Minerals

25 pages, 5595 KiB

Open AccessArticle

Neoproterozoic Subduction Zone Fluids and Sediment Melt-Metasomatized Mantle Magmatism on the Northern Yangtze Block: Constraints from the Ca. 880 Ma Taoyuan Syenogranite

by Shilei Liu, Yiduo Li, Han Liu, Peng Wang, Shizhen Zhang and Fenglin Chen

Minerals 2025, 15(7), 730; https://doi.org/10.3390/min15070730 (registering DOI) - 12 Jul 2025

Abstract

The Yangtze Block, with its widespread Neoproterozoic mafic–felsic magmatic rock series and volcanic–sedimentary rock assemblages, is one of the key windows for reconstructing the assembly and fragmentation process of Rodinia. This study focuses on the Taoyuan syenogranite from the Micangshan Massif on the [...] Read more.

The Yangtze Block, with its widespread Neoproterozoic mafic–felsic magmatic rock series and volcanic–sedimentary rock assemblages, is one of the key windows for reconstructing the assembly and fragmentation process of Rodinia. This study focuses on the Taoyuan syenogranite from the Micangshan Massif on the northern Yangtze Block, by conducting systematic chronology, mineralogy, and geochemistry analyses to investigate their source, petrogenesis, and tectonic setting. LA-ICP-MS U–Pb geochronology reveals that the medium- to coarse-grained and medium- to fine-grained syenogranites have crystallization ages of 878 ± 4.2 Ma and 880 ± 6.5 Ma, respectively. These syenogranites have aluminum saturation index (A/CNK) values ranging from 0.79 to 1.06, indicating quasi-aluminous to weakly peraluminous compositions, and are classified as calc-alkaline I-type granites. The geochemical indicators of these rocks, including Mg^#(44–48, mean 46), Zr/Hf (40.07), Nb/La (0.4), and zircon εHf(t) values (+9.2 to +10.9), collectively indicate a depleted lithospheric mantle source. The mantle source was metasomatized by subduction-derived fluids and sediment melts prior to partial melting as evidenced by their higher Mg^#, elevated Ba content, and distinctive ratios (Rb/Y, Nb/Y, Th/Yb, Th/Sm, Th/Ce, and Ba/La). Integrating regional data, this study confirms crust–mantle interaction along the northern Yangtze during the early Neoproterozoic, supporting a sustained subduction-related tectonic setting. Full article

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

13 pages, 6501 KiB

Open AccessArticle

Pyrite-Hosted Inclusions in the Southern Ore Belt of the Bainaimiao Porphyry Cu Deposit: Composition and δ³⁴S Characteristics

by Liwen Wu, Yushan Zuo, Yongwang Zhang, Jianjun Yang, Yimin Liu, Guobin Zhang, Hong Zhang, Peng Zhang and Rui Liu

Minerals 2025, 15(7), 729; https://doi.org/10.3390/min15070729 (registering DOI) - 12 Jul 2025

Abstract

This study presents a comprehensive case analysis of pyrite-hosted solid inclusions and their metallogenic significance in the Bainaimiao porphyry Cu deposit in NE China, which is genetically linked to the early Silurian granodiorite intrusion and porphyry dykes. Solid inclusions in pyrite from the [...] Read more.

This study presents a comprehensive case analysis of pyrite-hosted solid inclusions and their metallogenic significance in the Bainaimiao porphyry Cu deposit in NE China, which is genetically linked to the early Silurian granodiorite intrusion and porphyry dykes. Solid inclusions in pyrite from the deposit’s southern ore belt were analyzed across distinct mineralization stages. Using Electron Probe Micro-Analysis (EPMA) and in situ sulfur isotope analysis (MC-ICP-MS), inclusion assemblages in pyrite were identified, including pyrrhotite-chalcopyrite solid solutions, biotite, and dolomite. The results demonstrate that these inclusions primarily formed through coprecipitation with pyrite during crystal growth. Early-stage mineralizing fluids exhibited extreme temperatures exceeding 700 °C, coupled with low oxygen fugacity (fO₂) and low sulfur fugacity (fS₂). Sulfur isotope compositions (δ³⁴S: −5.85 to −4.97‰) indicate a dominant mantle-derived magmatic sulfur source, with contributions from reduced sulfur in sedimentary rocks. Combined with regional geological evolution, the Bainaimiao deposit is classified as a porphyry-type deposit. Its ore-forming materials were partially derived from Mesoproterozoic submarine volcanic exhalative sedimentary source beds, which were later modified and enriched by granodiorite porphyry magmatism. Full article

(This article belongs to the Section Mineral Deposits)

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13 pages, 750 KiB

Open AccessReview

Inclusions, Nitrogen Occurrence Modes, and C-N Isotopic Compositions of Diamonds as Indicators for Exploring the Genesis Mechanism of Diamond: A Review

by Xiao-Xia Wang, Yang-Yang Wang, Xiaodong Yao, Tianyin Chang, Xiang Li, Xiaomin Wang and Zihao Zhao

Minerals 2025, 15(7), 728; https://doi.org/10.3390/min15070728 (registering DOI) - 12 Jul 2025

Abstract

Diamond, a crucial carbon phase in the deep Earth, forms under ultrahigh-pressure (UHP, P > 4 GPa) conditions and serves as an important indicator mineral for the UHP environment. Based on their host rocks, diamonds are classified into mantle-derived diamonds, UHP metamorphic diamonds, [...] Read more.

Diamond, a crucial carbon phase in the deep Earth, forms under ultrahigh-pressure (UHP, P > 4 GPa) conditions and serves as an important indicator mineral for the UHP environment. Based on their host rocks, diamonds are classified into mantle-derived diamonds, UHP metamorphic diamonds, impact diamonds, etc. While carbon constitutes the primary component of diamonds, nitrogen represents one of the most significant impurity elements. The study of the occurrence mode of nitrogen and the C-N isotope composition is essential for exploring the formation mechanism of diamond. Nitrogen primarily exists in diamonds as either isolated atoms (N) or aggregated forms (N2 or N4), with the dominant mode being controlled by temperature and residence time in the mantle. As temperature and residence time increase, isolated nitrogen progressively transforms into aggregated forms. As a result, mantle-derived diamonds typically contain nitrogen predominantly as N2 or N4, whereas metamorphic diamonds and impact diamonds mainly retain isolated N. Global C-N isotopic composition of over 4400 diamonds reveals a wide compositional range, with δ¹³C ranging from −38.5‰ to +5.0‰, and δ¹⁵N from −39.4‰ to +15.0‰. These values significantly exceed the typical mantle δ¹³C and δ¹⁵N values of −5‰ ± 3‰, indicating that the diamond formation may be influenced by subducted crustal materials. During crystallization, diamonds can encapsulate surrounding materials as inclusions, which are divided into three types based on their formation sequence relative to the host diamond: preformed, syngenetic, and epigenetic. Syngenetic inclusions are particularly valuable for constraining crystallization conditions and the genesis of diamonds. Furthermore, geochronology studies of radioactive isotope-bearing syngenetic inclusions are helpful to clarify the age of diamond formation. Usually, mantle-derived diamonds exhibit Archean age, whereas metamorphic diamonds are associated with subduction, showing younger ages that could be associated with metamorphic events. Therefore, the formation conditions and genesis of diamonds can be clearly constrained through integrating investigations of inclusions, nitrogen occurrence modes, and C-N isotopic compositions. The characteristics of occurrence modes, inclusions, and C-N isotope compositions of different types of diamonds are systematically reviewed in this paper, providing critical insights into their genesis and contributing to a deeper understanding of diamond formation processes in Earth’s interior. Full article

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

15 pages, 570 KiB

Open AccessArticle

Optimization of Bioleaching Conditions Using Acidithiobacillus ferrooxidans at Low Temperatures in a Uranium Mining Environment

by Gaukhar Turysbekova, Yerkin Bektay, Akmurat Altynbek, Dmitriy Berillo, Bauyrzhan Shiderin and Maxat Bektayev

Minerals 2025, 15(7), 727; https://doi.org/10.3390/min15070727 - 11 Jul 2025

Abstract

Systematic studies were conducted at one of the uranium deposits in Kazakhstan. Native strains of Acidithiobacillus ferrooxidans bacteria were found in leaching solutions at the deposit. The modeling of iron species in the culturing medium was analyzed using Medusa software v.2.0.5. To intensify [...] Read more.

Systematic studies were conducted at one of the uranium deposits in Kazakhstan. Native strains of Acidithiobacillus ferrooxidans bacteria were found in leaching solutions at the deposit. The modeling of iron species in the culturing medium was analyzed using Medusa software v.2.0.5. To intensify the process, the bacterial strains were propagated in laboratory conditions, and strains available in the laboratory were added. The ability of bacteria to oxidize divalent iron to trivalent iron at 8 °C in laboratory conditions was established, but the oxidation rate was low. It was found that the limiting stage of bioleaching use in deposit conditions is the temperature mode, the content of divalent iron, and oxygen. A biomass volume of 15 L was initially cultivated under laboratory conditions, and subsequently scaled up to 3 m³ in production using three 1 m³ pachucas with air aeration. In addition, pilot tests were carried out directly in production conditions and biomass in the volume of over 30 m³ was produced. The kinetics of the oxidation process of divalent iron to trivalent iron in 1 g/h under production conditions was established. The features of the bioleaching process at the field are shown as follows: since production, the solution contains the main microelements for the nutrition and reproduction of bacteria, and recommendations for the use of bioleaching are proposed. Research has established that under conditions of a shortage of divalent iron in the solution, sulfuric acid is formed due to sulfur-containing substances. It was observed that for the effective conversion of divalent iron to trivalent iron, bacteria of the provided strain and air (oxygen) supply are sufficient. The corresponding recommendations were issued during the work. Full article

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

58 pages, 36912 KiB

Open AccessArticle

The Mazenod–Sue–Dianne IOCG District of the Great Bear Magmatic Zone Northwest Territories, Canada

by A. Hamid Mumin and Mark Hamilton

Minerals 2025, 15(7), 726; https://doi.org/10.3390/min15070726 - 11 Jul 2025

Abstract

The Mazenod Lake region of the southern Great Bear Magmatic Zone (GBMZ) of the Northwest Territories, Canada, comprises the north-central portion of the Faber volcano-plutonic belt. Widespread and abundant surface exposure of several coalescing hydrothermal systems enables this paper to document, without ambiguity, [...] Read more.

The Mazenod Lake region of the southern Great Bear Magmatic Zone (GBMZ) of the Northwest Territories, Canada, comprises the north-central portion of the Faber volcano-plutonic belt. Widespread and abundant surface exposure of several coalescing hydrothermal systems enables this paper to document, without ambiguity, the relationships between geology, structure, alteration, and mineralization in this well exposed iron-oxide–copper–gold (IOCG) mineral system. Mazenod geology comprises rhyodacite to basaltic-andesite ignimbrite sheets with interlayered volcaniclastic sedimentary rocks dominated by fine-grained laminated tuff sequences. Much of the intermediate to mafic nature of volcanic rocks is masked by low-intensity but pervasive metasomatism. The region is affected by a series of coalescing magmatic–hydrothermal systems that host the Sue–Dianne magnetite–hematite IOCG deposit and several related showings including magnetite, skarn, and iron oxide apatite (IOA) styles of alteration ± mineralization. The mid to upper levels of these systems are exposed at surface, with underlying batholith, pluton and stocks exposed along the periphery, as well as locally within volcanic rocks associated with more intense alteration and mineralization. Widespread alteration includes potassic and sodic metasomatism, and silicification with structurally controlled giant quartz complexes. Localized tourmaline, skarn, magnetite–actinolite, and iron-oxide alteration occur within structural breccias, and where most intense formed the Sue–Dianne Cu-Ag-Au diatreme-like breccia deposit. Magmatism, volcanism, hydrothermal alteration, and mineralization formed during a negative tectonic inversion within the Wopmay Orogen. This generated a series of oblique offset rifted basins with continental style arc magmatism and extensional structures unique to GBMZ rifting. All significant hydrothermal centers in the Mazenod region occur along and at the intersections of crustal faults either unique to or put under tension during the GBMZ inversion. Full article

(This article belongs to the Special Issue Footprints of Mineral Systems with IOCG, IOA and Affiliated Critical Metal Deposits: From Metasomatism to Metamorphism)

21 pages, 8512 KiB

Open AccessArticle

Geogenic and Anthropogenic Origins of Mercury and Other Potentially Toxic Elements in the Ponce Enriquez Artisanal and Small-Scale Gold Mining District, Southern Ecuador

by Silvia Fornasaro, Paolo Fulignati, Anna Gioncada, Daniel Garces and Maurizio Mulas

Minerals 2025, 15(7), 725; https://doi.org/10.3390/min15070725 - 11 Jul 2025

Abstract

Artisanal and small-scale gold mining (ASGM) poses significant environmental challenges globally, particularly due to mercury (Hg) use. As an example, in Ecuador, Hg use still persists, despite its official ban in 2015. This study investigated the geogenic and anthropogenic contributions of potentially toxic [...] Read more.

Artisanal and small-scale gold mining (ASGM) poses significant environmental challenges globally, particularly due to mercury (Hg) use. As an example, in Ecuador, Hg use still persists, despite its official ban in 2015. This study investigated the geogenic and anthropogenic contributions of potentially toxic elements (PTEs) in the Ponce Enriquez Mining District (PEMD), a region characterized by hydrothermally altered basaltic bedrock and Au-mineralized quartz veins. To assess local baseline values and identify PTE-bearing minerals, a comprehensive geochemical, mineralogical, and petrographic analysis was conducted on bedrock and mineralized veins. These findings reveal distinct origins for the studied PTEs, which include Hg, As, Cu, Ni, Cr, Co, Sb, Zn, and V. Specifically, Hg concentrations in stream sediments downstream (up to 50 ppm) far exceed natural bedrock levels (0.03–0.707 ppm), unequivocally indicating significant anthropogenic input from gold amalgamation. Furthermore, copper shows elevated concentration primarily linked to gold extraction. Conversely, other elements like As, Ni, Cr, Co, Sb, Zn, and V are primarily exhibited to be naturally abundant in basalts due to the presence of primary mafic minerals and to hydrothermal alterations, with elevated concentrations particularly seen in sulfides like pyrite and arsenopyrite. To distinguish natural geochemical anomalies from mining-related contamination, especially in volcanic terrains, this study utilizes Upper Continental Crust (UCC) normalization and local bedrock baselines. This multi-faceted approach effectively helped to differentiate basalt subgroups and assess natural concentrations, thereby avoiding misinterpretations of naturally elevated element concentrations as mining-related pollution. Crucially, this work establishes a robust local geochemical baseline for the PEMD area, providing a critical framework for accurate environmental risk assessments and sustainable mineral resource management, and informing national environmental quality standards and remediation efforts in Ecuador. It underscores the necessity of evaluating local geology, including inherent mineralization, when defining environmental baselines and understanding the fate of PTEs in mining-impacted environments. Full article

(This article belongs to the Special Issue Mineralogical and Chemical Characterization of Rocks, Soils, Sediments, and Water Containing Hazardous Substances)

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21 pages, 6537 KiB

Open AccessArticle

The Peak Metamorphic P–T Conditions of the Sanbagawa Schists in the Shibukawa Area, Central Japan: Application of Raman Geothermobarometry

by Yuki Tomioka, Yui Kouketsu and Katsuyoshi Michibayashi

Minerals 2025, 15(7), 724; https://doi.org/10.3390/min15070724 - 11 Jul 2025

Abstract

The quantitative pressure (P)–temperature (T) conditions of low-grade metamorphic rocks, such as pumpellyite–actinolite and greenschist facies, are largely unknown mainly owing to the difficulty in applying thermodynamic methods despite their importance in understanding the protolith and metamorphism within subducting [...] Read more.

The quantitative pressure (P)–temperature (T) conditions of low-grade metamorphic rocks, such as pumpellyite–actinolite and greenschist facies, are largely unknown mainly owing to the difficulty in applying thermodynamic methods despite their importance in understanding the protolith and metamorphism within subducting oceanic crusts. In this study, Raman spectroscopy was applied to constrain the peak metamorphic conditions independent of thermodynamic methods for the lowest grade part (chlorite zone) of the Sanbagawa schists in the Shibukawa area, central Japan, where research on metamorphic conditions is limited. The metamorphic peak temperature of the pelitic schists estimated by Raman carbonaceous material geothermometry was 307 ± 27 °C to 395 ± 16 °C, which increased towards the northern fault (Median Tectonic Line). Raman geobarometry using the quartz-inclusions-in-spessartine system on a siliceous schist sample estimated a peak metamorphic pressure of 0.78–0.94 GPa at 360–390 °C. These results suggest that the rocks in the Shibukawa area were subducted to a depth equivalent to that of the garnet zone in central Shikoku and were then exhumed without experiencing further heating. The combination of Raman carbonaceous material geothermometry and Raman geobarometry (Raman geothermobarometry) can be effectively applied to estimate the metamorphic conditions of low-grade metamorphic rocks independent of thermodynamic methods. Full article

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

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17 pages, 5354 KiB

Open AccessArticle

Deep-Water Traction Current Sedimentation in the Lower Silurian Longmaxi Formation Siliceous Shales, Weiyuan Area, Sichuan Basin, China, Using Nano-Resolution Petrological Evidence

by Xiaofeng Zhou, Jun Zhao, Baonian Yan, Zeyu Zhu, Nan Yang, Pingping Liang and Wei Guo

Minerals 2025, 15(7), 723; https://doi.org/10.3390/min15070723 - 10 Jul 2025

Abstract

Despite the shale revolution triggering global shale oil and gas exploration, our understanding of the sedimentary environments of deep-water organic-matter-rich shale remains unclear. The sedimentary environment and facies of some siliceous shales at the bottom of the Longmaxi Formation in the Weiyuan area [...] Read more.

Despite the shale revolution triggering global shale oil and gas exploration, our understanding of the sedimentary environments of deep-water organic-matter-rich shale remains unclear. The sedimentary environment and facies of some siliceous shales at the bottom of the Longmaxi Formation in the Weiyuan area of the Sichuan Basin, China, were therefore analyzed. Nano-resolution petrological characterization and genesis analysis of the siliceous shales studied were conducted using nano-resolution petrologic image datasets. We identified these siliceous shales as microbial mats formed by deep-water traction current sedimentation. The microbial mats’ formation and burial diagenesis processes were divided into seven stages. The silt-grade bioclastic carpet deposits initially, colonizing mud-grade siliceous microbes and forming the siliceous microbial mat. Subsequently, carbohydrate-rich microbes thrive in sediment voids, forming the carbohydrate-rich microbial mat. Additionally, SOM undergoes four stages of burial diagenesis process, progressing from kerogens to pre-oil bitumen generation and ultimately transforming into porous pyrobitumen and nonporous pyrobitumen. This study will improve the understanding of deep-water traction current sedimentation and has implications for guiding shale gas exploration and development. Full article

(This article belongs to the Special Issue Deep-Time Source-to-Sink in Continental Basins)

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20 pages, 2516 KiB

Open AccessArticle

Utilisation of Pyrometallurgical Wastes: Recovery of Copper from the Spent Refractory Bricks from a Smelter in Namibia

by Titus Nghipulile, Godfrey Dzinomwa, Benjamin Mapani, Jaquiline Tatenda Kurasha and Chanda Anamela Kambobe

Minerals 2025, 15(7), 722; https://doi.org/10.3390/min15070722 - 10 Jul 2025

Abstract

The reprocessing of metallurgical wastes to recover much-needed metals such as copper not only ensures an adequate supply of metals but also contributes to the cleaning of the environment. A copper smelter in Namibia accumulated significant amounts of spent refractory bricks that are [...] Read more.

The reprocessing of metallurgical wastes to recover much-needed metals such as copper not only ensures an adequate supply of metals but also contributes to the cleaning of the environment. A copper smelter in Namibia accumulated significant amounts of spent refractory bricks that are enriched with metal values including copper. This supposedly waste material can potentially serve as a supplement to the ore concentrate, as a smelter feedstock for this toll smelter. Representative samples of crushed bricks, designated as Sample 1 and Sample 2, were used for mineralogical characterisation and flotation test work. The assays for Sample 1 and Sample 2 were 14% Cu and 18% Cu, respectively. Microscopy results identified various copper phases including metallic Cu, bornite, malachite and chalcopyrite. Batch flotation tests were conducted to investigate the effect of grind size (P₈₀ of 53, 75 and 106 μm), pulp pH (natural pulp pH, 10, 10.5 and 11) and collector (potassium amyl xanthate, PAX) dosage (70, 100 and 130 g/t) on the recovery of copper, concentrate grade and weight recovery. In some tests, a co-collector (dithiophosphate, DTP) and sulphidiser (Na₂S) were also added in the quest to maximise the recovery of copper. Based on the test conditions investigated in this study, the grind size is the key variable affecting the recovery of copper. The best copper recovery of 86% (with a weight recovery in the range of 42 to 45% (w/w) and concentrate grade of 37% Cu) was achieved for the finest grind size of 53 μm. The reagent suite that yielded the best recovery was 70 g/t PAX with no addition of the sulphidiser while the pH was 10. There is scope for developing the process routes to recover other valuable metals such as iron, lead and zinc that are also in the spent bricks, as well as potential reuse of the spent bricks (after recovering valuable metals) to make new refractory bricks. Full article

(This article belongs to the Special Issue Circular Economy of Remining Secondary Raw Materials)

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20 pages, 9353 KiB

Open AccessArticle

Genesis of the Shabaosi Gold Field in the Western Mohe Basin, Northeast China: Evidence from Fluid Inclusions and H-O-S-Pb Isotopes

by Xiangwen Li, Zhijie Liu, Lingan Bai, Jian Wang, Shiming Liu and Guan Wang

Minerals 2025, 15(7), 721; https://doi.org/10.3390/min15070721 - 10 Jul 2025

Abstract

The Shabaosi gold field is located in the western Mohe Basin, part of the northern Great Xing’an Range, NE China, and contains multiple gold deposits. However, the sources of the ore-forming materials, the fluid evolution, and the genesis of these gold deposits have [...] Read more.

The Shabaosi gold field is located in the western Mohe Basin, part of the northern Great Xing’an Range, NE China, and contains multiple gold deposits. However, the sources of the ore-forming materials, the fluid evolution, and the genesis of these gold deposits have been disputed, especially regarding the classification of these deposits as either epithermal or orogenic gold systems. Based on detailed field geological investigations and previous research, we conducted systematic research on the Shabaosi, Sanshierzhan, Laogou, and Balifang gold deposits using fluid inclusion and H-O-S-Pb isotope data, with the aim of constraining the fluid properties, sources, and mineralization processes. Fluid inclusion analyses reveal diverse types, including vapor-rich, vapor–liquid, CO₂-bearing, CO₂-rich, and pure CO₂. Additionally, only a very limited number of daughter mineral-bearing fluid inclusions have been observed exclusively in the Laogou gold deposit. During the early stages, the peak temperature primarily ranged from 240 °C to 280 °C, with salinity concentrations between 6 and 8 wt% NaCl equiv., representing a medium–low temperature, low salinity, and a heterogeneous CO₂-CH₄-H₂O-NaCl system. With the influx of meteoric water, the fluids evolved gradually into a simple NaCl-H₂O system with low temperatures (160–200 °C) and salinities (4–6 wt%). The main mineralization stage exhibited peak temperatures of 220–260 °C and salinities of 5–8 wt% NaCl equiv., corresponding to an estimated formation depth of 1.4–3.3 km. The δD_V-SMOW values (−138.3‰ to −97.0‰) and δ¹⁸O_V-SMOW values (−7.1‰ to 16.2‰) indicate that the magmatic–hydrothermal fluids were progressively diluted by meteoric water during mineralization. The sulfur isotopic compositions (δ³⁴S = −0.9‰ to 1.8‰) and lead isotopic ratios (²⁰⁸Pb/²⁰⁴Pb = 38.398–38.579, ²⁰⁷Pb/²⁰⁴Pb = 15.571–15.636, and ²⁰⁶Pb/²⁰⁴Pb = 18.386–18.477) demonstrate that the gold predominantly originated from deep magmatic systems, with potential crustal contamination. Comparative analyses indicate that the Shabaosi gold field should be classified as a epizonal orogenic gold system, which shows distinct differences from epithermal gold deposits and corresponds to the extensional tectonic setting during the late-stage evolution of the Mongol–Okhotsk orogenic belt. Full article

(This article belongs to the Special Issue Genesis and Metallogeny of Non-ferrous and Precious Metal Deposits, 2nd Edition)

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26 pages, 2032 KiB

Open AccessReview

A Cross-Disciplinary Review of Rare Earth Elements: Deposit Types, Mineralogy, Machine Learning, Environmental Impact, and Recycling

by Mustafa Rezaei, Gabriela Sanchez-Lecuona and Omid Abdolazimi

Minerals 2025, 15(7), 720; https://doi.org/10.3390/min15070720 - 9 Jul 2025

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Abstract

Rare-earth elements (REEs), including lanthanides, scandium, and yttrium, are important for advanced technologies such as renewable energy systems, electronics, medical diagnostics, and precision agriculture. Despite their relative crustal abundance, REE extraction is impeded by complex geochemical behavior, dispersed distribution, and environmental challenges. This [...] Read more.

Rare-earth elements (REEs), including lanthanides, scandium, and yttrium, are important for advanced technologies such as renewable energy systems, electronics, medical diagnostics, and precision agriculture. Despite their relative crustal abundance, REE extraction is impeded by complex geochemical behavior, dispersed distribution, and environmental challenges. This review presents a comprehensive overview of REE geochemistry, mineralogy, and major deposit types including carbonatites, alkaline igneous rocks, laterites, placer deposits, coal byproducts, and marine sediments. It also highlights the global distribution and economic potential of key REE projects. The integration of machine learning has further enhanced exploration by enabling deposit classification and geochemical modeling, especially in data-limited regions. Environmental and health challenges associated with REE mining, processing, and electronic waste (e-waste) recycling are studied, along with the expanding use of REEs in agriculture and medicine. Some recycling efforts offer promise for supply diversification, but significant technological and economic barriers remain. Ensuring a secure and sustainable REE supply will require integrated approaches combining advanced analytics, machine learning, responsible extraction, and coordinated policy efforts. The present review offers a general overview that can be useful for informing future studies and resource-related discussions. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: "Critical and Strategic Minerals", 2nd Edition)

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11 pages, 1263 KiB

Open AccessArticle

Characteristics of Laterite Soil for Potential Geopolymer Applications

by Zeyneb K. Nuru, Walied A. Elsaigh and Elsabe P. Kearsley

Minerals 2025, 15(7), 719; https://doi.org/10.3390/min15070719 - 9 Jul 2025

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Abstract

Laterite soil is widely found in various tropical and subtropical regions. This study focuses on the physical and chemical properties of laterite soil as a precursor for geopolymer synthesis. The characteristics of the soil were determined through experimental analyses, including XRF, XRD, SEM, [...] Read more.

Laterite soil is widely found in various tropical and subtropical regions. This study focuses on the physical and chemical properties of laterite soil as a precursor for geopolymer synthesis. The characteristics of the soil were determined through experimental analyses, including XRF, XRD, SEM, EDS, FTIR, TGA/DTA, and pH measurements. XRF analysis revealed that the primary chemical oxides are silica, alumina, and iron oxide, which are very essential for geopolymer production. Both XRD and FTIR assessments revealed that the calcination process applied to laterite diminishes its crystallinity while enhancing its amorphous nature, thereby improving its reactivity. TGA and DTA results confirmed significant weight loss and dihydroxylation between 400 °C and 700 °C, while temperatures above 700 °C showed minimal weight loss and no further dihydroxylation. The pH of the tested laterite soil was measured at 5.35, indicating strong acidic behaviour. Based on these combined chemical and physical analyses, this study concludes that laterite soil is a viable precursor material for geopolymer synthesis. Full article

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16 pages, 2052 KiB

Open AccessArticle

Exploring the Potential of Granite Sawing Sludge from Cuasso Al Monte (Italy) for the Development of Aluminosilicate Gel for a Sustainable Industry

by Sabrina Elettra Zafarana, Alessandro Achilli, Germana Barone, Danilo Bersani, Claudio Finocchiaro, Laura Fornasini, Silvia Portale and Paolo Mazzoleni

Minerals 2025, 15(7), 718; https://doi.org/10.3390/min15070718 - 9 Jul 2025

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Abstract

This study explores the feasibility of utilizing granite sawing sludge (FC) as a precursor to produce alkali-activated materials (AAMs). To enhance the reactivity of the system, metakaolin (MK) was added and binary mixtures were synthetized. A multidisciplinary approach, including mineralogical, chemical and mechanical [...] Read more.

This study explores the feasibility of utilizing granite sawing sludge (FC) as a precursor to produce alkali-activated materials (AAMs). To enhance the reactivity of the system, metakaolin (MK) was added and binary mixtures were synthetized. A multidisciplinary approach, including mineralogical, chemical and mechanical analysis, was employed to assess the suitability of these precursors to produce AAMs. X-Ray diffraction (XRD) and Fourier-Transform Infrared spectroscopy (FT-IR) confirmed the occurred activation reaction with the consequent increase in the amorphous content. Raman spectroscopy was used to further explore the mineralogical composition of the consolidated specimens, helping in the detection of salts, whose formation is ascribed to secondary carbonatation processes. Morphological analysis (SEM-EDS) displayed relatively uniform microstructures for all specimens. Compressive strength tests revealed that MK rich samples achieved best values compared to FC rich formulations, which exhibited reduced strength resistance. This study highlights, for the first time, the benefits of incorporating Cuasso al Monte granite sawing sludges into alkali-activated binders. Results suggested that the incorporation of FC is recommended for both environmental and economic advantages. Full article

(This article belongs to the Special Issue Recycling of Industrial Waste for the Development of Sustainable Materials)

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24 pages, 17095 KiB

Open AccessArticle

Origin of Dolomite in the Majiagou Formation (Ordovician) of the Liujiang Basin, China: Evidence from Crystal Structure, Isotope and Element Geochemistry

by Huaiyu Xue, Jianping Qian and Wentan Xu

Minerals 2025, 15(7), 717; https://doi.org/10.3390/min15070717 - 8 Jul 2025

Viewed by 175

Abstract

Research on dolomite has long been central in geoscience, yet understanding the origin of Middle Ordovician dolomite in the northeast of the North China Platform remains limited. Based on this, this study focuses on dolomite of Majiagou Formation in Liujiang Basin, and analyzes [...] Read more.

Research on dolomite has long been central in geoscience, yet understanding the origin of Middle Ordovician dolomite in the northeast of the North China Platform remains limited. Based on this, this study focuses on dolomite of Majiagou Formation in Liujiang Basin, and analyzes its genetic process. The research is based on the measured geological section and conducts high-precision analysis and testing, encompassing major and trace elements, rare earth elements, stable carbon and oxygen isotopes, strontium isotopes, crystal structure parameters, and micro-area elements of dolomite. Analysis of V/(V + Ni), Th/U, Sr/Ba, Mn/Sr, (Eu/Eu*) _N, (Ce/Ce*) _N, and the dolomite crystal parameters indicates that the formation of dolomite is related to evaporation. Furthermore, REE and micro-area characteristics of dolomite, as well as the significant negative deviation of δ¹³C and δ¹⁸O, in conjunction with ⁸⁷Sr/⁸⁶Sr deviating from the standard values of Ordovician seawater, suggest an origin of the dolomite in this formation with mixed-water dolomitization and burial dolomitization. A comprehensive assessment of dolomite formation suggests three distinct stages: early-stage evaporation dolomitization, subsequent mixed-water dolomitization, and later-stage burial dolomitization. The research further corroborated that dolomite formation is a complex outcome resulting from the interplay of various geological processes over space and time. Full article

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

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22 pages, 16452 KiB

Open AccessArticle

The Uranium Enrichment Mechanism of Hydrocarbon-Bearing Fluids in Aeolian Sedimentary Background Uranium Reservoirs of the Ordos Basin

by Tao Zhang, Jingchao Lei, Cong Hu, Xiaofan Zhou, Chao Liu, Lei Li, Qilin Wang, Yan Hao and Long Guo

Minerals 2025, 15(7), 716; https://doi.org/10.3390/min15070716 - 8 Jul 2025

Viewed by 213

Abstract

Significant uranium exploration breakthroughs have been achieved in the eolian deposits of the uranium reservoirs in the southwestern part of the Ordos Basin. The redox environment remains a crucial factor in controlling the migration and precipitation of uranium. This study, through rock mineralogical [...] Read more.

Significant uranium exploration breakthroughs have been achieved in the eolian deposits of the uranium reservoirs in the southwestern part of the Ordos Basin. The redox environment remains a crucial factor in controlling the migration and precipitation of uranium. This study, through rock mineralogical observations and hydrocarbon gas composition analysis, combined with the regional source rock and basin tectonic evolution history, reveals the characteristics of the reducing medium and the mineralization mechanisms involved in uranium ore formation. The Lower Cretaceous Luohe Formation uranium reservoirs in the study area exhibit a notable lack of common reducing media, such as carbonaceous debris and pyrite. However, the total hydrocarbon gases in the Luohe Formation range from 2967 to 20,602 μmol/kg, with an average of 8411 μmol/kg—significantly higher than those found in uranium reservoirs elsewhere in China, exceeding them by 10 to 100 times. Due to the absence of other macroscopically visible organic matter, hydrocarbon gases are identified as the most crucial reducing agent for uranium mineralization. These gases consist predominantly of methane and originate from the Triassic Yanchang Formation source rock. Faults formed during the Indosinian, Yanshanian, and Himalayan tectonic periods effectively connect the Cretaceous uranium reservoirs with the oil and gas reservoirs of the Triassic and Jurassic, providing pathways for the migration of deep hydrocarbon fluids into the Cretaceous uranium reservoirs. The multiphase tectonic evolution of the Ordos Basin since the Cenozoic has facilitated the development of faults, ensuring a sufficient supply of reducing media for uranium reservoirs in an arid sedimentary context. Additionally, the “Replenishment-Runoff-Drainage System” created by tectonic activity promotes a continuous supply of uranium- and oxygen-bearing fluids to the uranium reservoirs, resulting in a multi-energy coupling mineralization effect. Full article

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

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21 pages, 12768 KiB

Open AccessArticle

Applicability Analysis with the Improved Spectral Unmixing Models Based on the Measured Hyperspectral Data of Mixed Minerals

by Haonan Zhang, Lizeng Duan, Yang Zhang, Huayu Li, Donglin Li and Yan Li

Minerals 2025, 15(7), 715; https://doi.org/10.3390/min15070715 - 6 Jul 2025

Viewed by 346

Abstract

Hyperspectral technology can non-destructively identify and analyze minerals. However, the quantitative inversion of different components in mixed minerals remains difficult in mineral spectral analysis. A set of mineral samples was prepared from dolomite and gypsum, varying in their components. Three improved spectral decomposition [...] Read more.

Hyperspectral technology can non-destructively identify and analyze minerals. However, the quantitative inversion of different components in mixed minerals remains difficult in mineral spectral analysis. A set of mineral samples was prepared from dolomite and gypsum, varying in their components. Three improved spectral decomposition models were proposed: the Continuum Removal-Fully Constrained Linear Spectral Model (CR-FCLSM), the Natural Logarithm-Fully Constrained Linear Spectral Model (NL-FCLSM), and the Ratio Derivative Model (RDM). The unmixing Abundance Error (AE) was 0.161, 0.051, and 0.082 for CR-FCLSM, NL-FCLSM, and RDM. The results of the three improved linearized unmixing models are better than those of the traditional linear spectral unmixing model. The NL-FCLSM effectively enhanced the linear characteristics of the spectrum, making it more suitable for two mineral mixing scenarios. The systematic bias of CR-FCLSM may be due to its insufficient sensitivity to low-abundance signals. The stability of RDM depends on the selection of a strong linear band. The unmixing experiments of the measured spectra and the data from the USGS spectral library demonstrate that the improved linear unmixing model is more accurate than the traditional linear spectral model and simpler to calculate than the nonlinear spectral model, providing a new approach for demodulating hyperspectral images. Full article

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

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30 pages, 3010 KiB

Open AccessArticle

The Concentration of Nickel and Cobalt from Agios Ioannis Laterites by Multi-Gravity Separator

by Amina Eljoudiani, Moacir Medeiros Veras, Carlos Hoffmann Sampaio, Josep Oliva Moncunill, Stylianos Tampouris and Jose Luis Cortina Pallas

Minerals 2025, 15(7), 714; https://doi.org/10.3390/min15070714 - 4 Jul 2025

Viewed by 210

Abstract

Asbolane is a secondary source of cobalt (Co) and manganese (Mn), essential for battery and alloy production. Enhancing the utilization of low-grade ores, typically containing ~1.2% Co and 14.7% Mn, is vital for conserving high-grade resources. However, fine grinding for such ores presents [...] Read more.

Asbolane is a secondary source of cobalt (Co) and manganese (Mn), essential for battery and alloy production. Enhancing the utilization of low-grade ores, typically containing ~1.2% Co and 14.7% Mn, is vital for conserving high-grade resources. However, fine grinding for such ores presents challenges for conventional gravity separation. This study investigates the effectiveness of the Multi-Gravity Separator (MGS) in processing finely disseminated asbolane ore from Agios Ioannis, Greece. The study was conducted at the Mineral Processing Laboratory of UPC/Bases Manresa. Two size fractions, D₈₀ (−100 +50 µm and −50 µm), were tested under varying drum speeds, tilt angles, and wash water flows. Response surface methodology (RSM) was implemented using Python-optimized (version 3.15) process parameters. The results demonstrate that a concentrate with 2.6% Co and 32.5% Mn can be obtained, achieving 82.1% Co recovery. Independent and multi-objective optimizations confirm MGS as a viable method for recovering Co and Mn from complex low-grade ores, with reduced overgrinding-related energy losses essential for production. The study aimed to implement and enhance low-grade asbolane ore from a feed containing 2.6% Co and 32.5% Mn. Variables were optimized with a multi-objective target, demonstrating their effectiveness. Full article

(This article belongs to the Special Issue Recycling of Mining and Solid Wastes)

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20 pages, 1055 KiB

Open AccessArticle

Reduction-Driven Mobilization of Structural Fe in Clay Minerals with High Fe Content

by Anke Neumann, Luiza Notini, W. A. P. Jeewantha Premaratne, Drew E. Latta and Michelle M. Scherer

Minerals 2025, 15(7), 713; https://doi.org/10.3390/min15070713 - 4 Jul 2025

Viewed by 121

Abstract

Clay minerals contain significant amounts of Fe in their alumosilicate framework, and this structural Fe can be reduced and re-oxidized, constituting a potentially renewable source of reduction equivalents in sedimentary environments. However, dissolution and/or clay mineral transformations during microbial Fe reduction contradict this [...] Read more.

Clay minerals contain significant amounts of Fe in their alumosilicate framework, and this structural Fe can be reduced and re-oxidized, constituting a potentially renewable source of reduction equivalents in sedimentary environments. However, dissolution and/or clay mineral transformations during microbial Fe reduction contradict this concept. Here, we investigate how Fe reduction and re-oxidation affect the propensity of Fe to be released from the clay mineral structure and use selective sequential extractions in combination with Mössbauer spectroscopy. Negligible amounts of Fe were released in the sequential extraction of high Fe content clay minerals NAu-1 and NAu-2. Once aqueous Fe(II) was added as a reductant, the extraction procedure recovered the initially added Fe amount and up to 30% of the Fe from the clay mineral structure as both Fe(II) and Fe(III). Similar extents of Fe mobilization were found for clay minerals partly reduced (7%–20%) with dithionite, suggesting that mobilization was reduction-induced and independent of the source of reduction equivalents (Fe(II), dithionite). Although higher Fe reduction extents mobilized more structural Fe, i.e., >90% in fully reduced clay minerals, re-oxidation largely reverted the reduction-induced Fe mobilization in clay minerals. Our finding of reduction-driven Fe mobilization provides a plausible explanation for conflicting reports on Fe release from clay minerals and how extensive Fe atom exchange between aqueous and clay mineral Fe occurs. Full article

(This article belongs to the Special Issue Redox Reactivity of Iron Minerals in the Geosphere, 2nd Edition)

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15 pages, 2361 KiB

Open AccessArticle

Synergistic Leaching of Low-Grade Tungsten–Molybdenum Ore via a Novel KMnO₄-Na₂CO₃-NaHCO₃ Composite System Guided by Process Mineralogy

by Jian Kang, Linlin Tong, Qin Zhang, Han Zhao, Xinyao Wang, Bin Xiong and Hongying Yang

Minerals 2025, 15(7), 712; https://doi.org/10.3390/min15070712 - 3 Jul 2025

Viewed by 274

Abstract

The mineral processing of a low-grade tungsten-molybdenum ore (LGTMO) was investigated to assess the potential of recovering molybdenum (Mo) and tungsten (W). Techniques such as Polarizing Microscope (PM), Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS), Mineral Liberation Analysis (MLA), and Advanced Mineral Identification and [...] Read more.

The mineral processing of a low-grade tungsten-molybdenum ore (LGTMO) was investigated to assess the potential of recovering molybdenum (Mo) and tungsten (W). Techniques such as Polarizing Microscope (PM), Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS), Mineral Liberation Analysis (MLA), and Advanced Mineral Identification and Characterization System (AMICS) were employed. The recoverable metals in the ore are Mo (0.158% ± 0.03%) and W (0.076% ± 0.02%). Mo exists in two forms: 63.30% as molybdenite and 36.7% as powellite (CaMo_xW_1−xO₄). W is present as 75.26% scheelite and 24.74% powellite. The complete dissociation rates of molybdenite and scheelite-powellite are 27.14% and 88.87%, respectively. Particles of scheelite-powellite with a diameter less than 10 µm account for 34.61%, while molybdenite particles with a diameter below 10 µm make up 72.73%. Scheelite-powellite is mainly associated with olivine and dolomite, while molybdenite is mainly associated with pyroxene, calcite, and hornblende. Based on the process mineralogy, the mineralogical factors influencing the flotation recovery of molybdenite and scheelite-powellite were analyzed. Finally, a complete hydrometallurgical leaching test was carried out. The optimal experimental conditions are as follows: liquid-solid ratio of 6 mL/g, KMnO₄ concentration of 0.015 mol/L, Na₂CO₃ concentration of 0.12 mol/L, NaHCO₃ concentration of 0.024 mol/L, leaching time of 4 h, and leaching temperature of 85 °C. Under these conditions, the leaching efficiencies of Mo and W reach 79.23% and 41.41%, respectively. This study presents a novel approach for the recovery of refractory W and Mo resources in LGTMO while simultaneously providing a theoretical basis for the high-efficiency utilization of these resources. Full article

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

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24 pages, 6164 KiB

Open AccessArticle

Transformer–GCN Fusion Framework for Mineral Prospectivity Mapping: A Geospatial Deep Learning Approach

by Le Gao, Gnanachandrasamy Gopalakrishnan, Adel Nasri, Youhong Li, Yuying Zhang, Xiaoying Ou and Kele Xia

Minerals 2025, 15(7), 711; https://doi.org/10.3390/min15070711 - 3 Jul 2025

Viewed by 280

Abstract

Mineral prospectivity mapping (MPM) is a pivotal technique in geoscientific mineral resource exploration. To address three critical challenges in current deep convolutional neural network applications for geoscientific mineral resource prediction—(1) model bias induced by imbalanced distribution of ore deposit samples, (2) deficiency in [...] Read more.

Mineral prospectivity mapping (MPM) is a pivotal technique in geoscientific mineral resource exploration. To address three critical challenges in current deep convolutional neural network applications for geoscientific mineral resource prediction—(1) model bias induced by imbalanced distribution of ore deposit samples, (2) deficiency in global feature extraction due to excessive reliance on local spatial correlations, and (3) diminished discriminative capability caused by feature smoothing in deep networks—this study innovatively proposes a T-GCN model integrating Transformer with graph convolutional neural networks (GCNs). The model achieves breakthrough performance through three key technological innovations: firstly, constructing a global perceptual field via Transformer’s self-attention mechanism to effectively capture long-range geological relationships; secondly, combining GCNs’ advantages in topological feature extraction to realize multi-scale feature fusion; and thirdly, designing a feature enhancement module to mitigate deep network degradation. In practical application to the PangXD ore district, the T-GCN model achieved a prediction accuracy of 97.27%, representing a 3.76 percentage point improvement over the best comparative model, and successfully identified five prospective mineralization zones, demonstrating its superior performance and application value under complex geological conditions. Full article

(This article belongs to the Special Issue Application of Big Data Mining, Machine Learning and Artificial Intelligence in Geoscience, 2nd Edition)

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28 pages, 11235 KiB

Open AccessArticle

Petrogenesis, Tectonic Setting, and Metallogenic Constraints of Tin-Bearing Plutons in the Karamaili Granite Belt of Eastern Junggar, Xinjiang (NW China)

by Shuai Yuan, Qiwei Wang, Bowen Zhang, Xiaoping Gong and Chunmei Su

Minerals 2025, 15(7), 710; https://doi.org/10.3390/min15070710 - 3 Jul 2025

Viewed by 442

Abstract

The Karamaili Granite Belt (KGB) in the southern margin of the Eastern Junggar is the most important tin metallogenic belt in the southwestern Central Asian Orogenic Belt. The plutons in the western part have a close genetic relationship with tin mineralization. The zircon [...] Read more.

The Karamaili Granite Belt (KGB) in the southern margin of the Eastern Junggar is the most important tin metallogenic belt in the southwestern Central Asian Orogenic Belt. The plutons in the western part have a close genetic relationship with tin mineralization. The zircon U-Pb ages of the Kamusite, Laoyaquan, and Beilekuduke plutons are 315.1 ± 3.4 Ma, 313.6 ± 2.9 Ma, and 316.5 ± 4.6 Ma, respectively. The plutons have high silica (SiO₂ = 75.53%–77.85%), potassium (K₂O = 4.43%–5.42%), and alkalis (K₂O + Na₂O = 8.17%–8.90%) contents and low ferroan (Fe₂O₃^T = 0.90%–1.48%), calcium, and magnesium contents and are classified as metaluminous–peraluminous, high-potassium, calc-alkaline iron granite. The rocks are enriched in Rb, Th, U, K, Pb, and Sn and strongly depleted in Ba, Sr, P, Eu, and Ti. They have strongly negative Eu anomalies (δEu = 0.01–0.05), 10,000 Ga/Al = 2.87–4.91 (>2.6), showing the geochemical characteristics of A-type granite. The zircon U/Pb ratios indicate that the above granites should be I- or A-type granite, which is generally formed under high-temperature (768–843 °C), low-pressure, and reducing magma conditions. The high Rb/Sr ratio (a mean of 48 > 1.2) and low K/Rb ratio (53.93–169.94) indicate that the tin-bearing plutons have undergone high differentiation. The positive whole-rock εNd(t) values (3.99–5.54) and the relatively young Nd T_2DM model ages (616–455 Ma) suggest the magma is derived from partially melted juvenile crust, and the underplating of basic magma containing mantle materials that affected the source area. The results indicate the KGB was formed in the tectonic transition period in the late Carboniferous subduction post-collision environment. Orogenic compression influenced the tin-bearing plutons in the western part of the KGB, forming highly differentiated and reduced I, A-type transition granite. An extensional environment affected the plutons in the eastern sections, creating A-type granite with dark enclaves that suggest magma mixing with little evidence of tin mineralization. Full article

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

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18 pages, 4181 KiB

Open AccessArticle

Crystal Structure Features, Spectroscopic Characteristics and Thermal Conversions of Sulfur-Bearing Groups: New Natural Commensurately Modulated Haüyne Analogue, Na₆Ca_2−x(Si₆Al₆O₂₄)(SO₄²⁻,HS⁻,S₂^●−,S₄,S₃^●−,S₅²⁻)_2−y

by Nikita V. Chukanov, Natalia V. Zubkova, Roman Yu. Shendrik, Anatoly N. Sapozhnikov, Igor V. Pekov, Marina F. Vigasina, Nadezhda A. Chervonnaya, Dmitry A. Varlamov, Nadezhda B. Bolotina, Dmitry A. Ksenofontov and Dmitry Yu. Pushcharovsky

Minerals 2025, 15(7), 709; https://doi.org/10.3390/min15070709 - 3 Jul 2025

Viewed by 222

Abstract

A multimethodic approach based on infrared, Raman, electron spin resonance and photoluminescence spectroscopy, absorption spectroscopy in near infrared, visible and ultraviolet regions, single-crystal X-ray diffraction as well as electron microprobe analyses was applied to the characterization of a new commensurately modulated cubic haüyne [...] Read more.

A multimethodic approach based on infrared, Raman, electron spin resonance and photoluminescence spectroscopy, absorption spectroscopy in near infrared, visible and ultraviolet regions, single-crystal X-ray diffraction as well as electron microprobe analyses was applied to the characterization of a new commensurately modulated cubic haüyne analogue with the modulation parameter of 0.2 and unit-cell parameter of 45.3629(3) Å (designated as haüyne-45Å) from the Malobystrinskoe lazurite deposit, in the Baikal Lake area, Siberia, Russia, as well as associated SO₃²⁻-bearing afghanite. Haüyne-45Å is the second member, after vladimirivanovite, of the sodalite group with a commensurately modulated structure. The average structure is based on the tetrahedral aluminosilicate sodalite-type framework with sodalite cages of different sizes. The simplified formula of haüyne-45Å is Na₆Ca_2−x(Si₆Al₆O₂₄)(SO₄²⁻,HS⁻,S₂^●−,S₄,S₃^●−,S₅²⁻)_2−y. The structural modulations of the haüyne-45Å framework are presumably related to the regular alternation of SO₄²⁻ anions with polysulfide S₂^●−, S₃^●−, S₄, and S₅²⁻ groups detected by the spectroscopic methods. Mechanisms of thermal conversions of S-bearing groups in haüyne-45Å under oxidizing and reducing conditions at temperatures up to 800 °C are studied, and their geochemical importance is discussed. Full article

(This article belongs to the Special Issue Crystal Chemistry of Sulfate Minerals and Synthetic Compounds)

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4 pages, 151 KiB

Open AccessEditorial

Editorial for Special Issue “Isomorphism, Chemical Variability and Solid Solutions of Minerals and Related Compounds, 2nd Edition”

by Nikita V. Chukanov

Minerals 2025, 15(7), 708; https://doi.org/10.3390/min15070708 - 3 Jul 2025

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Abstract

The concepts of isomorphism and solid solutions are closely related to each other [...] Full article

(This article belongs to the Special Issue Isomorphism, Chemical Variability, and Solid Solutions of Minerals and Related Compounds, 2nd Edition)

3 pages, 335 KiB

Open AccessCorrection

Correction: Nikopoulou et al. Microscopic, Spectroscopic and Chemical Analysis of Emeralds from Habachtal, Austria. Minerals 2025, 15, 22

by Maria Nikopoulou, Stefanos Karampelas, Ugo Hennebois, Pierre Gruss, Eloïse Gaillou, Emmanuel Fritsch, Annabelle Herreweghe, Lambrini Papadopoulou, Vasilios Melfos, Nikolaos Kantiranis and Aurélien Delaunay

Minerals 2025, 15(7), 707; https://doi.org/10.3390/min15070707 - 3 Jul 2025

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Abstract

The original publication [...] Full article

(This article belongs to the Special Issue Gem Deposits: Mineralogical and Gemological Aspects, 2nd Edition)

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17 pages, 7952 KiB

Open AccessArticle

Achyrophanite, (K,Na)₃(Fe³⁺,Ti,Al,Mg)₅O₂(AsO₄)₅, a New Mineral with the Novel Structure Type from Fumarolic Exhalations of the Tolbachik Volcano, Kamchatka, Russia

by Igor V. Pekov, Natalia V. Zubkova, Natalia N. Koshlyakova, Dmitry I. Belakovskiy, Marina F. Vigasina, Atali A. Agakhanov, Sergey N. Britvin, Anna G. Turchkova, Evgeny G. Sidorov, Pavel S. Zhegunov and Dmitry Yu. Pushcharovsky

Minerals 2025, 15(7), 706; https://doi.org/10.3390/min15070706 - 2 Jul 2025

Viewed by 198

Abstract

The new mineral achyrophanite (K,Na)₃(Fe³⁺,Ti,Al,Mg)₅O₂(AsO₄)₅ was found in high-temperature sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, [...] Read more.

The new mineral achyrophanite (K,Na)₃(Fe³⁺,Ti,Al,Mg)₅O₂(AsO₄)₅ was found in high-temperature sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with aphthitalite-group sulfates, hematite, alluaudite-group arsenates (badalovite, calciojohillerite, johillerite, nickenichite, hatertite, and khrenovite), ozerovaite, pansnerite, arsenatrotitanite, yurmarinite, svabite, tilasite, katiarsite, yurgensonite, As-bearing sanidine, anhydrite, rutile, cassiterite, and pseudobrookite. Achyrophanite occurs as long-prismatic to acicular or, rarer, tabular crystals up to 0.02 × 0.2 × 1.5 mm, which form parallel, radiating, bush-like, or chaotic aggregates up to 3 mm across. It is transparent, straw-yellow to golden yellow, with strong vitreous luster. The mineral is brittle, with (001) perfect cleavage. D_calc is 3.814 g cm^–3. Achyrophanite is optically biaxial (+), α = 1.823(7), β = 1.840(7), γ = 1.895(7) (589 nm), 2V (meas.) = 60(10)°. Chemical composition (wt.%, electron microprobe) is: Na₂O 3.68, K₂O 9.32, CaO 0.38, MgO 1.37, MnO 0.08, CuO 0.82, ZnO 0.48, Al₂O₃ 2.09, Fe₂O₃ 20.42, SiO₂ 0.12, TiO₂ 7.35, P₂O₅ 0.14, V₂O₅ 0.33, As₂O₅ 51.88, SO₃ 1.04, and total 99.40. The empirical formula calculated based on 22 O apfu is Na_1.29K_2.15Ca_0.07Mg_0.34Mn_0.01Cu_0.11Zn_0.06Al_0.44Fe³⁺_2.77Ti_1.00Si_0.02P_0.02S_0.14V_0.04As_4.90O₂₂. Achyrophanite is orthorhombic, space group P222₁, a = 6.5824(2), b = 13.2488(4), c = 10.7613(3) Å, V = 938.48(5) Å³ and Z = 2. The strongest reflections of the PXRD pattern [d,Å(I)(hkl)] are 5.615(59)(101), 4.174(42)(022), 3.669(31)(130), 3.148(33)(103), 2.852(43)(141), 2.814(100)(042, 202), 2.689(29)(004), and 2.237(28)(152). The crystal structure of achyrophanite (solved from single-crystal XRD data, R = 4.47%) is unique. It is based on the octahedral-tetrahedral M-T-O pseudo-framework (M = Fe³⁺ with admixed Ti, Al, Mg, Na; T = As⁵⁺). Large-cation A sites (A = K, Na) are located in the channels of the pseudo-framework. The achyrophanite structure can be described as stuffed, with the defect heteropolyhedral pseudo-framework derivative of the orthorhombic Fe³⁺AsO₄ archetype. The mineral is named from the Greek άχυρον, straw, and φαίνομαι, to appear, in allusion to its typical straw-yellow color and long prismatic habit of crystals. Full article

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

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34 pages, 4392 KiB

Open AccessArticle

Post-Collisional Mantle Processes and Magma Evolution of the El Bola Mafic–Ultramafic Intrusion, Arabian-Nubian Shield, Egypt

by Khaled M. Abdelfadil, Hatem E. Semary, Asran M. Asran, Hafiz U. Rehman, Mabrouk Sami, A. Aldukeel and Moustafa M. Mogahed

Minerals 2025, 15(7), 705; https://doi.org/10.3390/min15070705 - 2 Jul 2025

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Abstract

The El Bola mafic–ultramafic intrusion (EBMU) in Egypt’s Northern Eastern Desert represents an example of Neoproterozoic post-collisional layered mafic–ultramafic magmatism in the Arabian–Nubian Shield (ANS). The intrusion is composed of pyroxenite, olivine gabbro, pyroxene gabbro, pyroxene–hornblende gabbro, and hornblende-gabbro, exhibiting adcumulate to heter-adcumulate [...] Read more.

The El Bola mafic–ultramafic intrusion (EBMU) in Egypt’s Northern Eastern Desert represents an example of Neoproterozoic post-collisional layered mafic–ultramafic magmatism in the Arabian–Nubian Shield (ANS). The intrusion is composed of pyroxenite, olivine gabbro, pyroxene gabbro, pyroxene–hornblende gabbro, and hornblende-gabbro, exhibiting adcumulate to heter-adcumulate textures. Mineralogical and geochemical analyses reveal a coherent trend of fractional crystallization. Compositions of whole rock and minerals indicate a parental magma of ferropicritic affinity, derived from partial melting of a hydrous, metasomatized spinel-bearing mantle source, likely modified by subduction-related fluids. Geothermobarometric calculations yield crystallization temperatures from ~1120 °C to ~800 °C and pressures from ~5.2 to ~3.1 kbar, while oxygen fugacity estimates suggest progressive oxidation (log fO₂ from −17.3 to −15.7) during differentiation. The EBMU displays Light Rare Earth element (LREE) enrichment, trace element patterns marked by Large Ion Lithophile Element (LILE) enrichment, Nb-Ta depletion and high LILE/HFSE (High Field Strength Elements) ratios, suggesting a mantle-derived source that remained largely unaffected by crustal contribution and was metasomatized by slab-derived fluids. Tectonic discrimination modeling suggests that EBMU magmatism was triggered by asthenospheric upwelling and slab break-off. Considering these findings alongside regional geologic features, we propose that the mafic–ultramafic intrusion from the ANS originated in a tectonic transition between subduction and collision (slab break-off) following the assembly of Gondwana. Full article

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

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32 pages, 22279 KiB

Open AccessArticle

Crafting Urban Landscapes and Monumental Infrastructure: Archaeometric Investigations of White Marble Architectural Elements from Roman Philippopolis (Bulgaria)

by Vasiliki Anevlavi, Walter Prochaska, Plamena Dakasheva, Zdravko Dimitrov and Petya Andreeva

Minerals 2025, 15(7), 704; https://doi.org/10.3390/min15070704 - 1 Jul 2025

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Abstract

This study explores the provenance of white marble architectural elements from Roman Philippopolis, with a particular focus on the Eastern Gate complex. By determining the origin of the marble, we aim to elucidate economic, social, and urban dynamics related to material selection and [...] Read more.

This study explores the provenance of white marble architectural elements from Roman Philippopolis, with a particular focus on the Eastern Gate complex. By determining the origin of the marble, we aim to elucidate economic, social, and urban dynamics related to material selection and trade networks. The investigation examines the symbolic significance of prestigious marble in elite representation and highlights the role of quarry exploitation in the region’s economic and technological development. The Eastern Gate, a monumental ensemble integrated into the city’s urban fabric, was primarily constructed with local Rhodope marble, alongside imported materials such as Prokonnesian marble. Analytical methods included petrographic examination, chemical analysis of trace elements (Mn, Mg, Fe, Sr, Y, V, Cd, La, Ce, Yb, and U), and stable isotope analysis (δ¹⁸O, δ¹³C). Statistical evaluations were performed for each sample (37 in total) and compared with a comprehensive database of ancient quarry sources. The results underscore the dominance of local materials while also indicating selective use of imports, potentially linked to symbolic or functional criteria. The findings support the hypothesis of local workshop activity in the Asenovgrad/Philippopolis area and shed light on regional and long-distance marble trade during the Roman Imperial period, reflecting broader economic and cultural interconnections. Full article

(This article belongs to the Special Issue Mineralogical and Mechanical Properties of Natural Building Stone)

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16 pages, 9459 KiB

Open AccessArticle

Recovery of Tetrahedrite from Mining Waste in Spain

by Ester Boixereu-Vila, Paula Adánez-Sanjuán, Ramón Jiménez-Martínez, Concepción Fernández-Leyva and Dulce Gómez-Limón

Minerals 2025, 15(7), 703; https://doi.org/10.3390/min15070703 - 30 Jun 2025

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Abstract

The present study is part of the Horizon Europe-START project, which aims to recover tetrahedrite-group minerals present in mine dumps to be used as raw materials for the manufacture of thermoelectric devices. The aim of this work is to identify the mining waste [...] Read more.

The present study is part of the Horizon Europe-START project, which aims to recover tetrahedrite-group minerals present in mine dumps to be used as raw materials for the manufacture of thermoelectric devices. The aim of this work is to identify the mining waste facilities selected in Spain for the recovery of tetrahedrite and to outline the mineral processing operations performed on samples from each site to separate and concentrate this mineral. Ore deposits across Spain were selected based on the potential presence of tetrahedrite in their mining waste. A total of five deposits have been sampled, at which subsequent mineral separation and concentration tests have been conducted. A separation flowsheet is proposed in order to extract a high-purity tetrahedrite concentrate. Experimental results indicate two distinct options for separation approaches, depending on a key parameter that proves decisive in the processing of this mineral, which is whether the mineral paragenesis includes siderite. This study has demonstrated the technical feasibility of concentrating minerals of the tetrahedrite group through simple, cost-effective physical separation techniques—specifically magnetic and gravity separation—where the liberation size of the tetrahedrite exceeds 0.063 mm. Full article

(This article belongs to the Special Issue Critical Minerals for Energy Transition: Advancing Energy Security and Sustainable Manufacturing)

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19 pages, 8756 KiB

Open AccessArticle

Predicting Industrial Copper Hydrometallurgy Output with Deep Learning Approach Using Data Augmentation

by Bagdaulet Kenzhaliyev, Nurtugan Azatbekuly, Serik Aibagarov, Bibars Amangeldy, Aigul Koizhanova and David Magomedov

Minerals 2025, 15(7), 702; https://doi.org/10.3390/min15070702 - 30 Jun 2025

Viewed by 236

Abstract

Sustainable copper extraction presents significant challenges due to waste generation and environmental impacts, requiring advanced predictive methodologies to optimize production processes. This study addresses a gap in applying deep learning to forecast hydrometallurgical copper production by comparing six recurrent neural network architectures: Vanilla [...] Read more.

Sustainable copper extraction presents significant challenges due to waste generation and environmental impacts, requiring advanced predictive methodologies to optimize production processes. This study addresses a gap in applying deep learning to forecast hydrometallurgical copper production by comparing six recurrent neural network architectures: Vanilla LSTM, Stacked LSTM, Bidirectional LSTM, GRU, CNN-LSTM, and Attention LSTM. Using time-series data from a full-scale industrial operation, we implemented a data augmentation approach to overcome data scarcity limitations. The models were evaluated through rigorous metrics and multi-step forecasting tests. The results demonstrated remarkable performance from five architectures, with Bidirectional LSTM and Attention LSTM achieving the highest accuracy (RMSE < 0.004, R² > 0.999, MAPE < 1%). These models successfully captured and reproduced complex cyclical patterns in copper mass production for up to 500 time steps ahead. The findings validate our data augmentation strategy for enabling models to learn complex known cyclical patterns from limited initial data and establish a promising foundation for implementing AI-driven predictive systems that can enhance process control, reduce waste, and advance sustainability in hydrometallurgical operations. However, these performance metrics reflect the models’ ability to reproduce patterns inherent in the augmented dataset derived from a single operational cycle; validation on entirely independent operational data is crucial for assessing true generalization and is a critical next step. Full article

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

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28 pages, 3379 KiB

Open AccessArticle

A Predictive Geometallurgical Framework for Flotation Kinetics in Complexes Platinum Group Metal Orebodies: Mode of Occurrence-Based Modification of the Kelsall Model Using Particle Swarm Optimization

by Alain M. Kabemba, Kalenda Mutombo and Kristian E. Waters

Minerals 2025, 15(7), 701; https://doi.org/10.3390/min15070701 - 30 Jun 2025

Viewed by 232

Abstract

Mineralogical variability exerts a profound influence on the flotation performance of Platinum Group Metal (PGM) ores, particularly those from the Platreef deposit, where complex associations and textures influence recovery, grade, and kinetics. This study integrates the Mode of Occurrence (MOC) and mineral associations [...] Read more.

Mineralogical variability exerts a profound influence on the flotation performance of Platinum Group Metal (PGM) ores, particularly those from the Platreef deposit, where complex associations and textures influence recovery, grade, and kinetics. This study integrates the Mode of Occurrence (MOC) and mineral associations into a modified Kelsall flotation kinetics model, optimized using a Particle Swarm Optimization (PSO) algorithm, to improve prediction accuracy. Batch flotation tests were conducted on eight samples from two lithologies—Pegmatoidal Feldspathic Pyroxenite (P-FPX) and Feldspathic Pyroxenite (FPX)—with mineralogical characterization performed using MLA, QEMSCAN, and XRD. PGMs in liberated (L) and sulfide-associated (SL) forms accounted for up to 90.6% (FPX1), exhibiting high fast-floating fractions (θ_f = 0.77–0.84) and fast flotation rate constants (K_f = 1.45–1.78 min⁻¹). In contrast, PGMs locked in silicates (G class) showed suppressed kinetics (K_f < 0.09 min⁻¹, K_s anomalies up to 8.67 min⁻¹) and were associated with lower recovery (P-FPX3 = 83.25%) and increased model error (P-FPX4 = 57.3). FPX lithologies achieved the highest cumulative recovery (FPX4 = 90.35%) and the best concentrate grades (FPX3 = 116.5 g/t at 1 min), while P-FPX1 had the highest gold content (10.45%) and peak recovery (94.37%). Grade-recovery profiles showed steep declines after 7 min, particularly in slow-floating types (e.g., P-FPX2, FPX2), with fast-floating lithologies stabilizing above 85% recovery at 20 min. The model yielded R² values above 0.97 across all samples. This validates the predictive power of MOC-integrated flotation kinetics for complex PGM ores and supports its application in geometallurgical plant design. Model limitations in capturing complex locked ore textures (SAG, G classes) highlight the need for reclassification based on floatability indices and further integration of machine learning methods. Full article

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

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Minerals, Volume 15, Issue 7 (July 2025) – 67 articles

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