Minerals

32 pages, 2465 KB

Open AccessReview

Mineralogy-Guided Processing of Mining and Metallurgical Wastes into Geopolymeric and Alkali-Activated Materials

by Aigerim Imash, Gaukhar Smagulova, Vladimir Efremov, Kaster Kamunur, Lyazzat Mussapyrova, Aisulu Batkal, Ryskul Azhigulova, Aisulu Zhussupova and Anton Kononov

Minerals 2026, 16(9), 936; https://doi.org/10.3390/min16090936 (registering DOI) - 13 Sep 2026

Abstract

Mining and metallurgical wastes contain potentially valuable mineral resources but pose growing environmental risks. This review proposes a mineralogy-guided framework for converting these wastes into low-carbon binders and construction materials. Rather than classifying residues by origin or bulk oxide composition, it distinguishes them [...] Read more.

Mining and metallurgical wastes contain potentially valuable mineral resources but pose growing environmental risks. This review proposes a mineralogy-guided framework for converting these wastes into low-carbon binders and construction materials. Rather than classifying residues by origin or bulk oxide composition, it distinguishes them according to the reaction roles of their mineral phases. The framework first distinguishes self-sufficient systems, in which activation unlocks the intrinsic mineral inventory of the waste sufficiently for matrix or product formation, from mineralogically compensated systems, in which additional functional mineral solids are required to supply deficient reactive Si, Al, Ca, sulfate, alkalinity, or other phase-forming components. Binary and multicomponent formulations are then interpreted according to the specific mineralogical functions supplied by the complementary solids and the resulting changes in reaction pathways and products. Thermal, hydrothermal, mechanochemical, alkaline, and carbonation-based processing routes are compared in relation to phase composition, co-precursor function, and the mechanical, thermal, and service properties of concretes, foams, and backfill materials. Evidence indicates that performance depends more on chemical complementarity than on maximizing waste content. Environmental benefits must also account for contaminant immobilization, carbon dioxide binding, and the energy and reagent demand of pretreatment. Mineralogy-informed machine-learning models may support inverse mixture design, but their transferability remains constrained by feedstock heterogeneity and limited standardized data. The framework links mineralogy, processing, reaction products, performance, and scale-up. Full article

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

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26 pages, 2357 KB

Open AccessArticle

Petrographic Identification from Small-Sample Thin-Section Images Using a Fine-Tuned Vision-Language Contrastive Learning Model

by Tao Zeng, Luyuan Wang, Xiaojie Gao, Lei Ding, Wenjun Wang, Long Tian, Hong Wang and Jiateng Guo

Minerals 2026, 16(9), 937; https://doi.org/10.3390/min16090937 (registering DOI) - 12 Sep 2026

Abstract

Accurate petrographic identification from thin-section images is important for geoscientific analysis but remains strongly dependent on expert interpretation. In this study, we organized 2634 polarized-light images from 324 distinct thin sections representing 108 lithologies and paired them with Chinese petrographic descriptions. Four conventional [...] Read more.

Accurate petrographic identification from thin-section images is important for geoscientific analysis but remains strongly dependent on expert interpretation. In this study, we organized 2634 polarized-light images from 324 distinct thin sections representing 108 lithologies and paired them with Chinese petrographic descriptions. Four conventional vision models were trained as closed-set lithology–classification baselines, and five CN_CLIP variants were fine-tuned for image–text alignment. To prevent overlap of images from the same thin section across outer folds, thin-section-wise three-fold evaluation was performed after excluding eight lithologies represented by fewer than three distinct thin sections; this protocol therefore comprised 2530 images from 311 thin sections and 100 eligible lithologies. At the fixed 20-epoch endpoint, CN_CLIP-ViT-L/14@336px and CN_CLIP-ViT-H/14 showed bidirectional image–text matching accuracies of 81.39 ± 1.97% and 81.31 ± 0.61%, respectively, whereas the conventional classifiers achieved Top-1 accuracies of 50.37%–58.20% under their separate closed-set task. These metrics correspond to different task formulations and are not directly comparable. Under the complementary image-level 8:1:1 protocol, CN_CLIP-ViT-H/14 achieved image-to-text and text-to-image matching accuracies of 93.75% and 93.38%, respectively, on the hold-out test subset. In an inference-stage ablation using the same checkpoint, hold-out test batches, and evaluation protocol, removing only the explicit lithology name reduced these accuracies to 82.72% and 77.21%, indicating that the rock-name token is informative but not the sole source of cross-modal discrimination. Without task-specific retraining, the same CN_CLIP framework also supported constrained lithology, major-mineral, and polarization-mode matching, with best task-specific accuracies of 90.57%, 66.51%, and 86.42%, respectively. Overall, the results support vision-language learning as a flexible framework for expert-assisted petrographic image–text matching on held-out thin sections within the available dataset, while emphasizing source-aware partitioning and cautious interpretation of task-specific accuracies. Full article

(This article belongs to the Topic Big Data and AI for Geoscience)

20 pages, 3494 KB

Open AccessArticle

Mechanical Activation of Vanadiferous Titanomagnetite: Characterization and Microstructural Behavior

by Hajar Atmani, Gervais Soucy, Jocelyn Veilleux, André Gauthier and Kristien Davenport

Minerals 2026, 16(9), 935; https://doi.org/10.3390/min16090935 (registering DOI) - 12 Sep 2026

Abstract

Mechanical activation (MA), an intensive milling process capable of inducing physicochemical changes in solid materials, was applied to a vanadiferous titanomagnetite (VTM) originating from the Lac Doré Complex, Chibougamau, QC, Canada. The objective of this study was to investigate the structural and microstructural [...] Read more.

Mechanical activation (MA), an intensive milling process capable of inducing physicochemical changes in solid materials, was applied to a vanadiferous titanomagnetite (VTM) originating from the Lac Doré Complex, Chibougamau, QC, Canada. The objective of this study was to investigate the structural and microstructural evolution of VTM under intensive milling conditions and the associated changes in particle characteristics, with particular emphasis on X-ray diffraction (XRD) peak intensity and broadening, microstrain, phase composition, particle size, and specific surface area. Mechanical activation was investigated by varying three milling parameters: milling time (5 g powder, 10 Hz, variable milling time), ball-to-powder ratio (variable powder mass, 10 Hz, 15 min), and milling frequency (5 g powder, variable frequency, 15 min). The XRD results reveal significant changes in the diffraction pattern of chamosite, including variations in peak intensity and pronounced peak broadening under the more intensive milling conditions of 5 g powder, 15 Hz, and 15 min. In contrast, the diffraction peaks associated with ilmenite and magnetite became more pronounced, while the calculated microstrain increased. Scanning electron microscopy (SEM) showed substantial changes in particle morphology following mechanical activation. Brunauer–Emmett–Teller (BET) analysis further demonstrated an increase in specific surface area with increasing milling frequency, while laser diffraction measurements revealed systematic variations in particle-size distribution among the three experimental series. Overall, the results demonstrate that mechanical activation produces measurable modifications to the mineralogical, structural, microstructural, and particle characteristics of Lac Doré VTM. These findings provide a basis for further investigation of the relationship between milling-induced structural changes, VTM reactivity, and subsequent metal-extraction performance. Full article

(This article belongs to the Collection Advances in Comminution: From Crushing to Grinding Optimization)

6 pages, 229 KB

Open AccessEditorial

Gravity, Magnetic, and Electromagnetic (GME) Geophysical Data Interpretation for Mineral Exploration and Crustal Structure Investigation—An Overview

by Letian Zhang, Sheng Jin, Zhaoxi Chen and Chengliang Xie

Minerals 2026, 16(9), 934; https://doi.org/10.3390/min16090934 - 11 Sep 2026

Abstract

The growing demand for critical minerals, precious and base metals, industrial minerals, geothermal energy, and other subsurface resources is pushing geophysical exploration toward greater depths and increasingly complex geological settings [...] Full article

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

28 pages, 54036 KB

Open AccessArticle

Fluid Inclusion Constraints on Ore-Forming Fluid Evolution and Cassiterite Precipitation in the Xianglin Sn Polymetallic Deposit, Eastern Himalaya

by Wenpeng Su, Zhi Zhang, Miao Sun, Guotao Ma, Yiyun Wang, Lei Dong and Yi Yang

Minerals 2026, 16(9), 933; https://doi.org/10.3390/min16090933 - 11 Sep 2026

Abstract

The Xianglin Sn polymetallic deposit, located on the northwestern margin of the Cuonadong dome in the eastern Tethyan Himalaya, represents an important Sn-W-Be polymetallic system recently recognized in southern Tibet. This study investigates the nature and evolution of the ore-forming fluids and the [...] Read more.

The Xianglin Sn polymetallic deposit, located on the northwestern margin of the Cuonadong dome in the eastern Tethyan Himalaya, represents an important Sn-W-Be polymetallic system recently recognized in southern Tibet. This study investigates the nature and evolution of the ore-forming fluids and the mechanisms of cassiterite precipitation. Fluid inclusion petrography, microthermometry, and laser Raman spectroscopy were applied to inclusions from the cassiterite–sulfide, proximal cassiterite–quartz vein, distal cassiterite–quartz vein, and late fluorite–quartz vein stages. The fluid inclusions mainly comprise liquid-rich, vapor-rich, H₂O-CO₂ three-phase, and minor daughter-mineral-bearing inclusions. The cassiterite–sulfide stage contains the most complex inclusion assemblage, with homogenization temperatures of 326–399 °C and salinities of 2.4–10.5 wt.% NaCl equiv. The proximal cassiterite–quartz vein stage yields homogenization temperatures of 280–361 °C and salinities of 2.4–9.6 wt.% NaCl equiv., whereas the distal cassiterite–quartz vein stage records lower temperatures of 195–295 °C. The fluorite–quartz vein stage is characterized by low-temperature and low-salinity fluids. Raman spectra identify CO₂, N₂, CH₄, H₂S, and CaCO₃ daughter minerals, indicating a volatile-rich, relatively reduced H₂O-CO₂-NaCl hydrothermal system. These features suggest that the principal ore-forming fluids were dominantly magmatic–hydrothermal fluids exsolved from highly fractionated Miocene leucogranites. During upward and outward migration from the main detachment zone to peripheral fractures, the fluids experienced boiling, cooling, mixing, and multistage hydrothermal overprinting. Cassiterite precipitation during the cassiterite–sulfide stage was mainly triggered by boiling or phase separation, whereas the proximal cassiterite–quartz veins were controlled by progressive cooling and local phase separation. In contrast, distal cassiterite precipitation was more strongly influenced by fluid mixing and cooling. These results indicate that the Xianglin deposit records a structurally controlled proximal-to-distal magmatic–hydrothermal Sn mineralizing system related to the Cuonadong dome. Full article

(This article belongs to the Special Issue Mineralogy, Geochemistry and Geochronology of W-Sn Polymetallic Deposits, 2nd Edition)

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21 pages, 63147 KB

Open AccessArticle

Color Genesis and Formation Process of Green Quartzite Jade “Shetaicui” from Inner Mongolia

by Xibei Zhang, Yue Li, Zixuan Wang, Shanwen Zheng and Feng Bai

Minerals 2026, 16(9), 932; https://doi.org/10.3390/min16090932 - 11 Sep 2026

Abstract

“Shetaicui” is a distinctive quartzite jade from the Dashetai area of Inner Mongolia. Its green variety has attracted considerable academic attention because of its characteristic color and relatively high economic value, yet its color genesis and formation process remain poorly understood. Here, green [...] Read more.

“Shetaicui” is a distinctive quartzite jade from the Dashetai area of Inner Mongolia. Its green variety has attracted considerable academic attention because of its characteristic color and relatively high economic value, yet its color genesis and formation process remain poorly understood. Here, green “Shetaicui” was examined by petrographic observation, infrared and Raman spectroscopy, ultraviolet–visible (UV–Vis) absorption spectroscopy, colorimetric measurements, X-ray fluorescence spectroscopy (XRF), and electron probe microanalysis (EPMA). These methods were used to characterize its mineral composition and textures and investigate its color genesis and formation process. The results show that the jade is a fine-grained muscovite quartzite, whereas the wall rock is a fine-grained chlorite–quartz–muscovite schist. Coloration is mainly associated with Cr-bearing muscovite. Cr is the principal chromogenic element, whereas Fe contributes to coloration to a lesser extent. Pearson correlation analysis and multiple linear regression show that Cr₂O₃ is most strongly correlated with a* and C*, whereas FeO^T is most strongly correlated with L* and shows a weaker positive correlation with b*. Petrographic textures and mineral assemblages indicate that the jade and its wall rock underwent regional metamorphism broadly consistent with greenschist-facies conditions. Formation proceeded through three stages: sedimentary protolith formation, regional metamorphism, and jade formation during late fluid alteration. During regional metamorphism, quartz-rich sandy horizons formed a Qtz I-dominated pre-jade quartzite, whereas muddy horizons formed the chlorite–quartz–muscovite schist wall rock. Subsequent fluid alteration led to the formation of Cr-bearing muscovite and Qtz II within the pre-jade quartzite. Cr-bearing muscovite imparted the characteristic green coloration, completing the transformation of the pre-jade quartzite into “Shetaicui” jade. These results clarify the correlations between chromogenic elements and colorimetric parameters in green “Shetaicui” and provide petrographic and mineralogical evidence for this three-stage formation process. Full article

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

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27 pages, 4418 KB

Open AccessArticle

Battery and Base Metals in Chilean Copper Mine Tailings: A National Screening of Cobalt, Nickel and Copper from Public Geochemical Data

by Brian Keith-Norambuena, Elizabeth Lam-Esquenazi, Ítalo Montofré-Bacigalupo, Rodrigo Rojas-Ardiles, Angélica Flores-Bustos, Carolina Flores-Bustos and Fernando Álvarez-Castillo

Minerals 2026, 16(9), 931; https://doi.org/10.3390/min16090931 - 11 Sep 2026

Abstract

Chile, the world’s leading copper producer, accumulates hundreds of tailings deposits whose battery metals were never a recovery target. We screened cobalt, nickel and residual copper across the national tailings inventory using the public geochemical survey of the Chilean National Geology and Mining [...] Read more.

Chile, the world’s leading copper producer, accumulates hundreds of tailings deposits whose battery metals were never a recovery target. We screened cobalt, nickel and residual copper across the national tailings inventory using the public geochemical survey of the Chilean National Geology and Mining Service (SERNAGEOMIN, ∼2100 surface samples), deriving representative compositions for 649 deposits integrated with the October 2025 cadastre. Each metal returns a different answer. Residual copper is ubiquitous (median 0.15%, above 0.2% in 260 deposits) and its indicative endowment of ∼24 Mt, where the impoundments are counted at their authorised capacity, or ∼20 Mt on the tonnage actually deposited, over 90% of it in twenty impoundments above 100 Mt, is the most robust target. Cobalt sits just below crustal abundance (median 14 g/t) but shows an enriched tail: 104 deposits exceed twice the crustal reference, up to 1080 g/t, concentrated in small, old deposits. A discontinuity in the source release splits the nickel determinations into two segments with medians of 70 and 7.9 g/t; chromium, vanadium and a regional soil background all place the lower segment on the rock, so nickel is reported over its 304 deposits, at a median of 7.9 g/t, one sixth of the crustal reference. Cu, Co and Ni are uncorrelated at the deposit level (

ρ \leq 0.13

), so surface geochemistry gives a plant no signal on which to base joint recovery. A comparison of surface against depth over twelve paired deposits also differs by metal: copper ordering is preserved, while the same twelve pairs are too few to resolve whether surface cobalt orders the interior. Assessing the battery metals of these tailings, therefore, requires sampling at depth, and the screening names the deposits where that campaign should start. Full article

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

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16 pages, 2867 KB

Open AccessFeature PaperArticle

Bioleaching Rare Earth Elements from Abandoned Coal Mine Drainage as an Unconventional Feedstock for Biomining

by Anna Vietmeier, Meghan Beebe, Samuel Flett, Nancy Trun and Djuna Gulliver

Minerals 2026, 16(9), 930; https://doi.org/10.3390/min16090930 - 11 Sep 2026

Abstract

Abandoned coal-mine drainage (CMD) is a domestic source of rare earth elements (REEs) that can be biomined. Pennsylvania has ~11,000 abandoned mines, with ~500 CMD passive remediation systems (PRSs). REEs found in CMD accumulate as solid precipitants in PRSs. Microbial biogeochemical manganese (Mn) [...] Read more.

Abandoned coal-mine drainage (CMD) is a domestic source of rare earth elements (REEs) that can be biomined. Pennsylvania has ~11,000 abandoned mines, with ~500 CMD passive remediation systems (PRSs). REEs found in CMD accumulate as solid precipitants in PRSs. Microbial biogeochemical manganese (Mn) resolubilization could co-resolubilize REEs, producing an affordable and valuable leachate. However, microbial mechanisms that contribute to REE resolubilization are poorly understood. We have previously isolated six acidogenic bacteria (four Bacillus spp. and two Corynebacterium spp.) that solubilize Mn oxide. Here, we determined all acidogenic isolates can solubilize Mn from Glasgow CMD solids, and that B. mycoides JR07 and B. pseudomycoides KB7 can solubilize (bioleach) REEs from four REE-enriched acidic CMD PRSs (Glasgow, Scootac, Sterrett, Kentucky Hollow). Successful REE bioleaching by B. mycoides JR07 and B. pseudomycoides KB7 is likely due to lactic acid production, interactions with CMD solids, and biofilm formation. We found that aluminum (Al) solubilization is a better indicator of CMD REE release than Mn. Determining the microbial metabolism and genes involved in the release of REEs from CMD solids is crucial to optimizing biomining. Our work addresses the growing need to develop novel REE recovery methods from unconventional domestic sources. Full article

(This article belongs to the Special Issue Critical Minerals and Associated Elements in Mine Effluent and Treatment Residuals: Management Strategies and Technologies for Resource Recovery)

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Graphical abstract

30 pages, 24060 KB

Open AccessArticle

Soil Geochemical Characterization Associated with Fe–Cu Mineralization (Northeastern Aksaray, Türkiye) Using Geochemical Anomaly Classification and Multivariate Statistical Analyses

by Mustafa Haydar Terzi and Emre Turfan

Minerals 2026, 16(9), 929; https://doi.org/10.3390/min16090929 - 10 Sep 2026

Abstract

This study investigated the soil geochemistry associated with magnetite-bearing Fe–Cu mineralization in northeastern Aksaray (Türkiye). Reservoir normalization, threshold-based geochemical anomaly classification, and multivariate statistical analyses were combined to evaluate the effects of parent lithology, weathering, and mineralization. Reservoir normalization analysis showed pronounced Cu [...] Read more.

This study investigated the soil geochemistry associated with magnetite-bearing Fe–Cu mineralization in northeastern Aksaray (Türkiye). Reservoir normalization, threshold-based geochemical anomaly classification, and multivariate statistical analyses were combined to evaluate the effects of parent lithology, weathering, and mineralization. Reservoir normalization analysis showed pronounced Cu enrichment, together with high geochemical variability, suggesting an influence beyond lithological inheritance alone. The depletion of relatively mobile components and the variable behavior of S further suggested modification of primary geochemical signatures during weathering. Threshold-based anomaly classification showed that positive Cu and Zn anomalies are closely associated with the known Fe–Cu mineralization zones, whereas Fe₂O₃, Co, and V anomalies primarily reflect basaltic parent rocks and the positive Zr anomaly reflects felsic lithological influence. The multivariate statistical analyses, including correlation analysis (CA), hierarchical cluster analysis (HCA), and principal component analysis (PCA), revealed coherent geochemical associations corresponding to basaltic parent rocks, felsic lithologies, and mineralization-related element assemblages. PCA resolved three principal components reflecting a mafic–felsic lithological contrast (PC1), the survey-scale compositional variability in the As–Pb–Rb–Zr association (PC2), and a Cu–Zn–S mineralization-related signature (PC3). Overall, the results indicate that soil geochemical patterns reflect the overlapping influences of parent lithology, weathering, and Fe–Cu mineralization, emphasizing the importance of local geological background and lithological variability in geochemical anomaly interpretation. Full article

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

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27 pages, 40824 KB

Open AccessArticle

Evaluating the Durability of Afyon–İscehisar Marbles Against Salt Mist: A Mineralogical, Petrographic, and Physical Perspective

by Metin Bağcı and Sevgi Çetintaş

Minerals 2026, 16(9), 928; https://doi.org/10.3390/min16090928 - 10 Sep 2026

Abstract

Degradation processes forming as a result of direct and indirect environmental interactions with soluble salts are important for the structural material of marble and in geotechnical applications. This is necessary, not only to identify the source and describe the material, but also to [...] Read more.

Degradation processes forming as a result of direct and indirect environmental interactions with soluble salts are important for the structural material of marble and in geotechnical applications. This is necessary, not only to identify the source and describe the material, but also to ensure the sustainability of artifacts and to be able to provide appropriate material for preservation and restoration. In this study, the durability of Afyon–İscehisar marbles (calcitic and dolomitic) to cyclic salt mist was investigated in a laboratory environment by considering weight, color, and ultrasonic pulse velocity values. Additionally, comprehensive experiments including mineralogical and petrographic investigations (polarizing microscope, X-ray diffractometry, scanning electron microscope (SEM/EDX), geochemical investigations, and physical and mechanical tests) were performed to evaluate the durability against the effect of salt mist. The results show that the calcite content in the calcitic marbles varied from 96% to 99%, while the dolomite content in the dolomitic marbles reached 64%–74%, in line with microscopic and semi-quantitative XRD analyses and geochemical investigations. The calcitic–dolomitic differentiation was tightly controlled by the magnesium (Mg) content. With the effect of salt mist, the samples had negligible weight changes (0.02% in the KH sample) and there was no significant material loss in any of the groups. For color analyses, total color differences (ΔE) in the KH and MN samples reached 4.39 and 4.06, respectively, and exceeded the human perception threshold. The dolomitic KS and PB samples and calcitic KP sample had increases identified for ultrasonic pulse velocity. Contrary to this, the GR (calcitic) sample was found to have a 15.15% reduction in ultrasonic pulse velocity. These findings provide critical selection, performance prediction and preservation criteria for Afyon–İscehisar marbles in both modern structural engineering applications and in archeological studies. Full article

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

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15 pages, 6107 KB

Open AccessArticle

ZirconMelt-H₂O–fO₂: Integrated Software for Estimating Magmatic Water Content and Oxygen Fugacity from Zircon Trace-Element Data

by Zongjing Zhang, Wei Ding, Bing Zhao and Liyan Ma

Minerals 2026, 16(9), 927; https://doi.org/10.3390/min16090927 - 10 Sep 2026

Abstract

Magmatic oxygen fugacity (fO₂) and dissolved H₂O content are fundamental physicochemical parameters governing redox conditions, volatile behavior, mineral stability, and multivalent-element partitioning during magma evolution. Analysis of magmatic fO₂ and H₂O helps constrain magma differentiation, volatile [...] Read more.

Magmatic oxygen fugacity (fO₂) and dissolved H₂O content are fundamental physicochemical parameters governing redox conditions, volatile behavior, mineral stability, and multivalent-element partitioning during magma evolution. Analysis of magmatic fO₂ and H₂O helps constrain magma differentiation, volatile evolution, and magmatic–hydrothermal processes. ZirconMelt-H₂O–fO₂ was developed to calculate these parameters from zircon trace-element data paired with user-provided melt compositions or user-designated representative whole-rock proxies, using LREE-I-assisted data review, Ti-in-zircon thermometry, Ce–U–Ti oxybarometry, lattice-strain fitting for melt Ce⁴⁺/Ce³⁺ estimation, NBO/T calculation, and H₂O inversion. The graphical interface is available in English and Simplified Chinese and supports batch import and sample-identifier matching of CSV and Excel datasets, user confirmation of calculation settings, export of results to Excel, CSV, and JSON, and generation of standardized plots in SVG, PDF, and PNG formats. Full article

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

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22 pages, 3876 KB

Open AccessArticle

Quenched Inclusions in Uralian-Alaskan Placer Pt-Fe Nuggets, Ecuador: Rare Cu-PGM Telluride-Sulfide Parageneses

by B. Jane Barron, Lawrence Barron and Karsten Goemann

Minerals 2026, 16(9), 926; https://doi.org/10.3390/min16090926 - 9 Sep 2026

Abstract

PGM (platinum-group mineral) melt inclusions set in two Pt-Fe alloy nuggets are from the Camumbi River placer, Ecuador. Inclusion bulk compositions are strongly fractionated, mutually exsolved melts Pt–Rh–Pd–Cu > Fe–Ni sulfide-rich and Pt–Cu–Rh ≈ Pd > Fe–Ni telluride-rich respectively, with metal/ligand ratios ~1. [...] Read more.

PGM (platinum-group mineral) melt inclusions set in two Pt-Fe alloy nuggets are from the Camumbi River placer, Ecuador. Inclusion bulk compositions are strongly fractionated, mutually exsolved melts Pt–Rh–Pd–Cu > Fe–Ni sulfide-rich and Pt–Cu–Rh ≈ Pd > Fe–Ni telluride-rich respectively, with metal/ligand ratios ~1. They are related to a higher T melt inclusion bulk composition Fe–Cu–Pt >>> Pd > Rh–S also a monosulfide. We use increasing Me/S,Te mineral ratios of inclusion PGM to define each inclusion PGM paragenesis. In the S-rich inclusion, skeletal cuprorhodsite crystallized first with co-exsolved Pt-Fe alloy upon cooling. Next crystallized are braggite, vysotskite, Pt-Fe alloy and oosterboschite. Last crystallized minerals are phase (Pd,Pt)₃(S,Se,Te)₂ and keithconnite (similar synthetic phases are stable at ~350 °C). Within the Te-rich S-bearing inclusion, cooperite first crystallized at high T (~1100 °C) from a subordinate, exsolved S-rich melt. The co-exsolved Te-rich melt next crystallized rare interstitial PGM Rh-bearing mitrofanovite, Rh-bearing moncheite, Rh-bearing monchetundraite, hongshiite, and six minor PGM. Experimental mitrofanovite and moncheite are stable at high T while monchetundraite is stable ~350 °C. We suggest that Rh-bearing mitrofanovite and Rh-bearing monchetundraite could form separate solid solution series with variable Pt–Rh and Ni–Rh respectively. Rh-bearing moncheite indicates a solid solution series with end-member UM (unnamed mineral) Rh(Te,Bi)₂ reported from Ethiopia. Six minor PGMs with extreme compositions are identified by phase mapping using pixel counts combined with BSE (backscattered electron) images. They are stable at lower T hydrothermal conditions and compare with pyrrhotite and pentlandite breakdown products of high T experimental MSS (monosufide solid solution). We suggest the inclusions represent decompression melts formed in the apices of ascending unknown Alaskan–Uralian-type intrusion(s)/volcanics within the Cretaceous Naranjal accreted arc terrane. The melt inclusions are late-formed in the long-fractionating history of this previously defined ore system, and lack detectable As, Sb and Bi suggesting exsolution of higher temperature melts. Full article

(This article belongs to the Special Issue Platinum-Group Elements, Chromium and Nickel in Ultrabasic-Basic Complexes: New Results)

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14 pages, 24388 KB

Open AccessArticle

Fluorapatite from Pegmatites of the Oxford Pegmatite Field, Maine—Chemistry, Color and Morphology

by Alexander U. Falster, William B. Simmons, Karen L. Webber and Encarnación Roda-Robles

Minerals 2026, 16(9), 925; https://doi.org/10.3390/min16090925 - 9 Sep 2026

Abstract

Apatite is widespread in pegmatites in the Oxford Pegmatite Field and is dominantly fluorapatite. Hydroxylapatite does occur but is rare. Carbonate-rich fluorapatite occurs as a partial replacement of beryllonite. True chlorapatite does not occur, but some fluorapatites contain a small amount of chloride. [...] Read more.

Apatite is widespread in pegmatites in the Oxford Pegmatite Field and is dominantly fluorapatite. Hydroxylapatite does occur but is rare. Carbonate-rich fluorapatite occurs as a partial replacement of beryllonite. True chlorapatite does not occur, but some fluorapatites contain a small amount of chloride. Apatite occurs throughout the pegmatites, both in the massive pegmatite as grains and as well-formed crystals in primary and secondary miarolitic cavities and in small interstitial voids. A correlation between color, crystal forms and composition, mainly with respect to Mn and Fe, has been observed. We focused on apatite in miarolitic cavities in these pegmatites and, notably, the well-studied Emmons pegmatite. The goal of the study was to demonstrate that a relationship exists among composition, color and morphology. Full article

(This article belongs to the Special Issue Geochemistry, Petrogenesis and Exploration of Li-Rich Granite-Pegmatite Systems)

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19 pages, 19714 KB

Open AccessPerspective

Splinter Tectonics and the Reworking of Forearc Crust in Timor, Indonesia

by Michael Earle

Minerals 2026, 16(9), 924; https://doi.org/10.3390/min16090924 - 8 Sep 2026

Abstract

Timor is situated in the Lesser Sunda chain of islands in the non-volcanic outer Banda Arc of the Australia–Southeast Asia orogen. Diachronous collision of the irregular passive margin of Australia with the detached margin of SE Asia in the Miocene produced an assemblage [...] Read more.

Timor is situated in the Lesser Sunda chain of islands in the non-volcanic outer Banda Arc of the Australia–Southeast Asia orogen. Diachronous collision of the irregular passive margin of Australia with the detached margin of SE Asia in the Miocene produced an assemblage of nappes, mélanges and metamorphic terranes that characterise the complex geology of Timor. This article has been developed from a keynote presentation delivered at the 6th International Geoscience Conference of the Institute of Geosciences of Timor-Leste (IGTL), held in Dili in February 2026. In keeping with that format, the paper is a synthesis and interpretive review of Timor’s metamorphic terranes, and a fuller explanation of the concept of ‘splinter tectonics’ that was introduced. Field, petrographic and geochemical evidence show that the unique features of the Boi metamorphic massif on West Timor can be explained by a process whereby blocks and slices of deeply buried upper-plate crust were dragged down adjacent to the subduction channel, and juxtaposed against hot forearc mantle before being tectonically exhumed. The Boi Massif is therefore interpreted as a case study that provides new insights into the tectonic evolution of the Banda Arc and possible processes operating within convergent margin systems elsewhere. Full article

(This article belongs to the Special Issue Geosciences in the Banda Arc Region: Resources, Hazards and Sustainable Development)

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47 pages, 14942 KB

Open AccessArticle

A Precambrian Rare-Metal Granite Dike as a Natural Experiment: Constraints on Extraction and Quenching at the Melt-Hydrothermal Transition (Salmi Batholith, Karelia, Russia)

by Artem A. Konyshev, Yana O. Alferyeva, Ekatherina N. Sokolova and Vasily D. Shcherbakov

Minerals 2026, 16(9), 923; https://doi.org/10.3390/min16090923 - 7 Sep 2026

Abstract

This work is devoted to the investigation of rare-metal granites associated with anorthosite–rapakivi granite rock complexes. This article evaluates the physicochemical conditions that governed the formation of a rare-metal granite dike. It also explores assumptions regarding the geological characteristics of the magmatic chamber, [...] Read more.

This work is devoted to the investigation of rare-metal granites associated with anorthosite–rapakivi granite rock complexes. This article evaluates the physicochemical conditions that governed the formation of a rare-metal granite dike. It also explores assumptions regarding the geological characteristics of the magmatic chamber, describes evidence for liquid immiscibility, and addresses the post-entrapment evolution of hydrosilicate liquids. In addition, new mineralogical data are presented. The methods employed include optical and electron microscopy, Raman spectroscopy, secondary ion mass spectrometry, laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS), melt inclusion homogenisation experiments, and fluid inclusion study. The investigated granitic dike formed under low pressure (60–110 MPa) and temperatures of about 580–600 °C, from a specific volatile-saturated magma rich in H₂O (up to 16.76 wt% in quenched hydrosilicate liquid products) and in F (up to 4.16 wt%) and Li (up to 3804 ppm), as indicated by homogenised melt inclusions. At the time of emplacement, a silicate melt, a probable Ca-fluoride melt, an Mg-Fe Al-Si-rich hydrosilicate liquid (either mutually soluble with or mixed with the inferred Ca-fluoride melt), and an essentially aqueous fluid coexisted. Depolymerisation of the silicate melt and the presence of complex ions probably promoted the dissolution and transport of high field strength elements (HFSE) and large ion lithophile elements (LILE) elements by the Mg-Fe Al-Si-rich hydrosilicate liquid. During the final stage of evolution of the granitic magmatic system, Mg behaved incompatibly because of its negligible partitioning into mica; rather than accumulating in the silicate melt, it entered the hydrosilicate liquid as a major component. The residual silicate melt consequently attained even lower Zr/Hf, Nb/Ta, and Y/Ho ratios than the studied rock. Full article

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

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25 pages, 6659 KB

Open AccessArticle

Comparative Mineralogical Characterization and Metal Leaching Behavior of Phosphogypsum Produced by Hemihydrate–Dihydrate and Dihydrate Processes

by Si Yang, Meilun Zhang, Wen Fang, Zhiguo Zhang, Yuefei Zhang, Jin Lv and Nan Yang

Minerals 2026, 16(9), 922; https://doi.org/10.3390/min16090922 - 7 Sep 2026

Abstract

Phosphogypsum (PG) produced by different wet-process phosphoric acid routes exhibits distinct mineralogical characteristics and metal ion release behaviors, which may influence its environmental risk and resource utilization potential. In this study, PG generated from the hemihydrate–dihydrate (HH-DH) and dihydrate (DH) processes was systematically [...] Read more.

Phosphogypsum (PG) produced by different wet-process phosphoric acid routes exhibits distinct mineralogical characteristics and metal ion release behaviors, which may influence its environmental risk and resource utilization potential. In this study, PG generated from the hemihydrate–dihydrate (HH-DH) and dihydrate (DH) processes was systematically investigated to elucidate the occurrence states, distribution characteristics, and leaching behavior of metal ions. Particle size distribution analysis, water-leaching experiments, Advanced Mineral Identification and Characterization System (AMICS), and Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) were employed to characterize the particle size distribution, mineral composition, elemental distribution, and mineral liberation behavior before and after leaching. The results showed that gypsum was the dominant mineral phase, while quartz and phosphorus-containing gypsum (PCG) were the major impurity minerals. K and Na mainly occurred in soluble mineral phases and exhibited high leaching rates, whereas Al, Fe, and Mg were primarily associated with relatively stable insoluble minerals and showed limited leaching behavior. After water leaching, the particle size distribution shifted toward finer particles, accompanied by decreases in gypsum content and mineral liberation degree, especially in HH-DH phosphogypsum. Significant differences in mineral association, metal occurrence states, and ion release behavior were observed between HH-DH and DH phosphogypsum. These findings provide a mineralogical basis for impurity removal, water washing pretreatment, environmental risk control, and the resource utilization of phosphogypsum. Full article

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

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24 pages, 11214 KB

Open AccessArticle

Sulfuric Acid Leaching of Zn, Cu, and Fe from Mechanically Treated Zinc Metallurgical Waste: Apparent Kinetics of Zn Dissolution

by Akmaral Duisen, Galymzhan Karamyrzayev, Timur Osserov, Lyazzat Mussapyrova, Aisulu Batkal, Aslan Akberliyev, Ryskul Azhigulova, Luisa Beisembayeva and Kaster Kamunur

Minerals 2026, 16(9), 921; https://doi.org/10.3390/min16090921 - 7 Sep 2026

Abstract

This work investigated the extraction behavior of Zn, Cu, and Fe during sulfuric acid leaching of metallurgical waste from the Ust-Kamenogorsk zinc production plant. At the same time, the detailed kinetic analysis was restricted to Zn dissolution. This study aimed to determine the [...] Read more.

This work investigated the extraction behavior of Zn, Cu, and Fe during sulfuric acid leaching of metallurgical waste from the Ust-Kamenogorsk zinc production plant. At the same time, the detailed kinetic analysis was restricted to Zn dissolution. This study aimed to determine the structural and morphological characteristics of metallurgical wastes and the extraction efficiencies of Zn, Cu, and Fe, and to evaluate the apparent kinetics of Zn dissolution comparatively. The phase composition of the initial and mechanically treated samples was studied by X-ray diffraction analysis, functional groups by FTIR spectroscopy, and morphological features by scanning electron microscopy. Leaching experiments were conducted to assess the effect of sulfuric acid concentration, temperature, and process duration. The results showed that mechanical treatment produced qualitative morphological and structural changes in the slag and was accompanied by improved extraction of Zn, Cu, and Fe during sulfuric acid leaching. The extraction behavior depended on the experimental variable investigated. In the sulfuric acid concentration series, extraction from the mechanically treated sample reached 70.55 ± 0.88% for Zn, 90.50 ± 0.47% for Cu, and 42.37 ± 0.47% for Fe at 1.0 M H₂SO₄. In the leaching time series conducted at 1.0 M H₂SO₄ and 75 °C, Zn extraction reached 78.06 ± 0.92% at 120 min after mechanical treatment, whereas Cu extraction reached its maximum of 90.78 ± 0.55% at 60 min. The time-dependent extraction behavior differed among the investigated metals, and no single leaching time maximized Zn, Cu, and Fe extraction simultaneously. Comparative analysis using Shrinking Core Model expressions indicated that both surface-reaction and product-layer-diffusion expressions provided comparable descriptions of the Zn leaching data; however, the limited number of kinetic data points does not allow definitive identification of a unique rate-controlling mechanism. For Zn dissolution, the apparent activation energies were 8.16 and 10.17 kJ mol⁻¹ for the surface chemical reaction expression and 14.37 and 17.81 kJ mol⁻¹ for the product-layer diffusion expression before and after mechanical treatment, respectively. A conceptual leaching pathway based on the available experimental observations was proposed to relate the observed structural and morphological changes to Zn extraction and the formation of a gypsum-containing solid residue. The results indicate that mechanical treatment is a promising pretreatment approach for improving the hydrometallurgical processing of the investigated metallurgical waste under the tested conditions. Full article

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

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25 pages, 4170 KB

Open AccessArticle

Hidden Sources of Bias in Mineral Resource Databases: Common Issues and Consequences

by Celeste Wilson, Kristin Chislett and Camilla da Silva

Minerals 2026, 16(9), 920; https://doi.org/10.3390/min16090920 - 7 Sep 2026

Abstract

Poorly governed geoscience databases introduce subtle but systematic biases that propagate through mineral resource estimation workflows, distorting grade continuity and resource classification. While the importance of data quality in mining is widely acknowledged, quantitative demonstrations of how specific data management decisions translate into [...] Read more.

Poorly governed geoscience databases introduce subtle but systematic biases that propagate through mineral resource estimation workflows, distorting grade continuity and resource classification. While the importance of data quality in mining is widely acknowledged, quantitative demonstrations of how specific data management decisions translate into downstream technical and economic impacts remain limited. This study addresses that gap through three case studies derived from real-world industry examples. The first case study quantifies operator-dependent data extraction bias by comparing two independently generated datasets sourced from the same database on the same day. Despite nominal equivalence, the datasets differed materially in record counts and grade distributions, producing only negligible global volumetric differences (~0.1%) but up to ~5% local geometric variability and a 19.5% difference in estimated copper grade, resulting in a ~36% divergence in projected revenue. The second case study evaluates analytical uncertainty near detection limits using duplicate assay pairs, demonstrating that relative error increases markedly at low concentrations and that this behavior reflects inherent analytical limitations rather than laboratory non-compliance. The third case study examines the common practice of assigning detection limit placeholder values to unassayed intervals, showing that such substitutions can artificially generate ore in barren domains, whereas retaining null values and applying assignments during post-processing yields geologically and statistically coherent results. Collectively, these case studies demonstrate that hidden data biases can exert a stronger influence on resource outcomes than estimation methodology alone. The results highlight the need for standardized extraction workflows, explicit treatment of low-grade uncertainty, and validation practices that extend beyond global reconciliation metrics. Robust data governance and transparent, reproducible workflows are essential to reducing compounding uncertainty and improving confidence in mineral resource models. All datasets have been anonymized, scaled, or modified to prevent identification of any specific project, company, or operation. No confidential or proprietary datasets are disclosed. Full article

(This article belongs to the Special Issue Digital Exploration and Assessment of Mineral Resources: Theories, Methods and Achievements, 2nd Edition)

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18 pages, 2493 KB

Open AccessArticle

Efficient Enrichment of Ultra-Low-Grade Associated Tantalum–Niobium Ore via Sodium Silicate Pre-Dispersion Combined with Gravity Separation: Mechanism and Performance

by Lei Wang, Guocheng Yao, Xinyue Shi, He Shang, Hongxia Li and Meilin Liu

Minerals 2026, 16(9), 919; https://doi.org/10.3390/min16090919 - 6 Sep 2026

Abstract

Tantalum and niobium are critical strategic rare refractory metals; however, most associated tantalum–niobium resources are characterized by ultra-low grade, finely disseminated grains, and severe argillization, which causes pronounced slime coating of gangue mica on valuable mineral surfaces and impedes efficient recovery via gravity [...] Read more.

Tantalum and niobium are critical strategic rare refractory metals; however, most associated tantalum–niobium resources are characterized by ultra-low grade, finely disseminated grains, and severe argillization, which causes pronounced slime coating of gangue mica on valuable mineral surfaces and impedes efficient recovery via gravity separation. In this study, an innovative beneficiation route combining sodium silicate pre-dispersion conditioning with shaking-table gravity separation was proposed to recover a spodumene-dominant pegmatitic lithium ore containing trace associated Nb–Ta minerals, with mica as the major slime-forming gangue. Process mineralogy analysis revealed that the raw ore has a total (Nb,Ta)₂O₅ grade of only 0.019%, with the main valuable minerals being columbite-(Mn), columbite–tantalite, and tantalite, whereas layered mica minerals constitute the primary argillization gangue that readily generates micro-fine slimes smaller than 5 μm. Single-factor tests demonstrated that the optimal grinding fineness was 84.4% passing 200 mesh, and the optimal feed pulp density for gravity separation was 28.6%. Adjusting pulp concentration alone, without a dispersant, yielded a Nb₂O₅ concentrate grade of merely 0.144%, as severe slime coating greatly limited separation selectivity. Following the introduction of sodium silicate for pre-dispersion, the separation performance improved markedly at the optimal dosage of 300 g/t: the concentrate Nb₂O₅ grade reached 1.28% (8-fold higher than the blank test), and the Ta₂O₅ grade increased to 0.47% (85-fold higher than the blank test). Multi-scale characterization, including zeta potential measurements, ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), was employed to elucidate the dispersion mechanism of sodium silicate. The results confirmed that sodium silicate undergoes selective chemisorption on mica surfaces by forming Si–O–Al bonds with surface Al–OH active sites, which substantially increases electrostatic repulsion between mineral particles and eliminates mica slime coating on tantalum–niobium minerals. In contrast, sodium silicate exhibits only weak physical adsorption on tantalum–niobium mineral surfaces, with no evident chemical bonding. This work provides a low-cost, eco-friendly pretreatment–gravity separation coupling technology for the efficient enrichment of argillized ultra-low-grade tantalum–niobium associated ores and offers theoretical guidance for the green utilization of complex tantalum–niobium tailings and low-grade mineral resources. Full article

(This article belongs to the Special Issue Innovative Strategies for the Sustainable Processing of Complex Polymetallic Resources)

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