Minerals

24 pages, 4930 KiB

Open AccessArticle

Traces of Cadmium Modulate the Morphology of Silver Crystals Produced from the Controlled Cooling of a Primary Lead Melt

by Steven King, Alberto Striolo, Paul F. Wilson, Geoff West, Mark A. Williams and Michael Piller

Minerals 2025, 15(8), 853; https://doi.org/10.3390/min15080853 (registering DOI) - 12 Aug 2025

Abstract

This work probes the possibility of controlling the morphology of silver crystals through inoculation of trace-level metallic species, building on an industrial-scale cooling process. The obtained crystals are analyzed via X-ray tomography (XRT), dynamic picture analysis, and scanning electron microscopy (SEM). The results [...] Read more.

This work probes the possibility of controlling the morphology of silver crystals through inoculation of trace-level metallic species, building on an industrial-scale cooling process. The obtained crystals are analyzed via X-ray tomography (XRT), dynamic picture analysis, and scanning electron microscopy (SEM). The results reveal assemblages composed of octahedral crystals and triangular platelets. X-ray tomography yields pore size distributions that correlate with Ag% composition. Out of several trace metals tested, cadmium was found to yield a greater number of octahedral morphologies with pronounced twinning, contributing to a fibrous structure. This behavior is consistent with the energetic preference of cadmium atoms to integrate on Ag (111) planes and the limitation of twinning to the (111) planes in FCC metals. Faceting of the interiors of the triangular facets of octahedral crystals is noted in all SEM images of acid-washed samples. These physical features are interpreted as a product of crystal growth and not selective acid etching. The generation of octahedral silver crystals from a molten melt and the presence of faceting are research firsts, such crystal morphologies being previously generated only from aqueous chemical reduction systems. Adding traces of cadmium to primary lead melts is promising for producing silver nanocrystals with desired morphologies. Full article

(This article belongs to the Special Issue Thermodynamics, Mechanism and Kinetics of Metallurgical Processes, 2nd Edition)

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20 pages, 3791 KiB

Open AccessArticle

Clay Schists from Barrancos (Portugal): An Approach Toward Sustainable Ceramic Raw Material Use

by Carla Candeias, Sónia Novo and Fernando Rocha

Minerals 2025, 15(8), 852; https://doi.org/10.3390/min15080852 (registering DOI) - 11 Aug 2025

Abstract

This study presents a comprehensive mineralogical, chemical, and technological characterization of clay schist samples from Barrancos (southern Portugal), aiming to evaluate their suitability for sustainable ceramic production. The work integrated X-ray diffraction (XRD), X-ray fluorescence (XRF), thermal analysis (TGA, DTA, and dilatometry), and [...] Read more.

This study presents a comprehensive mineralogical, chemical, and technological characterization of clay schist samples from Barrancos (southern Portugal), aiming to evaluate their suitability for sustainable ceramic production. The work integrated X-ray diffraction (XRD), X-ray fluorescence (XRF), thermal analysis (TGA, DTA, and dilatometry), and other assays. After simple dry milling, the clay schist samples’ texture supported their use in plastic ceramic pastes but indicated a need for blending with coarser materials to meet extrusion requirements. Mineralogical analysis confirmed a dominance of illite (82%–85%), with minor kaolinite and chlorite. Chemical composition revealed significant Al₂O₃ (21.65%–28.24%) and SiO₂ (52.27%–58.99%) contents, while Fe₂O₃ (4.41%–8.89%) supported their use in red ceramics. The presence of K₂O (up to 5.43%) and Na₂O (up to 1.63%) contribute to the fluxing capacity, promoting vitrification. Cation exchange capacity and specific surface area were low, consistent with the mineralogy dominated by illite and kaolinite. Thermal analysis confirmed the formation of mullite after firing at 1100 and 1150 °C, alongside residual quartz and hematite. The ceramic bodies exhibited progressive densification and strength enhancement with increasing temperature. The mixture of two selected samples showed good mechanical properties and lower porosity, with no efflorescence observed. These results underscore the potential of these schists as sustainable raw materials for ceramic production, promoting regional economic valorization and reducing environmental impact by utilizing local resources. Full article

(This article belongs to the Section Clays and Engineered Mineral Materials)

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24 pages, 11454 KiB

Open AccessArticle

Hydrothermal Monazite Geochemistry and Petrochronology Signatures: Metallogenic Age and Tectonic Evolution Model of the Koka Gold Deposit, Eritrea

by Song Ouyang, Xiaojia Jiang, Xianquan Lei, Baoquan Wan, Zhenlong Quan and Yizhao Li

Minerals 2025, 15(8), 851; https://doi.org/10.3390/min15080851 - 11 Aug 2025

Abstract

The metallogenic process of gold deposits is typically characterized by multi-stage mineralization and complex tectonic evolution. Precise determination of metallogenic age is thus critical yet challenging for establishing ore-forming models and tectonic evolutionary frameworks. The Koka gold deposit in Eritrea represents the largest [...] Read more.

The metallogenic process of gold deposits is typically characterized by multi-stage mineralization and complex tectonic evolution. Precise determination of metallogenic age is thus critical yet challenging for establishing ore-forming models and tectonic evolutionary frameworks. The Koka gold deposit in Eritrea represents the largest gold discovery to date in the area, though its metallogenic age and tectonic evolution remain debated. This study employs in situ micro-analysis techniques to investigate major/trace elements and U-Pb geochronology of hydrothermal monazite coexisting with gold mineralization, providing new constraints on the metallogenic timeline and tectonic setting. Petrographic observations reveal well-crystallized monazite with structural associations to pyrite and native gold, indicating near-contemporaneous formation. Trace element geochemistry shows peak formation temperatures of 270–340 °C for monazite, consistent with fluid inclusion data. Genetic diagrams confirm a hydrothermal origin, enabling metallogenic age determination. Monazite Tera–Wasserburg lower intercept ages and weighted mean ²⁰⁸Pb/²³³Th ages yield 586 ± 8.7 Ma and 589 ± 2.3 Ma, respectively, overlapping error ranges with published sericite ⁴⁰Ar/³⁹Ar ages. This confirms Ediacaran gold mineralization, unrelated to the Koka granite (851 ± 2 Ma). Statistical analysis of reliable age data reveals a three-stage tectonic evolution model: (1) 1000–875 Ma, Rodinia supercontinental rifting, with depleted mantle-derived mafic oceanic crust formation and Mozambique Ocean spreading; (2) 875–630 Ma, subduction-driven crustal accretion and Koka granite emplacement; and (3) 630–570 Ma, post-collision crustal/lithospheric remelting, with mixed metamorphic–magmatic fluids and meteoric water input driving gold precipitation. Full article

(This article belongs to the Special Issue Role of Granitic Magmas in Porphyry, Epithermal, and Skarn Deposits)

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24 pages, 9320 KiB

Open AccessArticle

Permian Longtan Shale in Guizhou, China: From Mineralogy and Geochemistry to Paleoenvironments

by Ende Deng, Jinchuan Zhang, Qian Zhang, Zaigang Xu, Pingping Ye, Zhihua Yan and Bingren Jiang

Minerals 2025, 15(8), 850; https://doi.org/10.3390/min15080850 - 10 Aug 2025

Viewed by 148

Abstract

The depositional environment of the Permian Longtan shale (LS) in southwestern Guizhou Province, China, has been analyzed using mineralogical and geochemical approaches. Macroscopic observations of those studied LS samples showed that the LS is rather homogeneous and interbedded with coal strips, suggesting a [...] Read more.

The depositional environment of the Permian Longtan shale (LS) in southwestern Guizhou Province, China, has been analyzed using mineralogical and geochemical approaches. Macroscopic observations of those studied LS samples showed that the LS is rather homogeneous and interbedded with coal strips, suggesting a relatively stable and shallow water environment. A detailed microscopic analysis demonstrated that higher land plants contributed the predominant proportion of organic matter in the LS. Inorganic geochemical analysis revealed a mixed source of materials with relatively larger proportions of basalt and andesite. Semiarid to humid and warm climates corresponding to an overall intensive weathering were deduced in the late Permian periods. The LS was deposited in a brackish-to-marine water environment with an oxic to dysoxic redox condition. Sea level rise/down coupled with changes in climate, water salinity, and redox condition jointly controlled the formation of the Longtan shale. Mineralogical composition indicates that the LS mainly comprises of argillaceous with minor siliceous facies, which will likely bring challenges for hydraulic fracturing. Full article

(This article belongs to the Special Issue Organic Petrology and Geochemistry: Exploring the Organic-Rich Facies)

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18 pages, 2377 KiB

Open AccessArticle

Dependence of Bubble Size on Magnesite Flotation Recovery Using Sodium Oleate (NaOL) with Different Frothers

by Khandjamts Batjargal, Onur Güven, Orhan Ozdemir, Feridun Boylu and Mehmet Sabri Çelik

Minerals 2025, 15(8), 849; https://doi.org/10.3390/min15080849 - 9 Aug 2025

Viewed by 108

Abstract

Developments of new research tools in flotation studies, including bubble–particle attachment time efficiency and dynamic froth analysis, can help improve our understanding of particle–bubble interactions in flotation processes. In particular, the selection of new collectors and frothers, and their mixtures can provide a [...] Read more.

Developments of new research tools in flotation studies, including bubble–particle attachment time efficiency and dynamic froth analysis, can help improve our understanding of particle–bubble interactions in flotation processes. In particular, the selection of new collectors and frothers, and their mixtures can provide a wide distribution of bubble sizes at their respective concentrations. In the literature, several studies have reported the effect of different frothers and collector mixtures on bubble characteristics like bubble size and critical coalescence concentration (CCC). The general trend obtained from these studies showed that the addition of frothers, along with collectors, which also act as frothers during flotation, resulted in finer bubbles and required lower concentrations of frothers, which in turn positively affected the flotation recoveries. In this study, an attempt was made to study fine-sized magnesite in the presence of sodium oleate (NaOL) and five different types of frothers (PPG600, PPG400, BTPG, BDPG, and MIBC). Bubble–particle attachment time with different sized capillary tubes and dynamic froth analysis values in a liquid–air system, along with flotation recoveries in a micro-flotation cell, were interpreted to show possible correlations and provide an optimum bubble/particle size ratio in the presence of different frothers. Full article

(This article belongs to the Special Issue Particle–Bubble Interactions in the Flotation Process)

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23 pages, 3551 KiB

Open AccessArticle

Evaluation of Pore Structure Characteristics and Permeability of In Situ-Blasted Leachable Ore in Stopes Under Varying Particle-Size Gradations

by Kun Liu, Deqing Gan and Zhenlin Xue

Minerals 2025, 15(8), 848; https://doi.org/10.3390/min15080848 - 9 Aug 2025

Viewed by 164

Abstract

In recent years, in situ blasting–leaching, in the stope has emerged as an economically viable and environmentally sustainable mining technique for low-grade ore deposits. While the leaching efficiency is influenced by factors such as ore type, solution composition, and spraying speed, the most [...] Read more.

In recent years, in situ blasting–leaching, in the stope has emerged as an economically viable and environmentally sustainable mining technique for low-grade ore deposits. While the leaching efficiency is influenced by factors such as ore type, solution composition, and spraying speed, the most significant factor is the effect of post-blasting crushed-stone particle size and gradation on the pore structure, which subsequently influences seepage and leaching performance. To investigate how particle size and gradation affect the pore structure of granular media, physical models of ore particles with varying sizes and gradations were constructed. These models were scanned and three-dimensionally reconstructed using CT scanning technology and Avizo software (Avizo, Version 2023.1; Thermo Fisher Scientific: Waltham, MA, USA, 2023) enabling quantitative analysis of pore structure parameters. The results indicate that the coefficient of uniformity (Cu) is approximately negatively correlated with porosity, while the vertical absolute permeability (kz) follows an attenuated exponential trend. When the fine-particle content (L8 > L3 > L1) increases by 1.5-fold and 9-fold, the number of pore throats increases by 8.71% and 30.91%, respectively, the average pore size decreases by 75.1% and 64.4%, the average throat size decreases by 66.3% and 60%, and the connectivity rate decreases by 92% and 77.8%. This study further evaluates permeability based on the aforementioned pore structure parameters. Multiple regression analysis reveals that the connectivity rate and throat size have the most significant influence on permeability. Accordingly, permeability analysis and prediction are conducted using the improved Purcell formula, which demonstrates a strong correlation with the experimentally measured results. Full article

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

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22 pages, 10413 KiB

Open AccessArticle

Metallogenic Mechanisms of the Lower Triassic Dongping Sedimentary Manganese Deposit in the South China Block: Mineralogical and Geochemical Evidence

by Rong-Zhi Li, Sha Jiang, Peng Long, Tao Long, Da-Qing Ding, Ling-Nan Zhao, Yi Zhang and Qin Huang

Minerals 2025, 15(8), 847; https://doi.org/10.3390/min15080847 - 8 Aug 2025

Viewed by 180

Abstract

The Dongping manganese (Mn) deposit, located within the Lower Triassic Shipao Formation of the Youjiang Basin, is one of South China’s most significant sedimentary Mn carbonate ore deposits. To resolve longstanding debates over its metallogenic pathway, we conducted integrated sedimentological, mineralogical, and geochemical [...] Read more.

The Dongping manganese (Mn) deposit, located within the Lower Triassic Shipao Formation of the Youjiang Basin, is one of South China’s most significant sedimentary Mn carbonate ore deposits. To resolve longstanding debates over its metallogenic pathway, we conducted integrated sedimentological, mineralogical, and geochemical analyses on three drill cores (ZK5101, ZK0301, and ZK1205) spanning the Mn ore body. X-ray diffraction and backscatter electron imaging reveal that the ores are dominated by kutnohorite, with subordinate quartz, calcite, dolomite, and minor sulfides. The low enrichment of U/Al, V/Al, and Mo/Al, as well as positive Ce anomalies, consistently suggest that Mn, in the form of oxides, was deposited in an oxic water column. Carbon isotope compositions of Mn carbonate ores (δ¹³C_VPDB: −2.3 to −6.1‰) and their negative correlation with MnO suggest that Mn carbonate, predominantly kutnohorite, show a diagenetic reduction in pre-existing Mn oxides via organic-matter oxidation in anoxic sediments pore waters. Elemental discrimination diagramms (Mn-Fe-(Co+Ni+Cu) × 10 and Co/Zn vs. Co+Cu+Ni) uniformly point to a hydrothermal Mn source. We therefore propose that hydrothermal fluids supplied dissolved Mn²⁺ to an oxic slope-basin setting, precipitating initially as Mn oxides, which were subsequently transformed to Mn carbonates during early diagenesis. This model reconciles both the hydrothermal and sedimentary-diagenetic processes of the Dongping Mn deposit. Full article

(This article belongs to the Section Mineral Deposits)

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29 pages, 5233 KiB

Open AccessReview

Surface Properties and Beneficiation of Quartz with Flotation

by Can Gungoren, Orhan Ozdemir and Safak Gokhan Ozkan

Minerals 2025, 15(8), 846; https://doi.org/10.3390/min15080846 - 8 Aug 2025

Viewed by 71

Abstract

This review aims to advance quartz processing technology by examining the surface properties, flotation behavior, and selective flotation mechanisms of quartz mineral. Characterized by a strong negative charge over a wide pH range and an isoelectric point around pH 2, quartz surfaces allow [...] Read more.

This review aims to advance quartz processing technology by examining the surface properties, flotation behavior, and selective flotation mechanisms of quartz mineral. Characterized by a strong negative charge over a wide pH range and an isoelectric point around pH 2, quartz surfaces allow physical adsorption of cationic collectors, particularly amines, which render the quartz surface hydrophobic and enhance bubble–particle interactions. In contrast, flotation with anionic collectors requires prior surface activation via multivalent metal cations such as Ca²⁺. The pH value of the medium plays a critical role in both collector adsorption and flotation selectivity. Both direct and reverse flotation strategies can be used, depending on whether quartz is targeted as a valuable mineral or a gangue mineral. In direct flotation, depressants like carboxymethyl cellulose and starch are used to depress gangue minerals, while in reverse flotation, quartz is depressed using chemicals such as fluoride ions and cationic polymers. To improve the efficiency and selectivity of quartz flotation, further research is needed on surface chemistry, collector adsorption mechanisms, and the transition from laboratory-scale experiments to industrial applications. Full article

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

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19 pages, 6094 KiB

Open AccessArticle

TiO₂ Supported on Kaolinite via Sol–Gel Method for Thermal Stability of Photoactivity in Ceramic Tile Produced by Single-Firing Process

by Eloise de Sousa Cordeiro, Jucilene de Souza Feltrin, Melissa Gurgel Adeodato Vieira and Agenor De Noni Junior

Minerals 2025, 15(8), 845; https://doi.org/10.3390/min15080845 - 8 Aug 2025

Viewed by 195

Abstract

Anatase is well known for its photocatalytic properties. However, it can be irreversibly transformed into rutile at temperatures above 600–850 °C. This is a major limitation for ceramic tiles with self-cleaning properties, which are usually single-fired at 1100–1250 °C. To avoid this issue, [...] Read more.

Anatase is well known for its photocatalytic properties. However, it can be irreversibly transformed into rutile at temperatures above 600–850 °C. This is a major limitation for ceramic tiles with self-cleaning properties, which are usually single-fired at 1100–1250 °C. To avoid this issue, functionalized tiles are often produced by double firing, where the second firing stays below 850 °C. Supporting TiO₂ on kaolinite helps to stabilize the anatase phase even at temperatures above 850 °C. In this study, a photocatalytic coating was specially developed to be suitable for the single-firing ceramic tile process. TiO₂ and TiO₂ with Nb₂O₅ (from 0 to 12 wt.%) were supported on kaolinite. This material was mixed with a glass frit to create a surface texture typical of ceramic tiles. The coated tiles were single-fired at 1185 °C. The self-cleaning performance was evaluated using contact angle (CA) measurements and methylene blue (MB) degradation under UV-A light, on both unpolished and polished surfaces. The polished sample containing 12 wt.% TiO₂ showed the best photocatalytic activity: it degraded 57% of MB and the contact angle decreased from 64° to 30° after UV-A exposure. XPS, FTIR, and FEG-SEM analyses confirmed the effective presence of TiO₂. The results demonstrate that kaolinite-supported TiO₂ is a promising approach for producing self-cleaning ceramic tiles using a single-firing process. Full article

(This article belongs to the Special Issue From Clay Minerals to Ceramics: Progress and Challenges)

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24 pages, 12489 KiB

Open AccessArticle

Hyperspectral Lithological Classification of 81 Rock Types Using Deep Ensemble Learning Algorithms

by Shanjuan Xie, Yichun Qiu, Shixian Cao and Wenyuan Wu

Minerals 2025, 15(8), 844; https://doi.org/10.3390/min15080844 - 8 Aug 2025

Viewed by 172

Abstract

To address overfitting due to limited sample size, and the challenges posed by “Spectral Homogeneity with Material Heterogeneity (SHMH)” and “Material Consistency with Spectral Divergence (MCSD)”—which arise from subtle spectral differences and limited classification accuracy—this study proposes a deep integration model that combines [...] Read more.

To address overfitting due to limited sample size, and the challenges posed by “Spectral Homogeneity with Material Heterogeneity (SHMH)” and “Material Consistency with Spectral Divergence (MCSD)”—which arise from subtle spectral differences and limited classification accuracy—this study proposes a deep integration model that combines the Adaptive Boosting (AdaBoost) algorithm with a convolutional recurrent neural network (CRNN). The model adopts a dual-branch architecture integrating a 2D-CNN and gated recurrent unit to effectively fuse spatial and spectral features of rock samples, while the integration of the AdaBoost algorithm optimizes performance by enhancing system stability and generalization capability. The experiment used a hyperspectral dataset containing 81 rock samples (46 igneous rocks and 35 metamorphic rocks) and evaluated model performance through five-fold cross-validation. The results showed that the proposed 2D-CRNN-AdaBoost model achieved 92.55% overall accuracy, which was significantly better than that of other comparative models, demonstrating the effectiveness of multimodal feature fusion and ensemble learning strategy. Full article

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

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39 pages, 13361 KiB

Open AccessArticle

Mineralogical, Petrological, 3D Modeling Study and Geostatistical Mineral Resources Estimation of the Zone C Gold Prospect, Kofi (Mali)

by Jean-Jacques Royer and Niakalé Camara

Minerals 2025, 15(8), 843; https://doi.org/10.3390/min15080843 - 8 Aug 2025

Viewed by 336

Abstract

A 3D model integrating mineralogical, petrological, and geostatistical resource estimation was developed for Zone C of the Kofi Birimian gold deposit in Western Mali. Petrographic analysis identified two forms of gold mineralization: (i) native gold or electrum inclusions within pyrite, and (ii) disseminated [...] Read more.

A 3D model integrating mineralogical, petrological, and geostatistical resource estimation was developed for Zone C of the Kofi Birimian gold deposit in Western Mali. Petrographic analysis identified two forms of gold mineralization: (i) native gold or electrum inclusions within pyrite, and (ii) disseminated native gold along pyrite fractures. Four types of hydrothermal alteration–epidotization, chloritization, carbonatization, and albitization were observed microscopically. Statistical analysis of geochemical data classified five lithologies: mafic dyke, felsic dyke, diabase, faulted breccia, and intermediate quartz diorite. Minerals identified petrographically were corroborated by multivariate correlations among elements (Cr, Fe, Ni, Al, Ti, Na, and Ca), as revealed by Principal Component Analysis (PCA). A 3D borehole-based model revealed spatial correlations between hydrothermal alteration zones and associated geochemical anomalies, notably tourmalinization (B) and albitization (Na), with the latter serving as a key indicator for new exploration targets. The spatial associations of anomalous Ag, B, Hg, As, and Na commonly linked to tourmalinization suggest favorable zones for gold and silver mineralization. Geostatistical analysis identified isotropic continuous mineralized structures for most elements, including gold. Spherical isotropic variograms with ranges from 35 to 75 m were fitted for in situ resource estimation (e.g., silver ≈ 40 m; gold ≈ 60 m). The resulting estimated resources (indicated + inferred), based on a 1.0 g/t Au cut-off, are 2.476 Mt at 3.5 g/t Au indicated (0.278 Moz or 8.67 t), and 1.254 Mt at 2.78 g/t Au inferred (0.112 Moz or 3.49 t). This study provides a framework for identifying new mineralized zones, and the multidisciplinary approach demonstrates the connections between mineralogy and the information embedded in geochemical datasets, which are revealed through appropriate tools and an understanding of the underlying processes. Full article

(This article belongs to the Special Issue Advancements in Mineral Resource Characterization Using Machine Learning)

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20 pages, 7776 KiB

Open AccessArticle

Integrated Gravity Data Interpretation for Potash Exploration in the Vientiane Basin, Laos

by Juncheng Liu, Tao Xu, Tie Gao, Dexiang Geng and Wei Du

Minerals 2025, 15(8), 842; https://doi.org/10.3390/min15080842 - 8 Aug 2025

Viewed by 195

Abstract

Gravity exploration, an Earth science method leveraging gravitational field variations due to density differences in geological structures, is a pivotal tool for subterranean investigation due to its cost-effectiveness and efficient data acquisition. This study focuses on potash, a vital agricultural resource, which forms [...] Read more.

Gravity exploration, an Earth science method leveraging gravitational field variations due to density differences in geological structures, is a pivotal tool for subterranean investigation due to its cost-effectiveness and efficient data acquisition. This study focuses on potash, a vital agricultural resource, which forms low-density geological deposits manifesting gravitational anomalies. The research delineates favorable regions for potash enrichment within an exploration zone in Laos, utilizing gravity data, geological information, drilling records, and insights into mineralization mechanisms. The study employed analytic continuation, residual anomaly calculation, and vertical derivative analysis to interpret anomalies and identify low-density potash targets. Apparent density calculations revealed significant variations at different depths. Fault identification using integrated methods identified 16 fault lines, predominantly north–south and northeast oriented. Primary potash targets are in the northeastern and northwestern parts, with secondary targets in the central-western and southeast regions. The study acknowledges limitations such as potential field ambiguity, restricted resolution, and scarce geological data. It recommends integrating other geophysical methods, denser exploration grids, and prompt drilling for verification to refine interpretations and improve understanding, laying a solid foundation for future exploration. Full article

(This article belongs to the Special Issue Gravity, Magnetic, and Electromagnetic (GME) Geophysical Data Interpretation for Mineral Exploration and Crustal Structure Investigation)

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18 pages, 6084 KiB

Open AccessArticle

Amphoteric Halloysite and Sepiolite Adsorbents by Amino and Carboxy Surface Modification for Effective Removal of Cationic and Anionic Dyes from Water

by Boutaina Boumhidi, Nadia Katir, Jamal El Haskouri, Khalid Draoui and Abdelkrim El Kadib

Minerals 2025, 15(8), 841; https://doi.org/10.3390/min15080841 - 8 Aug 2025

Viewed by 206

Abstract

Surface functionalization is a key enabler that imparts solid materials with excellent chemoselectivity. With this aim, halloysite and sepiolite clay particles were functionalized with carboxyethylsilanetriol sodium salt (CES) and 3-aminopropyltriethoxysilane (APTES), affording carboxy-terminated and amino-terminated clay, respectively. In the case of halloysite, the [...] Read more.

Surface functionalization is a key enabler that imparts solid materials with excellent chemoselectivity. With this aim, halloysite and sepiolite clay particles were functionalized with carboxyethylsilanetriol sodium salt (CES) and 3-aminopropyltriethoxysilane (APTES), affording carboxy-terminated and amino-terminated clay, respectively. In the case of halloysite, the grafting occurs at Al-OH groups of the lumen surface (tube inner surface) and Al-OH and Si-OH groups at the edges and external surface defects of the nanotubes. For sepiolite, silanol groups located on the edges of the structural channels were at the origin of a chemical reaction between this fibrous clay and the terminal alkoxysilane. The resulting modified clays were examined for removal of Congo red (CR) and malachite green (MG) as anionic and cationic dyes, respectively. Clay bearing only carboxylic groups display more affinity towards cationic dye (MG), recording 926 mg·g⁻¹ and 387 mg·g⁻¹ for HNT-CES and SEP-CES, respectively, while amino-functionalized clays show very high adsorption for anionic dye (CR), reaching 1232 and 1228 mg·g⁻¹ for HNT-APTES and SEP-APTES, respectively. Simultaneous grafting of the two silyl coupling reagents was also attempted through one-pot and sequential grafting method, with the latter being more appropriate to access amphoteric clay featuring both carboxylic and amino groups. The behavior of the bifunctional adsorbents was investigated with respect to pristine and monofunctional clay. The obtained results provide insights to fulfill the requirement for handling complex water effluent containing both anionic and cationic pollutants, towards more sustainable development. Full article

(This article belongs to the Special Issue Applications of Clay Minerals and Engineered Materials in Water and Wastewater Treatment)

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29 pages, 9860 KiB

Open AccessArticle

The Source and Evolution of Ore-Forming Fluids in the Xiaobaihegou Fluorite Deposit, Altyn-Tagh Orogen, NW China: Constraints from Trace Element, Fluid Inclusion, and Isotope Studies

by Kang Chen, Wenlei Song, Yuanwei Wang, Long Zhang, Yongkang Jing, Yi Zhang, Yongbao Gao, Ming Liu, Nan Deng and Junwei Wu

Minerals 2025, 15(8), 840; https://doi.org/10.3390/min15080840 - 8 Aug 2025

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Abstract

The Xiaobaihegou fluorite deposit is located in the southwest of the Altyn-Tagh Orogen, NW China. However, the provenance, thermodynamic properties, and enrichment mechanisms of the ore-forming fluids in this deposit remain unclear. Fluorite mineralization primarily occurs in the vicinity of the contact zone [...] Read more.

The Xiaobaihegou fluorite deposit is located in the southwest of the Altyn-Tagh Orogen, NW China. However, the provenance, thermodynamic properties, and enrichment mechanisms of the ore-forming fluids in this deposit remain unclear. Fluorite mineralization primarily occurs in the vicinity of the contact zone between the granite and the wall rocks. The zircon U-Pb age of the alkali-feldspar granite in the Xiaobaihegou fluorite deposit is 482.3 ± 4.1 Ma. The ore-hosting lithologies are mainly calcareous rock series of the Altyn Group. The ore bodies are controlled by NE-trending faults and consist primarily of veined, brecciated, massive, and banded ores. The ore mineral assemblage is primarily composed of calcite and fluorite. The rare earth element (REE) patterns of fluorite and calcite in the Xiaobaihegou deposit exhibit right-dipping LREE enrichment with distinct negative Eu anomalies, which closely resemble those of the alkali-feldspar granite. This similarity suggests that the REE distribution patterns of fluorite and calcite were likely inherited from the pluton. The ore-forming process can be divided into an early stage and a late stage. The massive ores formed in the early stage contain mainly gas-rich two-phase fluid inclusions and CO₂-bearing three-phase inclusions, with homogenization temperatures ranging from 235 °C to 426 °C and salinities from 28.59% to 42.40% NaCl equivalent. In the late stage, brecciated and stockwork ores were formed. They host liquid-rich two-phase and gas-rich two-phase fluid inclusions, with homogenization temperatures ranging from 129 °C to 350 °C and salinities from 0.88% to 21.61% NaCl equivalent. The results of hydrogen and oxygen isotope studies indicate that the ore-forming fluids were derived from a mixture of magmatic–hydrothermal and meteoric water. Fluorite precipitation in the early stage was mainly due to the mixing of magmatic–hydrothermal solution and meteoric water, as well as a water–rock reaction. In the late stage, fluid mixing further occurred, resulting in a decrease in temperature and the formation of brecciated and stockwork ores. The ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd ratios of fluorite from the deposit range from 0.71033 to 0.71272 and 0.511946 to 0.512073, respectively, indicating that the ore-forming material originates from the crust. Based on the ore-forming characteristics, it is proposed that Ca may be primarily leached from the strata formation, while F may predominantly originate from magmatic–hydrothermal solutions. The formation of fluorite deposits is closely related to the transition of the Central Altyn-Tagh Block and Qaidam Block from a compressional orogenic environment to an extensional tectonic environment. Full article

(This article belongs to the Section Mineral Deposits)

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17 pages, 4238 KiB

Open AccessArticle

Carbonatogenic Bacteria from Corallium rubrum Colonies

by Vincenzo Pasquale, Roberto Sandulli, Elena Chianese, Antonio Lettino, Maria Esther Sanz-Montero, Mazhar Ali Jarwar and Stefano Dumontet

Minerals 2025, 15(8), 839; https://doi.org/10.3390/min15080839 - 7 Aug 2025

Viewed by 162

Abstract

The precipitation of minerals, in particular carbonates, is a widespread phenomenon in all ecosystems, where it assumes a high relevance both from a geological and biogeochemical standpoint. Most carbonate rocks are of biological origin and made in an aquatic environment. In particular, bioprecipitation [...] Read more.

The precipitation of minerals, in particular carbonates, is a widespread phenomenon in all ecosystems, where it assumes a high relevance both from a geological and biogeochemical standpoint. Most carbonate rocks are of biological origin and made in an aquatic environment. In particular, bioprecipitation of carbonates is believed to have started in the Mesoproterozoic Era, thanks to a process often driven by photosynthetic microorganisms. Nevertheless, an important contribution to carbonate precipitation is also due to the metabolic activity of heterotrophic bacteria, which is not restricted to specific taxonomic groups or to specific environments, making this process a ubiquitous phenomenon. In this framework, the relationship between carbonatogenic microorganisms and other living organisms assumes a particular interest. This study aims to isolate and identify the culturable heterotrophic bacterial component associated with the coenosarc of Corallium rubrum in order to evaluate the occurrence of strains able to precipitate carbonates. In particular, the study was focused on the identification and characterisation of bacterial strains isolated from a coral coenosarc showing a high carbonatogenic capacity under laboratory conditions. Samples of C. rubrum were taken in the coastal waters of three Italian regions. The concentration of the aerobic heterotrophic microflora colonising C. rubrum coenosarc samples spanned from 3 to 6∙10⁶ CFU/cm². This variation in microbial populations colonising the C. rubrum coenosarc, spanning over 6 orders of magnitude, is not mirrored by a corresponding variability in the colony morphotypes recorded, with the mean being 5.1 (±2.1 sd). Among these bacteria, the carbonatogenic predominant species was Staphylococcus equorum (93% of the isolates), whereas Staphylococcus xylosus and Shewanella sp. accounted only for 3% of isolates each. All these strains showed a remarkable capacity of precipitating calcium carbonate, in the form of calcite crystals organised radially as well crystalised spherulites (S. equorum) or coalescing spherulites (Shewanella sp.). S. xylosus only produced amorphous precipitates of calcium carbonate. All bacterial strains identified were positive both for the production of urease and carbon anhydrase in vitro at 30 °C. It seems that they potentially possess the major biochemical abilities conducive to Ca²⁺ precipitation, as they showed in vitro. In addition, all our carbonatogenic isolates were able to hydrolyse the phytic acid calcium salt and then were potentially able to induce precipitation of calcium phosphates also through such a mechanism. Full article

(This article belongs to the Special Issue Carbonate Petrology and Geochemistry, 2nd Edition)

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12 pages, 1502 KiB

Open AccessArticle

A Study on the Beneficiation of Very Fine Particle Rutile Ore Using Flotation

by Oyku Bilgin and Ilhan Ehsani

Minerals 2025, 15(8), 838; https://doi.org/10.3390/min15080838 - 7 Aug 2025

Viewed by 115

Abstract

This study investigates the beneficiation of finely grinded rutile ore utilizing a combination of flocculation and flotation methods. Rutile, a Ti-bearing mineral with industrial significance, is often associated with heavy minerals found in coastal and metamorphic environments. A rutile ore sample from Azıtepe [...] Read more.

This study investigates the beneficiation of finely grinded rutile ore utilizing a combination of flocculation and flotation methods. Rutile, a Ti-bearing mineral with industrial significance, is often associated with heavy minerals found in coastal and metamorphic environments. A rutile ore sample from Azıtepe (Alaşehir, Türkiye) was reduced to −63 µm and enriched under varying pH conditions (2.5–12) using different reagent combinations and was used for our investigation of both flocculation and flotation processes using reagents such as Aero801(SIPX), Aero825, tannic acid (TA), and pomace oil. The best results were achieved at pH: 8 using Aero801(SIPX) and pomace oil during flocculation, and Aero801(SIPX), Aero825, and Aerofroth88 during flotation, yielding a concentrate with an 8.99% TiO₂ grade and an 89.5% recovery rate. Meanwhile, a 7.00% TiO₂ grade concentrate was obtained with a recovery rate of 71.92% at neutral pH. This study found that pH and reagent selection had an important effect on TiO₂ enrichment efficiency in fine size, low-grade rutile ores. Future research is recommended to investigate selective depressants and multi-stage cleaning to improve separation. Full article

(This article belongs to the Special Issue Particle–Bubble Interactions in the Flotation Process)

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19 pages, 3872 KiB

Open AccessArticle

Sr-Nd-Hf Isotopic Characteristics of Ore-Bearing Intrusive Rocks in the Chating Cu-Au Deposit and Magushan Cu-Mo Deposit of Nanling-Xuancheng Ore Concentration Area and Their Geological Significance

by Linsen Jin, Xiaochun Xu, Xinyue Xu, Ruyu Bai, Zhongyang Fu, Qiaoqin Xie and Zhaohui Song

Minerals 2025, 15(8), 837; https://doi.org/10.3390/min15080837 - 7 Aug 2025

Viewed by 190

Abstract

The Chating Cu-Au and Magushan Cu-Mo deposits in Anhui province are two representative deposits within the recently defined Nanling-Xuancheng ore concentration area in the Middle and Lower Yangtze River Metallogenic Belt (MLYB). Magmatism and mineralization for the area are not well known at [...] Read more.

The Chating Cu-Au and Magushan Cu-Mo deposits in Anhui province are two representative deposits within the recently defined Nanling-Xuancheng ore concentration area in the Middle and Lower Yangtze River Metallogenic Belt (MLYB). Magmatism and mineralization for the area are not well known at present due to a lack of in-depth studies on the petrogenesis of ore-bearing intrusive rocks and their relationship with deposits. Here, the ore-bearing intrusive rocks of the two deposits are investigated through analyses of whole-rock geochemistry and Sr-Nd isotopes, zircon U-Pb ages, and zircon Hf isotopes. The results reflect the two intrusions, both formed in the Early Cretaceous (138.9 ± 0.8 Ma and 132.2 ± 1.3 Ma). They belong to the sub-alkaline high-K calc-alkaline series, while trace elements are enriched in LILEs and LREE and depleted in HFSEs. However, the intrusions of the Chating deposit (I_sr = 0.7064–0.7068; ε_Nd(t) = −8.5–−7.3; ε_Hf(t) = −11.9–−7.0) have obviously different Sr-Nd-Hf isotopic compositions from the intrusions of the Magushan deposit (I_sr = 0.7079–0.7081; ε_Nd(t) = −5.7–−5.4; ε_Hf(t) = −5.4–−3.6). The characteristics indicate that the two intrusions were formed in the same diagenetic ages and tectonic settings and derived from a crust–mantle mixture with predominant mantle-derived materials. But the crust materials of sources are different, which further leads to different metallogenic elements, showing that the Chating deposit is enriched in Cu and Au, while the Magushan deposit is enriched in Mo. Moreover, the characteristics and magma sources of two intrusions and metallogenic elements correspond respectively to the Tongling Cu-Au polymetallic ore concentration area in the MLYB and the southern Anhui Mo polymetallic ore concentration area in the Jiangnan orogen. The correlation implies differences in magmatism and mineralization between the northwestern and southeastern parts of the Nanling-Xuancheng ore concentration area, demarcated by the Jiangnan Deep Fault. These variations were mainly controlled by the Pre-Sinian crustal basement. Full article

(This article belongs to the Section Mineral Deposits)

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23 pages, 4687 KiB

Open AccessArticle

Mineralogical and Geochemical Characterization of the Benavila (Portugal) Bentonites

by Javier García-Rivas, Maria Isabel Dias, Isabel Paiva, Paula G. Fernandes, Rosa Marques, Emilia García-Romero and Mercedes Suárez

Minerals 2025, 15(8), 836; https://doi.org/10.3390/min15080836 - 7 Aug 2025

Viewed by 179

Abstract

This work aims to perform a detailed mineralogical, crystal-chemical, and geochemical characterization of bentonites from the Benavila outcrop, the largest known deposit of bentonites in continental Portugal. Bulk samples and different size fractions were characterized through X-Ray Diffraction (XRD). Structural formulae of the [...] Read more.

This work aims to perform a detailed mineralogical, crystal-chemical, and geochemical characterization of bentonites from the Benavila outcrop, the largest known deposit of bentonites in continental Portugal. Bulk samples and different size fractions were characterized through X-Ray Diffraction (XRD). Structural formulae of the smectites were fitted from point analyses acquired by analytical electron microscopy (AEM) with transmission electron microscopy (TEM). Smectites are the major component with variable amounts of calcite and minor amounts of quartz, feldspar, illite, and chlorite. Occasionally, amphiboles and dolomite have also been identified. The high content of carbonates in different parts of the sampling area is related to the circulation of carbonate-rich fluids. The smectites present high-layer charge, are intermediate terms of the montmorillonite–beidellite series, and also show an intermediate cisvacant–transvacant configuration. Major and trace elements concentrations were determined by ICP-MS. The geochemical analysis of the samples indicates an enrichment in SiO₂ and Al₂O₃ and a depletion of the more clayey materials in REE, HFSE, and Y, among others. The calculation of the PIA and CIA alteration indices, along with other parameters observed, shows the possible alteration pathways of the Benavila deposit. Research to evaluate the ability of these bentonites to be used as engineering barrier systems (EBS) and sealing materials for radioactive waste repositories is ongoing. Full article

(This article belongs to the Special Issue Clay Minerals: From Paleoclimatic and Paleoenvironmental Indicators to Industrial Raw Materials)

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20 pages, 6776 KiB

Open AccessArticle

Computational Approaches to Assess Flow Rate Efficiency During In Situ Recovery of Uranium: From Reactive Transport to Streamline- and Trajectory-Based Methods

by Maksat Kurmanseiit, Nurlan Shayakhmetov, Daniar Aizhulov, Banu Abdullayeva and Madina Tungatarova

Minerals 2025, 15(8), 835; https://doi.org/10.3390/min15080835 - 6 Aug 2025

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Abstract

This study presents a comprehensive computational analysis of flow rate efficiency during uranium extraction via the In Situ Recovery method. Using field data from a deposit located in Southern Kazakhstan, a series of mathematical models were developed to evaluate the distribution and balance [...] Read more.

This study presents a comprehensive computational analysis of flow rate efficiency during uranium extraction via the In Situ Recovery method. Using field data from a deposit located in Southern Kazakhstan, a series of mathematical models were developed to evaluate the distribution and balance of leaching solution. A reactive transport model incorporating uranium dissolution kinetics and acid–rock interactions were utilized to assess the accuracy of both traditional and proposed methods. The results reveal a significant spatial imbalance in sulfuric acid distribution, with up to 239.1 tons of acid migrating beyond the block boundaries. To reduce computational demands while maintaining predictive accuracy, two alternative methods, a streamline-based and a trajectory-based approach were proposed and verified. The streamline method showed close agreement with reactive transport modeling and was able to effectively identify the presence of intra-block reagent imbalance. The trajectory-based method provided detailed insight into flow dynamics but tended to overestimate acid overflow outside the block. Both alternative methods outperformed the conventional approach in terms of accuracy by accounting for geological heterogeneity and well spacing. The proposed methods have significantly lower computational costs, as they do not require solving complex systems of partial differential equations involved in reactive transport simulations. The proposed approaches can be used to analyze the efficiency of mineral In Situ Recovery at both the design and operational stages, as well as to determine optimal production regimes for reducing economic expenditures in a timely manner. Full article

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

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35 pages, 8847 KiB

Open AccessArticle

From Pulp to Froth: Decoding the Role of Nanoparticle Colloidal Silica in Scheelite Flotation as a Calcite Depressant

by Borhane Ben Said, Suvarna Patil, Martin Rudolph, Daniel Goldmann and Lucas Pereira

Minerals 2025, 15(8), 834; https://doi.org/10.3390/min15080834 - 6 Aug 2025

Viewed by 307

Abstract

Colloidal silica acts as a multifunctional reagent in the froth flotation process of semi-soluble salt-type minerals, enabling the selective depression of calcite. This study investigates its effect on four key minerals—calcite, scheelite, apatite, and fluorite—using a comprehensive suite of techniques to identify the [...] Read more.

Colloidal silica acts as a multifunctional reagent in the froth flotation process of semi-soluble salt-type minerals, enabling the selective depression of calcite. This study investigates its effect on four key minerals—calcite, scheelite, apatite, and fluorite—using a comprehensive suite of techniques to identify the flotation subprocesses modulated by colloidal silica. This work also aims to determine the specific flotation zones affected by colloidal silica, assessing the influence of its dosage, surface modification, and specific surface area on metallurgical outcomes. Atomic force microscopy revealed mineral-specific surface responses to colloidal silica conditioning: calcite exhibited localized nanoparticle adsorption, whereas apatite underwent a dissolution–reprecipitation mechanism. Scheelite and fluorite, in contrast, showed minimal surface modifications. These differences are attributed to variations in surface reactivity, hydration behavior, and crystallographic structure, with calcite offering a uniquely favorable environment for colloidal silica attachment. Mechanistic insights show that colloidal silica—especially the aluminate-modified type with high specific surface area—influences both the pulp and froth zones by producing small, stable bubbles, enhancing fine scheelite recovery, stabilizing froth, and effectively depressing calcite. In contrast, non-functionalized colloidal silica resulted in poor bubble control and unstable froth. These findings elucidate the subprocess-specific mechanisms by which colloidal silica operates and highlight its potential as a tunable, multifunctional reagent for improving selectivity in the flotation of semi-soluble salt-type minerals. Full article

(This article belongs to the Special Issue Application of Nanomaterials in Mineral Processing)

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29 pages, 16357 KiB

Open AccessArticle

Evaluation of Heterogeneous Ensemble Learning Algorithms for Lithological Mapping Using EnMAP Hyperspectral Data: Implications for Mineral Exploration in Mountainous Region

by Soufiane Hajaj, Abderrazak El Harti, Amin Beiranvand Pour, Younes Khandouch, Abdelhafid El Alaoui El Fels, Ahmed Babeker Elhag, Nejib Ghazouani, Mustafa Ustuner and Ahmed Laamrani

Minerals 2025, 15(8), 833; https://doi.org/10.3390/min15080833 - 5 Aug 2025

Viewed by 335

Abstract

Hyperspectral remote sensing plays a crucial role in guiding and supporting various mineral prospecting activities. Combined with artificial intelligence, hyperspectral remote sensing technology becomes a powerful and versatile tool for a wide range of mineral exploration activities. This study investigates the effectiveness of [...] Read more.

Hyperspectral remote sensing plays a crucial role in guiding and supporting various mineral prospecting activities. Combined with artificial intelligence, hyperspectral remote sensing technology becomes a powerful and versatile tool for a wide range of mineral exploration activities. This study investigates the effectiveness of ensemble learning (EL) algorithms for lithological classification and mineral exploration using EnMAP hyperspectral imagery (HSI) in a semi-arid region. The Moroccan Anti-Atlas mountainous region is known for its complex geology, high mineral potential and rugged terrain, making it a challenging for mineral exploration. This research applies core and heterogeneous ensemble learning methods, i.e., boosting, stacking, voting, bagging, blending, and weighting to improve the accuracy and robustness of lithological classification and mapping in the Moroccan Anti-Atlas mountainous region. Several state-of-the-art models, including support vector machines (SVMs), random forests (RFs), k-nearest neighbors (k-NNs), multi-layer perceptrons (MLPs), extra trees (ETs) and extreme gradient boosting (XGBoost), were evaluated and used as individual and ensemble classifiers. The results show that the EL methods clearly outperform (single) base classifiers. The potential of EL methods to improve the accuracy of HSI-based classification is emphasized by an optimal blending model that achieves the highest overall accuracy (96.69%). The heterogeneous EL models exhibit better generalization ability than the baseline (single) ML models in lithological classification. The current study contributes to a more reliable assessment of resources in mountainous and semi-arid regions by providing accurate delineation of lithological units for mineral exploration objectives. Full article

(This article belongs to the Special Issue Feature Papers in Mineral Exploration Methods and Applications 2025)

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21 pages, 1124 KiB

Open AccessReview

Advances in Graphite Recycling from Spent Lithium-Ion Batteries: Towards Sustainable Resource Utilization

by Maria Joriza Cañete Bondoc, Joel Hao Jorolan, Hyung-Sub Eom, Go-Gi Lee and Richard Diaz Alorro

Minerals 2025, 15(8), 832; https://doi.org/10.3390/min15080832 - 5 Aug 2025

Viewed by 255

Abstract

Graphite has been recognized as a critical material by the United States (US), the European Union (EU), and Australia. Owing to its unique structure and properties, it is utilized in many industries and has played a key role in the clean energy sector, [...] Read more.

Graphite has been recognized as a critical material by the United States (US), the European Union (EU), and Australia. Owing to its unique structure and properties, it is utilized in many industries and has played a key role in the clean energy sector, particularly in the lithium-ion battery (LIB) industries. With the projected increase in global graphite demand, driven by the shift to clean energy and the use of EVs, as well as the geographically concentrated production and reserves of natural graphite, interest in graphite recycling has increased, with a specific focus on using spent LIBs and other waste carbon material. Although most established and developing LIB recycling technologies are focused on cathode materials, some have started recycling graphite, with promising results. Based on the different secondary sources and recycling paths reported, hydrometallurgy-based treatment is usually employed, especially for the purification of graphite; greener alternatives are being explored, replacing HF both in lab-scale research and in industry. This offers a viable solution to resource dependency and mitigates the environmental impact associated with graphite production. These developments signal a trend toward sustainable and circular pathways for graphite recycling. Full article

(This article belongs to the Special Issue Graphite Minerals and Graphene, 2nd Edition)

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24 pages, 9491 KiB

Open AccessArticle

Provenance of the Upper Permian Longtan Formation in Southern Anhui Province in the Lower Yangtze Region, China: Insights from Sedimentary and Geochemical Characteristics

by Sizhe Deng, Dujie Hou and Wenli Ma

Minerals 2025, 15(8), 831; https://doi.org/10.3390/min15080831 - 5 Aug 2025

Viewed by 234

Abstract

There are many controversies over the material sources of the Late Paleozoic strata in the Lower Yangtze region, and there is a lack of consensus on the basin source–sink system, which hinders the reconstruction of Late Paleozoic paleogeography and exploration of energy and [...] Read more.

There are many controversies over the material sources of the Late Paleozoic strata in the Lower Yangtze region, and there is a lack of consensus on the basin source–sink system, which hinders the reconstruction of Late Paleozoic paleogeography and exploration of energy and mineral resources in the area. This study aimed to clarify the sedimentary provenance and tectonic background of the Upper Permian Longtan Formation in the Chizhou area of southern Anhui Province. The key objectives were to: (i) analyze the geochemical characteristics of sandstones using major, trace, and rare earth elements; (ii) determine the tectonic setting of the sediment source region based on discrimination diagrams; and (iii) integrate geochemical, sedimentological, and paleocurrent data to reconstruct the source-to-sink system. The geochemical data suggest that the sandstone samples exhibit relatively high SiO₂, Fe₂O₃, MgO, and Na₂O content and relatively low TiO₂, Al₂O₃, and K₂O content, consistent with average values of post-Archean Australian shale (PAAS) and the upper continental crust (UCC). The chondrite-normalized rare earth element patterns resemble PAAS, with enrichment in light REEs and depletion in heavy REEs. Tectonic discrimination diagrams indicate a provenance from active continental margins and continental island arcs, with minor input from passive continental margins. Combined with regional tectonic context and paleocurrent measurements, the results suggest that the Longtan Formation sediments primarily originated from the Neoproterozoic Jiangnan orogenic belt and the Cathaysia Block, notably the Wuyi terrane. These research results not only provide new geological data for further clarifying the provenance of Late Paleozoic sedimentary basins in the Lower Yangtze region but also establish the foundation for constructing the Late Paleozoic tectonic paleogeographic pattern in South China. Full article

(This article belongs to the Special Issue Selected Papers from the 7th National Youth Geological Congress)

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20 pages, 4576 KiB

Open AccessArticle

Physical, Chemical, Mineralogical, and Toxicological Characterization of Active and Inactive Tailings in the Arequipa Region, Peru

by Dery Castillo, Karol Palma, Lizbeth Santander, Héctor Bolaños, Gregorio Palma and Patricio Navarro

Minerals 2025, 15(8), 830; https://doi.org/10.3390/min15080830 - 5 Aug 2025

Viewed by 277

Abstract

Mining activity in Peru generates environmental liabilities with the potential to release toxic metals into the environment. This study conducted a comprehensive physical, chemical, mineralogical, and toxicological characterization of ten active and inactive tailings samples from the Arequipa region in southern Peru. Particle [...] Read more.

Mining activity in Peru generates environmental liabilities with the potential to release toxic metals into the environment. This study conducted a comprehensive physical, chemical, mineralogical, and toxicological characterization of ten active and inactive tailings samples from the Arequipa region in southern Peru. Particle size distribution analysis, inductively coupled plasma atomic emission spectroscopy (ICP-AES), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and the Toxicity Characteristic Leaching Procedure (TCLP) followed by ICP-MS were employed. The results revealed variable particle size distributions, with the sample of Secocha exhibiting the finest granulometry. Chemically, 8 out of 10 samples exhibited concentrations of at least two metals surpassing the Peruvian Environmental Quality Standards (EQS) for soils with values reaching >6000 mg/kg of arsenic (Paraiso), 193.1 mg/kg of mercury (Mollehuaca), and 2309 mg/kg of zinc (Paraiso). Mineralogical analysis revealed the presence of sulfides such as arsenopyrite, cinnabar, galena, and sphalerite, along with uraninite in the Otapara sample. In the TCLP tests, 5 out of 10 samples released at least two metals exceeding the environmental standards on water quality, with concentrations up to 0.401 mg/L for mercury (Paraiso), 0.590 mg/L for lead (Paraiso), and 9.286 mg/L for zinc (Kiowa Cobre). These results demonstrate elevated levels of Potentially Toxic Elements (PTEs) in both solid and dissolved states, reflecting a critical geochemical risk in the evaluated areas. Full article

(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)

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23 pages, 7821 KiB

Open AccessArticle

The Multiple Stages of Regional Triassic Crustal Reworking in Eastern Tianshan, NW China: Evidence from the Xigebi Area

by Ming Wei, Haiquan Li, Wenxiao Zhou, Mahemuti Muredili, Ernest Chi Fru and Thomas Sheldrick

Minerals 2025, 15(8), 829; https://doi.org/10.3390/min15080829 - 4 Aug 2025

Viewed by 303

Abstract

The eastern Tianshan region in the Central Asian Orogenic Belt (CAOB) is characterized by multiple complex tectonic activity of uncertain historical contribution to the construction of the CAOB. This study utilizes a multi-proxy geochemical approach to characterize I-type monzogranite pluton rocks and their [...] Read more.

The eastern Tianshan region in the Central Asian Orogenic Belt (CAOB) is characterized by multiple complex tectonic activity of uncertain historical contribution to the construction of the CAOB. This study utilizes a multi-proxy geochemical approach to characterize I-type monzogranite pluton rocks and their associated hornblende-rich dioritic enclaves to decipher the tectonic and magmatic evolution of the Xigebi area, eastern Tianshan. Zircon geochronology indicates a Triassic and Permian crystallization age of ca. 224.2 ± 1.7 Ma and ca. 268.3 ± 3.0 Ma for the host monzogranites and the dioritic enclaves, respectively. Major, trace and rare earth element distribution, together with Hf isotope systematics displaying noticeable positive εHf(t) anomalies for both rock types, point to partial melting of meta-mafic rocks in an intraplate extensional setting. The diorite was formed by the melting of lower crustal meta-igneous rocks mixed with mantle melts, and the monzogranite, predominantly from deep crustal meta-basalts contaminated by shallow metasedimentary rocks, with some degree of mixing with deeply sourced mantle magma. While both the host monzogranites and their dioritic enclaves are the products of upwelling magma, the younger Triassic monzogranites captured and preserved fragments of the dioritic Permian lower continental crust during crystallization. These multiple stages of magmatic underplating and crustal reworking associated with vertical stratification of the juvenile paleo-continental crust suggest the monzogranites and diorites indicate a change from a post-collisional setting to a regional intraplate regime on the southern margin of the CAOB. Full article

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

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2 pages, 316 KiB

Open AccessCorrection

Correction: Shikika et al. Extraction of Ta and Nb from a Coltan Bearing Ore by Means of Ammonium Bifluoride Fluorination and Sulfuric Acid Leaching. Minerals 2021, 11, 1392

by Alidor Shikika, Francois Zabene, Fabrice Muvundja, Mac C. Mugumaoderha, Julien L. Colaux, Mohamed Aatach and Stoyan Gaydardzhiev

Minerals 2025, 15(8), 828; https://doi.org/10.3390/min15080828 (registering DOI) - 4 Aug 2025

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Abstract

The contact details of the author Alidor Shikika have been updated [...] Full article

(This article belongs to the Special Issue Moving towards the Crystal Structure, Molecular or Atomic-Scale for Green and Novel Hydrometallurgical Processing)

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34 pages, 4961 KiB

Open AccessArticle

Study on Grinding Optimization of Cassiterite Polymetallic Sulfide Ore Based on Single-Factor Test Method

by Jinlin Yang, Pengyan Zhu, Xingjian Deng, Hengjun Li, Shaojian Ma and Dingzheng Wang

Minerals 2025, 15(8), 827; https://doi.org/10.3390/min15080827 - 3 Aug 2025

Viewed by 217

Abstract

Cassiterite polymetallic sulfide ore exhibits a complex mineral composition and significant variations in mineral properties, which frequently lead to issues such as the over-grinding of cassiterite and under-grinding of sulfide minerals during the grinding process. These issues consequently impair liberation performance in subsequent [...] Read more.

Cassiterite polymetallic sulfide ore exhibits a complex mineral composition and significant variations in mineral properties, which frequently lead to issues such as the over-grinding of cassiterite and under-grinding of sulfide minerals during the grinding process. These issues consequently impair liberation performance in subsequent beneficiation stages. Among these factors, the grinding media ratios stand as one of the critical factors influencing grinding efficiency. Based on these, the paper adopts the single-factor test method to systematically study the influence law of factors such as grinding time, mill rotational rate, and mill filling rate on the particle size composition of ore grinding products and the grinding technology efficiency under different media conditions; in addition, it is compared with the influence law of different conditions of media ratios on the grinding efficiency of ore. The results show that the optimal parameters of the grinding operation are obtained at the grinding time of 4 min, the mill rotational rate of 60%, and the filling rate of 35%. The grinding time and mill filling rate have a relatively more significant effect on the product particle size distribution, while the effect of the mill rotational rate is relatively less significant. When the parameters of grinding operations are optimal, the yield of qualified particle size and grinding technical efficiency are used as the evaluation indices, respectively. Overall, the order of the grinding effect of different media conditions was as follows: steel ball combination of Φ20 mm and Φ25 mm > steel balls of three single sizes > steel ball combination of Φ20 mm and Φ30 mm. The optimal grinding media ratios are Φ20 mm and Φ25 mm (the percentage of the Φ20 mm ball is 90%). The reasonable media ratios will effectively coordinate the optimal grinding effect between different media. The research results can provide the necessary basic data for the subsequent grinding optimization of cassiterite polymetallic sulfide ores. Full article

(This article belongs to the Special Issue Experimental and Numerical Studies of Mineral Comminution: 3rd Edition)

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29 pages, 30467 KiB

Open AccessArticle

Clay-Hosted Lithium Exploration in the Wenshan Region of Southeastern Yunnan Province, China, Using Multi-Source Remote Sensing and Structural Interpretation

by Lunxin Feng, Zhifang Zhao, Haiying Yang, Qi Chen, Changbi Yang, Xiao Zhao, Geng Zhang, Xinle Zhang and Xin Dong

Minerals 2025, 15(8), 826; https://doi.org/10.3390/min15080826 - 2 Aug 2025

Viewed by 380

Abstract

With the rapid increase in global lithium demand, the exploration of newly discovered lithium in the bauxite of the Wenshan area in southeastern Yunnan has become increasingly important. However, the current research on clay-type lithium in the Wenshan area has primarily focused on [...] Read more.

With the rapid increase in global lithium demand, the exploration of newly discovered lithium in the bauxite of the Wenshan area in southeastern Yunnan has become increasingly important. However, the current research on clay-type lithium in the Wenshan area has primarily focused on local exploration, and large-scale predictive metallogenic studies remain limited. To address this, this study utilized multi-source remote sensing data from ZY1-02D and ASTER, combined with ALOS 12.5 m DEM and Sentinel-2 imagery, to carry out remote sensing mineral identification, structural interpretation, and prospectivity mapping for clay-type lithium in the Wenshan area. This study indicates that clay-type lithium in the Wenshan area is controlled by NW, EW, and NE linear structures and are mainly distributed in the region from north of the Wenshan–Malipo fault to south of the Guangnan–Funing fault. High-value areas of iron-rich silicates and iron–magnesium minerals revealed by ASTER data indicate lithium enrichment, while montmorillonite and cookeite identification by ZY1-02D have strong indicative significance for lithium. Field verification samples show the highest Li₂O content reaching 11,150 μg/g, with six samples meeting the comprehensive utilization criteria for lithium in bauxite (Li₂O ≥ 500 μg/g) and also showing an enrichment of rare earth elements (REEs) and gallium (Ga). By integrating stratigraphic, structural, mineral identification, geochemical characteristics, and field verification data, ten mineral exploration target areas were delineated. This study validates the effectiveness of remote sensing technology in the exploration of clay-type lithium and provides an applicable workflow for similar environments worldwide. Full article

(This article belongs to the Special Issue Hyperspectral Imaging of Rocks: Mineralogical Characteristics and Classification)

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24 pages, 3631 KiB

Open AccessArticle

Mineral–Soil–Plant–Nutrient Synergism: Carbonate Rock Leachate Irrigation Enhances Soil Nutrient Availability, Improving Crop Yield and Quality

by Yifei Du, Xiao Ge, Yimei Du, Hongrui Ding and Anhuai Lu

Minerals 2025, 15(8), 825; https://doi.org/10.3390/min15080825 - 2 Aug 2025

Viewed by 344

Abstract

In the rock–soil–biology–water ecosystem, rock weathering provides essential plant nutrients. However, its supply is insufficient for rising crop demands under population growth and climate change, while excessive fertilizer causes soil degradation and pollution. This study innovatively irrigated with carbonate rock leachates to enhance [...] Read more.

In the rock–soil–biology–water ecosystem, rock weathering provides essential plant nutrients. However, its supply is insufficient for rising crop demands under population growth and climate change, while excessive fertilizer causes soil degradation and pollution. This study innovatively irrigated with carbonate rock leachates to enhance soil nutrient availability. A pot experiment with lettuce showed that irrigation significantly increased soil NO₃⁻-N (+102.20%), available K (+16.45%), available P (+17.95%), Ca (+6.04%), Mg (+11.65%), and Fe (+11.60%), and elevated the relative abundance of Firmicutes. Lettuce biomass per plant rose by 23.78%, with higher leaf minerals (P, K, Ca, and Mg) and antioxidants (carotenoids and ascorbic acid). A field experiment further confirmed improvement of soil nutrient availability and peanut yield. This carbonate rock leachate irrigation technique effectively enhances soil quality and crop productivity/quality, offering a sustainable approach for green agriculture. Full article

(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)

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Open AccessArticle

Coupled Eu Anomalies and Fe Isotopes Reveal a Hydrothermal Iron Source for Superior-Type Iron Formations: A Case Study from the Wilgena Hill Iron Formation, South Australia

by Shuo Chen, Jian Sun, Xiangkun Zhu and Yuelong Chen

Minerals 2025, 15(8), 824; https://doi.org/10.3390/min15080824 - 2 Aug 2025

Viewed by 212

Abstract

Superior-type iron formations (IFs) represent a globally significant source of iron ore; yet, their origin remains a subject of ongoing debate. Early models proposed a continental weathering source for the iron, whereas later interpretations—mainly supported by positive europium (Eu) anomalies—favored a hydrothermal source. [...] Read more.

Superior-type iron formations (IFs) represent a globally significant source of iron ore; yet, their origin remains a subject of ongoing debate. Early models proposed a continental weathering source for the iron, whereas later interpretations—mainly supported by positive europium (Eu) anomalies—favored a hydrothermal source. However, the hydrothermal model largely relies on REE systematics, and whether iron and REEs in Superior-type IFs share the same source remains uncertain. As iron isotopes directly trace the sources and fractionation history of iron, a spatial co-variation between Fe isotopes and Eu anomalies would shed new light on the iron source issue of IFs. In this study, we present new Fe isotope and REE data from the drill core WILDD004 at Wilgena Hill and integrate them with reported data for two additional drill cores: HKDD4 (Hawks Nest) and GWDD1 (Giffen Well). All three cores are stratigraphically equivalent to the Wilgena Hill Jaspilite Formation but span a lateral distance of ~100 km across the Gawler Craton, South Australia. While the Hawks Nest and Giffen Well samples exhibit both positive Eu anomalies and elevated δ⁵⁶Fe values, the Wilgena Hill samples show positive yet smaller Eu/Eu* (1.17–2.41) and negative δ⁵⁶Fe values (−0.60‰ to −1.63‰). The consistent presence of Eu anomalies and the systematic spatial correlation between δ⁵⁶Fe and Eu/Eu* across all three locations provide direct, Fe-based geochemical evidence for a hydrothermal source of iron in this Superior-type IF. Full article

(This article belongs to the Special Issue Geochemical, Isotopic, and Biotic Records of Banded Iron Formations)

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Minerals, Volume 15, Issue 8 (August 2025) – 88 articles

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