogonal Tests and Applications
by Guobin Wang, Qingfei Xiao, Xiaojiang Wang, Yunxiao Li, Saizhen Jin, Mengtao Wang, Yunfeng Shao, Qian Zhang, Yingjie Pei and Ruitao Liu
Minerals 2025, 15(2), 193; https://doi.org/10.3390/min15020193 - 19 Feb 2025
Viewed by 584
Abstract
The unreasonable parameters of mill liner lifter bars will not only decrease the operating rate of the mill and increase electricity consumption but, also, seriously restrict the production capacity of the mill. Therefore, optimizing the parameters of liner lifter bars is helpful to [...] Read more.
The unreasonable parameters of mill liner lifter bars will not only decrease the operating rate of the mill and increase electricity consumption but, also, seriously restrict the production capacity of the mill. Therefore, optimizing the parameters of liner lifter bars is helpful to save energy, improve its production capacity, and increase benefits for enterprises. Given the unreasonable parameters of the lifter bars of the semi-autogenous grinding (SAG) mill in a beneficiation plant in Yunnan (China), the distinct element method (DEM) with orthogonal tests was used to conduct simulation, the simulation results demonstrating that the three parameters all had significant influence on the collision energy, with the order of group numbers > angles > heights by the analysis of range and variance, and the optimal parameters combination, with angles of 20°, groups of 12, and heights of 210 mm, was obtained. Then, the lifer bars optimized were applied in industrial tests to verify their effect, and the results illustrated that all of the service life of lifter bars, the operating rate, production capacity, and electricity consumption were significantly improved at 159 days, 92.32%, 54.37 t/h, and 21.45 kW·h/t, respectively. This paper proposes a reference for the similar design and optimization of lifter bars for the other beneficiation plants. Full article
(This article belongs to the Special Issue Recent Advances in Ore Comminution)
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17 pages, 4237 KiB  
Article
Prediction of Mine Waste Rock Drainage Quantity Using a Machine Learning Model with Physical Constraints
by Can Zhang, Liang Ma and Wenying Liu
Minerals 2025, 15(2), 194; https://doi.org/10.3390/min15020194 - 19 Feb 2025
Viewed by 537
Abstract
Mining activities generate substantial amounts of waste rock, which are often disposed of in waste rock piles. Drainage from these piles can pose serious environmental risks. It is crucial to reliably predict drainage properties in order to effectively manage them. In previous work, [...] Read more.
Mining activities generate substantial amounts of waste rock, which are often disposed of in waste rock piles. Drainage from these piles can pose serious environmental risks. It is crucial to reliably predict drainage properties in order to effectively manage them. In previous work, we developed a machine learning model to predict waste rock drainage quantity using weather monitoring data as the input and drainage flow rate as the output. However, this model lacked physical constraints, limiting its interpretability, reliability, and applicability. In this study, we introduced a new machine learning model designed with physical constraints to improve the predictions of drainage quantity. This new model incorporates a weather refining sub-model and integrates physical constraints to enhance the overall reliability of the model predictions. The weather refining sub-model transforms primary weather features (total precipitation and temperature) into secondary features (rainfall, snowmelt, and evaporation) through established mathematical relationships. These secondary features were then used as inputs for the machine learning model to predict drainage quantity. To embed physical principles within the machine learning model, we integrated a water balance equation into the neural network architecture and modified the loss function accordingly. In addition, we included an adjustable bias term to optimize the balance between model performance and interpretability. Compared with our previous model, the incorporation of physical constraints into the machine learning model improved the accuracy of the drainage quantity predictions. More importantly, this approach ensures that the model outputs adhere to physical laws, thereby enhancing its interpretability, reliability, and applicability. Full article
(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)
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27 pages, 26571 KiB  
Article
Sources and Enrichment Mechanisms of Rare-Earth Elements in the Mosuoying Granites, Sichuan Province, Southwest China
by Xuepeng Xiao, Guoxin Li, Shuyi Dong, Lijun Qian and Lihua Ou
Minerals 2025, 15(2), 185; https://doi.org/10.3390/min15020185 - 17 Feb 2025
Viewed by 1299
Abstract
Ion-adsorption-type rare-earth element (iREE) deposits, a primary source of global heavy REE (HREE) ores, have attracted wide attention worldwide due to their concentrated distributions and irreplaceable role in the field of cutting-edge technologies. In recent years, iREE mineralization has been reported in the [...] Read more.
Ion-adsorption-type rare-earth element (iREE) deposits, a primary source of global heavy REE (HREE) ores, have attracted wide attention worldwide due to their concentrated distributions and irreplaceable role in the field of cutting-edge technologies. In recent years, iREE mineralization has been reported in the overlying weathering crust of the Mosuoying granites within the Dechang counties, Sichuan Province, Southwest China, suggesting great potential for the formation of iREE deposits. The Mosuoying granites, acting as the primary carrier of REE pre-enrichment, govern the contents and distribution patterns of REEs in their weathering crust. Therefore, investigating the sources and enrichment mechanisms of REEs in the parent rocks will provide a critical theoretical basis for the scientific exploitation and utilization of iREE deposits. In this study, we investigated the migration and enrichment of REEs in the Mosuoying granites (850–832 Ma) using petrography, geochronology, geochemical, and Sr-Nd-Hf isotopic data. The results reveal that the REE enrichment in the Mosuoying granites might be associated with both the melting of crustal felsic rocks and the magmatic-hydrothermal evolution. On the one hand, the granites exhibit different REE patterns. Compared to the light REE (LREE)-rich granites, the HREE-rich granites feature higher SiO2 contents, higher differentiation index (DI), lower Nb/Ta and Zr/Hf ratios, and more significant negative Eu anomalies, indicating that the crystal fractionation of magmas governed the differentiation of REEs. Furthermore, the hydrothermal fluids further promoted the formation of the HREE-rich granites. On the other hand, the geochemical characteristics suggest that they are A-type granites. Regarding the isotopic characteristics, the Mosuoying granites exhibit negative whole-rock εNd(t) and zircon εHf(t) values, suggesting an evolved crustal source. Therefore, we suggest that the high REE contents in the Mosuoying A-type granites might originate from the partial melting of felsic rocks in a shallow crustal source under high-temperature and low-pressure conditions. Specifically, the high-temperature A-type granitic magmas caused the partial melting of the felsic crustal materials to release REEs; concurrently, these magmas enhanced the solubility of REEs in melt during magmatic evolution, inhibiting the separation of REE-bearing minerals from the melts. These increased the REE contents of the granites. The high-temperature heat source might be associated with the process where the asthenospheric mantle experienced upwelling along slab windows and heated continental crust in the Neoproterozoic extensional setting. Full article
(This article belongs to the Section Mineral Deposits)
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16 pages, 8572 KiB  
Article
Effect of Flotation Variables on Slurry Rheological Properties and Flotation Performance of Lead–Zinc Sulfide Ores
by Kehua Luo, Chuanyao Sun and Tichang Sun
Minerals 2025, 15(2), 187; https://doi.org/10.3390/min15020187 - 17 Feb 2025
Viewed by 604
Abstract
A slurry’s rheological properties significantly affect flotation performance. Flotation variables—including mineral composition, slurry concentration, and ore particle size—influence these properties by altering the interaction forces between mineral particles and the slurry’s microstructure, thereby impacting flotation outcomes. This study investigated the effects of flotation [...] Read more.
A slurry’s rheological properties significantly affect flotation performance. Flotation variables—including mineral composition, slurry concentration, and ore particle size—influence these properties by altering the interaction forces between mineral particles and the slurry’s microstructure, thereby impacting flotation outcomes. This study investigated the effects of flotation variables on the rheological properties and flotation performance of lead–zinc sulfide ores in two ternary systems comprising galena or sphalerite + kaolinite and quartz. Cryo-scanning electron microscopy and atomic force microscopy were used to analyze the slurries’ interaction forces and microstructure. The results show that finer ore particle sizes increase the formation of particle agglomerates, leading to larger structures and higher slurry apparent viscosity. This improves the metal mineral recovery rate during flotation but simultaneously increases gangue mineral entrainment, reducing concentrate grade. As the slurry concentration increases, the ternary system with kaolinite as the main gangue mineral forms a denser and more rigid honeycomb network structure. This results in higher yield stress and apparent viscosity, which negatively impacts lead and zinc sulfide separation during flotation. In contrast, the quartz-dominated system forms a slightly denser, stacked structure that lacks a solid network and thus maintains lower yield stress and apparent viscosity, which favors mineral separation. Adding sodium hexametaphosphate enhances particle dispersion by increasing repulsive forces between mineral particles. This thins or disrupts the kaolinite network structure, reducing the slurry’s apparent viscosity and yield stress, thereby improving its rheological properties and facilitating the flotation separation of lead and zinc sulfide minerals. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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14 pages, 5211 KiB  
Article
Multianalytical Study of Archaeological Iron Nails of the Roman Period (First to Third Century) in Northern Spain
by Céline Rémazeilles, Maria Cruz Zuluaga, Egle Conforto, Abdelali Oudriss, Luis Ángel Ortega, Ana Martínez-Salcedo and Juan José Cepeda-Ocampo
Minerals 2025, 15(2), 168; https://doi.org/10.3390/min15020168 - 11 Feb 2025
Cited by 1 | Viewed by 750
Abstract
In the archaeometallurgical study of iron nails to investigate Roman manufacturing processes, multi-analyte characterization provides information on alloy composition and microstructure. Nails from the Roman sites of Forua, Aloria, and Iuliobriga (northern Spain) were studied. To characterize the iron phases and microstructures of [...] Read more.
In the archaeometallurgical study of iron nails to investigate Roman manufacturing processes, multi-analyte characterization provides information on alloy composition and microstructure. Nails from the Roman sites of Forua, Aloria, and Iuliobriga (northern Spain) were studied. To characterize the iron phases and microstructures of the nails, optical microscopy (OM), scanning electron microscopy coupled with electron-dispersive spectroscopy (SEM-EDX), micro-Raman spectroscopy, electron backscatter diffraction (EBSD) realized in environmental mode, and microhardness measurements were carried out. The chemical composition of the metal was determined by X-ray fluorescence (XRF). The corrosion mineralogical composition was determined by powder X-ray diffraction (XRD). Aggressive burial conditions had a significant effect on the forms of corrosion of the Forua nails to the point of complete iron loss. Examination of the metal of the nails from the Aloria site revealed that most of the ironwork was made in the villa’s own forge. In the case of the Iuliobriga nails, different degrees of forging were identified associated with different workshops. Full article
(This article belongs to the Special Issue The Significance of Applied Mineralogy in Archaeometry)
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12 pages, 1105 KiB  
Article
Cyanide Storage on Ferroan Brucite (MgxFe1−x(OH)2): Implications for Prebiotic Chemistry
by Ellie K. Hara and Alexis S. Templeton
Minerals 2025, 15(2), 141; https://doi.org/10.3390/min15020141 - 31 Jan 2025
Cited by 1 | Viewed by 1413
Abstract
Cyanide is a crucial reagent for the synthesis of biomolecules in prebiotic chemistry. However, effective organic synthesis requires cyanide to be concentrated. One proposed mechanism for cyanide storage and concentration on Early Earth involves the formation of aqueous ferrocyanide complexes. In basic pH [...] Read more.
Cyanide is a crucial reagent for the synthesis of biomolecules in prebiotic chemistry. However, effective organic synthesis requires cyanide to be concentrated. One proposed mechanism for cyanide storage and concentration on Early Earth involves the formation of aqueous ferrocyanide complexes. In basic pH conditions, cyanide will spontaneously form ferrocyanide complexes in the presence of aqueous Fe(II). While ferrocyanide aqueous complex formation is well defined, the potential for Fe(II)-bearing minerals to react with cyanide to form ferrocyanide complexes or store cyanide on the mineral surface has yet to be explored under prebiotically relevant conditions. In this study, we demonstrate that when cyanide interacts with ferroan brucite (MgxFe1−x(OH)2), cyanide will both form aqueous and mineral-surface-adsorbed ferrocyanide implying that there are two reservoirs that cyanide will partition into. In addition, we found that cyanide decreased the amount of hydrogen gas produced by the oxidation of ferroan brucite, indicating that cyanide alters the mineral’s redox reactivity. The cyanide adsorbed on brucite can be released by a decrease in pH, which leads to the dissolution of ferroan brucite, thus releasing the adsorbed cyanide. Our findings suggest that iron-bearing minerals may represent an overlooked storage reservoir of cyanide on Hadean Earth, potentially playing a significant role in cyanide availability for prebiotic chemistry. Full article
(This article belongs to the Special Issue Redox Reactivity of Iron Minerals in the Geosphere, 2nd Edition)
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39 pages, 48972 KiB  
Article
Volcanic Response to Post-Pan-African Orogeny Delamination: Insights from Volcanology, Precise U-Pb Geochronology, Geochemistry, and Petrology of the Ediacaran Ouarzazate Group of the Anti-Atlas, Morocco
by Mohamed Achraf Mediany, Nasrrddine Youbi, Mohamed Ben Chra, Oussama Moutbir, Ismail Hadimi, João Mata, Jörn-Frederik Wotzlaw, José Madeira, Miguel Doblas, Ezz El Din Abdel Hakim Khalaf, Rachid Oukhro, Warda El Moume, Jihane Ounar, Abdelhak Ait Lahna, Moulay Ahmed Boumehdi and Andrey Bekker
Minerals 2025, 15(2), 142; https://doi.org/10.3390/min15020142 - 31 Jan 2025
Viewed by 1899
Abstract
Post-collisional volcanism provides valuable insights into mantle dynamics, crustal processes, and mechanisms driving orogen uplift and collapse. This study presents geological, geochemical, and geochronological data for Ediacaran effusive and pyroclastic units from the Taghdout Volcanic Field (TVF) in the Siroua Window, Anti-Atlas Belt. [...] Read more.
Post-collisional volcanism provides valuable insights into mantle dynamics, crustal processes, and mechanisms driving orogen uplift and collapse. This study presents geological, geochemical, and geochronological data for Ediacaran effusive and pyroclastic units from the Taghdout Volcanic Field (TVF) in the Siroua Window, Anti-Atlas Belt. Two eruptive cycles are identified based on volcanological and geochemical signatures. The first cycle comprises a diverse volcanic succession of basalts, basaltic andesites, andesites, dacites, and rhyolitic crystal-rich tuffs and ignimbrites, exhibiting arc calc-alkaline affinities. These mafic magmas were derived from a lithospheric mantle metasomatized by subduction-related fluids and are associated with the gravitational collapse of the Pan-African Orogen. The second cycle is marked by bimodal volcanism, featuring tholeiitic basalts sourced from the asthenospheric mantle and felsic intraplate magmas. These units display volcanological characteristics typical of facies models for continental basaltsuccessions and continental felsic volcanoes. Precise CA-ID-TIMS U-Pb zircon dating constrains the volcanic activity to 575–557 Ma, reflecting an 18-million-year period of lithospheric thinning, delamination, and asthenospheric upwelling. This progression marks the transition from orogen collapse to continental rifting, culminating in the breakup of the Rodinia supercontinent and the opening of the Iapetus Ocean. The TVF exemplifies the dynamic interplay between lithospheric and asthenospheric processes during post-collisional tectonic evolution. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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29 pages, 20123 KiB  
Review
Secrets from the Depths of Space and Earth: Unraveling Newly Discovered High-Pressure Polymorphs in Meteorites and Diamond Inclusions
by Dmitry Pushcharovsky and Luca Bindi
Minerals 2025, 15(2), 144; https://doi.org/10.3390/min15020144 - 31 Jan 2025
Cited by 1 | Viewed by 1287
Abstract
Significant recent discoveries of a large group of high-pressure (HP) minerals are reviewed. These minerals can be classified into two genetic types: those formed in shocked meteorites and impact craters and those formed under static P-T conditions and found as inclusions in diamonds. [...] Read more.
Significant recent discoveries of a large group of high-pressure (HP) minerals are reviewed. These minerals can be classified into two genetic types: those formed in shocked meteorites and impact craters and those formed under static P-T conditions and found as inclusions in diamonds. Of particular interest are the HP-polymorphic modifications of minerals such as olivine, ilmenite, ulvöspinel, wollastonite, and feldspars. Some examples include asimowite, poirierite, ohtaniite, liuite, wangdaodeite, tschaunerite, breyite, davemaoite, lingunite, and liebermannite. Special attention is also devoted to new dense hydrous silicates, which show much better stability than other known hydrous minerals to act as water reservoirs in the early stage of Earth’s geological history. The crystal structures and compositions of these new HP-minerals provide valuable insights into the complex petrology of deep geospheres, otherwise not obtainable in laboratory experiments. Using such a rich database, further steps became appropriate and possible toward the directions of a more advanced knowledge of evolution, composition, and structure of Earth. Full article
(This article belongs to the Special Issue Crystal Structures and Phase Transitions of Minerals at Extreme Conditions, 2nd Edition)
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17 pages, 1551 KiB  
Article
Bioavailable and Bioaccessible Fractions of Potentially Toxic Elements in Copper Mining Wastes in the Southeastern Amazon
by Gabriela Vilhena de Almeida Pereira, Wendel Valter da Silveira Pereira, Sílvio Junio Ramos, José Tasso Felix Guimarães, Watilla Pereira Covre, Yan Nunes Dias and Antonio Rodrigues Fernandes
Minerals 2025, 15(2), 140; https://doi.org/10.3390/min15020140 - 30 Jan 2025
Cited by 1 | Viewed by 1473
Abstract
The Brazilian Amazon presents several artisanal and industrial Cu mines that generate significant amounts of waste. The objective of this study was to evaluate the risks to the environment and human health based on the bioavailable and bioaccessible concentrations of potentially toxic elements [...] Read more.
The Brazilian Amazon presents several artisanal and industrial Cu mines that generate significant amounts of waste. The objective of this study was to evaluate the risks to the environment and human health based on the bioavailable and bioaccessible concentrations of potentially toxic elements (PTEs; Ba, Co, Cr, Cu, Mo, Ni, Pb, and Zn) in artisanal and industrial Cu mining areas in the Carajás Mineral Province (CMP), eastern Amazon. For this purpose, samples (0–20 cm depth) were collected from natural forest soils (considered as a reference), as well as areas where artisanal mining wastes (artisanal overburden–AO and artisanal rock waste–AR) and industrial mining tailings (IT) were deposited. Total PTE concentrations were obtained via acid digestion, bioavailable concentrations were obtained via sequential extraction, and oral bioaccessible concentrations were obtained via the simple bioaccessibility extraction test. Environmental indices were obtained from PTE concentrations. The results indicated contamination by elements such as Mo, Cr, Ni, and Cu, mainly in AR, which had the highest contamination levels. Sequential extraction revealed that most PTEs are in residual form, suggesting low environmental risk from the bioavailable fraction. The bioaccessible concentrations of Cr and Ni were associated with health risks for children in AR. The results of this study will be important for protecting the environment and public health in artisanal mining areas in the region. Full article
(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)
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22 pages, 9743 KiB  
Article
Machine Learning-Based Tectonic Discrimination Using Basalt Element Geochemical Data: Insights into the Carboniferous–Permian Tectonic Regime of Western Tianshan Orogen
by Hengxu Li, Mengqi Gao, Xiaohui Ji, Zhaochong Zhang, Zhiguo Cheng and M. Santosh
Minerals 2025, 15(2), 122; https://doi.org/10.3390/min15020122 - 26 Jan 2025
Viewed by 1195
Abstract
Identifying the tectonic setting of rocks is essential for gaining insights into the geological contexts in which these rocks were formed, aiding in tectonic plate reconstruction and enhancing our comprehensive understanding of the Earth’s history. The application of machine learning algorithms helps identify [...] Read more.
Identifying the tectonic setting of rocks is essential for gaining insights into the geological contexts in which these rocks were formed, aiding in tectonic plate reconstruction and enhancing our comprehensive understanding of the Earth’s history. The application of machine learning algorithms helps identify complex patterns and relationships between big data that may be overlooked by binary or ternary tectonomagmatic discrimination diagrams based on basalt compositions. In this study, three machine learning algorithms, i.e., Support Vector Machine (SVM), Random Forest (RF), and eXtreme Gradient Boosting (XGBoost), were employed to classify the basalts from seven diverse settings, including intraplate basalts, island arc basalts, ocean island basalts, mid-ocean ridge basalts, back-arc basin basalts, oceanic flood basalts, and continental flood basalts. Specifically, for altered and fresh basalt samples, we utilized 22 immobile elements and 35 major and trace elements, respectively, to construct discrimination models. The results indicate that XGBoost demonstrates the best performance in discriminating basalts into seven tectonic settings, achieving accuracies of 85% and 89% for the altered and fresh basalt samples, respectively. A key innovation of our newly developed tectonic discrimination model is the establishment of tailored models for altered and fresh basalts. Moreover, by omitting isotopic features during model construction, the new models offer broader applicability in predicting a wider range of basalt samples in practical scenarios. The classification models were applied to investigate the Carboniferous to Permian evolution in the Western Tianshan Orogen (WTO), revealing that the subduction of Tianshan Ocean ceased at the end of Carboniferous and the WTO evolved into a post-collisional orogenesis during the Permian. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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27 pages, 15736 KiB  
Article
Predicting Manganese Mineralization Using Multi-Source Remote Sensing and Machine Learning: A Case Study from the Malkansu Manganese Belt, Western Kunlun
by Jiahua Zhao, Li He, Jiansheng Gong, Zhengwei He, Ziwen Feng, Jintai Pang, Wanting Zeng, Yujun Yan and Yan Yuan
Minerals 2025, 15(2), 113; https://doi.org/10.3390/min15020113 - 24 Jan 2025
Viewed by 1974
Abstract
This study employs multi-source remote sensing information and machine learning methods to comprehensively assess the geological background, structural features, alteration anomalies, and spectral characteristics of the Malkansu Manganese Ore Belt in Xinjiang. Manganese mineralization is predicted, and areas with high mineralization potential are [...] Read more.
This study employs multi-source remote sensing information and machine learning methods to comprehensively assess the geological background, structural features, alteration anomalies, and spectral characteristics of the Malkansu Manganese Ore Belt in Xinjiang. Manganese mineralization is predicted, and areas with high mineralization potential are delineated. The results of the feature factor weight analysis indicate that structural density and lithological characteristics contribute most significantly to manganese mineralization. Notably, linear structures are aligned with the direction of the manganese belt, and areas exhibiting high controlling structural density are closely associated with the locations of mineral deposits, suggesting that structure plays a crucial role in manganese production in this region. The Area Under the Curve (AUC) values for the Random Forest (RF), Naïve Bayes (NB), and eXtreme Gradient Boosting (XGBoost) models were 0.975, 0.983, and 0.916, respectively, indicating that all three models achieved a high level of performance and interpretability. Among these, the NB model demonstrated the highest performance. By algebraically overlaying the predictions from these three machine learning models, a comprehensive mineralization favorability map was generated, identifying 11 prospective mineralization zones. The performance metrics of the machine learning models validate their robustness, while regional tectonics and stratigraphic lithology provide valuable characteristic factors for this approach. This study integrates multi-source remote sensing information with machine learning methods to enhance the effectiveness of manganese prediction, thereby offering new research perspectives for manganese forecasting in the Malkansu Manganese Ore Belt. Full article
(This article belongs to the Special Issue Advancements in Mineral Resource Characterization Using Machine Learning)
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15 pages, 8741 KiB  
Article
Iridescent Iron Oxides
by George R. Rossman and Chi Ma
Minerals 2025, 15(2), 108; https://doi.org/10.3390/min15020108 - 23 Jan 2025
Viewed by 1301
Abstract
Iridescent iron oxides known as rainbow hematite and turgite are found in a variety of localities worldwide and display a variety of beautiful interference colors. Usually, there is a thin layer of nanocrystals containing aluminum and phosphorous coats, such as with hematite, although [...] Read more.
Iridescent iron oxides known as rainbow hematite and turgite are found in a variety of localities worldwide and display a variety of beautiful interference colors. Usually, there is a thin layer of nanocrystals containing aluminum and phosphorous coats, such as with hematite, although one example of aluminum with arsenic is presented. Infrared spectra of samples with thicker layers of these nanocrystals show absorption in the phosphate region. The thin films that range from tens to hundreds of nanometers thick are believed to cause the color. High-resolution secondary electron imaging shows that the thin film consists of nanocrystals arranged in three directions (120° apart). The rod-shaped crystals have a width from 5 to 35 nm and display the same morphology on all samples, irrespective of if they contain phosphorus or arsenic. The minute crystals have failed to produce either an X-ray powder diffraction pattern, an electron back-scatter diffraction pattern in SEM, or an electron diffraction ring pattern under TEM. Raman spectra are dominated by hematite features. Infrared ATR spectra of the bulk material show mostly hematite with occasional minor amounts of goethite and phosphate. Full article
(This article belongs to the Section Crystallography and Physical Chemistry of Minerals & Nanominerals)
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20 pages, 10254 KiB  
Article
Discernible Orientation for Tortuosity During Oxidative Precipitation of Fe(II) in Porous Media: Laboratory Experiment and Micro-CT Imaging
by Wenran Cao, Ekaterina Strounina, Harald Hofmann and Alexander Scheuermann
Minerals 2025, 15(1), 91; https://doi.org/10.3390/min15010091 - 19 Jan 2025
Cited by 1 | Viewed by 1236
Abstract
In the mixing zone, where submarine groundwater carrying ferrous iron [Fe(II)] meets seawater with dissolved oxygen (DO), the oxidative precipitation of Fe(II) occurs at the pore scale (nm~μm), and the resulting Fe precipitation significantly influences the seepage properties at the Darcy scale (cm~m). [...] Read more.
In the mixing zone, where submarine groundwater carrying ferrous iron [Fe(II)] meets seawater with dissolved oxygen (DO), the oxidative precipitation of Fe(II) occurs at the pore scale (nm~μm), and the resulting Fe precipitation significantly influences the seepage properties at the Darcy scale (cm~m). Previous studies have presented a challenge in upscaling fluid dynamics from a small scale to a large scale, thereby constraining our understanding of the spatiotemporal variations in flow paths as porous media evolve. To address this limitation, this study simulated subsurface mixing by injecting Fe(II)-rich freshwater into a DO-rich saltwater flow within a custom-designed syringe packed with glass beads. Micro-computed tomography imaging at the representative elementary volume scale was utilized to track the development of Fe precipitates over time and space. Experimental observations revealed three distinct stages of Fe hydroxides and their effects on the flow dynamics. Initially, hydrous Fe precipitates were characterized by a low density and exhibited mobility, allowing temporarily clogged pathways to intermittently reopen. As precipitation progressed, the Fe precipitates accumulated, forming interparticle bonding structures that redirected the flow to bypass clogged pores and facilitated precipitate flushing near the syringe wall. In the final stage, a notable reduction in the macroscopic capillary number from 3.0 to 0.05 indicated a transition from a viscous- to capillary-dominated flow, which led to the construction of ramified, tortuous flow channels. This study highlights the critical role of high-resolution imaging techniques in bridging the gap between pore-scale and continuum-scale analyses of multiphase flows in hydrogeochemical processes, offering valuable insights into the complex groundwater–seawater mixing. Full article
(This article belongs to the Special Issue Mineral Dissolution and Precipitation in Geologic Porous Media)
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24 pages, 6969 KiB  
Article
The Short-Wave Infrared (SWIR) Spectral Exploration Identification and Indicative Significance of the Yixingzhai Gold Deposit, Shanxi Province
by Lifang Wang, Song Wu, Xiaodan Lai, Weili Yang, Rongliang Sun, Peng Liu, Yandong Yang and Yuxin Ren
Minerals 2025, 15(1), 83; https://doi.org/10.3390/min15010083 - 16 Jan 2025
Viewed by 1058
Abstract
The Yixingzhai gold deposit is the largest gold deposit in Shanxi Province and develops three types of mineralization: porphyry, quartz vein, and breccia. Spectral characteristic parameters of muscovite are studied by short-wave infrared (SWIR) spectral, and the exploration significance is discussed. The Al-OH [...] Read more.
The Yixingzhai gold deposit is the largest gold deposit in Shanxi Province and develops three types of mineralization: porphyry, quartz vein, and breccia. Spectral characteristic parameters of muscovite are studied by short-wave infrared (SWIR) spectral, and the exploration significance is discussed. The Al-OH wavelength of muscovite associated with porphyry mineralization gradually becomes shorter from the periphery (>2206 nm) to the center (2201–2205 nm), and the crystallinity (>2.6) gradually increases. In quartz vein mineralization, the wavelength gradually increases from the periphery (<2203 nm) to the center (2210–2211 nm), while the crystallinity does not change significantly and in a small value (<1.5). The wavelength variation range of breccia mineralization is 2198~2214 nm and is concentrated in 2201~2204 nm near the center, while the overall crystallinity is lesser than 5.5 and concentrated around 1–2.2 near the center. The wavelength and crystallinity of muscovite are mainly affected by Tschermak substitution and temperature. When the contents of Si, Fe, and Mg are low and AlVI is high, the wavelength tends toward the short-wave (SW) direction, while the opposite tends toward the long-wave (LW) direction. The high crystallinity (4.1–8.4) of muscovite can be used as an indicator of porphyry gold mineralization and also provides an important indicator to explore similar types of gold deposits. 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, 5574 KiB  
Article
Investigation of Interfacial Characteristics as a Key Aspect of the Justification of the Reagent Regime for Coal Flotation
by Tatyana N. Aleksandrova, Valentin V. Kuznetsov and Evgeniya O. Prokhorova
Minerals 2025, 15(1), 76; https://doi.org/10.3390/min15010076 - 14 Jan 2025
Cited by 1 | Viewed by 799
Abstract
This work presents a comprehensive approach for the justification of the reagent regime of coal flotation by investigating the interfacial characteristics of flotation phases with various techniques. For the energy characterization of the surface processes in flotation systems, a method of establishing the [...] Read more.
This work presents a comprehensive approach for the justification of the reagent regime of coal flotation by investigating the interfacial characteristics of flotation phases with various techniques. For the energy characterization of the surface processes in flotation systems, a method of establishing the components of the specific surface Gibbs energy on the basis of a numerical estimation of surface free energy change during the adsorption of flotation reagents using the Owens–Wendt–Rabel–Kaelble technique was proposed. Using the developed approach, the features of the kinetics of n-hexane sorption on the surface of coal samples were established. The substantiation of differences in the potential mechanisms of the fixation of strictly apolar and aromatic reagents is based on the results of the quantum–chemical modeling of the states of the coal–adsorbate system using the software packages Avogadro and Orca. The simulation shows the possibility of aliphatic and aromatic reagents’ synergetic effects on coal surface hydrophobization. Based on the results of quantum–chemical modeling, it was found that for the physical adsorption of an oxyethylated nonyl-phenol molecule on a molecular fragment of the coal surface, according to the Weiser model, the decrease in the energy of the system was 0.05562 eV, which indicates the high thermodynamic probability of the physical sorption of this compound. The parameters of the Langmuir monomolecular model for the sorption of oxyethylated nonyl-phenol on the surface of the studied coal samples were established. The criterion characterizing the interphase phenomena in the flotation system based on the results of potentiometric studies of the interfacial characteristics, Ef, was proposed. It was found that for the studied values of the flow rate of oxyethylated nonyl-phenol, the highest value of Ef was achieved when the value of the sorption of the reagent equaled 63.99% of the limiting sorption capacity. The performance of the proposed reagents for coal flotation was confirmed by flotation tests. Full article
(This article belongs to the Special Issue Harnessing Surface Chemistry for Enhanced Mineral Recovery)
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21 pages, 4425 KiB  
Article
Transition of CO2 from Emissions to Sequestration During Chemical Weathering of Ultramafic and Mafic Mine Tailings
by Xiaolin Zhang, Long-Fei Gou, Liang Tang, Shen Liu, Tim T. Werner, Feng Jiang, Yinger Deng and Amogh Mudbhatkal
Minerals 2025, 15(1), 68; https://doi.org/10.3390/min15010068 - 12 Jan 2025
Viewed by 1310
Abstract
Weather-enhanced sulphide oxidation accelerates CO2 release into the atmosphere. However, over extended geological timescales, ultramafic and mafic magmatic minerals may transition from being sources of CO2 emissions to reservoirs for carbon sequestration. Ultramafic and mafic mine tailings present a unique opportunity [...] Read more.
Weather-enhanced sulphide oxidation accelerates CO2 release into the atmosphere. However, over extended geological timescales, ultramafic and mafic magmatic minerals may transition from being sources of CO2 emissions to reservoirs for carbon sequestration. Ultramafic and mafic mine tailings present a unique opportunity to monitor carbon balance processes, as mine waste undergoes instantaneous and rapid chemical weathering, which shortens the duration between CO2 release and absorption. In this study, we analysed 30 vanadium-titanium magnetite mine tailings ponds with varying closure times in the Panxi region of China, where ~60 years of mineral excavation and dressing have produced significant outcrops of mega-mine waste. Our analysis of anions, cations, saturation simulations, and 87Sr/86Sr; δ13C and δ34S isotopic fingerprints from mine tailings filtrates reveals that the dissolution load of mine tailings may depend significantly on early-stage sulphide oxidation. Despite the abundance of ultramafic and mafic minerals in tailings, dolomite dominates chemical weathering, accounting for ~79.2% of the cationic load. Additionally, due to sulphuric-carbonate weathering, the filtrates undergo deacidification along with sulphide depletion. The data in this study suggest that pristine V-Ti-Fe tailings ponds undergo CO2 emissions in the first two years but subsequently begin to absorb atmospheric CO2 along with the filtrates. Our results provide valuable insights into monitoring weathering transitions and carbon balance in ultramafic and mafic rocks. Full article
(This article belongs to the Special Issue CO2 Mineralization and Utilization)
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33 pages, 8053 KiB  
Article
Geochemical and Mineralogical Insights into Organic Matter Preservation in the Gondwana and Post-Gondwana Shale of the Lesser Himalayas, Nepal
by Kumar Khadka, Shuxun Sang, Sijie Han, Junjie He, Upendra Baral, Saunak Bhandari and Debashish Mondal
Minerals 2025, 15(1), 63; https://doi.org/10.3390/min15010063 - 9 Jan 2025
Viewed by 1433
Abstract
The depositional environments, weathering and provenance, organic matter enrichment, and preservation in the Gondwana and post-Gondwana units of the Lesser Himalayas, Nepal, are studied through geochemical and mineralogical analyses using petrography, X-ray diffraction, XRF, and ICP-MS. Mineralogical findings indicate that shales comprise 55% [...] Read more.
The depositional environments, weathering and provenance, organic matter enrichment, and preservation in the Gondwana and post-Gondwana units of the Lesser Himalayas, Nepal, are studied through geochemical and mineralogical analyses using petrography, X-ray diffraction, XRF, and ICP-MS. Mineralogical findings indicate that shales comprise 55% to 72% clay, 25% to 55% quartz, and less than 10% carbonate minerals, with a significant presence of illite, suggesting a transition from fluvial to shallow marine environments during post-Gondwana deposition. The thin sections of the post-Gondwana sandstone reveal an increase in quartz, feldspar, and plagioclase content, with rounded to sub-angular quartz grains indicating moderate transportation before lithification, resulting from the Indo-Asian collision. Geochemical data, including major, trace, and rare earth elements (REE), along with bivariate discrimination diagrams, reveal distinct environmental changes; Gondwana sediments exhibit oxic, arid conditions with continental provenance, while post-Gondwana deposits indicate humid environments favorable for organic matter enrichment, primarily sourced from felsic-intermediate igneous rocks. The TOC is less than 1 wt.% in the Gondwana and is 0.75 to 2 wt.% in the post-Gondwana shale, indicating better organic matter preservation. The existing geological structural data and the research findings highlight the pivotal role of Himalayan tectonism in enhancing the thermal maturity and hydrocarbon generation potential of organic-rich post-Gondwana shales, attributed to their substantial organic matter content. Full article
(This article belongs to the Special Issue Mineralogical, Petrophysical and Hydromechanical Properties of Reservoirs and Caprocks, 2nd Edition)
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22 pages, 5456 KiB  
Article
Chemical and Mineralogical Characterization of Waste from Abandoned Copper and Manganese Mines in the Iberian Pyrite Belt, Portugal: A First Step Towards the Waste-to-Value Recycling Process
by Daniel P. S. de Oliveira, Teresa P. Silva, Igor Morais and João A. E. Fernandes
Minerals 2025, 15(1), 58; https://doi.org/10.3390/min15010058 - 7 Jan 2025
Viewed by 1674
Abstract
This study examines the chemical and mineralogical composition of waste materials from abandoned copper and manganese mines in the Iberian Pyrite Belt, Portugal, as a first step toward their potential recycling for critical and strategic raw materials (CRM and SRM). Using portable X-ray [...] Read more.
This study examines the chemical and mineralogical composition of waste materials from abandoned copper and manganese mines in the Iberian Pyrite Belt, Portugal, as a first step toward their potential recycling for critical and strategic raw materials (CRM and SRM). Using portable X-ray fluorescence (pXRF) and other analytical techniques, this research highlights the presence of valuable elements, including copper, manganese, and rare earth elements, in concentrations significantly above their crustal abundance. The findings underscore the dual potential of these wastes: as sources of secondary raw materials and for mitigating environmental hazards such as acid mine drainage (AMD). Recovered materials include chalcopyrite, pyrolusite, and rhodochrosite, with critical elements like cobalt, lithium, and tungsten identified. pXRF proved to be a reliable, cost-effective tool for rapid field and laboratory analyses, demonstrating high precision and good correlation with standard laboratory methods. The study emphasizes the importance of characterizing historical mining waste to support a circular economy, reduce reliance on foreign material imports, and address environmental challenges. This approach aligns with the European Union’s Critical Raw Materials Act, promoting sustainable resource use and the recovery of strategic resources from historical mining sites. Full article
(This article belongs to the Special Issue Mineralogical and Geochemical Characterization of Geological Materials)
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18 pages, 3501 KiB  
Article
Enhancing Biogenic Scorodite Formation Using Waste Iron Sludge: A Sustainable Approach for Arsenic Immobilization
by Kazuma Kimura and Naoko Okibe
Minerals 2025, 15(1), 56; https://doi.org/10.3390/min15010056 - 7 Jan 2025
Viewed by 913
Abstract
Arsenic (As) contamination in water poses significant environmental and health risks, particularly in mining regions. Scorodite (FeAsO4·2H2O) is a highly stable compound for As immobilization, traditionally synthesized under high As concentrations and extreme conditions, such as elevated temperatures and [...] Read more.
Arsenic (As) contamination in water poses significant environmental and health risks, particularly in mining regions. Scorodite (FeAsO4·2H2O) is a highly stable compound for As immobilization, traditionally synthesized under high As concentrations and extreme conditions, such as elevated temperatures and pressures. This study explores a sustainable alternative by utilizing Fe-sludge, a waste by-product from acid mine drainage (AMD) treatment, as a novel Fe source for biogenic scorodite formation mediated by the thermo-acidophilic archaeon Acidianus brierleyi. Through a systematic evaluation of Fe-sludge incorporation, the study investigates its impact on microbial activity, As immobilization efficiency, and scorodite crystallization mechanisms. Liquid and solid analyses demonstrate that Fe-sludge enhances the reaction rate and crystallinity of scorodite while bypassing the induction period required in Fe2+-only systems. Cross-sectional SEM imaging and EXAFS analysis reveal dynamic transformations on the Fe-sludge surface, supporting faster As adsorption and scorodite nucleation through Fe-S intermediates. Despite potential challenges to microbial activity at higher Fe-sludge concentrations, optimized conditions successfully balance cell viability and Fe utilization. This approach offers an eco-friendly, cost-effective pathway for As immobilization by repurposing AMD sludge, contributing to sustainable resource management and reducing environmental impact. Full article
(This article belongs to the Special Issue Microbial Biomineralization and Organimineralization)
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17 pages, 6772 KiB  
Article
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 1108
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  
Article
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 908
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  
Article
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 1193
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, 9945 KiB  
Article
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
Cited by 2 | Viewed by 1749
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  
Article
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
Cited by 1 | Viewed by 1123
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+1.99Al0.94Mg0.03Mn0.04)Σ3.00[IV(Si1.15Al0.85)Σ2.00O5] [(OH)3.92O0.08]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  
Article
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 1009
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  
Article
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 1740
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  
Article
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 1078
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  
Review
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 5 | Viewed by 2834
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  
Article
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 831
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  
Article
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 1364
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  
Article
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 1140
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  
Article
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 1050
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  
Article
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 825
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  
Article
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 2315
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  
Review
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
Cited by 1 | Viewed by 2166
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  
Article
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
Cited by 1 | Viewed by 1475
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  
Communication
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 985
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  
Article
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 892
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  
Article
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 1054
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  
Review
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 1381
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  
Article
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 1246
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  
Article
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 1264
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  
Article
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 1610
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  
Article
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 2 | Viewed by 1057
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  
Article
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 1100
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  
Article
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 1226
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  
Article
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 1394
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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