Minerals

13 pages, 2034 KB

Open AccessArticle

Rare Earth Elements in Bottom Sediments of the Northern Part of Lake Umbozero, Murmansk Region, Russia

by Eugenia Krasavtseva, Sergey Sandimirov, Irina Elizarova, Maria Malysheva, Dmitriy Makarov and Nikolay Kaganovich

Minerals 2025, 15(9), 973; https://doi.org/10.3390/min15090973 (registering DOI) - 14 Sep 2025

Abstract

The chemical composition of bottom sediments in the northern part of Lake Umbozero, located in close proximity to a closed rare metal mine in the Murmansk Region, was studied. This study is a continuation of our research into the impact of closed rare [...] Read more.

The chemical composition of bottom sediments in the northern part of Lake Umbozero, located in close proximity to a closed rare metal mine in the Murmansk Region, was studied. This study is a continuation of our research into the impact of closed rare metal mines and tailings on the environment. Samples were collected using an open gravity sampler in two sections of the lake in three replicates. The content of rare earth elements was determined using inductively coupled plasma mass spectrometry. The total content of elements was determined both in the surface layers of bottom sediments and in the deep layers that were formed in the preindustrial period and, thus, characterize the geochemical background of the study area. The average ∑REE in the surface layers of bottom sediments of Lake Umbozero in the wastewater reception area (Site 1) reaches 774 mg/kg, while for the area located north of the discharge site (Site 2), ∑REE was 208 mg/kg. The enrichment factor (EF), the geoaccumulation index (I_geo), the coefficient of the index of potential ecological risk (E_ir) and the index of potential ecological hazard (RI) were calculated. Assessing the total pollution of bottom sediments of Lake Umbozero with rare earth elements, the value of potential ecological risk reaches values corresponding to the level of low and moderate ecological risk of pollution (RI_{Site 1} = 164; RI_{Site 2} = 104). The conducted correlation analysis allowed us to establish the main phases containing rare earth elements in the bottom sediments of Lake Umbozero—oxyhydroxide complex compounds with iron and manganese. Full article

(This article belongs to the Special Issue Heavy Metal and Rare Earth Element Pollution in Soil and Water: Sources, Geochemical Behaviors and Ecological Effects, 2nd Edition)

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21 pages, 3304 KB

Open AccessArticle

The Average Structure of a Fine-Grained Nepheline to 900 °C: Disorder of O1, Al-Si, and K-Vacancy

by Sytle M. Antao

Minerals 2025, 15(9), 972; https://doi.org/10.3390/min15090972 (registering DOI) - 13 Sep 2025

Abstract

A fine-grained nepheline sample from Egan Chutes, Ontario, with the chemical composition (K_1.32▯_0.68)(Na_6.05Ca_0.22)[Al_7.77Si_8.21O₃₂], where ▯ represents vacancies, was studied through in situ synchrotron powder X-ray diffraction (XRD) data and [...] Read more.

A fine-grained nepheline sample from Egan Chutes, Ontario, with the chemical composition (K_1.32▯_0.68)(Na_6.05Ca_0.22)[Al_7.77Si_8.21O₃₂], where ▯ represents vacancies, was studied through in situ synchrotron powder X-ray diffraction (XRD) data and Rietveld structure refinement from 26 to 900 °C on heating and cooling. The average structure was refined in the space group P6₃. The satellite reflections in nepheline give rise to order–disorder transitions. The average <Al,Si-O>{4} distances in nepheline indicate a partially ordered Al-Si distribution, especially in the Al2 and Si2 sites at room T before heating. The nepheline structure shows that except for the positional disorder of the O1 oxygen atom, the other atoms are well defined and contain no unusual features. Vacancies, ▯, occur at the K site. Different satellite (s) reflections arise from (1) positional order of the O1 atoms to 299 °C (s1 disappears), (2) K-▯ order to 486 °C (s2 and s3 disappear), and (3) some Al-Si order 900 °C, where some satellite reflections are present. Complete Al-Si order is obtained at room T on cooling. Full article

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

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41 pages, 5058 KB

Open AccessReview

Review of Enargite Flotation—Part I: Surface Characterization and Advances in Selective Flotation

by Pablo Miranda-Villagrán, Rodrigo Yepsen, Andrés Ramírez-Madrid, Jorge H. Saavedra and Leopoldo Gutiérrez

Minerals 2025, 15(9), 971; https://doi.org/10.3390/min15090971 (registering DOI) - 13 Sep 2025

Abstract

Enargite (Cu₃AsS₄), a copper–arsenic sulfosalt, represents a critical challenge in copper mineral processing due to its high arsenic content, which poses significant environmental, metallurgical, and economic issues. Its flotation behavior closely resembles that of other copper sulfides such as [...] Read more.

Enargite (Cu₃AsS₄), a copper–arsenic sulfosalt, represents a critical challenge in copper mineral processing due to its high arsenic content, which poses significant environmental, metallurgical, and economic issues. Its flotation behavior closely resembles that of other copper sulfides such as chalcopyrite and chalcocite, complicating selective separation at early beneficiation stages. This review presents a comprehensive examination of enargite’s surface chemistry and electrochemical behavior, focusing on the influence of oxidation, pH, and pulp potential on surface reactivity, charge distribution (zeta potential), and hydrophobicity. Detailed insights into the formation of surface oxidation layers, passivation mechanisms, and contact angle variations are provided to elucidate collector-mineral interactions. Advances in selective flotation techniques are also discussed, including the use of depressant reagents, controlled redox environments, and reagent conditioning strategies. Special attention is given to flotation in seawater, where ionic strength and multivalent ions significantly influence mineral-reagent interactions and flotation outcomes. Galvanic interactions between enargite and other sulfide minerals are identified as critical factors affecting floatability and selectivity. The review consolidates findings from recent experimental and electrochemical studies, highlighting promising approaches to enhance enargite rejection and copper concentrate purity. It concludes with perspectives on future research aimed at optimizing flotation processes and developing sustainable solutions for processing arsenic-bearing copper ores. Full article

(This article belongs to the Special Issue Mineral Processing and Extractive Metallurgy of Sulfide Ores, 2nd Edition)

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19 pages, 3745 KB

Open AccessArticle

Anomaly Detection in Mineral Micro-X-Ray Fluorescence Spectroscopy Based on a Multi-Scale Feature Aggregation Network

by Yangxin Lu, Weiming Jiang, Molei Zhao, Yuanzhi Zhou, Jie Yang, Kunfeng Qiu and Qiuming Cheng

Minerals 2025, 15(9), 970; https://doi.org/10.3390/min15090970 (registering DOI) - 13 Sep 2025

Abstract

Micro-X-ray fluorescence spectroscopy (micro-XRF) integrates spatial and spectral information and is widely employed for multi-elemental analyses of rock-forming minerals. However, its inherent limitation in spatial resolution gives rise to significant pixel mixing, thereby hindering the accurate identification of fine-scale or anomalous mineral phases. [...] Read more.

Micro-X-ray fluorescence spectroscopy (micro-XRF) integrates spatial and spectral information and is widely employed for multi-elemental analyses of rock-forming minerals. However, its inherent limitation in spatial resolution gives rise to significant pixel mixing, thereby hindering the accurate identification of fine-scale or anomalous mineral phases. Furthermore, most existing methods heavily rely on manually labeled data or predefined spectral libraries, rendering them poorly adaptable to complex and variable mineral systems. To address these challenges, this paper presents an unsupervised deep aggregation network (MSFA-Net) for micro-XRF imagery, aiming to eliminate the reliance of traditional methods on prior knowledge and enhance the recognition capability of rare mineral anomalies. Built on an autoencoder architecture, MSFA-Net incorporates a multi-scale orthogonal attention module to strengthen spectral–spatial feature fusion and employs density-based adaptive clustering to guide semantically aware reconstruction, thus achieving high-precision responses to potential anomalous regions. Experiments on real-world micro-XRF datasets demonstrate that MSFA-Net not only outperforms mainstream anomaly detection methods but also transcends the physical resolution limits of the instrument, successfully identifying subtle mineral anomalies that traditional approaches fail to detect. This method presents a novel paradigm for high-throughput and weakly supervised interpretation of complex geological images. Full article

(This article belongs to the Special Issue Gold–Polymetallic Deposits in Convergent Margins)

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25 pages, 863 KB

Open AccessReview

Clay Minerals as Enzyme Carriers for Pollutant Removal from Wastewater: A Comprehensive Review

by Naima Sayahi, Bouthaina Othmani, Wissem Mnif, Zaina Algarni, Moncef Khadhraoui and Faouzi Ben Rebah

Minerals 2025, 15(9), 969; https://doi.org/10.3390/min15090969 (registering DOI) - 13 Sep 2025

Abstract

Water pollution continues to pose a critical global challenge, largely due to the unregulated discharge of industrial, agricultural, and municipal effluents. Among emerging solutions, enzymatic bioremediation stands out as a sustainable and environmentally friendly approach, offering high specificity and efficiency under mild conditions. [...] Read more.

Water pollution continues to pose a critical global challenge, largely due to the unregulated discharge of industrial, agricultural, and municipal effluents. Among emerging solutions, enzymatic bioremediation stands out as a sustainable and environmentally friendly approach, offering high specificity and efficiency under mild conditions. Nonetheless, the practical application of free enzymes is hindered by their inherent instability, poor reusability, and susceptibility to denaturation. To address these limitations, the immobilization of enzymes onto solid supports, particularly clay minerals, has garnered increasing attention. This review presents a detailed analysis of clay minerals as promising carriers for enzyme immobilization in wastewater treatment. It explores their classification, structural characteristics, and physicochemical properties, highlighting key advantages such as a large surface area, cation exchange capacity, and thermal stability. Functionalization techniques, including acid/base activation, intercalation, grafting, and pillaring, are discussed in terms of improving enzyme compatibility and catalytic performance. Various immobilization methods such as physical adsorption, covalent bonding, entrapment, crosslinking, and intercalation are critically evaluated with regard to enhancing enzyme activity, stability, and recyclability. Recent case studies demonstrate the effective removal of pollutants such as dyes, pharmaceuticals, and heavy metals using enzyme–clay composites. Despite these advances, challenges such as enzyme leaching, mass transfer resistance, and variability in clay composition persist. This review concludes by outlining future prospects, including the development of hybrid and magnetic clay-based systems and their integration into advanced water treatment technologies. Overall, enzyme immobilization on clay minerals represents a promising and scalable approach for the next generation of wastewater bioremediation strategies. 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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15 pages, 5846 KB

Open AccessArticle

The Effect of Ore Pre-Heating on the Operation of a 300 kVA Submerged Arc Furnace for High Carbon Ferromanganese Alloy Production—Pilot Study Results

by Matale Samuel Moholwa, Sello Peter Tsebe, Derek Hayman, Sanda Moloane, Joalet Steenkamp, Martin Sitefane and Driaan Bezuidenhout

Minerals 2025, 15(9), 968; https://doi.org/10.3390/min15090968 (registering DOI) - 13 Sep 2025

Abstract

The effect of ore pre-heating on the operation of a 300 kVA Submerged Arc Furnace (SAF) for high carbon ferromanganese (HCFeMn) alloy was investigated. The two types of Mn ores from the Kalahari Manganese Field (KMF) were used in the investigation (Ore #1 [...] Read more.

The effect of ore pre-heating on the operation of a 300 kVA Submerged Arc Furnace (SAF) for high carbon ferromanganese (HCFeMn) alloy was investigated. The two types of Mn ores from the Kalahari Manganese Field (KMF) were used in the investigation (Ore #1 and Ore #2). Quartz and coke sourced from South Africa were used as a fluxing agent and a reductant, respectively. The Mn ores, reductant and fluxing agent were delivered to Mintek with a size range of +6–20 mm and were sent to our in-house laboratories to determine the chemical and physical properties. The samples were taken for Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), combustion method (LECO), proximate analysis and quantitative X-ray diffraction (QXRD). A newly designed and constructed pilot facility at Mintek was used in the investigation. The facility included a 1 t/h rotary kiln coupled to an electric arc furnace supplied with an alternating current (AC) with a 300 kVA tap-changer transformer. The main aim of the investigation was to demonstrate the effect of ore pre-heating to 600 °C on the furnace energy consumption and CO/CO₂ emissions. The experimental approach adopted involved feeding Mn ore to establish baseline operating conditions, followed by feeding of Mn ore pre-heated with a rotary kiln to compare operational parameters. The pilot campaign experienced several operational challenges but there were periods of stable operation that enabled data collection for furnace energy consumption and CO/CO₂ emissions. The effect of pre-heating the ore to 600 °C on the SAF energy consumption and CO/CO₂ emissions was demonstrated successfully and revealed that energy savings and reduction in furnace CO₂ emissions is achievable. Pre-heating Mn ore to 600 °C lowered the furnace energy consumption by an average of 22.5% and CO₂ emissions by an average of 37%. The campaign also achieved an overall manganese recovery of 86%. Operating the furnace with hot feed increased the heat losses through the roof by 300% compared to heat losses observed during cold feed. There were also no significant changes in the furnace electrical parameters observed between the two feed modes. Full article

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

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20 pages, 18970 KB

Open AccessArticle

Process Mineralogy Study and Flotation Testwork of a Complex Lead–Gold Rougher Concentrate

by Guomin Chen, Han Zhao, Joe Zhou, Zilong Liu and Hongying Yang

Minerals 2025, 15(9), 967; https://doi.org/10.3390/min15090967 - 12 Sep 2025

Abstract

A lead–gold rougher concentrate was studied to investigate the efficiency of mineral processing. Using process mineralogy as the guiding theory, mineralogical parameters such as chemical composition, mineral composition, mineral particle size, and symbiotic association between minerals were studied in detail. A systematic lead [...] Read more.

A lead–gold rougher concentrate was studied to investigate the efficiency of mineral processing. Using process mineralogy as the guiding theory, mineralogical parameters such as chemical composition, mineral composition, mineral particle size, and symbiotic association between minerals were studied in detail. A systematic lead flotation testwork program was carried out to obtain the optimal flotation and separation conditions, and the products obtained were analyzed. The results show that the concentrate contains a wide variety of minerals with complex material composition, and the lead mineral was mainly galena with a relative content of 3.43% and a particle size −37 μm accounting for 94.72%, while the gold minerals were dominated by electrum. The grades of gold, silver, and lead in the balland obtained through the flotation closed-circuit test were 512.10 g/t, 1632.80 g/t, and 40.38%, and the recoveries were 70.65%, 73.86%, and 75.37%, respectively. The gold lost in the flotation tailings was mainly dominated by gold encapsulated in metal sulfide (accounting for 55.67%), and the lead lost was mainly in gangue and metal oxides (accounting for 62.72%). Full article

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

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17 pages, 7660 KB

Open AccessArticle

Subresolution Porosity Estimation of Porous Rocks from CT Images: Incorporating X-Ray Mass Attenuation Coefficients

by Jianhuang Chen, Zhongjian Zhang, Zhenyu Long, Qiong Zhang and Zhongqi Yue

Minerals 2025, 15(9), 966; https://doi.org/10.3390/min15090966 - 12 Sep 2025

Abstract

Rock porosity is a key parameter for quantifying fluid flow properties and predicting mechanical behaviour. Although X-ray CT imaging has been widely used to estimate porosity, the accuracy of such methods is still hindered by beam energy and mineralogical heterogeneity. In this study, [...] Read more.

Rock porosity is a key parameter for quantifying fluid flow properties and predicting mechanical behaviour. Although X-ray CT imaging has been widely used to estimate porosity, the accuracy of such methods is still hindered by beam energy and mineralogical heterogeneity. In this study, a methodology for the estimation of subresolution porosity is proposed, taking into account the relative relationship of X-ray mass attenuation coefficients (MACs) among minerals. The approach segments macroparticles, matrix, and macropores and calibrates their relative X-ray MAC relationships to establish the upper and lower bounds of the matrix LAC. Subresolution porosity is then estimated based on these calibrated limits. Taking Belgian Fieldstone and Bentheimer Sandstone as examples, the method described in this paper has stronger connectivity than does the binarised porosity estimation method and higher estimation accuracy than does the subresolution porosity calculation method, which does not consider the MAC. The proposed method is intended to refine the rationality of the subresolution porosity calculation and to broaden its theoretical scope of application. Full article

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

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28 pages, 4033 KB

Open AccessArticle

Assessing Jarosite Kinetic Dissolution Rates at Acidic Conditions and Different Temperatures

by Mateus De Souza Buriti, Marie Poulain, Pierre Cézac and Lidia Casás

Minerals 2025, 15(9), 965; https://doi.org/10.3390/min15090965 - 11 Sep 2025

Abstract

K-jarosite (KFe₃(SO₄)₂(OH)₆), the most common jarosite-type mineral in natural and industrial settings, has been widely studied to understand its dissolution behavior in both environmental and industrial contexts. However, reported kinetic data remain inconsistent due to [...] Read more.

K-jarosite (KFe₃(SO₄)₂(OH)₆), the most common jarosite-type mineral in natural and industrial settings, has been widely studied to understand its dissolution behavior in both environmental and industrial contexts. However, reported kinetic data remain inconsistent due to the combined influence of kinetic factors, despite the importance of such data for optimizing system conditions and improving process control and environmental management. The present work aims to help elucidate K-jarosite dissolution by carrying out new experiments in sulfuric acid medium (pH 1 and 2) at different temperatures (296, 323 and 343 K) and using two initial concentrations (0.4 and 1 g of K-jarosite/kg of solution). K-jarosite was synthesized and characterized by analytical techniques (XRD, SEM and BET), and the composition was determined by induction-coupled plasma optical emission spectroscopy (ICP-OES). Derivative (DVKM), Noyes–Whitney (NWKM) and Shrinking Core (SCKM) kinetic models previously used in the literature of jarosite-type compounds were adjusted to the data obtained here and compared. The results showed that higher temperatures and lower pH led to faster dissolution rates. Smaller initial concentrations decreased the rates slightly but had less impact than the other variables. Experiments at pH 1 led to the dissolution of all jarosite solids, while at pH 2 they led to incomplete dissolution. Remarkably, at pH 2 and at higher temperatures (mainly at 343 K), there was slight reprecipitation of the iron. XRD analysis identified no peak other than K-jarosite peaks after dissolution. DVKM and NWKM represented the effect of the studied parameters well. However, only using SCKM was a kinetic equation describing the dissolution process obtained. While the behavior of the kinetic curve is well established, the model fails to correctly describe the induction period. Under extreme conditions (>323 K, pH 1), dissolution is described by a chemical reaction controlling stage and it changes to mass transport in mild conditions. As theoretically expected, the results obtained in this work give important information about the prediction of the behavior of jarosite dissolution in terrestrial environments (acid mine and acid rock drainages) and hydrometallurgical process in mild acidic conditions and high temperatures. Full article

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

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21 pages, 3293 KB

Open AccessArticle

Initial Characterization of Titanium and Vanadium-Rich Magnetite from the Manastir Heights in Southeast Bulgaria Aiming at Future Environmentally Friendly Beneficiation

by Marinela Panayotova, Ivan Dimitrov and Angelika Sofronieva

Minerals 2025, 15(9), 964; https://doi.org/10.3390/min15090964 - 11 Sep 2025

Abstract

Titanium (Ti) and vanadium (V) are metals critical for the sustainable development of our society. Their growing demand and the depletion of ores rich in these metals along with technological development lead to a reconsideration of sources that were previously considered unpromising. The [...] Read more.

Titanium (Ti) and vanadium (V) are metals critical for the sustainable development of our society. Their growing demand and the depletion of ores rich in these metals along with technological development lead to a reconsideration of sources that were previously considered unpromising. The present work is devoted to the study of an iron (Fe) ore from southeastern Bulgaria, containing Ti and V in low but potentially recoverable concentrations. The aim was to check whether it is possible to obtain an iron concentrate containing Ti and V in concentrations comparable to those in similar market products. The material was examined by optical microscopy, XRD, SEM-EDS, and ICP MS. Magnetic separation was applied with and without predating gravity separation. By applying wet gravity beneficiation followed by a low-intensity magnetic field, an iron concentrate (40%–65% Fe) bearing 3%–5% Ti and 0.4%–0.59% V was obtained. Using only a low-intensity magnetic field, without gravity separation, an iron concentrate (59.4% Fe) containing 3.5% Ti and 0.44% V was obtained. Vanadium was extracted in the highly magnetic material, while a significant amount of Ti was left in the weak magnetic fraction. An additional 1.5% may be recovered by applying a high-intensity magnetic field. The main processing challenge appears to be the recovery, without flotation beneficiation, of magnetite that is oxidized to non-magnetic hematite and maghemite. Using magnetic separation (with or without preliminary wet gravity beneficiation) avoids pollution of the processing waste with reagents. Thus, the waste from the beneficiation of the studied type of ore can be used as a soil improver. As a result, the extraction of critical metals using a practically waste-free technology may be achieved. Full article

(This article belongs to the Special Issue Advances in Physical Separation of Gold, Iron Ore and Rare Earth Minerals)

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20 pages, 9171 KB

Open AccessArticle

New Insights into Chromogenic Mechanism and the Genesis of Blue Jadeite from Guatemala

by Yining Liu, Bo Xu, Siyi Zhao, Mengxi Zhao, Zitong Li and Wenxin Hao

Minerals 2025, 15(9), 963; https://doi.org/10.3390/min15090963 - 11 Sep 2025

Abstract

While existing studies on Guatemalan jadeite have predominantly focused on green varieties, the coloration mechanisms and origin of its blue counterparts remain poorly understood. Therefore, the present study provides the first comprehensive investigation of the Guatemalan blue jadeite using an integrated analytical approach, [...] Read more.

While existing studies on Guatemalan jadeite have predominantly focused on green varieties, the coloration mechanisms and origin of its blue counterparts remain poorly understood. Therefore, the present study provides the first comprehensive investigation of the Guatemalan blue jadeite using an integrated analytical approach, which combines Raman spectroscopy, micro X-ray fluorescence (µ-XRF), electron microprobe analysis (EMPA), X-ray diffraction (XRD), UV-Vis spectroscopy, and Cathodoluminescence (CL) imaging on seven representative samples. The results demonstrate that these jadeites consist of two distinct phases: a primary jadeite phase (NaAlSi₂O₆) and a secondary omphacite that form by metasomatic alteration by Mg-Ca-Fe-rich fluids. Spectroscopic analysis reveals that the blue coloration is primarily controlled by Fe³⁺ electronic transitions (with characteristic absorption at 381 nm and 437 nm) coupled with Fe²⁺-Ti⁴⁺ intervalence charge transfer, supported by μ-XRF mapping showing strong Fe-Ti spatial correlation with color intensity. CL imaging documents a multi-stage formation history involving initial high-pressure crystallization (Jd-I) followed by fluid-assisted recrystallization forming Jd-II and omphacite. The detection of CH₄, CO and H₂O in the fluid inclusions by Raman spectroscopy indicates formation in a serpentinization-related reducing environment, while distinct CL zoning patterns confirm a fluid-directed crystallization (P-type) origin. These findings not only clarify the chromogenic processes and petrogenesis of Guatemalan blue jadeite but also establish key diagnostic criteria for its identification, advancing our understanding of fluid-derived jadeite formation in subduction zone environments. Full article

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

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26 pages, 7402 KB

Open AccessArticle

Hybrid Architecture for Tight Sandstone: Automated Mineral Identification and Quantitative Petrology

by Lanfang Dong, Chenxu Sun, Xiaolu Yu, Xinming Zhang, Menglian Chen and Mingyang Xu

Minerals 2025, 15(9), 962; https://doi.org/10.3390/min15090962 - 11 Sep 2025

Abstract

This study proposes an integrated computer vision system for automated petrological analysis of tight sandstone micro-structures. The system combines Zero-Shot Segmentation SAM (Segment Anything Model), Mask R-CNN (Region-Based Convolutional Neural Networks) instance segmentation, and an improved MetaFormer architecture with Cascaded Group Attention (CGA) [...] Read more.

This study proposes an integrated computer vision system for automated petrological analysis of tight sandstone micro-structures. The system combines Zero-Shot Segmentation SAM (Segment Anything Model), Mask R-CNN (Region-Based Convolutional Neural Networks) instance segmentation, and an improved MetaFormer architecture with Cascaded Group Attention (CGA) attention mechanism, together with a parameter analysis module to form a hybrid deep learning system. This enables end-to-end mineral identification and multi-scale structural quantification of granulometric properties, grain contact relationships, and pore networks. The system is validated on proprietary tight sandstone datasets, SMISD (Sandstone Microscopic Image Segmentation Dataset)/SMIRD (Sandstone Microscopic Image Recognition Dataset). It achieves 92.1% mIoU segmentation accuracy and 90.7% mineral recognition accuracy while reducing processing time from more than 30 min to less than 2 min per sample. The system provides standardized reservoir characterization through automated generation of quantitative reports (Excel), analytical images (JPG), and structured data (JSON), demonstrating production-ready efficiency for tight sandstone evaluation. Full article

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

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15 pages, 2807 KB

Open AccessArticle

Investigation of the Coloration Mechanisms of Yellow-Green Nephrite from Ruoqiang (Xinjiang), China

by Boling Huang, Mingxing Yang, Xihan Yang, Xuan Wang, Ting Fang, Hongwei Han and Shoucheng Wang

Minerals 2025, 15(9), 961; https://doi.org/10.3390/min15090961 - 10 Sep 2025

Abstract

This study systematically investigates the color origin and coloration mechanisms of yellow-green nephrite from Ruoqiang, Xinjiang, using multiple analytical techniques including hyperspectral colorimetry, X-ray fluorescence (XRF) spectroscopy, titrimetry, laser ablation inductively coupled plasma–mass spectrometry (LA-ICP-MS), Raman spectroscopy and ultraviolet–visible (UV-Vis) spectroscopy. A pioneering [...] Read more.

This study systematically investigates the color origin and coloration mechanisms of yellow-green nephrite from Ruoqiang, Xinjiang, using multiple analytical techniques including hyperspectral colorimetry, X-ray fluorescence (XRF) spectroscopy, titrimetry, laser ablation inductively coupled plasma–mass spectrometry (LA-ICP-MS), Raman spectroscopy and ultraviolet–visible (UV-Vis) spectroscopy. A pioneering quantitative model (R² = 0.942) was established between hue (H) and the Fe₂O₃ ratio (Fe₂O₃/TFe), revealing that the coloration mechanism is jointly governed by Fe³⁺ charge transfer (300–400 nm absorption band) and Fe²⁺→Fe³⁺ transitions (600–630 nm absorption band). Furthermore, the intensity variation in the 3651 cm⁻¹ Raman peak serves to further confirm the critical role of Fe³⁺ occupancy in the tremolite lattice for color modulation. In combination with the partition patterns of Rare Earth elements (REEs) (right-leaning LREE distribution with negative Eu anomaly) and trace element characteristics, this study supports the classification of Ruoqiang yellow-green nephrite as a high oxygen fugacity magnesian marble-type deposit. In this type of deposit, the ore-forming environment facilitates Fe³⁺ enrichment and yellow-green hue formation. The findings provide new theoretical insights into the chromatic genesis of yellow-green nephrite and hold significant implications for its identification, quality grading, and research on metallogenic mechanisms. Full article

(This article belongs to the Special Issue Gems Under the Microscope: New Insights into Mineral Structures and Properties)

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16 pages, 2262 KB

Open AccessArticle

Geochemistry and Th–U–Total Pb Chemical Ages of Late Variscan Uranium Mineralisation at Shkhara, Greater Caucasus

by Franziska D. H. Wilke, Avtandil Okrostsvaridze, David Bluashvili and Rabi Gabrielashvili

Minerals 2025, 15(9), 960; https://doi.org/10.3390/min15090960 - 9 Sep 2025

Abstract

We present the chemical composition and the U-Pb chemical age of the recently discovered uranium mineralisation occurrence in the crystalline Shkhara Massif in the Greater Caucasus. The mineralisation consists of hydrothermal uraninites from veins that intersect into the Late Variscan biotite–plagioclase-rich granite and [...] Read more.

We present the chemical composition and the U-Pb chemical age of the recently discovered uranium mineralisation occurrence in the crystalline Shkhara Massif in the Greater Caucasus. The mineralisation consists of hydrothermal uraninites from veins that intersect into the Late Variscan biotite–plagioclase-rich granite and migmatites. The chemical composition and the Th–U total Pb chemical age of the uraninites were determined. Results show thorium-rich, (∑LREE/∑HREE)_N unfractionated uraninites that had been formed under higher temperatures above 450 ± 50 °C. Fifty-eight measurements on 14 grains revealed homogeneous and unaltered uraninites. Th–U–total Pb ages of the uraninite were calculated from 55 chemical analyses, among which 37 plot between 275 and 305 Ma. The weighted median age of the 55 data points corresponds to 291 ± 14 Ma: the boundary between the Carboniferous and Permian periods. These dates suggest that uraninite mineralisation is related to the late orogenic extensional process of the Great Caucasus structure. During this process, hydrothermal fluids permeated the biotite-+ and plagioclase-rich magmatic rocks of the Main Range zone and formed U- and Th-rich veins and uraninite mineralisation. This study shows that the Shkhara uranium occurrence correlates with most of the late Variscan uranium deposits in Central and Western Europe in terms of geodynamic setting, composition, age and type of mineralisation. Full article

(This article belongs to the Special Issue Advances in Uranium Metallogenic Theory, Exploration and Exploitation)

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16 pages, 3535 KB

Open AccessArticle

Flotation Behavior and Mechanism of Andalusite and Quartz Under the Sodium Dodecyl Sulfonate System

by Liqiang Lin, Guanfei Zhao, Tingsheng Qiu, Chong Deng, Wenhui Yang and Xiaowen Zhou

Minerals 2025, 15(9), 959; https://doi.org/10.3390/min15090959 - 9 Sep 2025

Abstract

The paper systematically investigated the flotation behavior and interaction mechanisms of andalusite and quartz under sodium dodecyl sulfonate (SDS) through integrated experimental and computational approaches, including zeta potential measurements, Fourier-transform infrared (FTIR) spectroscopy, Materials Studio (MS)-based quantum chemical calculations, and single-mineral flotation tests. [...] Read more.

The paper systematically investigated the flotation behavior and interaction mechanisms of andalusite and quartz under sodium dodecyl sulfonate (SDS) through integrated experimental and computational approaches, including zeta potential measurements, Fourier-transform infrared (FTIR) spectroscopy, Materials Studio (MS)-based quantum chemical calculations, and single-mineral flotation tests. The results of zeta potential and infrared spectroscopy analysis indicated that SDS underwent strong chemical adsorption on the surface of andalusite, while the adsorption effect on the surface of quartz was not obvious. MS calculations showed that the {100} surface energy of andalusite was the lowest, and it was the most important dissociation surface. After SDS was adsorbed on the {100} surface of andalusite, the aluminum atoms on the surface of andalusite lost electrons, resulting in a significant increase in the number of positive charges they carried. The activity of oxygen atoms was enhanced, while the number of charges carried by silicon atoms changed relatively little. It was indicated that SDS adsorbed the active sites of Al atoms on the surface of andalusite. The results of the pure mineral flotation test further verified the accuracy of the previous test results, indicating that andalusite and quartz had a good flotation separation effect under the SDS system. Full article

(This article belongs to the Special Issue Harnessing Surface Chemistry for Enhanced Mineral Recovery)

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10 pages, 790 KB

Open AccessArticle

An Integrated Separation Approach for Beneficiation of Low-Grade Iron Ore

by Mahdi Ostadrahimi, Saeed Farrokhpay, Tooraj Zare, Mohammad Aghajanlou, Khodakaram Gharibi and Mohammad Mahdi Salari Rad

Minerals 2025, 15(9), 958; https://doi.org/10.3390/min15090958 - 8 Sep 2025

Abstract

Iron ore beneficiation is crucial for sustainable utilization of low-grade iron ores. Conventional separation methods often fail to efficiently upgrade the iron ores containing complex mineral phases, such as hematite, goethite, ankerite, and limonite. This study evaluated an integrated roasting–leaching–magnetic separation approach applied [...] Read more.

Iron ore beneficiation is crucial for sustainable utilization of low-grade iron ores. Conventional separation methods often fail to efficiently upgrade the iron ores containing complex mineral phases, such as hematite, goethite, ankerite, and limonite. This study evaluated an integrated roasting–leaching–magnetic separation approach applied to an iron ore. Roasting at 800 °C for 90 min significantly enhanced the Fe(II) content and improved magnetic susceptibility, facilitating superior iron-containing minerals separation efficiency. Furthermore, sulfuric acid leaching effectively eliminated non-magnetic impurities such as calcite, improving iron recovery. Davis tube recovery experiments confirmed that this combination markedly enhanced weight recovery (R_w) and iron recovery (R_g), outperforming traditional methods. The findings highlight the synergistic effect of roasting and leaching for refining iron ores and propose an optimized beneficiation strategy. This approach offers an effective method for processing complex iron ores, particularly those with low Fe grade and challenging impurities, improving beneficiation efficiency and mineral extraction. Full article

(This article belongs to the Special Issue Advances in Physical Separation of Gold, Iron Ore and Rare Earth Minerals)

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15 pages, 2876 KB

Open AccessReview

Permanent Cathode Technologies in Copper Electrowinning: Development and Status

by Kalin Naidoo and Kathryn C. Sole

Minerals 2025, 15(9), 957; https://doi.org/10.3390/min15090957 - 8 Sep 2025

Abstract

The replacement of copper metal starter-sheet cathodes with the use of permanent cathode technology, in which the target metal is plated onto an inert blank template, has enabled significant benefits in the copper electrowinning process. These include the application of significantly higher current [...] Read more.

The replacement of copper metal starter-sheet cathodes with the use of permanent cathode technology, in which the target metal is plated onto an inert blank template, has enabled significant benefits in the copper electrowinning process. These include the application of significantly higher current density, which reduces tankhouse footprint and increases process intensity per unit area; improved operator safety with less reliance on manual electrode handling; and the implementation of process automation and robotics. Cathodes of >99.99% chemical purity and with a smooth and aesthetic surface morphology are consistently produced. This review considers the evolution and development of the permanent cathode process, its commercial adoption across the global copper industry, and the current technology status. Full article

(This article belongs to the Special Issue Innovations in Hydrometallurgy: Traditional and Emerging Approaches for Sustainable Metal Recovery)

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21 pages, 15357 KB

Open AccessArticle

The Fluid Evolution and Metallogenic Processes of the Liba Gold Deposit, West Qinling, China: Insights from the Texture, Trace Elements, and H-O Isotope Geochemistry of Quartz

by Yu Chen, Yuwang Wang, Jianping Wang, Dedong Li, Jian Geng, Jianxiang Luo and Rui Wang

Minerals 2025, 15(9), 956; https://doi.org/10.3390/min15090956 - 8 Sep 2025

Abstract

The evolution of ore-forming fluids in gold precipitation is a key aspect in understanding the genesis of orogenic gold deposits. Traditional fluid inclusion analyses are often limited in revealing the fluid property changes during mineralization, leading to significant debates on the mineralization temperature [...] Read more.

The evolution of ore-forming fluids in gold precipitation is a key aspect in understanding the genesis of orogenic gold deposits. Traditional fluid inclusion analyses are often limited in revealing the fluid property changes during mineralization, leading to significant debates on the mineralization temperature and fluid sources. In this study, we selected the Liba gold deposit in the West Qinling orogen and employed scanning electron microscope–cathodoluminescence (SEM-CL) and laser ablation–inductively coupled plasma mass spectrometry (LA-ICPMS) to analyze the microstructure and trace element characteristics of quartz veins, revealing the multi-stage evolution of ore-forming fluids and the mineralization mechanisms. SEM-CL imaging identified five distinct quartz stages. The pre-mineralization (Qz0) and early-stage mineralization (Qz1) fluids were predominantly magmatic–metamorphic in origin, as indicated by relatively high δ¹⁸O and δD values. During the primary metallogenic (Qz2a, Qz2b) and late-stage mineralization (Qz3), temperatures progressively decreased, and the gradual mixing of meteoric water and formation water was observed, which promoted gold precipitation. And the content of trace elements in post-mineralization quartz (Qz4) is significantly lower and similar to that in the Qz0 stage. Through the analysis of quartz trace elements (e.g., Al/Ti, Ge/Al ratios) and isotope data (δ18O = 8.25‰ to 12.67‰, δD = −119.1‰ to −79.8‰), the results indicate that the Liba gold deposit is a medium- to low-temperature orogenic gold deposit. Furthermore, the gold enrichment process was primarily driven by a hydrothermal system, with variations in the fluid composition during mineralization contributing to the concentration of gold. Full article

(This article belongs to the Section Mineral Deposits)

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27 pages, 3247 KB

Open AccessArticle

Impact of Historical Mining and Metallurgical Technologies on Soil and Sediment Composition Along the Ibar River

by Robert Šajn, Jasminka Alijagić and Trajče Stafilov

Minerals 2025, 15(9), 955; https://doi.org/10.3390/min15090955 - 6 Sep 2025

Abstract

This study systematically investigates soil and stream sediment along the 165 km Ibar River to examine the origin and transfer of pollutants. The research focuses on the environmental impact of long-term mining and irregular waste management, as well as natural enrichment related to [...] Read more.

This study systematically investigates soil and stream sediment along the 165 km Ibar River to examine the origin and transfer of pollutants. The research focuses on the environmental impact of long-term mining and irregular waste management, as well as natural enrichment related to weathering processes. A comprehensive sampling campaign was conducted, collecting 70 samples from 14 locations. At each location, samples of river sediment, floodplain soil (0–5 cm and 20–30 cm depths), and river terrace soil (same depths) were collected. The contents of 21 elements (Ag, Al, As, B, Ba, Ca, Cd, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, Pb, Sr, V, and Zn) were determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). Analysis of Variance (ANOVA) was performed to identify statistically significant differences in element contents between defined zones, sampled materials (river sediments, floodplain soils, and river terrace soils), and sampled soil horizons (topsoil, 0–5 cm, and subsoil, 20–30 cm). Multivariate analysis, including correlation coefficient, cluster analysis, and principal component analysis, revealed two distinct groups of elements with highly significant correlation coefficients (r > 0.7). The first group, comprising Ag, As, Cd, Cu, Mn, and Zn, indicates anthropogenic enrichment, likely resulting from mining and smelting activities in the middle flow of the Ibar River (The Mining and Metallurgical Complex Trepča). The second group, consisting of Cr, Mg, and Ni, suggests enrichment related to the weathering of elements from the ophiolite zone in the lower Ibar River. The study found high enrichment ratios of toxic elements like arsenic, cadmium, lead, and zinc, particularly in stream sediments and floodplains. Notably, arsenic contents exceeded European averages by up to 57 times in stream sediments, posing a significant environmental concern due to its high content. Full article

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

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