Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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Review

26 pages, 11780 KiB  
Review
Peridotite Weathering and Ni Redistribution in New Caledonian Laterite Profiles: Influence of Climate, Hydrology, and Structure
by Michel Cathelineau, Yoram Teitler, Jean-Louis Grimaud, Sylvain Favier, Fabrice Golfier, Erick Ramanaidou, Sylvain Grangeon, Yohann Kerreveur, Julie Jeanpert, Samuel Étienne, Manuel Muñoz and Marc Ulrich
Minerals 2024, 14(11), 1082; https://doi.org/10.3390/min14111082 - 27 Oct 2024
Viewed by 1285
Abstract
The peridotite massifs of New Caledonia are characterised by complex hydrodynamics influenced by intense inherited fracturing, uplift, and erosion. Following the formation of the erosion surfaces and alteration processes, these processes drive chemical redistribution during weathering; particularly lateritisation and saprolitisation. Magnesium, silica, and [...] Read more.
The peridotite massifs of New Caledonia are characterised by complex hydrodynamics influenced by intense inherited fracturing, uplift, and erosion. Following the formation of the erosion surfaces and alteration processes, these processes drive chemical redistribution during weathering; particularly lateritisation and saprolitisation. Magnesium, silica, and trace elements such as nickel and cobalt—released as the dissolution front advances—are redistributed through the system. New observations and interpretations reveal how lateritic paleo-land surfaces evolved, and their temporal relationship with alteration processes since the Oligocene. Considering the geometry of discontinuity networks ranging from micro-fractures to faults, the transfers occur in dual-permeability environments. Olivine dissolution rates are heterogeneously due to differential solution renewal caused by erosion and valley deepening. Differential mass transfer occurs between mobile regions of highly transmissive faults, while immobile areas correspond to the rock matrix and the secondary fracture network. The progression of alteration fronts controls the formation of boulders and the distribution of nickel across multiple scales. In the saprolite, nickel reprecipitates mostly in talc-like phases, as well as minor nontronite and goethite with partial diffusion in inherited serpentine. The current nickel distribution results from a complex interplay of climatic, hydrological and structural factors integrated into a model across different scales and times. Full article
(This article belongs to the Special Issue Chemical Weathering Studies)
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21 pages, 1691 KiB  
Review
Ultrasonic Enhancement for Mineral Flotation: Technology, Device, and Engineering Applications
by Xiaoou Zhang, Huaigang Cheng, Kai Xu, Danjing Ding, Xin Wang, Bo Wang and Zhuohui Ma
Minerals 2024, 14(10), 986; https://doi.org/10.3390/min14100986 - 30 Sep 2024
Cited by 4 | Viewed by 1893
Abstract
In the past five years, the number of articles related to ultrasonic mineral flotation has increased by about 50 per year, and the overall trend is on the rise. The most recent developments in ultrasonics for flotation process intensification are reviewed herein, including [...] Read more.
In the past five years, the number of articles related to ultrasonic mineral flotation has increased by about 50 per year, and the overall trend is on the rise. The most recent developments in ultrasonics for flotation process intensification are reviewed herein, including effects of ultrasound treatment on an aqueous slurry, improvement in flotation methods and technological processes, device development tracking, and application effects in mineral process engineering. At this point in time, there are pilot-scale flotation tests to evaluate the feasibility of ultrasonic pretreatment technology for industrial use to enhance residue flotation separation, and the results showed that the recovery rate of concentrate is increased by about 10%. Four aspects of ultrasonic flotation process improvement are summarized, namely, changing the ultrasonic parameters, the synergistic effect of ultrasound and reagents, the ultrasonic effect of particles with different-sized fractions, and application to new systems. In addition, the effect of ultrasonic flotation mechanisms is explored through a quadratic model and numerical simulation. The combination of ultrasonic flotation with other fields, such as magnetic fields, to enhance the separation efficiency and recovery of minerals is also a future trend. It is also proposed that ultrasonic flotation technology will be used with big data, industrial Internet of Things, and automatic control technology to achieve deep bundling, optimizing the flotation process by implementing remote monitoring and control of the flotation process. Full article
(This article belongs to the Special Issue Industrial Minerals Flotation—Fundamentals and Applications)
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42 pages, 852 KiB  
Review
Chiral Minerals
by David Avnir
Minerals 2024, 14(10), 995; https://doi.org/10.3390/min14100995 - 30 Sep 2024
Cited by 2 | Viewed by 2014
Abstract
Hundreds of minerals are chiral, that is, they appear in nature in two forms—left-handed and right-handed. Yet except for quartz, this key structural property has remained, by and large, in shadow in the world of minerals in research, in museum displays and for [...] Read more.
Hundreds of minerals are chiral, that is, they appear in nature in two forms—left-handed and right-handed. Yet except for quartz, this key structural property has remained, by and large, in shadow in the world of minerals in research, in museum displays and for collectors. This review is devoted to providing a full picture of chiral minerals in nature. It starts with a general outline of the crystallographic background needed for the characterization of chiral minerals, continues with a detailed description of the many chemical and physical processes leading to their formation and follows with their chemical reactivities and transformations, with their physical properties and with the ways to analyze and identify them. Many tables with listings of various types of chiral minerals are provided. The “missing-glove” situation, in which the recognition that a chiral mineral appears in nature in two distinctly forms is, by and large, missing, is described, and it is hoped that this review will spark interest in this aspect of nature’s crystals. Full article
20 pages, 6163 KiB  
Review
Review on the Challenges of Magnesium Removal in Nickel Sulfide Ore Flotation and Advances in Serpentinite Depressor
by Fengxiang Yin, Chengxu Zhang, Yao Yu, Chenyang Lv, Zhengbo Gao, Bingang Lu, Xiaohui Su, Chunhua Luo, Xiangan Peng, Belinda McFadzean and Jian Cao
Minerals 2024, 14(10), 965; https://doi.org/10.3390/min14100965 - 25 Sep 2024
Cited by 2 | Viewed by 1301
Abstract
Nickel is an important raw metal material in industry, which has been identified as a strategic mineral resource by the Chinese Ministry of Land and Resources. Nickel sulfide ore accounts for 40% of all nickel ores worldwide. However, magnesium silicate gangue minerals in [...] Read more.
Nickel is an important raw metal material in industry, which has been identified as a strategic mineral resource by the Chinese Ministry of Land and Resources. Nickel sulfide ore accounts for 40% of all nickel ores worldwide. However, magnesium silicate gangue minerals in sulfide nickel ores, particularly serpentine, pose significant challenges to the flotation of nickel sulfide ores. The presence of magnesium silicate gangue leads to a series of issues, including increased energy consumption in subsequent smelting processes, accelerated equipment wastage, and increased SO2 emissions, which severely impact the comprehensive utilization of nickel resources in sulfide nickel ores. In this regard, flotation depressants are the most direct and effective method to reduce adverse influences caused by magnesium silicate gangue in the flotation of nickel sulfide ore concentrate. Based on the characteristics of the typical magnesium-containing nickel sulfide ore, this review illustrates the difficulties of the depression of magnesium silicate gangue during the flotation of nickel sulfide ore and gives an overview of the common depressants from six aspects (chelation depressants, dispersion depressants, flocculation depressants, depressants for grinding, depressants for slurry adjustment and combination depressants). Each section summarizes the relevant depression mechanisms and analyzes the advantages and disadvantages of various reagents, providing a reference for designing depressants specifically targeting serpentine. Full article
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39 pages, 3652 KiB  
Review
Coal and Coal By-Products as Unconventional Lithium Sources: A Review of Occurrence Modes and Hydrometallurgical Strategies for Metal Recovery
by Ewa Rudnik
Minerals 2024, 14(8), 849; https://doi.org/10.3390/min14080849 - 22 Aug 2024
Cited by 5 | Viewed by 2416
Abstract
Lithium, a critical material for the global development of green energy sources, is anomalously enriched in some coal deposits and coal by-products to levels that may be considered economically viable. Recovering lithium from coal, particularly from coal gangue or coal ashes, offers a [...] Read more.
Lithium, a critical material for the global development of green energy sources, is anomalously enriched in some coal deposits and coal by-products to levels that may be considered economically viable. Recovering lithium from coal, particularly from coal gangue or coal ashes, offers a promising alternative for extracting this element. This process could potentially lead to economic gains and positive environmental impacts by more efficiently utilizing coal-based waste materials. This review focuses on lithium concentrations in coal and coal by-products, modes of lithium occurrence, methods used to identify lithium-enriched phases, and currently available hydrometallurgical recovery methods, correlated with pretreatment procedures that enable lithium release from inert aluminosilicate minerals. Leaching of raw coal appears inefficient, whereas coal gangue and fly ash are more feasible due to their simpler composition and higher lithium contents. Lithium extraction can achieve recovery rates of over 90%, but low lithium concentrations and high impurity levels in the leachates require advanced selective separation techniques. Bottom ash has not yet been evaluated for lithium recovery, despite its higher lithium content compared to feed coal. Full article
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25 pages, 3020 KiB  
Review
Exploring Low-Grade Iron Ore Beneficiation Techniques: A Comprehensive Review
by Mompati Mpho Bulayani, Prasad Raghupatruni, Tirivaviri Mamvura and Gwiranai Danha
Minerals 2024, 14(8), 796; https://doi.org/10.3390/min14080796 - 2 Aug 2024
Cited by 6 | Viewed by 5728
Abstract
The beneficiation of low-grade iron ores is a key research and development topic in the mineral processing industry. The gradual exhaustion of high-grade iron ore reserves, and rising consumer iron and steel demand globally necessitate efficient low-quality iron ore beneficiation to meet steelmaking [...] Read more.
The beneficiation of low-grade iron ores is a key research and development topic in the mineral processing industry. The gradual exhaustion of high-grade iron ore reserves, and rising consumer iron and steel demand globally necessitate efficient low-quality iron ore beneficiation to meet steelmaking quality requirements. This comprehensive review explores various beneficiation techniques for low-quality iron ore, focusing on conventional methods including comminution, froth flotation and gravity separation. This article discusses the principles, processes, and equipment used in these techniques and highlights recent advancements and research efforts in the field. This review also emphasizes the importance of effective beneficiation processes in enhancing economic viability, sustainable resource management, and environmental conservation. Furthermore, it presents a case study of iron ore deposits in Botswana, highlighting the potential economic growth and sustainable development that can be achieved by maximizing resource utilization through reductive roasting, followed by magnetic separation of iron ore using semi-bituminous coal as a reductant. Overall, this review provides valuable insights into low-grade iron ore beneficiation techniques and their significance in meeting the growing demand for high-quality iron and steel products. Full article
(This article belongs to the Special Issue Recent Advances in Extractive Metallurgy)
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27 pages, 380 KiB  
Review
Recent Uses of Ionic Liquids in the Recovery and Utilization of Rare Earth Elements
by Francisco Jose Alguacil, Jose Ignacio Robla and Olga Rodriguez Largo
Minerals 2024, 14(7), 734; https://doi.org/10.3390/min14070734 - 22 Jul 2024
Cited by 5 | Viewed by 2425
Abstract
The importance of rare earth elements as a basis for the development of new technologies or the improvement of existing ones makes their recovery from raw and waste materials necessary. In this recovery, hydrometallurgy and its derivative solvometallurgy play key roles due to [...] Read more.
The importance of rare earth elements as a basis for the development of new technologies or the improvement of existing ones makes their recovery from raw and waste materials necessary. In this recovery, hydrometallurgy and its derivative solvometallurgy play key roles due to their operational characteristics, which are emphasized with the use of ionic liquids. This manuscript reviews the most recent advances (2023 and 2024) in the use of ionic liquids in unit operations (leaching and separation technologies) aimed at the recovery of these valuable and strategic metals. Moreover, a comprehensive review is presented of the use of these chemicals in the development of advanced materials containing some of these rare earth elements. Full article
25 pages, 3064 KiB  
Review
The Catalytic Potential of Modified Clays: A Review
by Altantuya Ochirkhuyag and Jadambaa Temuujin
Minerals 2024, 14(6), 629; https://doi.org/10.3390/min14060629 - 20 Jun 2024
Cited by 6 | Viewed by 3615
Abstract
The need for innovative catalysts and catalytic support materials is continually growing due to demanding requirements, stricter environmental demands, and the ongoing development of new chemical processes. Since about 80% of all industrial processes involve catalysts, there is a continuing need to develop [...] Read more.
The need for innovative catalysts and catalytic support materials is continually growing due to demanding requirements, stricter environmental demands, and the ongoing development of new chemical processes. Since about 80% of all industrial processes involve catalysts, there is a continuing need to develop new catalyst materials and supports with suitable qualities to meet ongoing industrial demands. Not only must new catalysts have tailored properties, but they must also be suitable for large-scale production through environmentally friendly and cost-effective processes. Clay minerals, with their rich history in medicine and ceramics, are now emerging as potential catalysts. Their transformative potential is exemplified in applications such as hydrogenating the greenhouse gas CO2 into carbohydrate fuel, a crucial step in meeting the rising electrical demand. Moreover, advanced materials derived from clay minerals are proving their mettle in diverse photocatalytic reactions, from organic dye removal to pharmaceutical pollutant elimination and photocatalytic energy conversion through water splitting. Clay minerals in their natural state show a low catalytic activity, so to increase their reactivity, they must be activated. Depending on the requirements of a particular application, selecting an appropriate activation method for modifying a natural clay mineral is a critical consideration. Traditional clay mineral processing methods such as acid or alkaline treatment are used. Still, these have drawbacks such as high costs, long processing times, and the formation of hazardous by-products. Other activation processes, such as ultrasonication and mechanical activation routes, have been proposed to reduce the production of hazardous by-products. The main advantage of ultrasonication and microwave-assisted procedures is that they save time, whereas mechanochemical processing is simple and efficient. This short review focuses on modifying clay minerals using various new methods to create sophisticated and innovative new materials. Recent advances in catalytic reactions are specifically covered, including organic biogeochemical processes, photocatalytic processes, carbon nanotube synthesis, and energy conversion processes such as CO2 hydrogenation and dry reforming of methane. Full article
(This article belongs to the Section Clays and Engineered Mineral Materials)
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27 pages, 2235 KiB  
Review
Clay Minerals and Biopolymers in Film Design: Overview of Properties and Applications
by Pollyana Trigueiro, Juliane P. de L. Pereira, Mirelly G. Ferreira, Lucas B. Silva, Luan Neves and Ramón R. Peña-Garcia
Minerals 2024, 14(6), 613; https://doi.org/10.3390/min14060613 - 15 Jun 2024
Cited by 4 | Viewed by 2227
Abstract
Research to replace petroleum-based plastics has been quite challenging. Currently, there is a lot of interest in biopolymers as an alternative. However, biopolymers do not have suitable mechanical properties when in film form, which limits their applications. To resolve this issue, clay minerals [...] Read more.
Research to replace petroleum-based plastics has been quite challenging. Currently, there is a lot of interest in biopolymers as an alternative. However, biopolymers do not have suitable mechanical properties when in film form, which limits their applications. To resolve this issue, clay minerals are being incorporated as a strategy. Clay minerals offer the films good barrier, thermal, rheological, optical, and mechanical properties. They can also work with other additives to promote antioxidant and antimicrobial activity. This brief review focuses on incorporating clay minerals with other nanofillers and bioactives to improve their physical, chemical, and functional characteristics. The synergy of these materials gives the films exceptional properties and makes them suitable for applications such as food coatings, packaging materials, dressings, and bandages for treating skin wounds. Full article
(This article belongs to the Special Issue Applications of Clay-Based Materials)
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34 pages, 8938 KiB  
Review
Phosphates on Mars and Their Importance as Igneous, Aqueous, and Astrobiological Indicators
by E. M. Hausrath, C. T. Adcock, J. A. Berger, L. M. Cycil, T. V. Kizovski, F. M. McCubbin, M. E. Schmidt, V. M. Tu, S. J. VanBommel, A. H. Treiman and B. C. Clark
Minerals 2024, 14(6), 591; https://doi.org/10.3390/min14060591 - 4 Jun 2024
Cited by 3 | Viewed by 3232
Abstract
This paper reviews the phosphate phases in meteorites and those measured by landed spacecraft, what they reveal about past igneous and aqueous conditions on Mars, and important implications for potential prebiotic chemistry, past habitability, and potential biosignatures that could be detected in samples [...] Read more.
This paper reviews the phosphate phases in meteorites and those measured by landed spacecraft, what they reveal about past igneous and aqueous conditions on Mars, and important implications for potential prebiotic chemistry, past habitability, and potential biosignatures that could be detected in samples returned from Mars. A review of the 378 martian meteorites as of 2023 indicate that of the two most common phosphate minerals in Mars meteorites, merrillite and apatites, the apatite composition is largely F- and Cl-rich, with shergottites containing more OH. The phosphate concentrations examined across multiple missions show a relatively narrow range of phosphate, with higher concentrations observed in the Mount Sharp Group in Gale crater and Wishstone at Gusev crater and lower concentrations observed at Jezero crater floor and Jezero fan. Possible secondary phosphates detected on Mars, including Fe phosphates at Jezero crater and Gusev crater and Ca- and Al-bearing secondary phosphates, temperatures of formation of secondary phases and their dissolution rates and solubilities are reviewed and summarized. Despite this wealth of information about phosphates on Mars, due to their fine scale and relatively low concentrations, Mars Sample Return is needed to better understand phosphate and its implications for the igneous, aqueous, and astrobiological history of Mars. Full article
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28 pages, 4087 KiB  
Review
Advanced Processing Techniques and Impurity Management for High-Purity Quartz in Diverse Industrial Applications
by Hailin Long, Deqing Zhu, Jian Pan, Siwei Li, Congcong Yang and Zhengqi Guo
Minerals 2024, 14(6), 571; https://doi.org/10.3390/min14060571 - 30 May 2024
Cited by 11 | Viewed by 7112
Abstract
While numerous studies have explored the mineralogical characteristics and purification techniques of high-purity quartz (HPQ), discussions on impurity control during various purification processes and their applications in photovoltaics, electronics, and optics remain limited. This review delves into the adverse effects of impurities such [...] Read more.
While numerous studies have explored the mineralogical characteristics and purification techniques of high-purity quartz (HPQ), discussions on impurity control during various purification processes and their applications in photovoltaics, electronics, and optics remain limited. This review delves into the adverse effects of impurities such as aluminum, iron, and sodium in the manufacturing processes of these industries, emphasizing their critical role as these impurities can degrade material performance. This paper focuses on analyzing the types of impurities found in quartz and evaluates existing purification technologies such as acid washing, ultrasonic acid washing, chlorination roasting, and calcination quenching. It highlights the limitations of current technologies in processing quartz ore and discusses the advantages of different impurity types under various technological treatments. Moreover, it explores the environmental and economic impacts of these high-purity processes, underlining the necessity for more environmentally friendly and cost-effective purification techniques. The purpose of this review is to provide a comprehensive technical and strategic framework for the use of high-purity quartz in high-tech applications, supporting future research and industrial applications in this critical material field. Full article
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44 pages, 21329 KiB  
Review
The Chemistry and Mineralogy (CheMin) X-ray Diffractometer on the MSL Curiosity Rover: A Decade of Mineralogy from Gale Crater, Mars
by David Blake, Valerie Tu, Thomas Bristow, Elizabeth Rampe, David Vaniman, Steve Chipera, Philippe Sarrazin, Richard Morris, Shaunna Morrison, Albert Yen, Robert Downs, Robert Hazen, Allan Treiman, Douglas Ming, Gordon Downs, Cherie Achilles, Nicholas Castle, Tanya Peretyazhko, David De Marais, Patricia Craig, Barbara Lafuente, Benjamin Tutolo, Elisabeth Hausrath, Sarah Simpson, Richard Walroth, Michael Thorpe, Johannes Meusburger, Aditi Pandey, Marc Gailhanou, Przemyslaw Dera, Jeffrey Berger, Lucy Thompson, Ralf Gellert, Amy McAdam, Catherine O’Connell-Cooper, Brad Sutter, John Michael Morookian, Abigail Fraeman, John Grotzinger, Kirsten Siebach, Soren Madsen and Ashwin Vasavadaadd Show full author list remove Hide full author list
Minerals 2024, 14(6), 568; https://doi.org/10.3390/min14060568 - 29 May 2024
Cited by 7 | Viewed by 3952
Abstract
For more than a decade, the CheMin X-ray diffraction instrument on the Mars Science Laboratory rover, Curiosity, has been returning definitive and quantitative mineralogical and mineral–chemistry data from ~3.5-billion-year-old (Ga) sediments in Gale crater, Mars. To date, 40 drilled rock samples and [...] Read more.
For more than a decade, the CheMin X-ray diffraction instrument on the Mars Science Laboratory rover, Curiosity, has been returning definitive and quantitative mineralogical and mineral–chemistry data from ~3.5-billion-year-old (Ga) sediments in Gale crater, Mars. To date, 40 drilled rock samples and three scooped soil samples have been analyzed during the rover’s 30+ km transit. These samples document the mineralogy of over 800 m of flat-lying fluvial, lacustrine, and aeolian sedimentary rocks that comprise the lower strata of the central mound of Gale crater (Aeolis Mons, informally known as Mt. Sharp) and the surrounding plains (Aeolis Palus, informally known as the Bradbury Rise). The principal mineralogy of the sedimentary rocks is of basaltic composition, with evidence of post-depositional diagenetic overprinting. The rocks in many cases preserve much of their primary mineralogy and sedimentary features, suggesting that they were never strongly heated or deformed. Using aeolian soil composition as a proxy for the composition of the deposited and lithified sediment, it appears that, in many cases, the diagenetic changes observed are principally isochemical. Exceptions to this trend include secondary nodules, calcium sulfate veining, and rare Si-rich alteration halos. A surprising and yet poorly understood observation is that nearly all of the ~3.5 Ga sedimentary rocks analyzed to date contain 15–70 wt.% of X-ray amorphous material. Overall, this >800 m section of sedimentary rock explored in lower Mt. Sharp documents a perennial shallow lake environment grading upward into alternating lacustrine/fluvial and aeolian environments, many of which would have been habitable to microbial life. Full article
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18 pages, 6244 KiB  
Review
A Review of Relationship between the Metallogenic System of Metallic Mineral Deposits and Lithospheric Electrical Structure: Insight from Magnetotelluric Imaging
by Sheng Jin, Yue Sheng, Chenggong Liu, Wenbo Wei, Gaofeng Ye, Jianen Jing, Letian Zhang, Hao Dong, Yaotian Yin and Chengliang Xie
Minerals 2024, 14(6), 541; https://doi.org/10.3390/min14060541 - 24 May 2024
Cited by 1 | Viewed by 1821
Abstract
In development over 70 years, magnetotelluric (MT) sounding, a high-resolution technique for subsurface electrical resistivity imaging, has been widely applied in resource exploration in the Earth. The key factors of the metallogenic system of metallic mineral deposits can be closely correlated to the [...] Read more.
In development over 70 years, magnetotelluric (MT) sounding, a high-resolution technique for subsurface electrical resistivity imaging, has been widely applied in resource exploration in the Earth. The key factors of the metallogenic system of metallic mineral deposits can be closely correlated to the electrical anomalies of the lithosphere. In this paper, we review the relationship between the electrical resistivity model of the lithosphere and the metallogenic system. At the beginning, we indicate why the electrical parameters relate to the metallogenic system in all geophysical parameters. The advantage of MT sounding in sketching an electrical resistivity model of the lithosphere is subsequently discussed, and some methods of data processing, analysis and inversion are also introduced. Furthermore, we summarize how to bridge the relationship between the electrical resistivity model of the lithosphere and metallogenic system, and analyze the influence of the rheological variation estimated from conductivity in the lithosphere on mineralization. In the end, we list some typical cases of the application of MT sounding in mineral exploration, and also give some suggestions for future work. This study is aimed at providing guidance in discussing the metallogenic system using an electrical resistivity model. Full article
(This article belongs to the Special Issue Geoelectricity and Electrical Methods in Mineral Exploration)
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20 pages, 2798 KiB  
Review
Are Clay Minerals Systematically the Products of Aqueous Alteration in Cosmic Bodies?
by Abderrazak El Albani, Ibtissam Chraiki, Hasnaa Chennaoui Aoudjehane, Mohamed Ghnahalla, Fatima Abdelfadel, Ahmed Abd Elmola, Olabode Bankole, Julie Ngwal’ghoubou Ikouanga, Anna El Khoury, Claude Fontaine, El Hafid Bouougri, France Westall and Alain Meunier
Minerals 2024, 14(5), 486; https://doi.org/10.3390/min14050486 - 3 May 2024
Viewed by 2069
Abstract
The formation of chondrite materials represents one of the earliest mineralogical processes in the solar system. Phyllosilicates are encountered at various stages of the chondrule formation, from the initial stages (IDP agglomerates) to the final steps (chondrule internal alteration). While typically linked to [...] Read more.
The formation of chondrite materials represents one of the earliest mineralogical processes in the solar system. Phyllosilicates are encountered at various stages of the chondrule formation, from the initial stages (IDP agglomerates) to the final steps (chondrule internal alteration). While typically linked to aqueous alteration, recent studies reveal that phyllosilicates could precipitate directly from residual fluids in post-magmatic or deuteric conditions and under a wide range of temperatures, pressures, water/rock ratios, and H2/H2O ratio conditions. This study re-examined the formation of hydrated phyllosilicates in chondrules and associated fine-grained rims (FGRs) using published petrographical, mineralogical, and chemical data on carbonaceous chondrites. Given that chondrules originate from the melting of interplanetary dust particles, the water liberated by the devolatilization of primary phyllosilicates, including clay minerals or ice melting, reduces the melting temperature and leads to water dissolution into the silicate melt. Anhydrous minerals (e.g., olivine and diopside) form first, while volatile and incompatible components are concentrated in the residual liquid, diffusing into the matrix and forming less porous FGRs. Serpentine and cronstedtite are the products of thermal metamorphic-like mineral reactions. The mesostasis in some lobated chondrules is composed of anhydrous and hydrous minerals, i.e., diopside and serpentine. The latter is probably not the alteration product of a glassy precursor but rather a symplectite component (concomitant crystallization of diopside and serpentine). If so, the symplectite has been formed at the end of the cooling process (eutectic-like petrographical features). Water trapped inside chondrule porosity can lead to the local replacement of olivine by serpentine without external water input (auto-alteration). In the absence of water, hydrated phyllosilicates do not crystallize, forming a different mineral assemblage. Full article
(This article belongs to the Section Clays and Engineered Mineral Materials)
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48 pages, 8568 KiB  
Review
Global Occurrence, Geology and Characteristics of Hydrothermal-Origin Kaolin Deposits
by Ömer Işık Ece and Hatice Ünal Ercan
Minerals 2024, 14(4), 353; https://doi.org/10.3390/min14040353 - 28 Mar 2024
Cited by 6 | Viewed by 4876
Abstract
Kaolin-group minerals occur in nature as the result of high-sulfidation acid sulfate, sulfur-poor HCl-, HF- and H2CO3-rich acidic fluid-related hydrothermal alterations and in situ geochemical weathering. These minerals possess different crystallographic and chemical properties that determine their application areas, [...] Read more.
Kaolin-group minerals occur in nature as the result of high-sulfidation acid sulfate, sulfur-poor HCl-, HF- and H2CO3-rich acidic fluid-related hydrothermal alterations and in situ geochemical weathering. These minerals possess different crystallographic and chemical properties that determine their application areas, mainly in the ceramic and paper industries, and as nanocomposite materials. The physicochemical properties of hydrothermal kaolin deposits are the result of the type of parent rock, the effect of the regional tectonism-associated magmatism, and the chemical features of hydrothermal fluids that interact with the deep basement rocks. However, understanding these geothermal systems is one of the most challenging issues due to the rich mineralogical assemblages, complex geochemistry and isotopic data of hydrothermal alteration zones. This study evaluates the formation of hydrothermal-origin kaolin-group minerals by considering their characteristics of hydrothermal alteration, isotopic compositions and differences in characteristic properties of low- and high-sulfidation occurrences; this paper also addresses mineralogical and structural differences between hypogene and supergene kaolin formations, and kaolin–alunite–pyrophyllite association, and it provides examples of worldwide occurrences. The study of the mineralogical assemblages, geochemistry and isotopic data of the hydrothermal alteration zones is one of the most challenging subjects in terms of gaining a detailed understanding of the geothermal systems. Silicification processes are subsequent to late-stage alteration after the completion of kaolinization processes, erasing existing hydrothermal mineralogical and geochemical traces and making interpretation difficult. In the early stages involving magmatic–hydrothermal-origin acidic geothermal fluids, the latter comes from the disproportionation of SO2 (+H2O) and H2S oxidation to H2SO4 in hydrothermal environments. In the later stages, due to spatial and temporal changes over time in the chemistry of geothermal fluids, the system comes to have a more alkali–chloride composition, with neutral pH waters frequently saturated with amorphous silica which characteristically precipitate as siliceous sinter deposits containing large amounts of opal-A. Full article
(This article belongs to the Section Mineral Deposits)
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18 pages, 2383 KiB  
Review
Advancements in Machine Learning for Optimal Performance in Flotation Processes: A Review
by Alicja Szmigiel, Derek B. Apel, Krzysztof Skrzypkowski, Lukasz Wojtecki and Yuanyuan Pu
Minerals 2024, 14(4), 331; https://doi.org/10.3390/min14040331 - 24 Mar 2024
Cited by 9 | Viewed by 4279
Abstract
Flotation stands out as a successful and extensively employed method for separating valuable mineral particles from waste rock. The efficiency of this process is subjected to the distinct physicochemical attributes exhibited by various minerals. However, the complex combination of multiple sub-processes within flotation [...] Read more.
Flotation stands out as a successful and extensively employed method for separating valuable mineral particles from waste rock. The efficiency of this process is subjected to the distinct physicochemical attributes exhibited by various minerals. However, the complex combination of multiple sub-processes within flotation presents challenges in controlling this mechanism and achieving optimal efficiency. Consequently, there is a growing dependence on machine learning methods in mineral processing research. This paper provides a comprehensive overview of machine learning and artificial intelligence techniques, presenting their potential applications in flotation processes. The review demonstrates advancements discussed in scholarly research over the past decade and highlights a growing interest in utilizing machine learning methods for monitoring and optimizing flotation processes, as demonstrated by the increasing number of studies in this field. Recent trends also suggest that the course of flotation process monitoring, and control will increasingly focus on the refinement and deployment of deep learning networks developed specifically for froth image extraction and analysis. Full article
(This article belongs to the Special Issue Advances in Industrial Flotation Applications)
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20 pages, 2230 KiB  
Review
Calcium Orthophosphate–Clay Composites—Preparation, Characterisation, and Applications: A Review
by Monika Šupová
Minerals 2024, 14(2), 169; https://doi.org/10.3390/min14020169 - 4 Feb 2024
Cited by 2 | Viewed by 1914
Abstract
Calcium orthophosphates and clays and their composites are one of the most important groups in the field of new, modern, and technologically advanced materials that are accessible, inexpensive, and environmentally friendly. This review provides a summary of recent research on calcium orthophosphate–clay composites, [...] Read more.
Calcium orthophosphates and clays and their composites are one of the most important groups in the field of new, modern, and technologically advanced materials that are accessible, inexpensive, and environmentally friendly. This review provides a summary of recent research on calcium orthophosphate–clay composites, their preparation, characterisation, and use in various applications. An introduction to the subject is followed by a detailed description of the chemical and physical properties of calcium orthophosphates, clays, and clay minerals. This is followed by a general summary of preparation methods for calcium orthophosphate–clay composites. Particular attention is paid to the description of individual applications, i.e., environmental applications, biomaterials science (tissue engineering, pharmacology), and other emerging applications. Finally, future perspectives are summarised and discussed. Full article
(This article belongs to the Special Issue Clay Minerals and Waste Fly Ash Ceramics, Volume II)
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38 pages, 13006 KiB  
Review
Wrapping a Craton: A Review of Neoproterozoic Fold Belts Surrounding the São Francisco Craton, Eastern Brazil
by Alexandre Uhlein, Gabriel Jubé Uhlein, Fabrício de Andrade Caxito and Samuel Amaral Moura
Minerals 2024, 14(1), 43; https://doi.org/10.3390/min14010043 - 29 Dec 2023
Cited by 2 | Viewed by 3425
Abstract
A synthesis of the evolution of the Neoproterozoic belts or orogens surrounding the São Francisco craton (SFC) in northeastern and southeastern Brazil is presented. Emphasis is placed on recognizing the superposition of sedimentary basins, from rift to passive margin to retroarc and foreland, [...] Read more.
A synthesis of the evolution of the Neoproterozoic belts or orogens surrounding the São Francisco craton (SFC) in northeastern and southeastern Brazil is presented. Emphasis is placed on recognizing the superposition of sedimentary basins, from rift to passive margin to retroarc and foreland, as well as identifying three diachronic continental collisions in the formation of the SFC. The Tonian passive margin occurs in the southern Brasília Belt with the Vazante, Canastra, and Araxá Groups. During the Tonian, island magmatic arcs and basins developed in front and behind these arcs (fore- and back-arcs). Subsequently, in the Cryogenian–Ediacaran, a retroarc foreland basin developed with part of the Araxá Group and the Ibiá Group, and finally, a foreland basin developed, which was filled by the Bambuí Group. A tectonic structure of superimposed nappes, with subhorizontal S1–2 foliation, formed between 650 and 610 Ma, is striking. In the northern Brasília Belt, there is the Stenian passive margin of the Paranoá Group, the Tonian intrusion of the Mafic–Ultramafic Complexes, and the Mara Rosa Island magmatic arc, active since the Tonian, with limited volcanic–sedimentary basins associated with the arc. A thrust–fold belt structure is prominent, with S1 foliation and late transcurrent, transpressive tectonics characterized by the Transbrasiliano (TB) lineament. The Cryogenian–Ediacaran collision between the Paranapanema and São Francisco cratons is the first collisional orogenic event to the west. In the Rio Preto belt, on the northwestern margin of the São Francisco craton, the Cryogenian–Ediacaran Canabravinha rift basin is prominent, with gravitational sediments that represent the intracontinental termination of the passive margin that occurs further northeast. The rift basin was intensely deformed at the Ediacaran–Cambrian boundary, as was the Bambuí Group. On the northern and northeastern margins of the São Francisco craton, the Riacho do Pontal and Sergipano orogens stand out, showing a comparable evolution with Tonian and Cryogenian rifts (Brejo Seco, Miaba, and Canindé); Cryogenian–Ediacaran passive margin, where the Monte Orebe ophiolite is located; and Cordilleran magmatic arcs, which developed between 620 and 610 Ma. In the Sergipano fold belt, with a better-preserved outer domain, gravitational sedimentation occurs with glacial influence. A continental collision between the SFC and the PEAL (Pernambuco-Alagoas Massif) occurred between 610 and 540 Ma, with intense deformation of nappes and thrusts, with vergence to the south and accommodation by dextral transcurrent shear zones, such as the Pernambuco Lineament (PE). The Araçuaí belt or orogen was formed at the southeastern limit of the SFC by a Tonian intracontinental rift, later superimposed by a Cryogenian–Ediacaran rift–passive margin of the Macaúbas Group, with gravitational sedimentation and glacial influence, and distally by oceanic crust. It is overlain by a retroarc basin with syn-orogenic sedimentation of the Salinas Formation, partly derived from the Rio Doce cordilleran magmatic arc and associated basins, such as the Rio Doce and Nova Venécia Groups. A third continental collision event (SF and Congo cratons), at the end of the Ediacaran (580–530 Ma), developed a thrust–fold belt that deforms the sediments of the Araçuaí Belt and penetrates the Paramirim Corridor, transitioning to the south to a dextral strike-slip shear zone that characterizes the Ribeira Belt. Full article
(This article belongs to the Special Issue Geological Evolution of South American Cratons)
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34 pages, 1192 KiB  
Review
Reactivity of Basaltic Minerals for CO2 Sequestration via In Situ Mineralization: A Review
by Muhammad Hammad Rasool and Maqsood Ahmad
Minerals 2023, 13(9), 1154; https://doi.org/10.3390/min13091154 - 31 Aug 2023
Cited by 21 | Viewed by 10465
Abstract
The underground storage of CO2 (carbon dioxide) in basalt presents an exceptionally promising solution for the effective and permanent sequestration of CO2. This is primarily attributed to its geochemistry and the remarkable presence of reactive basaltic minerals, which play a [...] Read more.
The underground storage of CO2 (carbon dioxide) in basalt presents an exceptionally promising solution for the effective and permanent sequestration of CO2. This is primarily attributed to its geochemistry and the remarkable presence of reactive basaltic minerals, which play a pivotal role in facilitating the process. However, a significant knowledge gap persists in the current literature regarding comprehensive investigations on the reactivity of basaltic minerals in the context of CO2 sequestration, particularly with respect to different basalt types. To address this gap, a comprehensive investigation was conducted that considered seven distinct types of basalts identified through the use of a TAS (total alkali–silica) diagram. Through a thorough review of the existing literature, seven key factors affecting the reactivity of basaltic minerals were selected, and their impact on mineral reactivity for each basalt type was examined in detail. Based on this analysis, an M.H. reactivity scale was introduced, which establishes a relationship between the reactivity of dominant and reactive minerals in basalt and their potential for carbonation, ranging from low (1) to high (5). The study will help in choosing the most suitable type of basalt for the most promising CO2 sequestration based on the percentage of reactive minerals. Additionally, this study identified gaps in the literature pertaining to enhancing the reactivity of basalt for maximizing its CO2 sequestration potential. As a result, this study serves as an important benchmark for policymakers and researchers seeking to further explore and improve CO2 sequestration in basaltic formations. Full article
(This article belongs to the Special Issue Carbon Dioxide Storage, Utilization & Reduction)
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15 pages, 3398 KiB  
Review
Dating Amber: Review and Perspective
by Su-Chin Chang, Yuling Li and Daran Zheng
Minerals 2023, 13(7), 948; https://doi.org/10.3390/min13070948 - 15 Jul 2023
Cited by 4 | Viewed by 3487
Abstract
Amber is a fossilized tree resin that ranges in age from the Carboniferous to the Cenozoic. It occurs globally from the Arctic to Antarctica. As the resin petrifies and turns into amber, it can enclose and preserve other materials. Amber with inclusions can [...] Read more.
Amber is a fossilized tree resin that ranges in age from the Carboniferous to the Cenozoic. It occurs globally from the Arctic to Antarctica. As the resin petrifies and turns into amber, it can enclose and preserve other materials. Amber with inclusions can help reconstruct past biodiversity and ecosystems. Some amber contains fossils representing the oldest and most detailed records of critical evolutionary traits or markers. Inclusions can even capture behavioral indicators previously only observed in extant organisms. Evidence of insect pollination of flowering plants and dragonfly mating behavior appears in amber, as does the morphological specialization of insects, indicating sociality and social parasitism. Dating amber deposits can help calibrate evolutionary events and inform reconstructions of past ecosystems. While the direct dating of amber remains impossible, age constraints on most amber deposits are based on correlations or relative dating, methods that come with significant uncertainties. This study discusses two cases using 40Ar/39Ar and U–Pb geochronologic methods to constrain the ages of amber deposits in China and the paleo-ecosystems they record. This paper also summarizes how radio-isotopic dating and other techniques combined with the analysis of inclusions in amber can help elucidate biogeography and the dynamic relationship between life and the physical environment. Full article
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20 pages, 3154 KiB  
Review
Treatment Technology and Research Progress of Residual Xanthate in Mineral Processing Wastewater
by Jiaqiao Yuan, Suqi Li, Zhan Ding, Jie Li, Anmei Yu, Shuming Wen and Shaojun Bai
Minerals 2023, 13(3), 435; https://doi.org/10.3390/min13030435 - 18 Mar 2023
Cited by 30 | Viewed by 4620
Abstract
Xanthate is the most widely used and effective collector in the flotation of sulfide minerals. However, the residual xanthate in flotation wastewater may cause serious environmental pollution and even human health hazards. At present, a variety of treatment technologies have been developed to [...] Read more.
Xanthate is the most widely used and effective collector in the flotation of sulfide minerals. However, the residual xanthate in flotation wastewater may cause serious environmental pollution and even human health hazards. At present, a variety of treatment technologies have been developed to degrade xanthate pollutants in wastewater, with the aim of meeting safe discharge standards. This work reviews the research status of xanthate wastewater treatment technologies in recent years. Treatment technologies are evaluated, including coagulation flocculation, adsorption, microbiological, Fenton, ozone oxidation, and photocatalytic methods. The reaction mechanisms and advantages, as well as disadvantages, of the various treatment technologies are summarized. Future research on the treatment of xanthate wastewater should focus on combined methods, which will be conducive to achieving a high efficiency and low cost, with no secondary pollution, and with the aim of generating further original and innovative technologies. Full article
(This article belongs to the Special Issue Clean Utilization of Nonferrous Metal Resources)
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22 pages, 851 KiB  
Review
Potential Future Alternative Resources for Rare Earth Elements: Opportunities and Challenges
by Vysetti Balaram
Minerals 2023, 13(3), 425; https://doi.org/10.3390/min13030425 - 16 Mar 2023
Cited by 59 | Viewed by 15394
Abstract
Currently, there is an increasing industrial demand for rare earth elements (REE) as these elements are now integral to the manufacture of many carbon-neutral technologies. The depleting REE ores and increasing mining costs are prompting us to consider alternative sources for these valuable [...] Read more.
Currently, there is an increasing industrial demand for rare earth elements (REE) as these elements are now integral to the manufacture of many carbon-neutral technologies. The depleting REE ores and increasing mining costs are prompting us to consider alternative sources for these valuable metals, particularly from waste streams. Although REE concentrations in most of the alternative resources are lower than current REE ores, some sources including marine sediments, coal ash, and industrial wastes, such as red mud, are emerging as promising with significant concentrations of REE. This review focuses on the alternative resources for REE, such as ocean bottom sediments, continental shelf sediments, river sediments, stream sediments, lake sediments, phosphorite deposits, industrial waste products, such as red mud and phosphogypsum, coal, coal fly ash and related materials, waste rock sources from old and closed mines, acid mine drainage, and recycling of e-waste. Possible future Moon exploration and mining for REE and other valuable minerals are also discussed. It is evident that REE extractions from both primary and secondary ores alone are not adequate to meet the current demand, and sustainable REE recovery from the alternative resources described here is also necessary to meet the growing REE demand. An attempt is made to identify the potential of these alternative resources and sustainability challenges, benefits, and possible environmental hazards to meet the growing challenges of reaching the future REE requirements. Full article
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21 pages, 3515 KiB  
Review
Application of Clay Materials for Sorption of Radionuclides from Waste Solutions
by Bhupendra Kumar Singh and Wooyong Um
Minerals 2023, 13(2), 239; https://doi.org/10.3390/min13020239 - 8 Feb 2023
Cited by 14 | Viewed by 3807
Abstract
The wide application of nuclear resources in various fields has resulted in the production of radioactive waste, which poses a serious threat to lives and the environment. Nuclear waste contains long-lived radionuclides and, due to its mobility in environments, the proper management of [...] Read more.
The wide application of nuclear resources in various fields has resulted in the production of radioactive waste, which poses a serious threat to lives and the environment. Nuclear waste contains long-lived radionuclides and, due to its mobility in environments, the proper management of generated waste is necessary. To impede the mobility of radionuclides in environments, various materials have been tested as suitable sorbents under different experimental conditions. In this review, we thoroughly discuss some key and recent contributions to the application of natural clays (NCs) and modified/functionalized clays (MCs) for the sorption of various radionuclides in their cationic and anion forms from (simulated) waste solutions under different experimental conditions. More specifically, we discuss the key developments toward the use of natural clays for the efficient sorption of various radioactive contaminates. Later, this review targets the modification/functionalization of natural clays using various organic moieties to improve their removal capacities for various radionuclides/hazardous ions present in waste solutions. Finally, we summarize the major aspects and highlight the key challenges to be addressed in future studies to further enhance the application of clays and clay-based materials for selective and effective removal of various radionuclides from waste solutions. Full article
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12 pages, 1790 KiB  
Review
A Tentative Model for the Origin of A-Type Granitoids
by Åke Johansson
Minerals 2023, 13(2), 236; https://doi.org/10.3390/min13020236 - 7 Feb 2023
Cited by 10 | Viewed by 6557
Abstract
A-type granites are typically formed in stable intra-plate, back-arc or postcollisional settings and are characterized by highly ferroan and potassic major element compositions, and by strong enrichment in incompatible trace elements. Unlike I-, S- and M-type granites, where the letters denote the dominant [...] Read more.
A-type granites are typically formed in stable intra-plate, back-arc or postcollisional settings and are characterized by highly ferroan and potassic major element compositions, and by strong enrichment in incompatible trace elements. Unlike I-, S- and M-type granites, where the letters denote the dominant source material (igneous, sedimentary or mantle derived), there is no consensus on the source and processes giving rise to A-type magmas. In this contribution, a conceptual model for the origin of A-type granitoids, using the Bornholm A-type granitoid complex in southern Fennoscandia as an example, is presented. In this model, underplated mantle-derived basaltic magma may develop into intermediate and siliceous A-type magma, which is ferroan, potassic and highly enriched in incompatible trace elements, through a combination of fractional crystallization leading to cumulate formation, and partial melting and crustal assimilation, in a process akin to zone refining in metallurgy. The key factor is a relatively stable tectonic environment (postcollisional, anorogenic, or extensional), where there is little or no replenishment of more primitive basaltic magma to the system, allowing it to attain more evolved, enriched and extreme compositions. The A-type granitoids may then be viewed as a more evolved counterpart of subduction-related I-type granitoids. Full article
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18 pages, 1485 KiB  
Review
Mining Wastes as Road Construction Material: A Review
by Pauline Segui, Amine el Mahdi Safhi, Mustapha Amrani and Mostafa Benzaazoua
Minerals 2023, 13(1), 90; https://doi.org/10.3390/min13010090 - 6 Jan 2023
Cited by 60 | Viewed by 13832
Abstract
The mining industry manages large volumes of tailings, sludge, and residues that represent a huge environmental issue. This fact has prompted research into valorization of these wastes as alternative aggregates for concrete production, embankments, pavement material, etc. The use of mining wastes as [...] Read more.
The mining industry manages large volumes of tailings, sludge, and residues that represent a huge environmental issue. This fact has prompted research into valorization of these wastes as alternative aggregates for concrete production, embankments, pavement material, etc. The use of mining wastes as a resource for construction presents two benefits: conserving natural resources and reducing the environmental impacts of mining. In the case of road construction, the use of mining wastes has not yet been developed on a large scale and there is a major lack of specific legislation. This gap is due to the variety of exploited rocks, the diversity of tailings, mine residues, or valuable by-products slated for valorization, and the environmental specifics. This paper presents a review on recycling mine wastes as road construction material, including waste rock and mine tailings. Those materials were mostly used in infrastructure where soils had initially poor geotechnical properties (low bearing capacity, frost susceptibility, swelling risk, etc.). Different mining wastes were used directly or stabilized by a hydraulic binder through geopolymerization or, in some cases, with bituminous treatment. Overall, the use of mine wastes for road construction will have a considerable environmental impact by reducing the volume of waste and offering sustainable raw materials. Full article
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81 pages, 10617 KiB  
Review
A Review of Particle Shape Effects on Material Properties for Various Engineering Applications: From Macro to Nanoscale
by Ugur Ulusoy
Minerals 2023, 13(1), 91; https://doi.org/10.3390/min13010091 - 6 Jan 2023
Cited by 121 | Viewed by 24265
Abstract
It is well known that most particle technology studies attempting to predict secondary properties based on primary properties such as size and shape begin with particle characterization, which means the process of determining the primary properties of particles in a wide spectrum from [...] Read more.
It is well known that most particle technology studies attempting to predict secondary properties based on primary properties such as size and shape begin with particle characterization, which means the process of determining the primary properties of particles in a wide spectrum from macro to nanoscale. It is a fact that the actual shape of engineering particles used in many industrial applications or processes is neglected, as they are assumed to be “homogeneous spheres” with easily understood behavior in any application or process. In addition, it is vital to control the granular materials used in various industries or to prepare them in desired shapes, to develop better processes or final products, and to make the processes practical and economical. Therefore, this review not only covers basic shape definitions, shape characterization methods, and the effect of particle shape on industrial material properties, but also provides insight into the development of the most suitably shaped materials for specific applications or processes (from nanomaterials used in pharmaceuticals to proppant particles used in hydrocarbon production) by understanding the behavior of particles. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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13 pages, 1672 KiB  
Review
Advances in Carbon Nanomaterial–Clay Nanocomposites for Diverse Applications
by Jayanta S. Boruah and Devasish Chowdhury
Minerals 2023, 13(1), 26; https://doi.org/10.3390/min13010026 - 23 Dec 2022
Cited by 17 | Viewed by 2772
Abstract
Clay materials are widely used in sheet-type platforms with peculiar characteristics and diverse applications. However, due to some disadvantages—such as weak mechanical strength and low reactivity—they are often subjected to modifications. Such tuning leads to better output than pure clay materials. This review [...] Read more.
Clay materials are widely used in sheet-type platforms with peculiar characteristics and diverse applications. However, due to some disadvantages—such as weak mechanical strength and low reactivity—they are often subjected to modifications. Such tuning leads to better output than pure clay materials. This review describes some of the clay hybrids in the form of nanocomposites with carbon nanomaterials. Generally, graphene oxide or its derivatives—such as reduced graphene oxide, carbon nanotubes, carbon dots, carbon nanoclusters, and polymeric components—have been utilized so far to make efficient clay composites that have applications such as catalysis, wastewater treatment for toxin removal, cargo delivery, stimulus-responsive advanced tools, optoelectronics, mechanically stable films for filtration, etc. It is interesting to note that nearly all of these applications tend to show the efficacy of modified clay nanocomposites as being significantly greater than that of pure clay, especially in terms of mechanical strength, loading capacity, increased surface area, and tunable functionality. According to the literature, the evidence proves the beneficial effects of these clay nanocomposites with carbon nanomaterials. Full article
(This article belongs to the Special Issue Recent Advances in Clay-Based Nanocomposites)
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37 pages, 2914 KiB  
Review
The Role of Microorganisms in the Nucleation of Carbonates, Environmental Implications and Applications
by Ana Robles-Fernández, Camila Areias, Daniele Daffonchio, Volker C. Vahrenkamp and Mónica Sánchez-Román
Minerals 2022, 12(12), 1562; https://doi.org/10.3390/min12121562 - 3 Dec 2022
Cited by 39 | Viewed by 6161
Abstract
Microbially induced carbonate precipitation (MICP) is an important process in the synthesis of carbonate minerals, and thus, it is widely explored as a novel approach with potential for many technological applications. However, the processes and mechanisms involved in carbonate mineral formation in the [...] Read more.
Microbially induced carbonate precipitation (MICP) is an important process in the synthesis of carbonate minerals, and thus, it is widely explored as a novel approach with potential for many technological applications. However, the processes and mechanisms involved in carbonate mineral formation in the presence of microbes are not yet fully understood. This review covers the current knowledge regarding the role of microbial cells and metabolic products (e.g., extracellular polymeric substances, proteins and amino acids) on the adsorption of divalent metals, adsorption of ionic species and as templates for crystal nucleation. Moreover, they can play a role in the mineral precipitation, size, morphology and lattice. By understanding how microbes and their metabolic products promote suitable physicochemical conditions (pH, Mg/Ca ratio and free CO32− ions) to induce carbonate nucleation and precipitation, the manipulation of the final mineral precipitates could be a reality for (geo)biotechnological approaches. The applications and implications of biogenic carbonates in areas such as geology and engineering are presented and discussed in this review, with a major focus on biotechnology. Full article
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60 pages, 13465 KiB  
Review
Order–Disorder Diversity of the Solid State by NMR: The Role of Electrical Charges
by Luis Sánchez-Muñoz, Pierre Florian, Zhehong Gan and Francisco Muñoz
Minerals 2022, 12(11), 1375; https://doi.org/10.3390/min12111375 - 29 Oct 2022
Cited by 3 | Viewed by 2689
Abstract
The physical explanations and understanding of the order–disorder phenomena in the solid state are commonly inferred from the experimental capabilities of the characterization techniques. Periodicity is recorded according to the averaging procedure of the conventional reciprocal-space techniques (RSTs) in many solids. This approach [...] Read more.
The physical explanations and understanding of the order–disorder phenomena in the solid state are commonly inferred from the experimental capabilities of the characterization techniques. Periodicity is recorded according to the averaging procedure of the conventional reciprocal-space techniques (RSTs) in many solids. This approach gives rise to a sharp trimodal view including non-crystalline or amorphous compounds, aperiodic crystals and periodic crystals. However, nuclear magnetic resonance (NMR) spectroscopy offers an alternative approach that is derived from the distinct character of the measurements involved at the local scale. Here, we present a sequence of progressive order–disorder states, from amorphous structures up to fully ordered mineral structures, showing the great diversity existing in the solid state using multinuclear NMR spectroscopy. Some examples in glasses and products of their crystallization are used, as well as several minerals (including beryl-group and feldspar-group minerals) at magnetic fields up to 35.2 T, and some examples from literature. This approach suggests that the solid state is a dynamic medium, whose behavior is due to atomic adjustments from local compensation of electrical charges between similar structural states, which explains Ostwald’s step rule of successive reactions. In fully ordered feldspar minerals, we propose that the electronic structure of the elements of the cavity site is involved in bonding, site morphology and feldspar topology. Furthermore, some implications are derived about what is a mineral structure from the point of view of the NMR experiments. They open the possibility for the development of the science of NMR Mineralogy. Full article
(This article belongs to the Special Issue NMR Spectroscopy in Mineralogy and Crystal Structures)
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15 pages, 7043 KiB  
Review
On the Origin of New and Rare Minerals Discovered in the Othrys and Vermion Ophiolites, Greece: An Overview
by Maria Economou-Eliopoulos and Federica Zaccarini
Minerals 2022, 12(10), 1214; https://doi.org/10.3390/min12101214 - 26 Sep 2022
Viewed by 2158
Abstract
In this contribution we review the mineralogical characteristics of five new and rare minerals discovered in the Othrys and Vermion ophiolites located in Greece, with the aim to better understand their origin. Three new minerals, namely tsikourasite Mo3Ni2P(1+x) [...] Read more.
In this contribution we review the mineralogical characteristics of five new and rare minerals discovered in the Othrys and Vermion ophiolites located in Greece, with the aim to better understand their origin. Three new minerals, namely tsikourasite Mo3Ni2P(1+x) (x < 0.25), grammatikopoulosite NiVP and eliopoulosite V7S8, were found in the chromitite from the Agios Stefanos deposit, whereas arsenotučekite Ni18Sb3AsS16 was discovered in the Eretria (Tsangli) chromium mine, located in the Othrys ophiolite complex. The formation of the new phosphides tsikourasite and grammatikopoulosite and the sulfide eliopoulosite from Agios Stefanos took place after the precipitation of the host chromitite. Very likely, they formed at lower pressure in an extremely low fO2 and reducing environment during the serpentinization that affected the host ophiolite. The origin of arsenotučekite in chromitites coexisting with Fe–Ni–Cu-sulfide mineralization and magnetite at the Eretria (Tsangli) mine, is believed to be related to a circulating hydrothermal system. The most salient feature of theophrastite Ni(OH)2 and associated unnamed (Ni,Co,Mn)(OH)2 with a varying compositional range and a concentrating development, as successive thin layers, composed by fine fibrous crystals. The extremely tiny crystals of these hydroxides and the spatial association of mixed layers of Ni-silicides with theophrastite may reflect the significant role of the interaction process between adjacent layers on the observed structural features. The scarcity in nature of the new minerals reviewed in this paper is probably due to the required extreme physical-chemical conditions, which are rarely precipitated. Full article
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18 pages, 2080 KiB  
Review
Data Quality in Geochemical Elemental and Isotopic Analysis
by V. Balaram and M. Satyanarayanan
Minerals 2022, 12(8), 999; https://doi.org/10.3390/min12080999 - 8 Aug 2022
Cited by 14 | Viewed by 4402
Abstract
Appropriate sampling, sample preparation, choosing the right analytical instrument, analytical methodology, and adopting proper data generation protocols are essential for generating data of the required quality for both basic and applied geochemical research studies. During the last decade, instrumental advancements, in particular further [...] Read more.
Appropriate sampling, sample preparation, choosing the right analytical instrument, analytical methodology, and adopting proper data generation protocols are essential for generating data of the required quality for both basic and applied geochemical research studies. During the last decade, instrumental advancements, in particular further developments in ICP-MS, such as the use of tandem ICP-MS, high-resolution mass spectrometry to resolve several interferences, and the use of the second path with a collision/reaction cell in multi-collector ICP-MS (MC-ICP-MS) to effectively resolve interferences, have brought in remarkable improvements in accuracy and precision in both elemental and isotopic analyses. The availability of a number of well-characterized geological certified reference samples having both elemental and isotopic data-enabled matrix-matching calibrations and contributed to the quality and traceability of the geochemical data in several cases. There have been some developments in the sample dissolution methods also. A range of quality issues related to sampling, packaging and transport, powdering, dissolution, the application of suitable instrumental analytical techniques, calibration methods, accuracy, and precision are addressed which are helpful in geochemical studies. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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23 pages, 2489 KiB  
Review
Application of Raman Spectroscopy for Studying Shocked Zircon from Terrestrial and Lunar Impactites: A Systematic Review
by Dmitry A. Zamyatin
Minerals 2022, 12(8), 969; https://doi.org/10.3390/min12080969 - 29 Jul 2022
Cited by 6 | Viewed by 3447
Abstract
A highly resistant mineral, zircon is capable of preserving information about impact processes. The present review paper is aimed at determining the extent to which Raman spectroscopy can be applied to studying shocked zircons from impactites to identify issues and gaps in the [...] Read more.
A highly resistant mineral, zircon is capable of preserving information about impact processes. The present review paper is aimed at determining the extent to which Raman spectroscopy can be applied to studying shocked zircons from impactites to identify issues and gaps in the usage of Raman spectroscopy, both in order to highlight recent achievements, and to identify the most effective applications. Method: Following PRISMA guidelines, the review is based on peer-reviewed papers indexed in Google Scholar, Scopus and Web of Science databases up to 5 April 2022. Inclusion criteria: application of Raman spectroscopy to the study of shocked zircon from terrestrial and lunar impactites. Results: A total of 25 research papers were selected. Of these, 18 publications studied terrestrial impact craters, while 7 publications focused on lunar breccia samples. Nineteen of the studies were focused on the acquisition of new data on geological structures, while six examined zircon microstructures, their textural and spectroscopic features. Conclusions: The application of Raman spectroscopy to impactite zircons is linked with its application to zircon grains of various terrestrial rocks and the progress of the electron backscatter diffraction (EBSD) technique in the early 2000s. Raman spectroscopy was concluded to be most effective when applied to examining the degree of damage, as well as identifying phases and misorientation in zircon. Full article
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19 pages, 4187 KiB  
Review
Evolution of Sulfidic Legacy Mine Tailings: A Review of the Wheal Maid Site, UK
by Verity Fitch, Anita Parbhakar-Fox, Richard Crane and Laura Newsome
Minerals 2022, 12(7), 848; https://doi.org/10.3390/min12070848 - 1 Jul 2022
Cited by 2 | Viewed by 4153
Abstract
Historic tailings dams and their associated mine waste can pose a significant risk to human and environmental health. The Wheal Maid mine site, Cornwall, UK, serves as an example of the temporal evolution of a tailings storage facility after mining has ceased and [...] Read more.
Historic tailings dams and their associated mine waste can pose a significant risk to human and environmental health. The Wheal Maid mine site, Cornwall, UK, serves as an example of the temporal evolution of a tailings storage facility after mining has ceased and the acid-generating waste subjected to surficial processes. This paper discusses its designation as a contaminated land site and reviews our current understanding of the geochemistry, mineralogy, and microbiology of the Wheal Maid tailings, from both peer-reviewed journal articles and unpublished literature. We also present new data on waste characterisation and detailed mineral chemistry and data from laboratory oxidation experiments. Particularly of interest at Wheal Maid is the presence of pyrite-bearing “Grey Tailings”, which, under typical environmental conditions at the Earth’s surface, would be expected to have undergone oxidation and subsequently formed acidic and metalliferous mine drainage (AMD). The results identified a number of mechanisms that could explain the lack of pyrite oxidation in the Grey Tailings, including a lack of nutrients inhibiting microbial Fe(II) oxidation, passivation of pyrite mineral surfaces with tailings processing chemicals, and an abundance of euhedral pyrite grains. Such research areas need further scrutiny in order to inform the design of future tailings facilities and associated AMD management protocols. Full article
(This article belongs to the Special Issue Management of Abandoned Mine)
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17 pages, 1176 KiB  
Review
Sustainable Production of Rare Earth Elements from Mine Waste and Geoethics
by Marouen Jouini, Alexandre Royer-Lavallée, Thomas Pabst, Eunhyea Chung, Rina Kim, Young-Wook Cheong and Carmen Mihaela Neculita
Minerals 2022, 12(7), 809; https://doi.org/10.3390/min12070809 - 25 Jun 2022
Cited by 22 | Viewed by 7041
Abstract
The vulnerability of the rare earth element (REE) supply in a global context of increasing demands entails important economic and political issues, and has encouraged several countries to develop their own REE production projects. This study comparatively evaluated the production of REEs from [...] Read more.
The vulnerability of the rare earth element (REE) supply in a global context of increasing demands entails important economic and political issues, and has encouraged several countries to develop their own REE production projects. This study comparatively evaluated the production of REEs from primary and secondary resources in terms of their sustainability and contribution to the achievement of the Geoethics concept as responsibility towards oneself, colleagues, society, and the Earth system. Twelve categories of potential environmental and social impacts were selected: human health toxicity, global warming or climate change, terrestrial and aquatic eutrophication, acidification potential, particulate matter, resource depletion, water consumption, fresh water ecotoxicity, ionizing radiation, fossil fuel consumption, and ozone depletion. The results showed that the environmental impact of REE production from secondary sources is much lower relative to primary sources. A comparison of conventional and non-conventional REE resources showed that significant impact categories were related to particulate matter formation, abiotic resource depletion, and fossil fuel depletion, which could result from avoiding the tailings disposal before reuse. Based on these findings, governments and stakeholders should be encouraged to increase the recycling of secondary REE sources with Geoethics in mind, in order to balance the high demand of REEs while minimizing the overexploitation of non-renewable resources. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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34 pages, 5813 KiB  
Review
Geoenvironmental Model for Roll-Type Uranium Deposits in the Texas Gulf Coast
by Katherine Walton-Day, Johanna Blake, Robert R. Seal II, Tanya J. Gallegos, Jean Dupree and Kent D. Becher
Minerals 2022, 12(6), 780; https://doi.org/10.3390/min12060780 - 20 Jun 2022
Cited by 9 | Viewed by 4498
Abstract
Geoenvironmental models were formulated by the U.S. Geological Survey in the 1990s to describe potential environmental effects of extracting different types of ore deposits in different geologic and climatic regions. This paper presents a geoenvironmental model for roll-front (roll-type) uranium deposits in the [...] Read more.
Geoenvironmental models were formulated by the U.S. Geological Survey in the 1990s to describe potential environmental effects of extracting different types of ore deposits in different geologic and climatic regions. This paper presents a geoenvironmental model for roll-front (roll-type) uranium deposits in the Texas Coastal Plain. The model reviews descriptive and quantitative information derived from environmental studies and existing databases to depict existing conditions and potential environmental concerns associated with mining this deposit type. This geoenvironmental model describes how features of the deposits including host rock; ore and gangue mineralogy; geologic, hydrologic, and climatic settings; and mining methods (legacy open-pit and in situ recovery [ISR]) influence potential environmental effects from mining. Element concentrations in soil and water are compared to regulatory thresholds to depict ambient surface water and groundwater conditions. Although most open-pit operations in this region have been reclaimed, concerns remain about groundwater quality at three of the four former mills that supported former open-pit mines and are undergoing closure activities. The primary environmental concerns with ISR mining are (1) radon gas at active ISR operations, (2) radiation or contaminant leakage during production and transport of ISR resin or yellowcake, (3) uranium excursions into groundwater surrounding active ISR operations, and (4) contamination of groundwater after ISR mining. Although existing regulations attempt to address these concerns, some problems remain. Researchers suggest that reactive transport modeling and a better understanding of geology, stratigraphy, and geochemistry of ISR production areas could minimize excursions into surrounding aquifers and improve results of groundwater restoration. Full article
(This article belongs to the Special Issue Environmentally Sound In-Situ Recovery Mining of Uranium)
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20 pages, 1343 KiB  
Review
Overview on the Development of Intelligent Methods for Mineral Resource Prediction under the Background of Geological Big Data
by Shi Li, Jianping Chen and Chang Liu
Minerals 2022, 12(5), 616; https://doi.org/10.3390/min12050616 - 12 May 2022
Cited by 31 | Viewed by 6260
Abstract
In the age of big data, the prediction and evaluation of geological mineral resources have gradually entered a new stage, intelligent prospecting. This review briefly summarizes the research development of textual data mining and spatial data mining. It is considered that the current [...] Read more.
In the age of big data, the prediction and evaluation of geological mineral resources have gradually entered a new stage, intelligent prospecting. This review briefly summarizes the research development of textual data mining and spatial data mining. It is considered that the current research on mineral resource prediction has integrated logical reasoning, theoretical models, computational simulations, and other scientific research models, and has gradually advanced toward a new model. This type of new model has tried to mine unknown and effective knowledge from big data by intelligent analysis methods. However, many challenges have come forward, including four aspects: (i) discovery of prospecting big data based on geological knowledge system; (ii) construction of the conceptual prospecting model by intelligent text mining; (iii) mineral prediction by intelligent spatial big data mining; (iv) sharing and visualization of the mineral prediction data. By extending the geological analysis in the process of prospecting prediction to the logical rules associated with expert knowledge points, the theory and methods of intelligent mineral prediction were preliminarily established based on geological big data. The core of the theory is to promote the flow, invocation, circulation, and optimization of the three key factors of “knowledge”, “model”, and “data”, and to preliminarily constitute the prototype of intelligent linkage mechanisms. It could be divided into four parts: intelligent datamation, intelligent informatization, intelligent knowledgeization, and intelligent servitization. Full article
(This article belongs to the Special Issue GIS, AI, and Modelling of Mineralization Process and Prospectivity)
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20 pages, 3363 KiB  
Review
The Challenges and Prospects of Recovering Fine Copper Sulfides from Tailings Using Different Flotation Techniques: A Review
by Muhammad Bilal, Ilhwan Park, Vothy Hornn, Mayumi Ito, Fawad Ul Hassan, Sanghee Jeon and Naoki Hiroyoshi
Minerals 2022, 12(5), 586; https://doi.org/10.3390/min12050586 - 6 May 2022
Cited by 29 | Viewed by 12304
Abstract
Flotation is a common mineral processing method used to upgrade copper sulfide ores; in this method, copper sulfide mineral particles are concentrated in froth, and associated gangue minerals are separated as tailings. However, a significant amount of copper is lost into tailings during [...] Read more.
Flotation is a common mineral processing method used to upgrade copper sulfide ores; in this method, copper sulfide mineral particles are concentrated in froth, and associated gangue minerals are separated as tailings. However, a significant amount of copper is lost into tailings during the processing; therefore, tailings can be considered secondary resources or future deposits of copper. Particle–bubble collision efficiency and particle–bubble aggregate stability determines the recovery of target particles; this attachment efficiency plays a vital role in the selectivity process. The presence of fine particles in the flotation circuit is because of excessive grinding, which is to achieve a higher degree of liberation. Complex sulfide ores of markedly low grade further necessitate excessive grinding to achieve the maximum degree of liberation. In the flotation process, fine particles due to their small mass and momentum are unable to collide with rising bubbles, and their rate of flotation is very slow, further lowering the recovery of target minerals. This collision efficiency mainly depends on the particle–bubble size ratio and the concentration of particles present in the pulp. To overcome this problem and to maintain a favorable particle–bubble size ratio, different techniques have been employed by researchers to enhance particle–bubble collision efficiency either by increasing particle size or by decreasing bubble size. In this article, the mechanism of tailing loss is discussed in detail. In addition, flotation methods for fine particles recovery such as microbubble flotation, column flotation, nanobubble flotation, polymer flocculation, shear flocculation, oil agglomeration, and carrier flotation are reviewed, and their applications and limitations are discussed in detail. Full article
(This article belongs to the Special Issue Sustainable Production of Metals for Low-Carbon Technologies)
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33 pages, 4834 KiB  
Review
Review on the Development and Utilization of Ionic Rare Earth Ore
by Xianping Luo, Yongbing Zhang, Hepeng Zhou, Kunzhong He, Caigui Luo, Zishuai Liu and Xuekun Tang
Minerals 2022, 12(5), 554; https://doi.org/10.3390/min12050554 - 28 Apr 2022
Cited by 69 | Viewed by 8949
Abstract
Rare earth, with the reputation of “industrial vitamins”, has become a strategic key metal for industrial powers with increasingly significant industrial application value. As a unique rare earth resource, ionic rare earth ore (IREO) has the outstanding advantages of complete composition, rich resource [...] Read more.
Rare earth, with the reputation of “industrial vitamins”, has become a strategic key metal for industrial powers with increasingly significant industrial application value. As a unique rare earth resource, ionic rare earth ore (IREO) has the outstanding advantages of complete composition, rich resource reserves, low radioactivity, and high comprehensive utilization value. IREO is the main source of medium and heavy rare earth raw materials, which are in great demand all over the world. Since the discovery of IREO, it has attracted extensive attention. Scientists in China and the around world have carried out a lot of research and practical work and achieved a series of important breakthroughs. This paper introduces the discovery process, metallogenic causes, deposit characteristics, and the prospecting research progress of IREO, so as to deepen the understanding of the global distribution of ionic rare earth resources and the prospecting direction of ionic rare earth deposits. The leaching principle of IREO, the innovation of leaching process, the influencing factors and technological development of in situ leaching process, and the technical adaptability of in situ leaching process are reviewed. The development of leachate purification and rare earth extraction technology is summarized. We aim to provide guidance for the industrial development of IREO through the above review analysis. Additionally, the problems existing in the development of IREO are pointed out from the aspects of technology, economy, and the environment. Ultimately, a series of suggestions are put forward, such as the development of ammonium free extraction technology in the whole exploitation process of in situ leaching and leachate purification and rare earth precipitation, research on enhancing of seepage and mass transfer process, and research on the development of new technologies for impurity removal of leachate and extraction of rare earth, so as to promote the development of green and efficient exploitation new technologies and sustainable development of ionic rare earth ore. Full article
(This article belongs to the Special Issue Recovery of Rare Earth Elements Minerals)
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28 pages, 2980 KiB  
Review
Accessing Metals from Low-Grade Ores and the Environmental Impact Considerations: A Review of the Perspectives of Conventional versus Bioleaching Strategies
by Rosina Nkuna, Grace N. Ijoma, Tonderayi S. Matambo and Ngonidzashe Chimwani
Minerals 2022, 12(5), 506; https://doi.org/10.3390/min12050506 - 20 Apr 2022
Cited by 51 | Viewed by 16795
Abstract
Mining has advanced primarily through the use of two strategies: pyrometallurgy and hydrometallurgy. Both have been used successfully to extract valuable metals from ore deposits. These strategies, without a doubt, harm the environment. Furthermore, due to decades of excessive mining, there has been [...] Read more.
Mining has advanced primarily through the use of two strategies: pyrometallurgy and hydrometallurgy. Both have been used successfully to extract valuable metals from ore deposits. These strategies, without a doubt, harm the environment. Furthermore, due to decades of excessive mining, there has been a global decline in high-grade ores. This has resulted in a decrease in valuable metal supply, which has prompted a reconsideration of these traditional strategies, as the industry faces the current challenge of accessing the highly sought-after valuable metals from low-grade ores. This review outlines these challenges in detail, provides insights into metal recovery issues, and describes technological advances being made to address the issues associated with dealing with low-grade metals. It also discusses the pragmatic paradigm shift that necessitates the use of biotechnological solutions provided by bioleaching, particularly its environmental friendliness. However, it goes on to criticize the shortcomings of bioleaching while highlighting the potential solutions provided by a bespoke approach that integrates research applications from omics technologies and their applications in the adaptation of bioleaching microorganisms and their interaction with the harsh environments associated with metal ore degradation. Full article
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41 pages, 2615 KiB  
Review
Aquatic Ecological Risk of Heavy-Metal Pollution Associated with Degraded Mining Landscapes of the Southern Africa River Basins: A Review
by Kennedy O. Ouma, Agabu Shane and Stephen Syampungani
Minerals 2022, 12(2), 225; https://doi.org/10.3390/min12020225 - 10 Feb 2022
Cited by 36 | Viewed by 11750
Abstract
Africa accounts for nearly 30% of the discovered world’s mineral reserves, with half of the world’s platinum group metals deposits, 36% of gold, and 20% of cobalt being in Southern Africa (SA). The intensification of heavy-metal production in the SA region has exacerbated [...] Read more.
Africa accounts for nearly 30% of the discovered world’s mineral reserves, with half of the world’s platinum group metals deposits, 36% of gold, and 20% of cobalt being in Southern Africa (SA). The intensification of heavy-metal production in the SA region has exacerbated negative human and environmental health impacts. In recent years, mining waste generated from industrial and artisanal mining has significantly affected the ecological integrity of SA aquatic ecosystems due to the accelerated introduction and deposition of heavy metals. However, the extent to which heavy-metal pollution associated with mining has impacted the aquatic ecosystems has not been adequately documented, particularly during bioassessments. This review explores the current aquatic ecological impacts on the heavily mined river basins of SA. It also discusses the approaches to assessing the ecological risks, inherent challenges, and potential for developing an integrated ecological risk assessment protocol for aquatic systems in the region. Progress has been made in developing rapid bioassessment schemes (RBS) for SA aquatic ecosystems. Nevertheless, method integration, which also involves heavy-metal pollution monitoring and molecular technology, is necessary to overcome the current challenges of the standardisation of RBS protocols. Citizenry science will also encourage community and stakeholder involvement in sustainable environmental management in SA. Full article
(This article belongs to the Special Issue Environmental Geochemistry in the Mining Environment)
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25 pages, 5926 KiB  
Review
X-ray Diffraction Techniques for Mineral Characterization: A Review for Engineers of the Fundamentals, Applications, and Research Directions
by Asif Ali, Yi Wai Chiang and Rafael M. Santos
Minerals 2022, 12(2), 205; https://doi.org/10.3390/min12020205 - 6 Feb 2022
Cited by 340 | Viewed by 64996
Abstract
X-ray diffraction (XRD) is an important and widely used material characterization technique. With the recent development in material science technology and understanding, various new materials are being developed, which requires upgrading the existing analytical techniques such that emerging intricate problems can be solved. [...] Read more.
X-ray diffraction (XRD) is an important and widely used material characterization technique. With the recent development in material science technology and understanding, various new materials are being developed, which requires upgrading the existing analytical techniques such that emerging intricate problems can be solved. Although XRD is a well-established non-destructive technique, it still requires further improvements in its characterization capabilities, especially when dealing with complex mineral structures. The present review conducts comprehensive discussions on atomic crystal structure, XRD principle, its applications, uncertainty during XRD analysis, and required safety precautions. The future research directions, especially the use of artificial intelligence and machine learning tools, for improving the effectiveness and accuracy of the XRD technique, are discussed for mineral characterization. The topics covered include how XRD patterns can be utilized for a thorough understanding of the crystalline structure, size, and orientation, dislocation density, phase identification, quantification, and transformation, information about lattice parameters, residual stress, and strain, and thermal expansion coefficient of materials. All these important discussions on XRD analysis for mineral characterization are compiled in this comprehensive review, so that it can benefit specialists and engineers in the chemical, mining, iron, metallurgy, and steel industries. Full article
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23 pages, 4724 KiB  
Review
Some Remarks on the Electrical Conductivity of Hydrous Silicate Minerals in the Earth Crust, Upper Mantle and Subduction Zone at High Temperatures and High Pressures
by Haiying Hu, Lidong Dai, Wenqing Sun, Yukai Zhuang, Kaixiang Liu, Linfei Yang, Chang Pu, Meiling Hong, Mengqi Wang, Ziming Hu, Chenxin Jing, Chuang Li, Chuanyu Yin and Sivaprakash Paramasivam
Minerals 2022, 12(2), 161; https://doi.org/10.3390/min12020161 - 28 Jan 2022
Cited by 8 | Viewed by 3566
Abstract
As a dominant water carrier, hydrous silicate minerals and rocks are widespread throughout the representative regions of the mid-lower crust, upper mantle, and subduction zone of the deep Earth interior. Owing to the high sensitivity of electrical conductivity on the variation of water [...] Read more.
As a dominant water carrier, hydrous silicate minerals and rocks are widespread throughout the representative regions of the mid-lower crust, upper mantle, and subduction zone of the deep Earth interior. Owing to the high sensitivity of electrical conductivity on the variation of water content, high-pressure laboratory-based electrical characterizations for hydrous silicate minerals and rocks have been paid more attention to by many researchers. With the improvement and development of experimental technique and measurement method for electrical conductivity, there are many related results to be reported on the electrical conductivity of hydrous silicate minerals and rocks at high-temperature and high-pressure conditions in the last several years. In this review paper, we concentrated on some recently reported electrical conductivity results for four typical hydrous silicate minerals (e.g., hydrous Ti-bearing olivine, epidote, amphibole, and kaolinite) investigated by the multi-anvil press and diamond anvil cell under conditions of high temperatures and pressures. Particularly, four potential influence factors including titanium-bearing content, dehydration effect, oxidation−dehydrogenation effect, and structural phase transition on the high-pressure electrical conductivity of these hydrous silicate minerals are deeply explored. Finally, some comprehensive remarks on the possible future research aspects are discussed in detail. Full article
(This article belongs to the Special Issue High-Pressure Physical and Chemical Behaviors of Minerals and Rocks)
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11 pages, 958 KiB  
Review
Confusion between Carbonate Apatite and Biological Apatite (Carbonated Hydroxyapatite) in Bone and Teeth
by Tetsuro Kono, Toshiro Sakae, Hiroshi Nakada, Takashi Kaneda and Hiroyuki Okada
Minerals 2022, 12(2), 170; https://doi.org/10.3390/min12020170 - 28 Jan 2022
Cited by 58 | Viewed by 15263
Abstract
Biological apatite in enamel, dentin, cementum, and bone is highly individualized hydroxyapatite with high tissue dependency. Often, standard and average textbook values for biological apatite do not apply to actual subjects, and the reported results of analyses differ among investigators. In particular, the [...] Read more.
Biological apatite in enamel, dentin, cementum, and bone is highly individualized hydroxyapatite with high tissue dependency. Often, standard and average textbook values for biological apatite do not apply to actual subjects, and the reported results of analyses differ among investigators. In particular, the term biological apatite is often confusingly and incorrectly used to describe carbonate apatite. The purpose of this review is to prevent further confusion. We believe that apatite should be well understood across disciplines and the terminology clearly defined. According to a definition by the International Mineralogical Association’s Commission on New Minerals Nomenclature and Classification, biological apatite formed by living organisms is a type of hydroxyapatite. More specifically, it is carbonated hydroxyapatite, which is quite different from frequently misnamed carbonate apatite. We hope that this definition will be widely adopted to remove confusion around the naming of apatite in many research and applied fields. Full article
(This article belongs to the Special Issue Bone and Teeth Mineral Properties in Mammals)
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25 pages, 3249 KiB  
Review
The Role of Microorganisms in the Formation, Dissolution, and Transformation of Secondary Minerals in Mine Rock and Drainage: A Review
by Jose Eric Ortiz-Castillo, Mohamad Mirazimi, Maryam Mohammadi, Eben Dy and Wenying Liu
Minerals 2021, 11(12), 1349; https://doi.org/10.3390/min11121349 - 30 Nov 2021
Cited by 21 | Viewed by 6898
Abstract
Mine waste rock and drainage pose lasting environmental, social, and economic threats to the mining industry, regulatory agencies, and society as a whole. Mine drainage can be alkaline, neutral, moderately, or extremely acidic and contains significant levels of sulfate, dissolved iron, and, frequently, [...] Read more.
Mine waste rock and drainage pose lasting environmental, social, and economic threats to the mining industry, regulatory agencies, and society as a whole. Mine drainage can be alkaline, neutral, moderately, or extremely acidic and contains significant levels of sulfate, dissolved iron, and, frequently, a variety of heavy metals and metalloids, such as cadmium, lead, arsenic, and selenium. In acid neutralization by carbonate and silicate minerals, a range of secondary minerals can form and possibly scavenge these potentially harmful elements. Apart from the extensively studied microbial-facilitated sulfide oxidation, the diverse microbial communities present in mine rock and drainage may also participate in the formation, dissolution, and transformation of secondary minerals, influencing the mobilization of these metals and metalloids. This article reviews major microbial-mediated geochemical processes occurring in mine rock piles that affect drainage chemistry, with a focus on the role of microorganisms in the formation, dissolution, and transformation of secondary minerals. Understanding this is crucial for developing biologically-based measures to deal with contaminant release at the source, i.e., source control. Full article
(This article belongs to the Special Issue Microorganisms and Minerals in Natural and Engineered Environments)
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15 pages, 2641 KiB  
Review
Interaction between Microbes, Minerals, and Fluids in Deep-Sea Hydrothermal Systems
by Shamik Dasgupta, Xiaotong Peng and Kaiwen Ta
Minerals 2021, 11(12), 1324; https://doi.org/10.3390/min11121324 - 26 Nov 2021
Cited by 6 | Viewed by 5390
Abstract
The discovery of deep-sea hydrothermal vents in the late 1970s widened the limits of life and habitability. The mixing of oxidizing seawater and reduction of hydrothermal fluids create a chemical disequilibrium that is exploited by chemosynthetic bacteria and archaea to harness energy by [...] Read more.
The discovery of deep-sea hydrothermal vents in the late 1970s widened the limits of life and habitability. The mixing of oxidizing seawater and reduction of hydrothermal fluids create a chemical disequilibrium that is exploited by chemosynthetic bacteria and archaea to harness energy by converting inorganic carbon into organic biomass. Due to the rich variety of chemical sources and steep physico-chemical gradients, a large array of microorganisms thrive in these extreme environments, which includes but are not restricted to chemolithoautotrophs, heterotrophs, and mixotrophs. Past research has revealed the underlying relationship of these microbial communities with the subsurface geology and hydrothermal geochemistry. Endolithic microbial communities at the ocean floor catalyze a number of redox reactions through various metabolic activities. Hydrothermal chimneys harbor Fe-reducers, sulfur-reducers, sulfide and H2-oxidizers, methanogens, and heterotrophs that continuously interact with the basaltic, carbonate, or ultramafic basement rocks for energy-yielding reactions. Here, we briefly review the global deep-sea hydrothermal systems, microbial diversity, and microbe–mineral interactions therein to obtain in-depth knowledge of the biogeochemistry in such a unique and geologically critical subseafloor environment. Full article
(This article belongs to the Special Issue Microorganisms and Minerals in Natural and Engineered Environments)
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39 pages, 7893 KiB  
Review
Replacing Fossil Carbon in the Production of Ferroalloys with a Focus on Bio-Based Carbon: A Review
by Marcus Sommerfeld and Bernd Friedrich
Minerals 2021, 11(11), 1286; https://doi.org/10.3390/min11111286 - 18 Nov 2021
Cited by 37 | Viewed by 8693
Abstract
The production of ferroalloys and alloys like ferronickel, ferrochromium, ferromanganese, silicomanganese, ferrosilicon and silicon is commonly carried out in submerged arc furnaces. Submerged arc furnaces are also used to upgrade ilmenite by producing pig iron and a titania-rich slag. Metal containing resources are [...] Read more.
The production of ferroalloys and alloys like ferronickel, ferrochromium, ferromanganese, silicomanganese, ferrosilicon and silicon is commonly carried out in submerged arc furnaces. Submerged arc furnaces are also used to upgrade ilmenite by producing pig iron and a titania-rich slag. Metal containing resources are smelted in this furnace type using fossil carbon as a reducing agent, which is responsible for a large amount of direct CO2 emissions in those processes. Instead, renewable bio-based carbon could be a viable direct replacement of fossil carbon currently investigated by research institutions and companies to lower the CO2 footprint of produced alloys. A second option could be the usage of hydrogen. However, hydrogen has the disadvantages that current production facilities relying on solid reducing agents need to be adjusted. Furthermore, hydrogen reduction of ignoble metals like chromium, manganese and silicon is only possible at very low H2O/H2 partial pressure ratios. The present article is a comprehensive review of the research carried out regarding the utilization of bio-based carbon for the processing of the mentioned products. Starting with the potential impact of the ferroalloy industry on greenhouse gas emissions, followed by a general description of bio-based reducing agents and unit operations covered by this review, each following chapter presents current research carried out to produce each metal. Most studies focused on pre-reduction or solid-state reduction except the silicon industry, which instead had a strong focus on smelting up to an industrial-scale and the design of bio-based carbon for submerged arc furnace processes. Those results might be transferable to other submerged arc furnace processes as well and could help to accelerate research to produce other metals. Deviations between the amount of research and scale of tests for the same unit operation but different metal resources were identified and closer cooperation could be helpful to transfer knowledge from one area to another. Life cycle assessment to produce ferronickel and silicon already revealed the potential of bio-based reducing agents in terms of greenhouse gas emissions, but was not carried out for other metals until now. Full article
(This article belongs to the Special Issue Ferroalloy Minerals Processing and Technology)
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23 pages, 9051 KiB  
Review
Phosphate Rocks: A Review of Sedimentary and Igneous Occurrences in Morocco
by Radouan El Bamiki, Otmane Raji, Muhammad Ouabid, Abdellatif Elghali, Oussama Khadiri Yazami and Jean-Louis Bodinier
Minerals 2021, 11(10), 1137; https://doi.org/10.3390/min11101137 - 16 Oct 2021
Cited by 73 | Viewed by 22667
Abstract
Phosphate rocks are a vital resource for world food supply and security. They are the primary raw material for phosphoric acid and fertilizers used in agriculture, and are increasingly considered to be a potential source of rare earth elements. Phosphate rocks occur either [...] Read more.
Phosphate rocks are a vital resource for world food supply and security. They are the primary raw material for phosphoric acid and fertilizers used in agriculture, and are increasingly considered to be a potential source of rare earth elements. Phosphate rocks occur either as sedimentary deposits or igneous ores associated with alkaline rocks. In both cases, the genesis of high-grade phosphate rocks results from complex concentration mechanisms involving several (bio)geochemical processes. Some of these ore-forming processes remain poorly understood and subject to scientific debate. Morocco holds the world’s largest deposits of sedimentary phosphate rocks, and also possesses several alkaline complexes with the potential to bear igneous phosphate ores that are still largely underexplored. This paper summarizes the main geological features and driving processes of sedimentary and igneous phosphates, and discusses their global reserve/resource situation. It also provides a comprehensive review of the published data and information on Moroccan sedimentary and igneous phosphates. It reveals significant knowledge gaps and a lack of data, inter alia, regarding the geochemistry of phosphates and basin-scale correlations. Owing to the unique situation of Moroccan phosphates on the global market, they clearly deserve more thorough studies that may, in turn, help to constrain future resources and/or reserves, and answer outstanding questions on the genesis of phosphates. Full article
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21 pages, 5149 KiB  
Review
Apatite U-Pb Thermochronology: A Review
by David M. Chew and Richard A. Spikings
Minerals 2021, 11(10), 1095; https://doi.org/10.3390/min11101095 - 5 Oct 2021
Cited by 52 | Viewed by 7794
Abstract
The temperature sensitivity of the U-Pb apatite system (350–570 °C) makes it a powerful tool to study thermal histories in the deeper crust. Recent studies have exploited diffusive Pb loss from apatite crystals to generate t-T paths between ~350–570 °C, by comparing apatite [...] Read more.
The temperature sensitivity of the U-Pb apatite system (350–570 °C) makes it a powerful tool to study thermal histories in the deeper crust. Recent studies have exploited diffusive Pb loss from apatite crystals to generate t-T paths between ~350–570 °C, by comparing apatite U-Pb ID-TIMS (isotope dilution-thermal ionisation mass spectrometry) dates with grain size or by LA-MC-ICP-MS (laser ablation-multicollector-inductively coupled plasma-mass spectrometry) age depth profiling/traverses of apatite crystals, and assuming the effective diffusion domain is the entire crystal. The key assumptions of apatite U-Pb thermochronology are discussed including (i) that Pb has been lost by Fickian diffusion, (ii) can experimental apatite Pb diffusion parameters be extrapolated down temperature to geological settings and (iii) are apatite grain boundaries open (i.e., is Pb lost to an infinite reservoir). Particular emphasis is placed on detecting fluid-mediated remobilisation of Pb, which invalidates assumption (i). The highly diverse and rock-type specific nature of apatite trace-element chemistry is very useful in this regard—metasomatic and low-grade metamorphic apatite can be easily distinguished from sub-categories of igneous rocks and high-grade metamorphic apatite. This enables reprecipitated domains to be identified geochemically and linked with petrographic observations. Other challenges in apatite U-Pb thermochronology are also discussed. An appropriate choice of initial Pb composition is critical, while U zoning remains an issue for inverse modelling of single crystal ID-TIMS dates, and LA-ICP-MS age traverses need to be integrated with U zoning information. A recommended apatite U-Pb thermochronology protocol for LA-MC-ICP-MS age depth profiling/traverses of apatite crystals and linked to petrographic and trace element information is presented. Full article
(This article belongs to the Special Issue Thermochronology at Temperatures Higher than 150 °C)
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26 pages, 55759 KiB  
Review
Merging Perspectives on Secondary Minerals on Mars: A Review of Ancient Water-Rock Interactions in Gale Crater Inferred from Orbital and In-Situ Observations
by Rachel Y. Sheppard, Michael T. Thorpe, Abigail A. Fraeman, Valerie K. Fox and Ralph E. Milliken
Minerals 2021, 11(9), 986; https://doi.org/10.3390/min11090986 - 9 Sep 2021
Cited by 24 | Viewed by 5639
Abstract
Phyllosilicates, sulfates, and Fe oxides are the most prevalent secondary minerals detected on Mars from orbit and the surface, including in the Mars Science Laboratory Curiosity rover’s field site at Gale crater. These records of aqueous activity have been investigated in detail in [...] Read more.
Phyllosilicates, sulfates, and Fe oxides are the most prevalent secondary minerals detected on Mars from orbit and the surface, including in the Mars Science Laboratory Curiosity rover’s field site at Gale crater. These records of aqueous activity have been investigated in detail in Gale crater, where Curiosity’s X-ray diffractometer allows for direct observation and detailed characterization of mineral structure and abundance. This capability provides critical ground truthing to better understand how to interpret Martian mineralogy inferred from orbital datasets. Curiosity is about to leave behind phyllosilicate-rich strata for more sulfate-rich terrains, while the Mars 2020 Perseverance rover is in its early exploration of ancient sedimentary strata in Jezero crater. It is thus an appropriate time to review Gale crater’s mineral distribution from multiple perspectives, utilizing the range of chemical, mineralogical, and spectral measurements provided by orbital and in situ observations. This review compares orbital predictions of composition in Gale crater with higher fidelity (but more spatially restricted) in situ measurements by Curiosity, and we synthesize how this information contributes to our understanding of water-rock interaction in Gale crater. In the context of combining these disparate spatial scales, we also discuss implications for the larger understanding of martian surface evolution and the need for a wide range of data types and scales to properly reconstruct ancient geologic processes using remote methods. Full article
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24 pages, 3541 KiB  
Review
Geochemical Occurrence of Rare Earth Elements in Mining Waste and Mine Water: A Review
by Konstantina Pyrgaki, Vasiliki Gemeni, Christos Karkalis, Nikolaos Koukouzas, Petros Koutsovitis and Petros Petrounias
Minerals 2021, 11(8), 860; https://doi.org/10.3390/min11080860 - 10 Aug 2021
Cited by 30 | Viewed by 7382
Abstract
Μining waste, processing by-products and mine water discharges pose a serious threat to the environment as in many cases they contain high concentrations of toxic substances. However, they may also be valuable resources. The main target of the current review is the comparative [...] Read more.
Μining waste, processing by-products and mine water discharges pose a serious threat to the environment as in many cases they contain high concentrations of toxic substances. However, they may also be valuable resources. The main target of the current review is the comparative study of the occurrence of rare earth elements (REE) in mining waste and mine water discharges produced from the exploitation of coal, bauxite, phosphate rock and other ore deposits. Coal combustion ashes, bauxite residue and phosphogypsum present high percentages of critical REEs (up to 41% of the total REE content) with ΣREY content ranging from 77 to 1957.7 ppm. The total REE concentrations in mine discharges from different coal and ore mining areas around the globe are also characterised by a high range of concentrations from 0.25 to 9.8 ppm and from 1.6 to 24.8 ppm, respectively. Acid mine discharges and their associated natural and treatment precipitates seem to be also promising sources of REE if their extraction is coupled with the simultaneous removal of toxic pollutants. Full article
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