Minerals

22 pages, 1613 KB

Open AccessArticle

Geochemical Characterisation of Soils in the Impact Zone of the Zhitikara Chrysotile Asbestos Quarry (Kostanay Region, Kazakhstan)

by Aliya Yskak, Zhumash Bekmyrza, Petr Lyanga, Yevgeniy Sokharev, Gulnaz Yermoldina, Vladimir Fominov, Kuanysh Zhumalynov, Zheniskul Bozhekenova and Zhassulan Irzhanov

Minerals 2026, 16(7), 762; https://doi.org/10.3390/min16070762 (registering DOI) - 22 Jul 2026

Abstract

Soils developing in ultramafic (serpentinite) provinces are naturally enriched in Mg, Ni and Cr, which makes it difficult to separate the natural geochemical background from technogenic contamination near chrysotile asbestos mining operations. This problem is examined for the agricultural soils in the impact [...] Read more.

Soils developing in ultramafic (serpentinite) provinces are naturally enriched in Mg, Ni and Cr, which makes it difficult to separate the natural geochemical background from technogenic contamination near chrysotile asbestos mining operations. This problem is examined for the agricultural soils in the impact zone of the Zhitikara chrysotile asbestos quarry (Kostanay Region, Kazakhstan), one of the largest such operations in the world. The elemental composition of the soils was characterised by portable X-ray fluorescence, verified against ICP-OES, and complemented by X-ray diffraction. When contamination was assessed against the global crustal background (upper continental crust), nickel and chromium appeared enriched; however, relative to the local geochemical background, these elements fall within the natural lithogenic range, showing that global crustal values generate false-positive contamination signals in ultramafic terrains. Magnesium was the only element enriched above the local background and the only one that decreased systematically with distance from the quarry, identifying it as the most sensitive tracer of aerogenic serpentinite dust among the elements measured. The discordance between total and acid-soluble chromium is consistent with chromium being hosted mainly in a refractory chromite phase, so that total chromium contents overestimate the environmentally relevant fraction. The study demonstrates the pitfall of applying global crustal backgrounds in ultramafic provinces and supports a locally referenced, differentiated approach to soil-contamination assessment in such settings. Full article

(This article belongs to the Special Issue Geochemical Characteristics and Contamination Risk Assessment of Soil, 2nd Edition)

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21 pages, 2692 KB

Open AccessArticle

Numerical Simulation of Mineral Separation Method Using an Isodynamic Magnetic Field

by Xubei Huang, Xiaofeng Cheng, Yingxin Zhang and Dong Dong

Minerals 2026, 16(7), 761; https://doi.org/10.3390/min16070761 - 22 Jul 2026

Abstract

An improved method for separating magnetic minerals based on an isodynamic magnetic field is proposed in this work. The magnetic field distribution generated by the system was first analyzed through numerical simulations performed with finite element electromagnetic simulation software, and the simulation accuracy [...] Read more.

An improved method for separating magnetic minerals based on an isodynamic magnetic field is proposed in this work. The magnetic field distribution generated by the system was first analyzed through numerical simulations performed with finite element electromagnetic simulation software, and the simulation accuracy was subsequently validated against experimental data. Through system modeling and parameter sensitivity analysis, the regulatory mechanisms of various parameters of the field properties were thoroughly investigated. Numerical results show that a constant magnetic force field forms in the separation zone at a 25° arc center angle of the curved pole head, while poor field uniformity occurs at 20° or 30°. A stable constant magnetic force field can be generated in the separation zone when the large arc radius of the curved pole head is 300 mm, 600 mm or 1200 mm, or when permanent magnet materials including N30–N45-grade neodymium iron boron (NdFeB) and ferrite are adopted. The large arc radius of the curved pole head, as well as the type and grade of the permanent magnet, only affect the magnitude of the magnetic force in the separation zone, with no significant correlation with the uniformity of the constant magnetic force field. A constant magnetic force field is generated when the thickness of the side patch magnet on the curved pole head is 40–70 mm and the magnetic system working air gap is 50–60 mm; the magnetic force field will lose uniformity once the parameters deviate from the above ranges. Full article

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

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15 pages, 2515 KB

Open AccessArticle

Lithium Recovery from Smectite Clays via Sulphate Roasting and Water Leaching

by Cara Philipa Haller and Christie Dorfling

Minerals 2026, 16(7), 760; https://doi.org/10.3390/min16070760 - 21 Jul 2026

Abstract

The growing lithium demand has led to increasing interest in low-grade clay deposits. In this study, a roast–leach process was investigated for the recovery of lithium from a Southern African smectite-rich clay deposit. Screening of various roasting additives showed that a binary system [...] Read more.

The growing lithium demand has led to increasing interest in low-grade clay deposits. In this study, a roast–leach process was investigated for the recovery of lithium from a Southern African smectite-rich clay deposit. Screening of various roasting additives showed that a binary system comprising sodium sulphate and calcium sulphate yielded the highest lithium dissolution during subsequent water leaching, and was therefore selected for optimisation tests. Roasting at 850 °C for 1.5 h, using a clay:total salt ratio of 2:1 and Na₂SO₄:CaSO₄ ratio of 1:2, followed by subsequent water leaching at 60 °C and 30% solids, resulted in 86.3% lithium dissolution after 2 h. Compared with direct acid leaching of the same clay deposit, the roast–leach process improved lithium selectivity over multivalent ions, modified the clay’s swelling behaviour to enable leaching at higher solids content, and produced an alkaline leach solution, eliminating the need for neutralisation. Full article

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

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31 pages, 66451 KB

Open AccessArticle

Geochemistry, Geostatistical Evaluation and Origin of Calcrete and Dolocrete Formed Within the Soil Profile Along the Konya Fault Zone (Central Türkiye)

by Arif Delikan and Swan Alfatlawi

Minerals 2026, 16(7), 759; https://doi.org/10.3390/min16070759 - 21 Jul 2026

Abstract

Terrestrial carbonates provide important archives for reconstructing paleoenvironmental, paleoclimatic and hydrogeological conditions in semi-arid to arid continental basins. This study investigates the origin, mineralogical characteristics and geochemical properties of calcrete and dolocrete occurrences developed along the Konya Fault Zone within the Konya Closed [...] Read more.

Terrestrial carbonates provide important archives for reconstructing paleoenvironmental, paleoclimatic and hydrogeological conditions in semi-arid to arid continental basins. This study investigates the origin, mineralogical characteristics and geochemical properties of calcrete and dolocrete occurrences developed along the Konya Fault Zone within the Konya Closed Basin (Central Türkiye). Field observations, petrography, XRD, SEM–EDS, major and trace element geochemistry, REE analyses, stable isotopes (δ¹³C–δ¹⁸O), geostatistical methods and ESR dating were employed. The results reveal two distinct terrestrial carbonate systems. Dolocretes occur within Quaternary alluvial fan deposits developed on ultramafic–ophiolitic rocks, whereas calcretes developed pedogenically within Quaternary alluvial fan deposits overlying carbonate bedrock. Calcite, dolomite, quartz, palygorskite and smectitic clay minerals constitute the principal mineral phases. Rhizoliths, tubular structures, nodules, microbial filaments and laminated carbonate horizons indicate pedogenic carbonate accumulation. The association of palygorskite with dolomite and smectitic clay minerals suggests alkaline, Mg-rich pore waters under semi-arid conditions. Elevated Sr concentrations indicate prolonged groundwater–carbonate interaction, whereas high Ni and Co contents in the dolocretes reflect the influence of ultramafic source rocks. REE distributions are characterized by LREE enrichment, weak Eu anomalies and locally developed negative Ce anomalies, indicating pedogenic fractionation under oxidizing meteoric conditions. Stable isotope data indicate precipitation from meteoric waters influenced by soil-derived CO₂ under semi-arid climatic conditions dominated by C3 vegetation. ESR ages ranging from approximately 390–217 ka indicate carbonate formation during the Middle Pleistocene (MIS 11–MIS 7). Integrated mineralogical, geochemical, isotopic and chronological evidence indicates that the Konya terrestrial carbonates formed predominantly through pedogenic processes within meteoric vadose-zone conditions controlled by bedrock lithology (carbonate and ultramafic rocks), groundwater circulation and Quaternary climatic variability. These deposits represent important archives of Middle Pleistocene paleoenvironmental and paleohydrological evolution in Central Anatolia. Full article

(This article belongs to the Special Issue Geostatistical Applications in Mineral Resource Evaluation and Environmental Geochemistry)

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21 pages, 7009 KB

Open AccessArticle

Study of the Role of Cu(II) in the Oxidation of H₂S in the Context of Leaching Chalcopyrite in Sulfuric Acidic Media

by Jordy Dinga, Thandazile Moyo-Mahlangu, Kathija Shaik and Jochen Petersen

Minerals 2026, 16(7), 758; https://doi.org/10.3390/min16070758 - 21 Jul 2026

Abstract

The leaching of chalcopyrite in sulfate or chloride media has been proposed to occur through a combined non-oxidative/oxidative mechanism, where H₂S forms an intermediary species, concurrently with direct oxidative leaching. Some studies have noted that elevated concentrations of Cu(II) improve chalcopyrite [...] Read more.

The leaching of chalcopyrite in sulfate or chloride media has been proposed to occur through a combined non-oxidative/oxidative mechanism, where H₂S forms an intermediary species, concurrently with direct oxidative leaching. Some studies have noted that elevated concentrations of Cu(II) improve chalcopyrite leaching in sulfate media. In this study, the role of Cu(II) was investigated in the non-oxidative/oxidative process through electrochemical tests on a chalcopyrite electrode, supported by bulk leach tests. The results of the electrochemical tests are consistent with the formation of H₂S through non-oxidative leaching of chalcopyrite. The H₂S subsequently reacts with Cu(II) to form intermediate cuprous sulfide species, which can be readily oxidized by dissolved oxygen. The bulk leach tests point to a synergy between Cu(II) and O₂, further pointing to the catalytic role of Cu(II). The findings support the feasibility of running heap leaching of chalcopyrite-rich ores at elevated copper concentrations in either chloride or sulfate systems. Full article

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

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38 pages, 8798 KB

Open AccessReview

Handheld Laser-Induced Breakdown Spectroscopy (LIBS) in the Exploration of Critical Metals: Recent Advancements and Challenges

by V. Balaram

Minerals 2026, 16(7), 757; https://doi.org/10.3390/min16070757 (registering DOI) - 20 Jul 2026

Abstract

Handheld Laser-Induced Breakdown Spectrometry (hLIBS) is capable of simultaneous multi-element analysis of a variety of geological materials such as rocks, minerals, ores, soils, sediments, and water. This is a transformative analytical technology that is currently revolutionizing the field of critical mineral exploration studies. [...] Read more.

Handheld Laser-Induced Breakdown Spectrometry (hLIBS) is capable of simultaneous multi-element analysis of a variety of geological materials such as rocks, minerals, ores, soils, sediments, and water. This is a transformative analytical technology that is currently revolutionizing the field of critical mineral exploration studies. By providing real-time, in situ elemental analysis in the field with detection and quantitative determination capabilities for light elements (such as Li, Be, and B), where other handheld techniques like portable XRF struggle, hLIBS empowers geologists to make faster and more informed decisions in the field, significantly accelerating the exploration process from prospecting to target delineation. Several important practical examples of the exploration of critical metals, such as lithium, rare earth elements, copper, cobalt, and titanium, are presented. In particular, the detection capability of indicator minerals and pathfinding elements by hLIBS is extremely valuable for critical mineral exploration studies. Similar instruments have also been successfully used in recent years in challenging environments like space and deep-sea environments. The capability of remotely operated miniature LIBS in hostile environments such as the deep sea, Moon, and Mars is discussed with examples. LIBS has become a key technology for in situ chemical analysis in both space and deep-sea exploration because of its ability to identify elemental composition rapidly and without physical contact. Full article

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

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26 pages, 29760 KB

Open AccessArticle

Oolitic Ironstones and Carbonate Mn Ores of the Marsyaty Deposit (Northern Urals, Russia): A Key Study of Mineralogy and Geochemistry

by Elena Belogub, Alexey Brusnitsyn, Konstantin Novoselov, Ksenia Filippova and Sergey Sadykov

Minerals 2026, 16(7), 756; https://doi.org/10.3390/min16070756 - 20 Jul 2026

Abstract

This article describes the mineralogical and geochemical features of the Marsyaty Mn–Fe sedimentary deposit in the Northern Urals (Russia). Oolitic ironstones of the deposit are localized in the Cenomanian coastal sandstones. Manganese ores (carbonate and carbonate–oxide types) lies within the Lower Paleocene siliciclastic [...] Read more.

This article describes the mineralogical and geochemical features of the Marsyaty Mn–Fe sedimentary deposit in the Northern Urals (Russia). Oolitic ironstones of the deposit are localized in the Cenomanian coastal sandstones. Manganese ores (carbonate and carbonate–oxide types) lies within the Lower Paleocene siliciclastic sediments and are separated from the oolitic ironstone (iron oxide and iron carbonate types) by a polymictic gravelite bed. Authigenic Fe³⁺ oxyhydroxides (goethite and ferrihydrite), chamosite/berthierine and late siderite predominate in the ironstones; kaolinite, apatite, perhamite, calcite and dolomite are minor constituents. Rhodochrosite and rancieite are the major minerals of the manganese ore; Mn-dominated phyllosilicates (parsettensite? and caryopilite?) are rare. Both ore types contain authigenic glauconite, montmorillonite, sulfides (sphalerite/wurtzite, galena, and pyrite), gibbsite/boehmite and REE phosphates. Both ore types contain detrital quartz, ilmenite, zircon, monazite, epidote, titanite, muscovite and feldspars. The δ¹³C_carb value (VPDB) varies from −18.5 to −23.3 in both ironstone types and from −10.0 to −41.0 ‰ in the manganese ore. The negative C isotopic composition and numerous organic remains indicate the involvement of microbial processes in the formation of both types of carbonate ores. The Fe and Mn ores belong to one transgression–regression sedimentation cycle and formed consecutively during the evolution of the West Siberian basin. A unique feature of the Marsyaty deposit includes two ore formation stages within a limited area and over a relatively short geological period: the accumulation of (i) oolitic ironstones enriched in Mn first and then (ii) manganese ores only. Full article

(This article belongs to the Section Mineral Deposits)

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22 pages, 30583 KB

Open AccessArticle

Non-Invasive Trace Element Fingerprinting of the Lion Man, a Left Mammoth Tusk and Mammoth Ivory Fragments Found at the Hohlenstein-Stadel Cave, Swabian Alb, Germany

by Ina Reiche, Katharina Müller, Quentin Lemasson, Laurent Pichon and Kurt Wehrberger

Minerals 2026, 16(7), 755; https://doi.org/10.3390/min16070755 - 19 Jul 2026

Abstract

The Lion Man sculpture (UNESCO World heritage), a left mammoth tusk and mammoth ivory fragments from the excavations in the Hohlenstein-Stadel cave, Lone valley, Swabian Alb, Germany, were non-invasively analysed by means of external ion beam analysis (IBA) at the microfocus beamline at [...] Read more.

The Lion Man sculpture (UNESCO World heritage), a left mammoth tusk and mammoth ivory fragments from the excavations in the Hohlenstein-Stadel cave, Lone valley, Swabian Alb, Germany, were non-invasively analysed by means of external ion beam analysis (IBA) at the microfocus beamline at the particle accelerator AGLAE. The Lion Man was reconstructed from about three hundred mammoth ivory fragments, while the tusk is a separate find, and the fragments are individual pieces that could not be placed in the Lion Man. A characteristic trace element fingerprint, based on zinc, bromine and strontium contents, was established according to previous IBA studies of Aurignacian-era mammoth ivory and allowed for a comparison of the mammoth ivory objects. The specific Hohlenstein-Stadel cave trace element fingerprint could be distinguished from that of other Aurignacian sites in Europe but closely resembles that of the contemporary ivories from the neighbouring Hohle Fels cave. Although this study highlights that the Lion Man sculpture is chemically inhomogeneous due to diagenetic alterations, the left tusk and individual ivory fragments are chemically very similar to the Lion Man. However, further analyses are required to relate them to the same animal. Secondary minerals such as black manganese oxide dendrites and iron-rich aluminosilicates could be identified on the Lion Man and the other ivory objects at the surface. While dendrites are a characteristic diagenetic feature of mammoth ivory, the origin of iron-rich aluminosilicates can be linked either to sediment traces or surface treatment and use wear of the sculpture. Iron-rich zones are identified on particular parts of the Lion Man, namely, at the snout and at the left forearm with decorative signs. The snout is also particularly enriched in carbon, whose origin still needs to be clarified. Full article

(This article belongs to the Special Issue Mineralogical and Geochemical Insights into Cultural Heritage Materials)

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35 pages, 28801 KB

Open AccessArticle

Features of the Metallogenic Potential of the Shyngys–Tarbagatai Folded System (Kazakhstan) from the Perspective of Modern Plate Tectonics

by Eleonora Y. Seitmuratova, Ansagan Dauletuly, Diyas O. Dautbekov, Moldir A. Mashrapova, Tauassar K. Karimbekov, Tatyana E. Pirogova, Saltanat Bakdauletkyzy and Yalkunzhan K. Arshamov

Minerals 2026, 16(7), 754; https://doi.org/10.3390/min16070754 - 19 Jul 2026

Abstract

The Shyngys–Tarbagatai folded system of Kazakhstan, located in the southwestern part of the Central Asian Orogenic Belt, represents a promising yet still insufficiently studied metallogenic region of Kazakhstan. The aim of the present study was to reassess its ore potential based on modern [...] Read more.

The Shyngys–Tarbagatai folded system of Kazakhstan, located in the southwestern part of the Central Asian Orogenic Belt, represents a promising yet still insufficiently studied metallogenic region of Kazakhstan. The aim of the present study was to reassess its ore potential based on modern geotectonic concepts and a comprehensive metallogenic analysis. An evaluation of the ore potential of nine structural–formational zones was carried out, and their metallogenic specialization was determined. The dominant role of gold and copper mineralization was established, along with the features of spatial distribution of ore occurrences and the most promising areas for further exploration. It was shown that the most ore-rich stratigraphic levels include the Early Cambrian, Late Ordovician, Early Silurian, Early Devonian, and Late Devonian units. It was demonstrated that the formation of the main ore types is closely related to productive geodynamic settings, including Early Paleozoic oceanic rifts, island-arc complexes, and the Devonian continental-margin volcano-plutonic belt. Based on the obtained results, a map of prospective areas at a scale of 1:1,500,000 was compiled, and these areas were ranked according to their degree of prospectivity. A total of 51 targets were identified as priority sites for follow-up prospecting, evaluation, and detailed exploration work. Full article

(This article belongs to the Section Mineral Deposits)

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23 pages, 4651 KB

Open AccessArticle

Geochemical Heterogeneity of Fracture-Filling Vein Pyrobitumen in Tectonically Reworked Reservoirs of the Western Jiangnan–Xuefeng Uplift, South China

by Chongjing Wang, Daiyong Cao and Guoshu Huang

Minerals 2026, 16(7), 753; https://doi.org/10.3390/min16070753 - 19 Jul 2026

Abstract

Vein-type pyrobitumen, widely developed along the western margin of the Jiangnan–Xuefeng Uplift, preserves important records of structural modification and post-accumulation alteration within tectonically reworked reservoirs. In this study, Rock-Eval pyrolysis, molecular geochemistry, Raman spectroscopy, X-ray diffraction (XRD), trace and rare earth element (REE) [...] Read more.

Vein-type pyrobitumen, widely developed along the western margin of the Jiangnan–Xuefeng Uplift, preserves important records of structural modification and post-accumulation alteration within tectonically reworked reservoirs. In this study, Rock-Eval pyrolysis, molecular geochemistry, Raman spectroscopy, X-ray diffraction (XRD), trace and rare earth element (REE) geochemistry, and fluid inclusion analyses were integrated to investigate the origin of geochemical heterogeneity and the evolution of residual hydrocarbons. The analyzed samples are uniformly overmature, with high T_max values (527–594 °C), extremely low S₁ and HI values, and poorly ordered turbostratic carbon structures composed of defect-rich aromatic domains. Despite the comparable thermal maturity, marked variations occur in n-alkane distributions, NSO fractions, asphaltene abundance, and aromatic hydrocarbon compositions. These differences are not systematically related to maturity parameters but instead appear to reflect selective retention and localized redistribution of pyrobituminous material during structural reworking. Late Indosinian–Early Yanshanian compression generated NE-trending shear fractures together with NW-oriented extensional faults, forming a fault–fracture network that served as the principal pathways for fluid circulation and localized emplacement of pyrobituminous material. Trace-element and REE signatures, together with fluid inclusion microthermometry, suggest localized fluid–rock interaction and possible hydrothermal overprinting during pyrobitumen emplacement. The combined results suggest that tectonically driven mobilization, selective compositional fractionation, and late-stage fluid–rock interaction collectively contributed to the observed compositional heterogeneity of the vein-type pyrobitumen. This study provides additional constraints on hydrocarbon redistribution and fluid evolution in structurally reworked, highly evolved petroleum reservoirs. Full article

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

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24 pages, 14139 KB

Open AccessArticle

Effect of Aggregate Fractal Dimension on Creep Behavior and Fractional-Order Constitutive Modeling of Cemented Coal Gangue Backfill

by Yongjin Zhang, Hui Yang, Xin Qu and Cheng Li

Minerals 2026, 16(7), 752; https://doi.org/10.3390/min16070752 - 19 Jul 2026

Abstract

To investigate the influence of aggregate fractal gradation on the time-dependent deformation of cemented coal gangue backfill, four groups of specimens with different aggregate fractal dimensions were prepared based on mass fractal theory. Multi-stage loading creep tests were conducted to examine the effects [...] Read more.

To investigate the influence of aggregate fractal gradation on the time-dependent deformation of cemented coal gangue backfill, four groups of specimens with different aggregate fractal dimensions were prepared based on mass fractal theory. Multi-stage loading creep tests were conducted to examine the effects of aggregate fractal dimension on creep strain, steady-state creep rate, and long-term strength. An improved fractional-order Burgers creep model incorporating a fractional Abel dashpot was then established to describe the creep response and to further interpret the relationship between aggregate gradation and model parameters. The results show that the creep deformation of cemented coal gangue backfill increased with increasing stress level and exhibited instantaneous deformation, decelerating creep, steady-state creep, and accelerating creep stages. With increasing aggregate fractal dimension, the creep deformation, steady-state creep rate, and damage accumulation first decreased and then increased. Among the tested aggregate fractal gradations, the specimen with D = 2.41 exhibited the best creep resistance, with a long-term strength of 8.83 MPa, approximately 33.40% higher than that of the specimen with D = 2.20. This behavior may be attributed to a more favorable coarse–fine particle proportion, which improves particle filling and skeleton continuity under the present material system. The comparison between experimental and fitted results indicates that the improved fractional-order Burgers model can effectively reproduce the creep process of cemented coal gangue backfill, with coefficients of determination greater than 0.97 for all tested specimens. These findings provide a useful reference for aggregate gradation optimization and creep-resistance evaluation of cemented coal gangue backfill under laboratory multi-stage loading conditions. Full article

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

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22 pages, 2492 KB

Open AccessArticle

PhotonAssay™: Reporting Code Disclosure and the Route to Technology Adoption

by Simon C. Dominy

Minerals 2026, 16(7), 751; https://doi.org/10.3390/min16070751 - 18 Jul 2026

Abstract

PhotonAssay™ is a rapid, non-destructive gold assay method that analyses large-mass crushed or pulverised samples while reducing turnaround time, hazardous reagent use, and environmental footprint relative to conventional fire assay. Its growing adoption, however, has exposed a persistent misconception, that CRIRSCO-based reporting codes [...] Read more.

PhotonAssay™ is a rapid, non-destructive gold assay method that analyses large-mass crushed or pulverised samples while reducing turnaround time, hazardous reagent use, and environmental footprint relative to conventional fire assay. Its growing adoption, however, has exposed a persistent misconception, that CRIRSCO-based reporting codes approve certain analytical methods as being “compliant.” This paper clarifies the reporting position for PhotonAssay™ and outlines the key requirements for its use in Exploration Results, Mineral Resource, and Ore/Mineral Reserve reporting, including sampling context, preparation protocol, quality assurance/quality control and method validation. It also frames adoption as a four-stage journey—awareness, consideration, intent, and implementation—in which peer learning, testwork, business-case development, and deployment planning are as important as analytical performance. Particular attention is given to representative sampling and to interpreting differences from fire assay, especially in coarse-gold systems where larger assay charges are likely to yield more representative results. Two test methods are recommended, the transitional feasibility study (bias between assay methods) and heterogeneity study (bias and precision). The PhotonAssay™ adoption journey is a multidisciplinary process, requiring engagement between practitioners and executives, and between geoscientists, mining and minerals engineers, chemists, data scientists and corporate managers. Full article

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

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34 pages, 6783 KB

Open AccessArticle

Mineralogical Tracers for Magmatic and Hydrothermal Controls on Nb–Ta–Li Mineralization: A Case Study from the Duanfengshan Deposit, Mufushan Area, Central China

by Jin Yin, Hao Zhang, Deqiang Shi, Ziliang Zhao, Jiankang Li, Hangchuan Zhang, Wensheng Zhang, Zhuo Chen, Qiang Li, Chao Sun and Peng Li

Minerals 2026, 16(7), 750; https://doi.org/10.3390/min16070750 - 18 Jul 2026

Abstract

The Duanfengshan deposit, located in the Mufushan area of the middle Jiangnan Orogen, is a large-scale pegmatite-type Nb-Ta deposit. Previous studies have explored the genetic linkage between regional magmatic evolution and Nb-Ta mineralization; however, the specific roles played by magmatic and hydrothermal processes [...] Read more.

The Duanfengshan deposit, located in the Mufushan area of the middle Jiangnan Orogen, is a large-scale pegmatite-type Nb-Ta deposit. Previous studies have explored the genetic linkage between regional magmatic evolution and Nb-Ta mineralization; however, the specific roles played by magmatic and hydrothermal processes in rare-metal mineralization remain poorly constrained. Focusing on the newly discovered No. 124 dyke with Li-Nb-Ta mineralization, this study systematically divides it into four internal zones, including the graphic texture zone (GT), coarse-grained albite zone (CGA), fine-grained albite zone (FGA), and lepidolite–quartz core (LQ). Monazite U-Pb age of 134.6 ± 1.1 Ma precisely constrains the emplacement age of the dyke to the Early Cretaceous. Coltan in the CGA and FGA exhibit primary homogeneous or oscillatory zoning and are identified as columbite–(Mn), whereas those in the LQ display patchy texture or Ta-enriched overgrowth rims. Mica compositions exhibit continuous evolutionary trends from GT to LQ, with progressive decreases in K/Rb and K/Cs ratios and synchronous increases in F, Li, Cs, Rb, and Ta contents. Such compositional variations drive the transformation of mica species from muscovite, via Li–phengite and zinnwaldite (Li–muscovite), to metasomatic lepidolite. Integrated magmatic–hydrothermal evolution controls overall Li-Nb-Ta mineralization of Dyke No. 124. Early Nb-Ta-Li pre-enrichment within GT and CGA zones is dominated by magmatic fractional crystallization. Mica-based Li-Cs-Rb Rayleigh fractionation evidence demonstrates that the FGA may represent a transitional stage governed by volatile-rich, fluid-unsaturated melts. Massive albite crystallization elevates melt ASI values, lowers coltan solubility, and thus induces extensive Nb-Ta mineral precipitation. Subsequent metasomatism by Ta-Li-F-rich hydrothermal fluids further causes prominent secondary Li and Ta enrichment. Compared with the global typical LCT pegmatites, Dyke No. 124 possesses highly evolved magmatic differentiation. Zone-specific mica geochemical signatures are well coupled with Nb-Ta and Li mineralization, highlighting the favorable integrated Li-Nb-Ta mineralization potential of the dyke. This study improves regional Li-Nb-Ta mineralization theories and supplies reliable geological constraints for further rare-metal prospecting in the Duanfengshan area. Full article

(This article belongs to the Special Issue New Approaches in the Exploration and Characterization of Critical Mineral Deposits)

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10 pages, 2819 KB

Open AccessArticle

Prediction of the Stability of Tutton Salts Using the Simple Salt Approximation

by Corissa P. McDonald and Claude H. Yoder

Minerals 2026, 16(7), 749; https://doi.org/10.3390/min16070749 - 18 Jul 2026

Abstract

The simple salt approximation (SSA) for lattice energies is used to rationalize the composition of Tutton salts with the formula A₂M(SO₄)₂(H₂O)₆, where A is a monovalent cation, usually K⁺, and M [...] Read more.

The simple salt approximation (SSA) for lattice energies is used to rationalize the composition of Tutton salts with the formula A₂M(SO₄)₂(H₂O)₆, where A is a monovalent cation, usually K⁺, and M is a divalent cation, usually a transition metal cation such as Cu²⁺. These salts have become increasingly advantageous due to their heat exchange and optical properties, as well as providing vehicles for the study of the Jahn–Teller effect. The SSA suggests that the solubility of a double salt will be about the same as, or slightly lower than, that of the constituent simple salts when the simple salts have similar solubilities. This generalization has been used to rationalize the stability of the double salts synthesized and reported herein using standard procedures (mixing of simple salt constituents followed by slow evaporation). As expected, the hexa-coordination of water was obtained only with small divalent cations. Of particular interest is the absence of Tutton salts containing small alkali metal cations, specifically Li⁺ and Na⁺, an observation that is seemingly inconsistent with the large lattice energies that these ions should confer on the double salts and the similar solubilities of their salts to those of the transition metal sulfate. Although analytical data appeared to provide evidence for Tutton salts when M = Li⁺, the PXRD patterns of the synthesized compounds clearly showed mixtures of the simple-salt-starting reagents. We conclude that inability to synthesize a Tutton salt using small alkali metal cations is predominantly due to the lower-than-expected lattice energies of these compounds and consequent greater solubilities than their simple salt constituents. Moreover, we can attribute this instability to the extensive hydrogen-bonding present in the Tutton structure, which produces long monovalent sulfate distances and weaker-than-supposed lattice energies. However, it is also true that both the heat of hydration of the Li⁺ ion and its entropy of hydration also conspire to provide greater solubility. Full article

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

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25 pages, 15912 KB

Open AccessArticle

Distribution of Selected Trace Elements and Mineralogical Features of the Kışlaköy Coal-Seam Profile, Afşin–Elbistan Basin, Türkiye

by Hatice Kara, Leyla Kalender, Mehmet Ali Ertürk, Cihan Yalçın, Mehmet Deniz Turan and Emine Cicioğlu Sütçü

Minerals 2026, 16(7), 748; https://doi.org/10.3390/min16070748 - 18 Jul 2026

Abstract

In the Afşin–Elbistan coal seam in Türkiye, this study investigates the vertical distribution, enrichment features, and mineralogical controls of trace elements and rare earth elements (REEs). Thirty coal samples were collected vertically from the Kışlaköy open-pit mine. Major oxide concentrations were determined by [...] Read more.

In the Afşin–Elbistan coal seam in Türkiye, this study investigates the vertical distribution, enrichment features, and mineralogical controls of trace elements and rare earth elements (REEs). Thirty coal samples were collected vertically from the Kışlaköy open-pit mine. Major oxide concentrations were determined by XRF for 29 samples, whereas trace element concentrations were determined by ICP–MS for all 30 samples. Mineralogical and textural characteristics were investigated in 15 selected samples by XRD and SEM–EDS. The coal is abundant in quartz, pyrite, and gypsum, along with trace amounts of calcite, clay minerals, and feldspars, which demonstrate the combined effects of detrital input, reducing depositional conditions, and post-depositional alteration. The major oxide composition is dominated by SiO₂, CaO, Al₂O₃, and Fe₂O₃, showing notable contributions from carbonate, aluminosilicate, and Fe-bearing mineral phases. Most trace elements occur at levels close to the world coal average, whereas V, Ni, and U are significantly enriched, and Cr and Co are slightly enriched. Total REE contents range from 21 to 125 ppm, averaging 51 ppm, and display light REE enrichment over heavy REEs. Weak negative Ce anomalies and slight positive Eu anomalies indicate variable redox conditions and the influence of terrigenous mineral input. Vertical distribution patterns indicate that during peat accumulation and early diagenesis, variations in detrital input, mineral matter abundance, and depositional redox conditions regulated trace element and REE distributions. REEs are mainly associated with aluminosilicate and locally phosphate-bearing phases, whereas V, Ni, and U are linked to organic matter and/or sulfide-rich intervals. These results show that the main factors influencing trace-element and REE behaviour in the Afşin–Elbistan coal seam are the mineralogical composition and redox evolution. Full article

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

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14 pages, 1510 KB

Open AccessArticle

Assessing the Feasibility of a Falcon Concentrator for the Recovery of Ultrafine Scheelite Particles from Historical Tailings

by Kathy Bru, Bradley Martin Guy, Maxime Boucheron and Solène Touzé

Minerals 2026, 16(7), 747; https://doi.org/10.3390/min16070747 - 18 Jul 2026

Abstract

This study investigates the potential of a Falcon Ultra-Fine (UF) concentrator for the recovery of ultrafine scheelite particles from a weathered tailing stockpile of an historical scheelite mine, as it could represent a valuable secondary tungsten resource. The tailings are characterized by a [...] Read more.

This study investigates the potential of a Falcon Ultra-Fine (UF) concentrator for the recovery of ultrafine scheelite particles from a weathered tailing stockpile of an historical scheelite mine, as it could represent a valuable secondary tungsten resource. The tailings are characterized by a P80 of 17.2 µm, with scheelite grains exhibiting a finer size distribution (P80 = 9.3 µm) and a high liberation degree (82 wt%). A three-stage Falcon concentration circuit was tested under varying operating conditions, including feed tank design, concentration of solids, particle size fraction, G-force and the number of treatment stages. Results showed that separation efficiency is primarily governed by the tank design and the feed particle size distribution, while variations in G-force and concentration of solids produced only minor effects. Hydrocyclone desliming to remove particles finer than 10 µm prior to concentration enhanced the separation selectivity of the Falcon-based concentration flowsheet. However, such pre-treatment of the material will require the implementation of a dedicated process to recover scheelite from the overflow to limit losses. These findings highlight the challenges of effective scheelite separation due to the fineness of these tailings. Full article

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

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19 pages, 1886 KB

Open AccessArticle

Enhanced Removal of Hexavalent Chromium by Iron-Modified Biochar: Sorption Kinetics and Isotherm Studies

by Dulith Rajapakshe, Herath Mudiyanselage Ishani P. Kulasekara and Charalambos Papelis

Minerals 2026, 16(7), 746; https://doi.org/10.3390/min16070746 - 17 Jul 2026

Abstract

Hexavalent chromium Cr(VI) is a highly toxic and mobile contaminant commonly detected in industrial effluents and groundwater, requiring efficient and scalable treatment strategies. In this study, a commercial unmodified biochar (UB) and an iron-modified biochar (IMB) were evaluated for Cr(VI) removal from aqueous [...] Read more.

Hexavalent chromium Cr(VI) is a highly toxic and mobile contaminant commonly detected in industrial effluents and groundwater, requiring efficient and scalable treatment strategies. In this study, a commercial unmodified biochar (UB) and an iron-modified biochar (IMB) were evaluated for Cr(VI) removal from aqueous solutions. Iron modification via FeCl₃ impregnation and alkaline precipitation (pH 9) increased surface iron content from 0.2% to 3.3%, based on Energy Dispersive X-ray (EDX) analysis and extractable Fe from 0.009% to 0.108% (FerroVer). X-ray Diffraction (XRD) analysis suggested the presence of iron-containing phases and Fourier Transform Infrared (FTIR) analysis indicated the appearance of an Fe-O band at 564 cm⁻¹. BET analysis showed a slight decrease in surface area from 359 to 317 m² g⁻¹, consistent with partial pore blockage following iron modification. Batch adsorption experiments (pH 2–10; initial Cr(VI) concentration 5–600 mg L⁻¹; adsorbent dosage 2 g L⁻¹) revealed a maximum Langmuir adsorption capacity of 158 mg g⁻¹ for IMB, nearly double that of UB (82 mg g⁻¹), with optimal performance at pH 4–6. At equilibrium, removal efficiencies of ~60% and ~80% were obtained for UB and IMB, respectively (C₀ = 100 mg L⁻¹; adsorbent dose = 2 g L⁻¹). Kinetics followed a pseudo-second-order model, with IMB reaching equilibrium within 8 h compared to 50 h for UB. Isotherm analysis is consistent with Langmuir behavior for UB and Freundlich behavior for IMB. The improved adsorption performance of IMB is likely associated with the increased iron content introduced during modification, demonstrating its potential as an effective adsorbent for Cr(VI) removal from water. 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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18 pages, 1818 KB

Open AccessReview

Industrial Relevance of Oxidants and Leaching Accelerants in Cyanidation of Gold Sulfide Ores

by Maria Matar, Bona Lim, Boris Albijanic, Elsayed Oraby, Emmanuel Baawuah, William Staunton and Kylie Blackwell

Minerals 2026, 16(7), 745; https://doi.org/10.3390/min16070745 - 17 Jul 2026

Abstract

Gold cyanidation remains one of the most important hydrometallurgical processes in the mining industry. Gold dissolution kinetics and cyanide consumption are governed by coupled anodic–cathodic electrochemical reactions and influenced by pulp pH, particle size, cyanide concentration, mineralogy, and solution chemistry. Despite extensive studies [...] Read more.

Gold cyanidation remains one of the most important hydrometallurgical processes in the mining industry. Gold dissolution kinetics and cyanide consumption are governed by coupled anodic–cathodic electrochemical reactions and influenced by pulp pH, particle size, cyanide concentration, mineralogy, and solution chemistry. Despite extensive studies on individual additives in gold cyanide leaching, a coherent synthesis of oxidants and leaching accelerants in modern gold cyanidation remains lacking. The main purpose of this paper is to present a critical review of the literature on leaching accelerants and oxidants used to enhance gold cyanide leaching kinetics and reduce cyanide consumption. The literature highlights that iron sulfide minerals, found in gold ores, can significantly increase cyanide and oxidant consumption through increased oxidant demand, surface passivation, and galvanic interactions that suppress gold dissolution kinetics. This review article summarises the leaching accelerants used, where lead nitrate plays a central role in gold cyanide leaching, and emphasises that its effectiveness is associated with suppression of sulfide-related passivation and favourable modification of surface electrochemistry of gold. The synergistic effects of leaching accelerants with different oxidants on leaching performance are also assessed, with emphasis on their electrochemical roles. Full article

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

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27 pages, 1363 KB

Open AccessReview

Sustainable, Novel Solvent Extraction Methods Based on Ionic Liquids and Deep Eutectic Solvents for the Separation of Platinum Group Metals—A Short Review

by Małgorzata A. Kaczorowska

Minerals 2026, 16(7), 744; https://doi.org/10.3390/min16070744 - 17 Jul 2026

Abstract

Platinum group metals (PGMs) play a key role in many industries. However, the growing demand for PGMs, the systematic decline in their natural resources, and the generation of large amounts of waste, constituting a secondary source, are closely related to the search for [...] Read more.

Platinum group metals (PGMs) play a key role in many industries. However, the growing demand for PGMs, the systematic decline in their natural resources, and the generation of large amounts of waste, constituting a secondary source, are closely related to the search for effective and environmentally safe methods for their separation. Although solvent extraction (SX) processes, long used to extract PGMs from various ores/waste leachates, typically allow for effective separation of these valuable metals, they rely primarily on the use of organic solvents, many of which are environmentally hazardous. Therefore, recent research efforts have focused, among others, on the utilization of potentially “greener” chemicals, such as ionic liquids (ILs) and deep eutectic solvents (DESs). Due to their tunable properties to specific applications, these chemicals usually enable not only efficient (often >90%) but also selective and more eco-safe separation of PGMs from various matrices. This review concerns the latest developments in the SX of PGM ions from aqueous solutions and suspensions using ILs and DESs (e.g., as extractants, solvents, and leaching agents), taking into account their most important advantages, limitations, and potential impact on the environment. IL- and DES-based SX methods fit into the green chemistry trend and are consistent with sustainable development goals. Full article

(This article belongs to the Special Issue Innovation in Solvent Extraction for Metal Recovery)

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