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Critical Metal Minerals, 2nd Edition
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Critical Metal Minerals, 2nd Edition

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Deposits".

Deadline for manuscript submissions: 1 July 2026 | Viewed by 30146

Special Issue Editors

Prof. Dr. Pei Ni

E-Mail Website
Guest Editor
1. State Key Laboratory for Mineral Deposits Research, Institute of Geofluids, Frontiers Science Center for Critical Earth Material Cycling, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
2. Joint Research Center for Circum-Pacific Strategic Mineral Resources, Nanjing 210000, China
Interests: hydrothermal ore deposits; mineral, fluid and melt inclusion; mineral resource prospecting and exploration; tectonics and metallogeny
Special Issues, Collections and Topics in MDPI journals
Prof. Ruoshi Jin

E-Mail Website
Guest Editor
1. Tianjin Center, China Geological Survey (North China Center for Geoscience Innovation), Tianjin 300170, China
2. Key Laboratory of Uranium Geology, China Geological Survey, Tianjin 300170, China
Interests: sandstone-type uranium deposits; mineral resource prospecting and exploration
Prof. Mincheng Xu

E-Mail Website
Guest Editor
1. Joint Research Center for Circum-Pacific Strategic Mineral Resources, Nanjing 210000, China
2. Nanjing Center, China Geological Survey, Nanjing 210016, China
Interests: regional metallogenesis; mineral resources prospecting and exploration
Special Issues, Collections and Topics in MDPI journals
Dr. Tiangang Wang

E-Mail Website
Guest Editor
1. Joint Research Center for Circum-Pacific Strategic Mineral Resources, Nanjing 210000, China
2. Nanjing Center, China Geological Survey, Nanjing 210016, China
Interests: hydrothermal ore deposits; ore-forming fluids; regional metallogenesis; mineral resources prospecting
Special Issues, Collections and Topics in MDPI journals
Dr. Yinhang Cheng

E-Mail Website
Guest Editor
1. Tianjin Center, China Geological Survey (North China Center for Geoscience Innovation), Tianjin 300170, China
2. Key Laboratory of Uranium Geology, China Geological Survey, Tianjin 300170, China
Interests: uranium deposits; tectonics and metallogeny; mineral resource prospecting and exploration
Special Issues, Collections and Topics in MDPI journals
Dr. Junyi Pan

E-Mail
Guest Editor
1. State Key Laboratory for Mineral Deposits Research, Frontiers Science Center for Critical Earth Material Cycling, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
2. Joint Research Center for Circum-Pacific Strategic Mineral Resources, Nanjing 210000, China
Interests: granite-related W-Sn deposits; porphyry-epithermal ore deposits; fluid and melt inclusion; LA-ICP-MS analytical techniques
Special Issues, Collections and Topics in MDPI journals
Dr. Yitao Cai

E-Mail
Guest Editor
School of Materials Engineering, Jinling Institute of Technology, Nanjing 211169, China
Interests: mineralogy; petrology; magmatic ore deposits; mineral resources evaluation

Special Issue Information

Dear Colleagues,

An increasingly wide range of mineral materials are used to enable the technologies that sustain our living standard in modern society. In particular, “Critical Metals” or “Critical Minerals” have been regarded as crucial strategic resources for global high-technology applications. In 2021–2022, we announced the Special Issue "Critical Metal Minerals" (https://www.mdpi.com/journal/minerals/special_issues/Critical_Metal_Minerals), and subsequently multiple contributions were published. We are now launching the 2nd Edition of the Special Issue, and we invite the latest research on critical metals to be published in this new Special Issue.

The critical metals generally consist of four major elemental groups: rare metals (e.g., Li, Be, Rb, Cs, W, Sn, Nb, Ta, Zr, Hf, U, and Th), rare earth elements (REEs, e.g., La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, and Y), rare dispersed elements (e.g., Ga, Ge, Se, Cd, In, Te, Re, and Tl), and other precious metals (e.g., PGE, Cr, and Co). Most of these elements are present at very low abundances in the Earth’s upper crust and/or are difficult to efficiently extract and utilize. The rapidly growing demand for critical mineral resources worldwide requires new understandings of the characterization of metal-host minerals, the geochemistry and ore genesis of critical metal deposits, and exploration advances aiding in the discovery of new economic targets. In this regard, the present Special Issue is focused on relevant topics, including, but not limited to (1) geochemical exploration, data handling, and statistical analysis for critical minerals of economic and/or environmental importance; (2) mineralogy, geochemistry, geochronology, fluid evolution, and isotopic constraints on the genesis of critical mineral deposits; (3) experimental advances in critical metal behavior during metallogenic processes; (4) geological controls of the global or regional distribution of critical mineral deposits; (5) 3D modeling of critical metal deposits; and (6) the resource assessment of critical minerals and developments in metal extraction and recovery.

We look forward to high quality submissions that complement contributions published as part of the 1st Edition.

Prof. Dr. Pei Ni
Prof. Ruoshi Jin
Prof. Mincheng Xu
Dr. Tiangang Wang
Dr. Yinhang Cheng
Dr. Junyi Pan
Dr. Yitao Cai
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • critical metals
  • geologic characteristics and setting
  • geochemical exploration
  • statistical data analysis
  • mineral geochemistry
  • petrogenesis and ore genesis
  • 3D modeling
  • resource assessment
  • mineral processing

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Related Special Issue

Published Papers (15 papers)

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24 pages, 5741 KB  
Article
Geochemistry and Sulfur Isotopes of Chalcopyrite in the Yuejin II Sandstone-Hosted Uranium Deposit, Qaidam Basin: Implications for Ore-Forming Fluid Sources and Processes
by Yi-Han Lin, Ming-Sen Fan, Pei Ni, Jun-Yi Pan, Jun-Ying Ding, Wen-Yi Wu, Chen Zhang, Zhe Chi, Bin Guo and Yi-Fan Gao
Minerals 2026, 16(5), 446; https://doi.org/10.3390/min16050446 - 24 Apr 2026
Viewed by 224
Abstract
Sandstone-hosted uranium deposits in the western Qaidam Basin are spatially associated with hydrocarbon-bearing structures, yet the specific roles of different sulfur sources in uranium mineralization remain poorly constrained. This study aims to distinguish the contributions of bacterial sulfate reduction and hydrocarbon-associated sulfate reduction [...] Read more.
Sandstone-hosted uranium deposits in the western Qaidam Basin are spatially associated with hydrocarbon-bearing structures, yet the specific roles of different sulfur sources in uranium mineralization remain poorly constrained. This study aims to distinguish the contributions of bacterial sulfate reduction and hydrocarbon-associated sulfate reduction to uranium precipitation by integrating detailed petrography, in situ trace element analyses, and sulfur isotope measurements of chalcopyrite from the Yuejin II deposit. Chalcopyrite is restricted to high-grade uranium ores and occurs intergrown with uranium minerals, pyrite, baryte, and carbonate cements. Trace element patterns indicate that oxidizing brines acted as the main transport medium for both uranium and copper, as evidenced by positive correlations between U and brine-related elements (Ba, Sr, Na, K). Positive U-Th correlations with relatively constant Th/U ratios (0.027–0.225) reflect a combination of source composition, fluid transport capacity, and limited thorium remobilization in this near-source, hydrocarbon-rich environment. Correlations between U and high field strength elements (Sn, W) point to a highly evolved granitic origin, with Altyn granitoids likely supplying the copper. Sulfur isotopes show a clear bimodal distribution: one group exhibits heavy δ34S values (+6.9‰ to +18.5‰), while the other shows extremely light values (–36.0‰ to –44.6‰). The light group reflects bacterial sulfate reduction in shallow strata, supported by framboidal pyrite textures, whereas the heavy group corresponds to surface-derived sulfate reduced at hydrocarbon-associated redox fronts, rather than direct incorporation of deep H2S. The lack of intermediate δ34S values indicates that two discrete sulfur reduction mechanisms coexisted within the same deposit, refining genetic models for uranium mineralization in petroliferous basins and challenging frameworks that invoke a single dominant sulfur source. Full article
(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)
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19 pages, 22953 KB  
Article
Magmatic–Hydrothermal Origin of Co Mineralization in the Qibaoshan Deposit, South China: Evidence from Deposit Geology, Mineralogy and In Situ S Isotope
by Fu Quan, Yongwen Zhang, Xinxin Liu, Qi Chen, Pengchao Shi, Xinghai Xu and Runling Zeng
Minerals 2026, 16(3), 299; https://doi.org/10.3390/min16030299 - 12 Mar 2026
Viewed by 417
Abstract
Hydrothermal cobalt (Co) deposits are a significant source of Co; however, the sources of Co and hydrothermal fluids for such deposits remain poorly understood. This study addresses this issue through an investigation of the geology, mineralogy, and in situ sulfur isotopes of the [...] Read more.
Hydrothermal cobalt (Co) deposits are a significant source of Co; however, the sources of Co and hydrothermal fluids for such deposits remain poorly understood. This study addresses this issue through an investigation of the geology, mineralogy, and in situ sulfur isotopes of the Qibaoshan Co-Pb-Zn-Cu deposit, a typical hydrothermal Co deposit in South China, to constrain the occurrence of Co and the sources of Co and hydrothermal fluids. Detailed scanning electron microscopy (SEM), TESCAN Integrated Mineral Analyzer (TIMA), and electron microprobe (EPMA) mapping analyses reveal that Co in the Qibaoshan deposit occurs predominantly as Co-bearing minerals in veinlet mineralization, mainly including cobaltite, skutterudite, and smaltite. EPMA elemental mappings reveal that cobaltite grains commonly show a compositional evolution from Ni-S-rich and As-Fe-poor cores to As-Fe-rich and Ni-S-poor rims. This evolution indicates a decrease in fluid temperature and Ni content, coupled with an increase in the As/S ratio during ore-forming processes. In situ S isotope analyses of various sulfides (pyrite, chalcopyrite, sphalerite, galena, and arsenopyrite) yield a wide range of δ34SV-CDT values from 0.24‰ to 19.08‰, with two dominant clusters at 2–5‰ and 15–17‰. This suggests two end-member sources for sulfur and hydrothermal fluids in the Qibaoshan deposit: magmatic and sedimentary sources. Arsenopyrite, which is closely associated with Co minerals, yields δ34SV-CDT values ranging from 2.17‰ to 5.99‰, pointing to a magmatic origin for Co in the Qibaoshan deposit. The Pb-Zn and Cu mineralization of the deposit was also likely mainly derived from magmatic sources, with the incorporation of sedimentary sulfur and fluids during the ore-forming processes. This study demonstrates that magmatic–hydrothermal fluids derived from depth can serve as sources of Co, even in hydrothermal deposits where no magmatic rock is exposed, which provides crucial implications for the metallogenic models and mineral exploration of hydrothermal Co deposits. Full article
(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)
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23 pages, 3740 KB  
Article
Predictive Modelling of Lithium Mineral Grades from Chemical Assays for Geometallurgical Applications
by Ivana Cupido, Sara Burness, Megan Becker and Glen Nwaila
Minerals 2026, 16(2), 139; https://doi.org/10.3390/min16020139 - 28 Jan 2026
Viewed by 737
Abstract
Routine chemical assays, which are more readily available than direct mineralogical analyses, offer a rapid and cost-efficient approach of estimating mineral grades for geometallurgical modelling. This paper addresses the prediction of ore minerology from chemical assays for lithium-bearing pegmatites by implementing and comparing [...] Read more.
Routine chemical assays, which are more readily available than direct mineralogical analyses, offer a rapid and cost-efficient approach of estimating mineral grades for geometallurgical modelling. This paper addresses the prediction of ore minerology from chemical assays for lithium-bearing pegmatites by implementing and comparing two element-to-mineral conversion (EMC) approaches: (1) mass balance techniques using two calculation variants and (2) machine learning methods (MLM). Both routines of the mass balance approach achieved satisfactory R2 values exceeding 0.8, although calculation routine 1 was unable to automatically differentiate between the two lithium-bearing phases (spodumene and cookeite). Of the eight algorithms applied for the MLM approach, the top three performing models achieved R2 values greater than 0.6 for both training and testing datasets, with slightly lower error evaluation metrics compared to the mass balance approach. Based on data accuracy requirements across the Mine Value Chain, the mass balance approach is suitable for the feasibility and operational stages, while the MLM approach meets the minimum data accuracy requirements of the scoping and pre-feasibility stages. However, it should be noted that the mass balance approach is limited to deposits with simple mineral assemblages while the MLM approach can handle deposits with greater elemental overlap among minerals. Full article
(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)
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16 pages, 16372 KB  
Article
An Efficient Zircon Separation Method Based on Acid Leaching and Automated Mineral Recognition: A Case Study of Xiugugabu Diabase
by Qiuyun Yuan, Haili Li, Yue Wu, Pengjie Cai, Jiadi Zhao, Weihao Yan, Ferdon Hamit, Ruotong Wang, Zhiqi Chen, Aihua Wang and Ahmed E. Masoud
Minerals 2026, 16(1), 20; https://doi.org/10.3390/min16010020 - 24 Dec 2025
Viewed by 796
Abstract
Cr and Platinum-Group Elements (PGEs), critical metallic elements, are mainly hosted in mafic and ultramafic rocks, but determining these rocks’ mineralization age has long been challenging. Zircon, the primary geochronological mineral, is scarce and fine-grained in such rocks, hindering conventional separation techniques (heavy [...] Read more.
Cr and Platinum-Group Elements (PGEs), critical metallic elements, are mainly hosted in mafic and ultramafic rocks, but determining these rocks’ mineralization age has long been challenging. Zircon, the primary geochronological mineral, is scarce and fine-grained in such rocks, hindering conventional separation techniques (heavy liquid separation, magnetic separation, manual hand-picking) with low efficiency, poor recovery, and significant sample bias. This study develops an integrated workflow: mixed acid leaching enrichment (120 °C), powder stirring for mount preparation, automated mineral identification, and in situ Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA–ICP–MS) dating. Validated on the Xiugugabu diabase in the western Yarlung–Tsangpo Suture Zone (southern Tibet), the workflow yielded weighted mean 206Pb/238U ages of 120.5 ± 3.3 Ma (MSWD = 0.13) and 120.5 ± 2.0 Ma (MSWD = 3.2) for two samples. Consistent with the published Yarlung–Tsangpo Suture Zone (YTSZ) diabase formation ages (130–110 Ma), these confirm the Xiugugabu diabase as an Early Cretaceous Neo–Te–thys oceanic lithosphere residual recording mid-stage spreading. The workflow overcomes traditional limitations: single-sample analytical cycles shorten from 30–50 to 10 days, fine–grained zircon recovery is 15x higher than manual picking, and U–Pb ages are stable. Suitable for large-scale mafic–ultramafic geochronological surveys, it can extend to in situ zircon Hf isotope and trace element analysis, offering multi-dimensional constraints on petrogenesis and tectonic evolution. Full article
(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)
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10 pages, 5106 KB  
Article
Sb-Rich Avicennite from the Khokhoy Gold Deposit (Aldan Shield, Russia)
by Galina S. Anisimova, Larisa A. Kondratieva, Veronika N. Kardashevskaia, Anatoly V. Kasatkin and Vladislav V. Gurzhiy
Minerals 2025, 15(12), 1294; https://doi.org/10.3390/min15121294 - 10 Dec 2025
Viewed by 625
Abstract
Sb-rich avicennite (first discovery in Russia) was found at the Khokhoy gold deposit, 120 km west of Aldan, Aldan district, Republic of Sakha (Yakutia), Eastern Siberia, Russia. The mineral of critical metal thallium forms irregularly shaped grains up to 0.25 mm in size, [...] Read more.
Sb-rich avicennite (first discovery in Russia) was found at the Khokhoy gold deposit, 120 km west of Aldan, Aldan district, Republic of Sakha (Yakutia), Eastern Siberia, Russia. The mineral of critical metal thallium forms irregularly shaped grains up to 0.25 mm in size, in association with amgaite, weissbergite, goethite, gold, and unidentified Tl-bearing phases. Aggregates of colloform structure prevail, represented by rhythmic-, concentric-zonal, kidney-shaped, and spherulitic varieties. Avicennite is black in color, with metallic luster, and it fractures unevenly. No cleavage is observed. The density value of avicennite, obtained using its empirical formula and the unit cell parameters calculated from the powder X-ray diffraction data, is 8.548 g/cm3. In reflected light, avicennite is light gray and isotropic. Internal reflections are absent. Reflection is very low; the reflectivity curve is of mixed type with a small maximum in the blue part. Its chemical composition (average value on 10 analyses, wt.%): Tl2O3—85.36, V2O5—0.73, As2O5—0.85, Sb2O5—12.98, Total—99.92; It corresponds to the following empirical formula (calculation for three atoms of O): Tl1.40Sb5+0.30V5+0.03As5+0.03O3. The unit cell parameters calculated from the powder X-ray diffraction data are as follows: the mineral is cubic, a = 10.496(6) Å, V = 1156(2) Å3. Full article
(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)
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23 pages, 12244 KB  
Article
The Petrology of Tuffisite in a Trachytic Diatreme from the Kızılcaören Alkaline Silicate–Carbonatite Complex, NW Anatolia
by Yalçın E. Ersoy, Hikmet Yavuz, İbrahim Uysal, Martin R. Palmer and Dirk Müller
Minerals 2025, 15(8), 867; https://doi.org/10.3390/min15080867 - 17 Aug 2025
Cited by 1 | Viewed by 1770
Abstract
The Kızılcaören alkaline silicate–carbonatite complex, located in the Sivrihisar (Eskişehir, NW Anatolia) region, includes phonolite, trachyte, carbonatite, pyroclastics, and REE mineralization (bastnäsite as a critical REE mineral). The emplacement and origin of this complex are poorly constrained, as previous studies mostly concentrated on [...] Read more.
The Kızılcaören alkaline silicate–carbonatite complex, located in the Sivrihisar (Eskişehir, NW Anatolia) region, includes phonolite, trachyte, carbonatite, pyroclastics, and REE mineralization (bastnäsite as a critical REE mineral). The emplacement and origin of this complex are poorly constrained, as previous studies mostly concentrated on the petrology of the alkaline rocks, carbonatite, and REE-mineralization, and little attention has been paid to the texture, composition, and origin of the pyroclastic rocks. The pyroclastic rocks in the region contain both rounded and angular-shaped cognate and wall-rock xenoliths derived from syenitic/trachytic hypabyssal rocks and carbonatites, as well as juvenile components such as carbonatite droplets and pelletal lapilli. The syenitic/trachytic hypabyssal rock fragments contain sanidine with high BaO (up to 3.3 wt.%) contents, amphibole (magnesio-fluoro-arfvedsonite), and apatite. Some clasts seem to have reacted with carbonatitic material, including high-SrO (up to 0.6 wt.%) calcite, dolomite, baryte, benstonite, fluorapatite. The carbonatite rock fragments are composed of calcite, baryte, fluorite, and bastnäsite. The carbonatite droplets have a spinifex-like texture and contain rhombohedral Mg-Fe-Ca carbonate admixtures, baryte, potassic-richterite, and parisite embedded in larger crystals of high-SrO (up to 0.7 wt.%) calcite. The spherical–elliptical pelletal lapilli (2–3 mm) contain a lithic center mantled by flow-aligned prismatic sanidine (with BaO up to 3.5 wt.%) microphenocrysts settled in a high-SrO (up to 0.7 wt.%) cryptocrystalline CaCO3 matrix. All these components are embedded in an ultra-fine-grained matrix. The EPMA results from the matrix reveal that, chemically, it consists largely of BaO-rich sanidine, with minor carbonate, baryte and Fe-Ti oxide. The presence of pelletal lapilli, which is one of the most common and characteristic features of diatreme fillings in alkaline silicate–carbonatite complexes, reveals that the pyroclastic rocks in the region represent a tuffisite formed by intrusive fragmentation and fluidization processes in the presence of excess volatile components consisting mainly of CO2 and F. Full article
(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)
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25 pages, 15689 KB  
Article
Mineralogical and Chemical Properties and REE Content of Bauxites in the Seydişehir (Konya, Türkiye) Region
by Muazzez Çelik Karakaya and Necati Karakaya
Minerals 2025, 15(8), 798; https://doi.org/10.3390/min15080798 - 29 Jul 2025
Cited by 4 | Viewed by 2341
Abstract
The most important bauxite deposits in Türkiye are located in the Seydişehir (Konya) and Akseki (Antalya) regions, situated along the western Taurus Mountain, with a total reserve of approximately 44 million tons. Some of the bauxite deposits have been exploited for alumina since [...] Read more.
The most important bauxite deposits in Türkiye are located in the Seydişehir (Konya) and Akseki (Antalya) regions, situated along the western Taurus Mountain, with a total reserve of approximately 44 million tons. Some of the bauxite deposits have been exploited for alumina since the 1970s. In this study, bauxite samples, collected from six different deposits were examined to determine their mineralogical and chemical composition, as well as their REE content, with the aim of identifying which bauxite types are enriched in REEs and assessing their economic potential. The samples included massive, oolitic, and brecciated bauxite types, which were analyzed using optical microscopy, X-ray diffraction (XRD), X-ray fluorescence (XRF) and inductive coupled plasma-mass spectrometry (ICP-MS), field emission scanning electron microscopy (FESEM-EDX), and electron probe micro-analysis (EPMA). Massive bauxites were found to be more homogeneous in both mineralogical and chemical composition, predominantly composed of diaspore, boehmite, and rare gibbsite. Hematite is the most abundant iron oxide mineral in all bauxites, while goethite, rutile, and anatase occur in smaller quantities. Quartz, feldspar, kaolinite, dolomite, and pyrite were specifically determined in brecciated bauxites. Average oxide contents were determined as 52.94% Al2O3, 18.21% Fe2O3, 7.04% TiO2, and 2.69% SiO2. Na2O, K2O, and MgO values are typically below 0.5%, while CaO averages 3.54%. The total REE content of the bauxites ranged from 161 to 4072 ppm, with an average of 723 ppm. Oolitic-massive bauxites exhibit the highest REE enrichment. Cerium (Ce) was the most abundant REE, ranging from 87 to 453 ppm (avg. 218 ppm), followed by lanthanum (La), which reached up to 2561 ppm in some of the massive bauxite samples. LREEs such as La, Ce, Pr, and Nd were notably enriched compared to HREEs. The lack of a positive correlation between REEs and major element oxides, as well as with their occurrences in distinct association with Al- and Fe-oxides-hydroxides based on FESEM-EDS and EPMA analyses, suggests that the REEs are present as discrete mineral phases. Furthermore, these findings indicate that the REEs are not incorporated into the crystal structures of other minerals through isomorphic substitution or adsorption. Full article
(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)
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53 pages, 7076 KB  
Article
The Diversity of Rare-Metal Pegmatites Associated with Albite-Enriched Granite in the World-Class Madeira Sn-Nb-Ta-Cryolite Deposit, Amazonas, Brazil: A Complex Magmatic-Hydrothermal Transition
by Ingrid W. Hadlich, Artur C. Bastos Neto, Vitor P. Pereira, Harald G. Dill and Nilson F. Botelho
Minerals 2025, 15(6), 559; https://doi.org/10.3390/min15060559 - 23 May 2025
Cited by 2 | Viewed by 2836
Abstract
This study investigates pegmatites with exceptionally rare mineralogical and chemical signatures, hosted by the 1.8 Ga peralkaline albite-enriched granite, which corresponds to the renowned Madeira Sn-Nb-Ta-F (REE, Th, U) deposit in Pitinga, Brazil. Four distinct pegmatite types are identified: border pegmatites, pegmatitic albite-enriched [...] Read more.
This study investigates pegmatites with exceptionally rare mineralogical and chemical signatures, hosted by the 1.8 Ga peralkaline albite-enriched granite, which corresponds to the renowned Madeira Sn-Nb-Ta-F (REE, Th, U) deposit in Pitinga, Brazil. Four distinct pegmatite types are identified: border pegmatites, pegmatitic albite-enriched granite, miarolitic pegmatite, and pegmatite veins. The host rock itself has served as the source for the fluids that gave rise to all these pegmatites. Their mineral assemblages mirror the rare-metal-rich paragenesis of the host rock, including pyrochlore, cassiterite, riebeckite, polylithionite, zircon, thorite, xenotime, gagarinite-(Y), genthelvite, and cryolite. These pegmatites formed at the same crustal level as the host granite and record a progressive magmatic–hydrothermal evolution driven by various physicochemical processes, including tectonic decompressing, extreme fractionation, melt–melt immiscibility, and internal fluid exsolution. Border pegmatites crystallized early from a F-poor, K-Ca-Sr-Zr-Y-HREE-rich fluid exsolved during solidification of the pluton’s border and were emplaced in contraction fractures between the pluton and country rocks. Continued crystallization toward the pluton’s core produced a highly fractionated melt enriched in Sn, Nb, Ta, Rb, HREE, U, Th, and other HFSE, forming pegmatitic albite-enriched granite within centimetric fractures. A subsequent pressure quench—likely induced by reverse faulting—triggered the separation of a supercritical melt, further enriched in rare metals, which migrated into fractures and cavities to form amphibole-rich pegmatite veins and miarolitic pegmatites. A key process in this evolution was melt–melt immiscibility, which led to the partitioning of alkalis between two phases: a K-F-rich aluminosilicate melt (low in H2O), enriched in Y, Li, Be, and Zn; and a Na-F-rich aqueous melt (low in SiO2). These immiscible melts crystallized polylithionite-rich and cryolite-rich pegmatite veins, respectively. The magmatic–hydrothermal transition occurred independently in each pegmatite body upon H2O saturation, with the hydrothermal fluid composition controlled by the local degree of melt fractionation. These highly F-rich exsolved fluids caused intense autometasomatic alteration and secondary mineralization. The exceptional F content (up to 35 wt.% F in pegmatite veins), played a central role in concentrating strategic and critical metals such as Nb, Ta, REEs (notably HREE), Li, and Be. These findings establish the Madeira system as a reference for rare-metal magmatic–hydrothermal evolution in peralkaline granites. Full article
(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)
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50 pages, 21988 KB  
Article
Transforming LCT Pegmatite Targeting Models into AI-Powered Predictive Maps of Lithium Potential for Western Australia and Ontario: Approach, Results and Implications
by Oliver P. Kreuzer and Bijan Roshanravan
Minerals 2025, 15(4), 397; https://doi.org/10.3390/min15040397 - 9 Apr 2025
Cited by 3 | Viewed by 6742
Abstract
Here, we present holistic targeting models for lithium–cesium–tantalum (LCT) pegmatites in Western Australia, the world’s largest supplier of hardrock lithium ores, and Ontario, an emerging hardrock lithium mining jurisdiction. In this study, the LCT pegmatite targeting models, informed by a review of this [...] Read more.
Here, we present holistic targeting models for lithium–cesium–tantalum (LCT) pegmatites in Western Australia, the world’s largest supplier of hardrock lithium ores, and Ontario, an emerging hardrock lithium mining jurisdiction. In this study, the LCT pegmatite targeting models, informed by a review of this deposit type and framed in the context of a mineral system approach, served to identify a set of targeting criteria that are mappable in the publicly available exploration data for Western Australia and Ontario. This approach, which formed the basis for artificial intelligence (AI)-powered mineral potential modeling (MPM), using multiple, complimentary modeling techniques, not only delivered the first published regional-scale views of lithium potential across the Archean to Proterozoic terrains of Western Australia and Ontario, but it also delivered an effective framework for exploration and revealed hidden trends. For example, we identified a statistically verifiable proximity relationship between lithium, gold, and nickel occurrences and confirmed a significant size differential between LCT pegmatites in Western Australia and Ontario, with the former typically containing much larger resources than the latter. Overall, this regional-scale targeting study served to demonstrate the power of precompetitive, high-quality geoscience data, not only for regional-scale targeting but also for the development of camp-scale targets that have the resolution to be investigated using conventional prospecting techniques. Importantly, MPM does not generate ‘treasure maps’. Rather, MPM provides another tool in the ‘exploration toolbox’, and its output should be taken as the starting point for further investigations. Full article
(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)
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23 pages, 16611 KB  
Article
Study on the Occurrence States and Enrichment Mechanisms of the Dispersed Elements Ga, Ge, and In in the Chipu Pb-Zn Deposit, Sichuan Province, China
by Tian Tan, Huijuan Peng, En Qin, Ziyue Wang and Xingxing Mao
Minerals 2025, 15(4), 341; https://doi.org/10.3390/min15040341 - 26 Mar 2025
Cited by 4 | Viewed by 1661
Abstract
The dispersed elements Ga, Ge, and In are crucial strategic mineral resources often enriched in Pb-Zn deposits. The Chipu Pb-Zn deposit, located on the western edge of the Yangtze Block, lies to the north of the Sichuan-Yunnan-Guizhou (SYG) Pb-Zn metallogenic province with large [...] Read more.
The dispersed elements Ga, Ge, and In are crucial strategic mineral resources often enriched in Pb-Zn deposits. The Chipu Pb-Zn deposit, located on the western edge of the Yangtze Block, lies to the north of the Sichuan-Yunnan-Guizhou (SYG) Pb-Zn metallogenic province with large amounts of Emeishan basalt. Based on trace element and in situ sulfur isotope analyses by (LA)-ICP-MS, sphalerite is the main carrier mineral for Ga (17~420 ppm), Ge (3.87~444 ppm), and In (31~720 ppm). Ga or Ge correlate significantly with Cu, while In substitutes for Zn in sphalerite alongside Fe. Key substitution reactions include Ga3+ + Cu+ ↔ 2Zn2+, Ge4+ + 2Cu+ ↔ 3Zn2+, and 2In3+ + Fe2+ ↔ 4Zn2+. Sphalerite crystallized at medium to low temperatures (114–195 °C). Sulfide δ34S values (+3.48 to +24.74‰) suggest sulfur mainly originated from Dengying Formation marine sulfates via thermochemical sulfate reduction (TSR). Metal-bearing fluid release at 30 Ma post-Emeishan mantle plume activity (261–257 Ma) coincides with the Chipu deposit’s mineralization period (230–200 Ma), suggesting the Chipu deposit is associated with Emeishan plume activity. The magmatic activity drove basinal brine circulation, extracting In from intermediate-felsic igneous rocks and metamorphic basement. Elevated temperatures promoted the coupling of Fe and In into sphalerite, causing anomalous In enrichment. Full article
(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)
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20 pages, 2493 KB  
Article
Evaluation and Classification of Uranium Prospective Areas in Madagascar: A Geochemical Block-Based Approach
by Datian Wu, Jun’an Liu, Mirana Razoeliarimalala, Tiangang Wang, Rachel Razafimbelo, Fengming Xu, Wei Sun, Bruno Ralison, Zhuo Wang, Yongheng Zhou, Yuandong Zhao and Jun Zhao
Minerals 2025, 15(3), 280; https://doi.org/10.3390/min15030280 - 10 Mar 2025
Viewed by 3113
Abstract
The Precambrian crystalline basement of Madagascar, shaped by its diverse geological history of magmatic activity, sedimentation, and metamorphism, is divided into six distinct geological units. Within this intricate geological framework, five primary types of uranium deposits are present. Despite the presence of these [...] Read more.
The Precambrian crystalline basement of Madagascar, shaped by its diverse geological history of magmatic activity, sedimentation, and metamorphism, is divided into six distinct geological units. Within this intricate geological framework, five primary types of uranium deposits are present. Despite the presence of these deposits, their resource potential remains largely unquantified. To address this, a comprehensive study was conducted on Madagascar’s uranium geochemical blocks. This study processed the original data of uranium elements across the region, following the “Theoretical Model Pedigree of Geochemical Block Mineralization” proposed by Xie Xuejin. The analysis is based on the geochemical mapping data of Madagascar at a scale of 1:100,000, which was jointly completed by the China–Madagascar team and involved the delineation of geochemical blocks and the division of their internal structures using the 15 km × 15 km window data. The study used an isoline with a uranium content greater than 3.2 × 10−6 as a boundary and considered five key factors for the classification of prospective areas. These factors included uranium bulk density, anomaly intensity, block structure, prospective area, and the tracing of uranium enrichment trajectories through the pedigree chart of 5-level geochemical blocks. By integrating these factors with potential resource assessment, uranium mining economics, and conditions for uranium mining and utilization, the study successfully classified and evaluated uranium resources in Madagascar. As a result, 10 uranium prospective areas were identified, ranging from Level I to IV, with 3 being Level I areas deemed highly promising for exploration and investment. For the first time, the study predicted a resource potential of 72,600 t of uranium resources, marking a significant step towards understanding Madagascar’s uranium endowment. Full article
(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)
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20 pages, 6276 KB  
Article
Critical Minerals in Tibetan Geothermal Systems: Their Distribution, Flux, Reserves, and Resource Effects
by Di Wang, Fei Xue, Lijian Ren, Xin Li, Songtao Wang and Xie Qibei Er
Minerals 2025, 15(1), 93; https://doi.org/10.3390/min15010093 - 20 Jan 2025
Cited by 1 | Viewed by 3710
Abstract
Critical mineral resources (CMRs) are essential for emerging high-tech industries and are geopolitically significant, prompting countries to pursue resource exploration and development. Tibetan geothermal systems, recognized for their CMR potential, have not yet been systematically evaluated. This study presents a comprehensive investigation of [...] Read more.
Critical mineral resources (CMRs) are essential for emerging high-tech industries and are geopolitically significant, prompting countries to pursue resource exploration and development. Tibetan geothermal systems, recognized for their CMR potential, have not yet been systematically evaluated. This study presents a comprehensive investigation of the spatial distributions, resource flux, reserves, and resource effects of CMRs, integrating and analyzing hydrochemical and discharge flow rate data. Geochemical findings reveal significant enrichment of lithium (Li), rubidium (Rb), cesium (Cs), and boron (B) in the spring waters and sediments, primarily located along the Yarlung Zangbo suture and north–south rift zones. Resource flux estimates include approximately 246 tons of Li, 54 tons of Rb, 233 tons of Cs, and 2747 tons of B per year, underscoring the mineral potential of the geothermal spring waters. Additionally, over 40,000 tons of Cs reserves are preserved in siliceous sinters in Tagejia, Gulu, and Semi. The Tibetan geothermal systems thus demonstrate considerable potential for CMRs, especially Cs, through stable discharge and widespread distribution, also serving as indicators for endogenous mineral exploration and providing potential sources for lithium in exogenous salt lakes. This study evaluates the CMR potential of the Tibetan geothermal systems, advancing CMR exploration while contributing to the future security of CMR supplies. Full article
(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)
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18 pages, 5748 KB  
Article
Investigating Physicochemical Methods to Recover Rare-Earth Elements from Appalachian Coals
by Rachel Yesenchak, Scott Montross and Shikha Sharma
Minerals 2024, 14(11), 1106; https://doi.org/10.3390/min14111106 - 30 Oct 2024
Cited by 5 | Viewed by 2415
Abstract
The demand for rare-earth elements is expected to grow due to their use in critical technologies, including those used for clean energy generation. There is growing interest in developing unconventional rare-earth element resources, such as coal and coal byproducts, to help secure domestic [...] Read more.
The demand for rare-earth elements is expected to grow due to their use in critical technologies, including those used for clean energy generation. There is growing interest in developing unconventional rare-earth element resources, such as coal and coal byproducts, to help secure domestic supplies of these elements. Within the U.S., Appalachian Basin coals are particularly enriched in rare-earth elements, but recovery of the elements is often impeded by a resistant aluminosilicate matrix. This study explores the use of calcination and sodium carbonate roasting pre-treatments combined with dilute acid leaching to recover rare-earth elements from Appalachian Basin coals and underclay. The results suggest that rare-earth element recovery after calcination is dependent on the original mineralogy of samples and that light rare-earth minerals may be more easily decomposed than heavy rare-earth minerals. Sodium carbonate roasting can enhance the recovery of both light and heavy rare-earth elements. Maximum recovery in this study, ranging from 70% to 84% of total rare-earth elements, was achieved using a combination of calcination and sodium carbonate roasting, followed by 0.25 M citric acid leaching. Full article
(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)
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Review

Jump to: Research

34 pages, 11347 KB  
Review
Core Spectral Technology in Sandstone-Type Uranium Deposits of Basins in Northern China: Applications and Challenges—A Review
by Wenyi Wu, Mingsen Fan, Pei Ni, Junyi Pan, Yihan Lin, Zhe Chi and Junying Ding
Minerals 2026, 16(5), 471; https://doi.org/10.3390/min16050471 - 30 Apr 2026
Viewed by 413
Abstract
Sandstone-type uranium deposits represent one of the most significant uranium deposit types in China, predominantly hosted in Meso-Cenozoic sedimentary basins in the northern part of the country. Due to characteristics such as deep burial of orebodies, fine grain size of ores, and strong [...] Read more.
Sandstone-type uranium deposits represent one of the most significant uranium deposit types in China, predominantly hosted in Meso-Cenozoic sedimentary basins in the northern part of the country. Due to characteristics such as deep burial of orebodies, fine grain size of ores, and strong heterogeneity, traditional geological logging methods have limitations in rapidly and accurately identifying alteration minerals and mineralization indicator information. Core spectral technology (wavelength range approximately 400–2500 nm), particularly short-wave infrared spectroscopy (SWIR, 1300–2500 nm), enables rapid, non-destructive, and quantitative extraction of alteration mineral information from drill cores. This provides robust technical support for reconstructing metallogenic environments, delineating oxidation–reduction zones, and prospecting and prediction in sandstone-type uranium deposits. This review systematically examines the spectral absorption characteristics and geological significance of key alteration minerals (e.g., clay minerals, carbonate minerals, iron oxides, and hydrocarbon substances) in sandstone-type uranium deposits. It elaborates on the current application status of core spectral technology in sandstone-type uranium exploration within typical basins in northern China, such as the Ordos, Songliao, Erlian, and Qaidam Basins. These applications include alteration mineral mapping, oxidation–reduction zone delineation, and metallogenic fluid tracing. Due to the unique characteristics of host rock lithology, alteration mineral assemblages, and fluid properties in sandstone-type uranium deposits, the application of this technology also faces certain challenges, such as difficulties in spectral interpretation and insufficient accuracy in quantitative inversion. Integrating this technique with multiple methods, including petrography and X-ray diffraction (XRD), will facilitate more effective applications in both metallogenic research and prospecting practices for sandstone-type uranium deposits in northern China. Full article
(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)
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18 pages, 1871 KB  
Review
Platinum Group Element Mineralization in Mongolia: Geological Setting, Occurrences, and Exploration Potential
by Jaroslav Dostal, Ochir Gerel and Turbold Sukhbaatar
Minerals 2026, 16(3), 317; https://doi.org/10.3390/min16030317 - 18 Mar 2026
Viewed by 606
Abstract
Platinum group elements (PGE) are six rare highly siderophile metals which have similar chemical characteristics and occur together in mineral deposits: platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir) and osmium (Os). In nature, they tend to exist in a metallic [...] Read more.
Platinum group elements (PGE) are six rare highly siderophile metals which have similar chemical characteristics and occur together in mineral deposits: platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir) and osmium (Os). In nature, they tend to exist in a metallic state or bond with sulfur and arsenic and occur as trace accessory minerals predominantly in mafic and ultramafic rocks. High industrial demand together with their scarcity in crustal rocks has been reflected in their inclusion in 2025 US Government’s List of Critical Minerals, European Union’s List of Critical Raw Materials and Mongolian List of 11 Critical Minerals. Although Mongolia is not currently a producer, it hosts four types of potentially economic PGE deposits: (1) Podiform chromitites associated with ophiolites; (2) Ni-Cu-PGE sulfide mineralization of rift-related mafic–ultramafic intrusions; (3) Alaskan–Uralian type arc related zoned mafic–ultramafic intrusions; and (4) Placers. Particularly promising are Permian Ni-Cu-PGE sulfide bearing mafic–ultramafic intrusions of the Khangai large igneous province which bear resemblance to mineralized Permian intrusions in Russia (e.g., Norilsk-Talnakh) and N.W. China (e.g., Kalatongke; Tarim basin). In addition, sub-economic ophiolite-hosted PGE mineralization can be extracted as a by-product during chromite mining. There is also the potential for PGE recovery as a by-product in existing gold placer operations in areas hosting ophiolitic massifs and Alaskan–Uralian type intrusions. Mongolia is a promising frontier for PGE exploration and mining. Full article
(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)
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