Minerals

21 pages, 3515 KiB

Open AccessFeature PaperEditor’s ChoiceReview

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 13 | Viewed by 3726

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

(This article belongs to the Special Issue Synthesis and Application of Porous Clay Materials in Heterogeneous Catalysis and Treatment of Hazardous Wastes)

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12 pages, 1790 KiB

Open AccessFeature PaperEditor’s ChoiceReview

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 6436

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

(This article belongs to the Special Issue Petrogenesis, Geochronology, Mineralization and Geochemistry of Granite Rocks)

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18 pages, 3140 KiB

Open AccessEditor’s ChoiceArticle

Pyrite Sulfur Isotope Systematics Suggest Low Marine Sulfate Levels across the Ediacaran–Cambrian Transition

by Songzhuo Li, Xianguo Lang, Han Wang, Shengxian Zhu, Kun Zhao and Mingcai Hou

Minerals 2023, 13(2), 227; https://doi.org/10.3390/min13020227 - 4 Feb 2023

Cited by 5 | Viewed by 2381

Abstract

The Ediacaran–Cambrian (E–C) transition was a critical period in Earth’s history, and it was characterized by variable but potentially significant increases in atmospheric oxygen levels (pO₂). Sulfate is an essential oxidant and plays a key role in regulating Earth’s surface redox [...] Read more.

The Ediacaran–Cambrian (E–C) transition was a critical period in Earth’s history, and it was characterized by variable but potentially significant increases in atmospheric oxygen levels (pO₂). Sulfate is an essential oxidant and plays a key role in regulating Earth’s surface redox conditions. However, there is uncertainty regarding seawater sulfate levels during the E–C transition. To address this issue, organic carbon (δ¹³C_org) and pyrite sulfur isotope (δ³⁴S_py) analyses of the Heyu section (the Dengying Formation) in the Sichuan Basin, South China, were carried out. The δ¹³C_org varies between −36.4‰ and −27.4‰, and δ³⁴S_py ranges from −6.6‰ to 27.3‰. The TOC and pyrite content ranges from 0.13 wt.% to 4.28 wt.% and from 0.01 wt.% to 0.94 wt.%, respectively. The marine sulfate concentration was modeled using a one-dimensional diffusion–advection–reaction model (1D-DAR). The modeling results indicate that the seawater sulfate level remained at a relatively low level of ~2–6 mM. The increased pyrite burial at extensive marine anoxia during the terminal Ediacaran period was likely a driver of such a low sulfate level. Full article

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

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18 pages, 4902 KiB

Open AccessEditor’s ChoiceArticle

Carbonate U-Pb Geochronology and Clumped Isotope Constraints on the Origin of Hydrothermal Dolomites: A Case Study in the Middle Permian Qixia Formation, Sichuan Basin, South China

by Yu Zou, Donghua You, Bo Chen, Huamin Yang, Zhixing Tian, Dongna Liu and Liyu Zhang

Minerals 2023, 13(2), 223; https://doi.org/10.3390/min13020223 - 3 Feb 2023

Cited by 3 | Viewed by 2466

Abstract

Reservoirs in the dolomites of the Middle Permian Qixia Formation in the Sichuan Basin are currently important oil and gas exploration objects in China. However, the questions concerning the sources of the dolomitized fluids and the control factors of the Qixia hydrothermal dolomites [...] Read more.

Reservoirs in the dolomites of the Middle Permian Qixia Formation in the Sichuan Basin are currently important oil and gas exploration objects in China. However, the questions concerning the sources of the dolomitized fluids and the control factors of the Qixia hydrothermal dolomites remain unclear. In this study, the original hydrothermal dolomites (the replacement dolomites (RDs) and saddle dolomites (SDs)) from the Qixia Formation in the southwestern Sichuan Basin (the PR1 well and Baoxing section) were mainly examined using novel in situ carbonate U-Pb dating with clumped isotopes (∆₄₇). Our results show that the U-Pb ages of the latest SDs from the PR1 well (located in the middle zone of the Emeishan large igneous province (ELIP) and distanced from the Orogenic Belt of Longmenshan) are 257.9–251.0 Ma, coincident with the period of main activity of the ELIP. Combined with the previous U-Pb dating, we propose that the high-temperature T_∆47 (82.2–108.4 °C and 127.5–205.9 °C) recorded for SDs from the PR1 well and Baoxing section may have responded to ELIP activity and Longmenshan orogeny activity, respectively. In addition, in the entire southwestern Sichuan Basin, the RDs and SDs yield similar δ¹³C and δ¹⁸O values, indicating that the dolomites were formed by hydrothermal fluids of similar sources, with marine hydrothermal fluids being a highly possible source. Finally, this study proposes a new hydrothermal dolomite genesis model for the Qixia Formation, emphasizing that the formation of hydrothermal dolomites mainly depends on the proximity to tectonic thermal events in space and time. Full article

(This article belongs to the Special Issue Carbonate Petrology and Geochemistry)

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19 pages, 11248 KiB

Open AccessEditor’s ChoiceArticle

The Effect of Iron- and Calcium-Rich Waste Rock’s Acid Baking Conditions on the Rare-Earth Extraction

by Vitor L. Gontijo, Leandro Augusto Viana Teixeira and Virgínia Sampaio Teixeira Ciminelli

Minerals 2023, 13(2), 217; https://doi.org/10.3390/min13020217 - 2 Feb 2023

Cited by 2 | Viewed by 3643

Abstract

The work investigates the effect of sulfuric acid baking on rare earth element (REE) extraction from two waste rock samples from a phosphate mine. The role of different mineralogical assemblages and the degree of alteration (i.e., weathering), and the behavior of the main [...] Read more.

The work investigates the effect of sulfuric acid baking on rare earth element (REE) extraction from two waste rock samples from a phosphate mine. The role of different mineralogical assemblages and the degree of alteration (i.e., weathering), and the behavior of the main impurities–iron, phosphorus, and calcium–on REE extraction are emphasized. For both samples, the sulfuric acid baking at 25 °C, during 15 min, H₂SO₄:sample (w/w) mass ratio of 0.45:1 is the best condition for achieving the selective leaching of REE. For the iron rich-sample, the increase in temperature reduces REE extraction and increases iron dissolution. The corresponding sulfuric acid consumed by goethite (α-FeOOH) from 25 °C to 160 °C acid baking is ten times higher than that required for the monazite (REEPO₄) reaction. Conversely, higher REE and lower iron extraction are observed by increasing (sulfuric acid/sample) mass ratio (0.95:1). Due to the high sulfuric concentration during dissolution, a local saturation zone close to the dissolution front caused the precipitation of iron oxyhydroxides. The calcium-rich sample shows lower REE extraction by leaching (63% maximum) mainly due to the entrapment of REE-bearing minerals by a gypsum layer, and lanthanide’s uptake by calcium sulfate compounds formed during leaching. The results were discussed with the help of a detailed characterization of the residues. Full article

(This article belongs to the Special Issue Leaching and Solution Treatments of Rare Earth Elements from Various Sources, Volume II)

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25 pages, 8802 KiB

Open AccessEditor’s ChoiceArticle

U-Pb Dating, Lead Isotopes, and Trace Element Composition of Pyrite Hosted in Black Shale and Magmatic Rocks, Malaysia: Implications for Orogenic Gold Mineralization and Exploration

by Charles Makoundi, Khin Zaw and Zakaria Endut

Minerals 2023, 13(2), 221; https://doi.org/10.3390/min13020221 - 2 Feb 2023

Cited by 5 | Viewed by 2458

Abstract

Several orogenic/sediment-hosted gold deposits are widely distributed in the Central Belt of Peninsular Malaysia. This study combines U-Pb dating with the isotope composition of lead as well as gold content in ore and magmatic rock-hosted pyrite. It aims to investigate the age of [...] Read more.

Several orogenic/sediment-hosted gold deposits are widely distributed in the Central Belt of Peninsular Malaysia. This study combines U-Pb dating with the isotope composition of lead as well as gold content in ore and magmatic rock-hosted pyrite. It aims to investigate the age of gold mineralization and possibly establish a link between gold mineralization and magmatic intrusion in the district. The results show that the S-type magmatic rocks yield crystallisation ages ranging from 204.1 ± 4.7 Ma to 223 ± 3.2 Ma with low magnetic susceptibility measurements below 3 × 10⁻³ SI unit. These ages fit within the 200–250 Ma Pb-Pb model age of the Pb isotopic composition of K-feldspars. Pyrite trace element mapping has shown that gold and lead show zoning patterns occurring at the same time in pyrite. The Pb isotope composition of the cores of pyrite grains indicate that the approximate model age of gold mineralization is 200 Ma. This age is close to 197–199 Ma (Early Jurassic), previously determined by K-Ar dating of sericite which was interpreted to be the age of gold mineralization. In this study, gold content varies up to 793 ppb in the analysed magmatic rock-hosted pyrites, indicative of a likely magmatic contribution to gold mineralization. Full article

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

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20 pages, 14689 KiB

Open AccessEditor’s ChoiceArticle

Geoelectric Signature of Gold Mineralization in the Alta Floresta Gold Province, Mato Grosso State, Brazil

by Eduardo Xavier Seimetz, Alexandre Santos Jeronimo da Costa, Welitom Rodrigues Borges, Marco Ianniruberto and Rafael Espindola Canata

Minerals 2023, 13(2), 203; https://doi.org/10.3390/min13020203 - 31 Jan 2023

Cited by 1 | Viewed by 2551

Abstract

The Alta Floresta Gold Province (PAAF) is abundant in gold deposits and, located in the state of Mato Grosso, Brazil, is an ideal place to study the geoelectric signature of gold mineralization. Auriferous mineralization occurs along shear zones in quartz veins and disseminated [...] Read more.

The Alta Floresta Gold Province (PAAF) is abundant in gold deposits and, located in the state of Mato Grosso, Brazil, is an ideal place to study the geoelectric signature of gold mineralization. Auriferous mineralization occurs along shear zones in quartz veins and disseminated granites in this region. Ores are associated with oxides and sulfides, mainly with pyrites. To identify primary gold or continuities of the mineralized zones, data were acquired using the geophysical methods of electrical resistivity and induced polarization in three gold mines: Raimunda, Truilio, and Porteira. Dipole–dipole arrays with electrode spacings of 20 and 25 m were used to investigate up to 100 m in depth. Resistivity and chargeability range scales were developed with statistical analyses of all the geophysical and geological data. The geophysical models of the Raimunda and Truilio gold mines showed coherence with the boreholes, but the geophysical models of the Porteira gold mine were not coherent with the boreholes. The resistivity and chargeability parameters indicated that the lithotypes (soils, saprolites, and monzogranites) could be characterized and identified as potential mineralized targets. The soils ranged from 1000 to 8000 ohm.m, the saprolites had values from 150 to 800 ohm.m, and the monzogranite values were from 1100 to 9000 ohm.m. The mineralized targets had values from 18 to 35 mV/V. The results confirm the efficiency of the resistivity and induced polarization methods to find sulfides in shear zones in the Alta Floresta Gold Province. Full article

(This article belongs to the Special Issue Footprints of Mineral Systems)

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18 pages, 5619 KiB

Open AccessEditor’s ChoiceArticle

Effect of Agitation on the Dissolution of APAM with Different Molecular Weights and the Equivalent Diameter of Coal Slime Settling Floc with Different Particle Sizes

by Jianbo Li, Wei Zhou, Chuanchuan Cai, Shujie Wang and Jinbo Zhu

Minerals 2023, 13(2), 204; https://doi.org/10.3390/min13020204 - 31 Jan 2023

Cited by 6 | Viewed by 1845

Abstract

There are still many problems in the stirring dissolution of flocculants: The law of stirring dissolution of flocculants with different molecular weights is not clear, the microstructure of settling floc with different particle sizes of coal slime is still to be explored, and [...] Read more.

There are still many problems in the stirring dissolution of flocculants: The law of stirring dissolution of flocculants with different molecular weights is not clear, the microstructure of settling floc with different particle sizes of coal slime is still to be explored, and how to apply the law of flocculant dissolution to industrialization? To solve these problems, firstly, mechanical stirring dissolution tests are carried out on anionic polyacrylamide (APAM) with different molecular weights to explore the stirring dissolution law of APAM with 3–25 million molecular weights. Results indicated that the optimal stirring speed of APAM with 3–6 million molecular weight is 800 r/min. The optimal stirring speed of 8–16 million molecular weight APAM is 600 r/min. The optimal stirring speed of 18–25 million molecular weight APAM is 800 r/min. The stirring power formula for APAM dissolution is improved by fitting the experimental data of 3–25 million molecular weight APAM stirring dissolution. Secondly, through APAM performance test, it is verified that the solubility of powdered APAM is the best under optimal solution. Thirdly, through the image measurement and analysis test of settling floc of coal slime, the change law of equivalent diameter of settling floc of different particle sizes of coal slime under the optimal dissolution parameters are explored. Results showed that when the mixing speed is 600 r/min, the equivalent diameter of −0.5 mm slime settling floc is the largest. When the mixing speed is 200 r/min or 400 r/min, the equivalent diameters of 0.5–0.25 mm, 0.25–0.125 mm, 0.125–0.075 mm, 0.075–0.045 mm and −0.045 mm slime settling floc are the largest. The equivalent diameter is positively correlated with the size of slime, and the equivalent diameter of −0.045 mm slime settling floc is the largest. The size of slime is the dominant factor in the change of fractal dimension. The fractal dimension of −0.5 mm slime settling floc is the largest, and the fractal dimension is little affected by mixing speed. Finally, the relationship between the important dissolution parameters of the APAM stirring dissolution test is numerically fitted. In view of the different geometrical parameters of the stirring barrel, a method of deducing the dissolution and stirring time of industrial flocculants is proposed. Full article

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

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46 pages, 43872 KiB

Open AccessEditor’s ChoiceArticle

Silicification of Wood: An Overview

by George E. Mustoe

Minerals 2023, 13(2), 206; https://doi.org/10.3390/min13020206 - 31 Jan 2023

Cited by 13 | Viewed by 10157

Abstract

For many decades, wood silicification has been viewed as a relatively simple process of permineralization that occurs when silica dissolved in groundwater precipitates to fill vacant spaces within the porous tissue. The presence of specific silica minerals is commonly ascribed to diagenetic changes. [...] Read more.

For many decades, wood silicification has been viewed as a relatively simple process of permineralization that occurs when silica dissolved in groundwater precipitates to fill vacant spaces within the porous tissue. The presence of specific silica minerals is commonly ascribed to diagenetic changes. The possibility of rapid silicification is inferred from evidence from modern hot springs. Extensive examination of silicified wood from worldwide localities spanning long geologic time suggests that these generalizations are not dependable. Instead, wood silicification may occur via multiple pathways, permineralization being relatively rare. Mineralization commonly involves silica precipitation in successive episodes, where changes in the geochemical environment cause various polymorphs to coexist in a single specimen. Diagenetic changes may later change the mineral composition, but for many specimens diagenesis is not the dominant process that controls mineral distribution. Rates of silicification are primarily related to dissolved silica levels and permeability of sediment that encloses buried wood. Rapid silica deposition takes place on wood in modern hot springs, but these occurrences have dissimilar physical and chemical conditions compared to those that exist in most geologic environments. The times required for silicification are variable, and cannot be described by any generalization. Full article

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15 pages, 3005 KiB

Open AccessEditor’s ChoiceArticle

In-Situ Single Crystal XRD and Raman Spectra Investigation of (Mg, Fe, Mn)CO₃ at Various Temperatures

by Lin Liang, Xinjian Bao, Wen Liang, Haipeng Song, Xiang Wu and Shan Qin

Minerals 2023, 13(2), 207; https://doi.org/10.3390/min13020207 - 31 Jan 2023

Cited by 2 | Viewed by 2644

Abstract

The in-situ X-ray diffraction (XRD) and Raman spectra of synthetic (Mg, Fe, Mn)CO₃ single crystals for (Mg_0.37Fe_0.31Mn_0.32)CO₃, (Mg_0.49Fe_0.51)CO₃, (Fe_0.47Mn_0.53)CO₃, and (Mg_0.50 [...] Read more.

The in-situ X-ray diffraction (XRD) and Raman spectra of synthetic (Mg, Fe, Mn)CO₃ single crystals for (Mg_0.37Fe_0.31Mn_0.32)CO₃, (Mg_0.49Fe_0.51)CO₃, (Fe_0.47Mn_0.53)CO₃, and (Mg_0.50Mn_0.50)CO₃ were investigated up to 871 K. Lattice parameters and the volumetric thermal expansion coefficients were achieved, demonstrating an inherent anisotropy of c/a near to 3.0. The Raman spectra of our intermediate components all exhibit a negative temperature dependence similar to that of the end members. The temperature dependence of the external modes T, L, anti-symmetric stretching mode ν₃, and out-of-plane bending mode 2ν₂ is generally more prominent than the in-plane bending mode ν₄ and symmetric stretching mode ν₁ except for siderite FeCO₃. Combining thermal expansion coefficients α_V with the relative changes in frequency δνi/δT of Raman spectra, the average thermodynamic Grüneisen parameters (γ_th) for (Mg_0.37Fe_0.31Mn_0.32)CO₃, (Fe_0.47Mn_0.53)CO₃, (Mg_0.50Mn_0.50)CO₃, MgCO₃, and MnCO₃ were obtained as 1.18, 1.36, 1.34, 1.13, and 1.53, respectively. The relationship between Fe²⁺ and Mn²⁺ contents and γ_th illustrates that the concentration of Fe²⁺ causes a negative effect while the concentration of Mn²⁺ causes a positive effect on γ_th. These results could provide a reference for the contribution of Fe²⁺ and Mn²⁺ on the structural and thermodynamic properties of (Mg, Fe, Mn)CO₃ carbonates. Full article

(This article belongs to the Special Issue Crystal Structures and Phase Transitions of Minerals at Extreme Conditions)

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21 pages, 9871 KiB

Open AccessEditor’s ChoiceArticle

Age and Composition of Columbite-Tantalite Group Minerals in the Spodumene Pegmatite from the Chakabeishan Deposit, Northern Tibetan Plateau and Their Implications

by Wenli Sun, Zhidan Zhao, Xuanxue Mo, Chunjing Wei, Guochen Dong, Xiaowei Li, Wanming Yuan, Tao Wang, Shuang Yang, Bingzhang Wang, Tong Pan, Jie Han, Hongliang Cao, Yan Tang and Liangliang Zhang

Minerals 2023, 13(2), 201; https://doi.org/10.3390/min13020201 - 30 Jan 2023

Cited by 11 | Viewed by 3130

Abstract

The Chakabeishan (CKBS) deposit is the first pegmatite-type Li-Be deposit discovered in the eastern North Qaidam Tectonic Belt (NQTB) of Tibetan Plateau. The correct understanding of its petrogenesis and the precise determination of its formation age are of great significance for further regional [...] Read more.

The Chakabeishan (CKBS) deposit is the first pegmatite-type Li-Be deposit discovered in the eastern North Qaidam Tectonic Belt (NQTB) of Tibetan Plateau. The correct understanding of its petrogenesis and the precise determination of its formation age are of great significance for further regional prospecting and the discovery of new economically valuable rare-metal deposits. Therefore, a systematic study of texture, major-element composition, and U-Pb dating of columbite-tantalite group minerals (CGMs) in the spodumene pegmatite dyke from the CKBS deposit was undertaken. Three types of CGMs were identified, including concentric oscillatory ferrocolumbite (CGMs-1), homogeneous ferrocolumbite (CGMs-2), and irregular ferrotantalite (minor manganocolumbite) with abundant early ferrocolumbite replacement remnants (CGMs-3). The zoning patterns and chemical compositions in the CGMs record the complex evolutionary history of their host pegmatite from the magmatic stage (CGMs-1, disequilibrium crystallization) to the magmatic-hydrothermal transition stage (CGMs-2, equilibrium crystallization) and then to the late metasomatic stage (CGMs-3, replacement/re-equilibrium). CGMs U-Pb dating results suggest that the spodumene pegmatite dyke (No.15) emplaced at 230.1 ± 2.6 Ma. Subsequently, it experienced fluid metasomatism at 221 ± 5.3 Ma. Based on the new age data and published geochronological data, it can be concluded that the spodumene pegmatite dykes in the CKBS deposit formed in an oceanic subduction-related setting, representing a new metallogenic event in western China. Except for the CKBS deposit, a large number of rare-metal pegmatite dykes have also been discovered in the eastern NQTB, indicating that the eastern NQTB may be an important potential rare-metal metallogenic belt that should be explored in detail and arouse painstaking attention. Full article

(This article belongs to the Special Issue Understanding Hydrothermal Ore Deposits: Insights from In-situ Analyses)

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21 pages, 5943 KiB

Open AccessEditor’s ChoiceArticle

HPHT-Treated Impact Diamonds from the Popigai Crater (Siberian Craton): XRD and Raman Spectroscopy Evidence

by Anatoly Chepurov, Sergey Goryainov, Sergey Gromilov, Egor Zhimulev, Valeriy Sonin, Aleksey Chepurov, Zakhar Karpovich, Valentin Afanasiev and Nikolay Pokhilenko

Minerals 2023, 13(2), 154; https://doi.org/10.3390/min13020154 - 20 Jan 2023

Cited by 3 | Viewed by 2189

Abstract

Phase change and graphitization of diamonds from the Popigai impact crater (Krasnoyarsk Territory, Siberian platform, Russia) exposed to high-pressure high-temperature (HPHT) conditions of 5.5 GPa and 2000–2200 °C are studied by Raman spectroscopy and X-ray diffractometry (XRD). Light-color diamonds of type 1, free [...] Read more.

Phase change and graphitization of diamonds from the Popigai impact crater (Krasnoyarsk Territory, Siberian platform, Russia) exposed to high-pressure high-temperature (HPHT) conditions of 5.5 GPa and 2000–2200 °C are studied by Raman spectroscopy and X-ray diffractometry (XRD). Light-color diamonds of type 1, free from inclusions, with 0 to 10 % lonsdaleite, are more resistant to HPHT effects than dark diamonds of type 2 rich in lonsdaleite and graphite. The lonsdaleite/diamond ratios in lonsdaleite-bearing impact diamonds become smaller upon annealing, possibly because lonsdaleite transforms to cubic diamond simultaneously with graphitization. Therefore, lonsdaleite is more likely a structure defect in diamond than a separate hexagonal phase. Full article

(This article belongs to the Topic Advanced Materials and Technologies in Deep Rock Engineering)

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14 pages, 5577 KiB

Open AccessEditor’s ChoiceArticle

Assessing the Baseline Uranium in Groundwater around a Proposed Uraninite Mine and Identification of a Nearby New Reserve

by Ravinder Bhavya, Kaveri Sivaraj and Lakshmanan Elango

Minerals 2023, 13(2), 157; https://doi.org/10.3390/min13020157 - 20 Jan 2023

Cited by 7 | Viewed by 2940

Abstract

The presence of uranium in groundwater is a cause of concern all over the world. In mineralized regions where elevated concentrations of uranium are possible in groundwater, mining activities can further degrade the water quality. Hence, it is essential to document the baseline [...] Read more.

The presence of uranium in groundwater is a cause of concern all over the world. In mineralized regions where elevated concentrations of uranium are possible in groundwater, mining activities can further degrade the water quality. Hence, it is essential to document the baseline uranium concentration in groundwater before the commencement of mining. This study was carried out with the objective of assessing the concentration of uranium in groundwater around a proposed uraninite mining site in the Gogi region, Karnataka, India. Gogi is a village in the Yadgir district of Karnataka where groundwater is the main source of water for domestic needs. The uranium mineralized zone in this region occurs along the major E-W trending Gogi-Kurlagere fault at a depth of about 150 m. Groundwater samples were collected every three months from January 2020 to October 2020 from 52 wells located in this area. The concentration of uranium in groundwater ranged from 1.5 ppb to 267 ppb. The USEPA and WHO have recommended a permissible limit of 30 ppb, while the Atomic Energy Regulatory Board of India has a limit of 60 ppb for the purpose of drinking water. Based on these permissible limits for uranium in drinking water, concentrations exceeded the limit in about 25% of wells within 20 km from the mineralized region. Wells present in the granitic and limestone terrain exhibited higher concentrations of uranium in this area. Uranium concentration in groundwater changes depending on the degree of weathering, lithology, and rainfall recharge. This study will serve as a baseline and will help to assess the impact of mining activities in this region in the future. In wells where the uranium concentration exceeds permissible limits, it is suggested not to use groundwater directly for drinking purposes. These sites need to be explored further for the possible presence of uranium-bearing minerals. Full article

(This article belongs to the Special Issue Radionuclides and Radiation Exposure in Mine Sites)

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18 pages, 3869 KiB

Open AccessEditor’s ChoiceArticle

Stabilization of As and Heavy Metal-Contaminated Soils by Two Mine Drainage-Treated Sludges

by Hyunji Tak, Seonhee Kim, Kyeongtae Kim, Sookyun Wang and Minhee Lee

Minerals 2023, 13(2), 148; https://doi.org/10.3390/min13020148 - 19 Jan 2023

Cited by 3 | Viewed by 2873

Abstract

This study explored and analyzed the potential of the practical use of acid mine drainage-treated sludge (AMDS) as a new soil stabilizer for arsenic (As) and heavy metals. Various analyses, toxicity evaluations, and extraction batch experiments were performed to investigate the characteristics of [...] Read more.

This study explored and analyzed the potential of the practical use of acid mine drainage-treated sludge (AMDS) as a new soil stabilizer for arsenic (As) and heavy metals. Various analyses, toxicity evaluations, and extraction batch experiments were performed to investigate the characteristics of the AMDS as a soil stabilizer and to identify the main mechanisms to fix As and heavy metals on the AMDS in soil. Two types of AMDS, copper metal mine drainage-treated sludge (MMDS) and coal mine drainage-treated sludge (CMDS) and four contaminated soils with different pollution scenarios were used in the experiments. ‘Soil A’ and ‘Soil D’ were mainly contaminated with Cd, Pb and Zn. ‘Soil B’ and ‘Soil C’ were contaminated with As. Results from XRD, XRF, SEM-EDS, TG-DTA, and BET analyses suggested that AMDS is mainly composed of Fe- and Ca- bearing minerals such as CaCO₃, Ca(OH)₂ and amorphous Fe-oxide (hydroxide), which have a large surface area and high adsorption capacity for As and heavy metals. From batch extraction experiments, the Pb stabilization efficiency of both of the AMDSs in soil A, which has a high Pb and Zn content, was higher than 90%. The high heavy metal stabilization efficiency comes directly from the electrostatic attraction between metal cations and the negatively charged AMDS surface and/or from the co-precipitation of metal oxide (hydroxide) and CaCO₃, which occurs comprehensively on the AMDS surface. In the case of Zn, the stabilization efficiency in soil A was somewhat low due to the adsorption competition with Pb, but the Zn stabilization efficiency of the CMDS in soil A was higher than 80% (70% or higher for the MMDS). For soil D, the Zn stabilization efficiency of two AMDSs was higher than 85% because of the lower concentration of other heavy metals in soil D, compared to in soil A. The As stabilization efficiency of the AMDSs in soil contaminated with As (soil B and soil C) was higher than 85%, (mostly > 95%). The overall stabilization efficiency of two AMDSs for heavy metals and As were higher than 75% and 85% (mostly > 90%), respectively, regardless of soil type. We concluded that this high As stabilization efficiency was due to the formation of a new complex by ligand exchange between the Fe- (oxide) hydroxide and the arsenate and also to the cation bridge effect between the AMDS surface and the arsenate as well as the co-precipitation. Full article

(This article belongs to the Special Issue Groundwater Protection Challenges in Mine: Retention of Hazardous Substances with Solidification/Stabilization Implementation)

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16 pages, 11387 KiB

Open AccessEditor’s ChoiceArticle

Effect of Content and Length of Polypropylene Fibers on Strength and Microstructure of Cementitious Tailings-Waste Rock Fill

by Bo Gao, Shuai Cao and Erol Yilmaz

Minerals 2023, 13(2), 142; https://doi.org/10.3390/min13020142 - 18 Jan 2023

Cited by 18 | Viewed by 2087

Abstract

The mechanical strength properties of cemented tailings backfill are very important for the safe and environmentally friendly mining of mineral resources. To check the impact of polypropylene fiber on strength and microstructure of cementitious tailings waste rock fill (CTWRF), diverse fiber lengths (6 [...] Read more.

The mechanical strength properties of cemented tailings backfill are very important for the safe and environmentally friendly mining of mineral resources. To check the impact of polypropylene fiber on strength and microstructure of cementitious tailings waste rock fill (CTWRF), diverse fiber lengths (6 and 12 mm) and dosages (0-control specimen, 0.3, 0.6, and 0.9 wt.%) were considered to prepare fiber-reinforced CTWRF (FRCTWRF) matrices. Experiments such as UCS (uniaxial compressive strength), X-ray CT (computed tomography), and SEM (scanning electron microscopy) were implemented to better characterize the backfills studied. Results showed that UCS performance of FRCTWRF was the highest (0.93 MPa) value at 6 mm fiber long and 0.6 wt.% fiber content. The peak strain of FRCTWRF was the highest (2.88%) at 12 mm fiber long and 0.3 wt.% fiber content. Growing the length of fiber within FRCTWRF can reduce its fracture volume, enhancing the crack resistance of FRCTWRF. Fiber and FRCTWRF are closely linked to each other by the products of cement hydration. The findings of this work will offer the efficient use of FRCTWRF in mining practice, presenting diverse perspectives for mine operators and owners, since this newly formed cementitious fill quickens the strengths required for stope backfilling. Full article

(This article belongs to the Special Issue Backfilling Materials for Underground Mining, Volume III)

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19 pages, 4773 KiB

Open AccessEditor’s ChoiceArticle

Tungsten–Gold Metallogenetic Potential of the Ziyunshan Pluton in Central Hunan, South China: Insights from Element Geochemistry of Granites

by Jiahao Leng, Yulong Lu, Xingqiang Li, Xiangying Zhao and Yang Liu

Minerals 2023, 13(2), 144; https://doi.org/10.3390/min13020144 - 18 Jan 2023

Cited by 4 | Viewed by 2461

Abstract

In order to reveal the metallogenic potential of the Indosinian Ziyunshan granite in central Hunan, the temporal, spatial and genetic relationship between the mineralization and the granite is discussed, and the concentrations of ore-forming elements for different granites are measured. The geochemistry of [...] Read more.

In order to reveal the metallogenic potential of the Indosinian Ziyunshan granite in central Hunan, the temporal, spatial and genetic relationship between the mineralization and the granite is discussed, and the concentrations of ore-forming elements for different granites are measured. The geochemistry of the elements, isotope geochemistry and chronology, and the data derived from the analysis on Au-W deposit in the area are compared with the geologic features of the regional metallogenic rock. The results indicate that Ziyunshan granite is an irregular shaped complex of late Indosinian by multi-stage intrusion. Elements such as W, Sn, Cu, Pb, Ag, Sb, Be, Li and Ta are enriched in the granite. The sulfophilic elements including Au, Pb, Zn and Ag are relatively enriched in the main body of the Ziyunshan granite, while the lithophilic elements including W and Sn are relatively enriched in the late phase of the Ziyunshan granite. The zoning of the ore-forming elements could be observed in the granite: Nb and Ta (inside the granite); W, Sn, Mo and Bi (inner contact zone); Pb, Zn and Cu (contact zone); and Au and Sb (outer contact zone). All the deposits in the area are formed after the intrusion of the Ziyunshan granite except the Ni-Ta-Sn ore formed simultaneously with the Ziyunshan granite. The Ziyunshan granite provides necessary heat, active fluid and partial ore-forming materials sources, which may show good metallogenic potential. Full article

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

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18 pages, 12916 KiB

Open AccessEditor’s ChoiceArticle

Ensemble Tree Model for Long-Term Rockburst Prediction in Incomplete Datasets

by Huanxin Liu, Guoyan Zhao, Peng Xiao and Yantian Yin

Minerals 2023, 13(1), 103; https://doi.org/10.3390/min13010103 - 9 Jan 2023

Cited by 6 | Viewed by 2251

Abstract

The occurrence of rockburst can seriously impact the construction and production of deep underground engineering. To prevent rockburst, machine learning (ML) models have been widely employed to predict rockburst based on some related variables. However, due to the costs and complicated geological conditions, [...] Read more.

The occurrence of rockburst can seriously impact the construction and production of deep underground engineering. To prevent rockburst, machine learning (ML) models have been widely employed to predict rockburst based on some related variables. However, due to the costs and complicated geological conditions, complete datasets to evaluate rockburst cannot always be obtained in rock engineering. To fill this limitation, this study proposed an ensemble tree model suitable for incomplete datasets, i.e., the histogram gradient boosting tree (HGBT), to build intelligent models for rockburst prediction. Three hundred fourteen rockburst cases were employed to develop the HGBT model. The hunger game search (HGS) algorithm was implemented to optimize the HGBT model. The established HGBT model had an excellent testing performance (accuracy of 88.9%). An incomplete database with missing values was applied to compare the performances of HGBT and other ML models (random forest, artificial neural network, and so on). HGBT received an accuracy of 78.8% in the incomplete database, and its capacity was better than that of other ML models. Additionally, the importance of input variables in the HGBT model was analyzed. Finally, the feasibility of the HGBT model was validated by rockburst cases from Sanshandao Gold Mine, China. Full article

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20 pages, 4829 KiB

Open AccessEditor’s ChoiceArticle

Comparison of Particle Shape, Surface Area, and Color Properties of the Calcite Particles Ground by Stirred and Ball Mill

by Ugur Ulusoy, Serkan Çayirli, Guler Bayar and Hasan Serkan Gokcen

Minerals 2023, 13(1), 99; https://doi.org/10.3390/min13010099 - 8 Jan 2023

Cited by 5 | Viewed by 3329

Abstract

Since the particle size, shape, specific surface area, and purity of the ground calcium carbonate (GCC) decide its usability in the paper, paint, and plastic industries, the effect of grinding is important. However, the effect of stirred and ball mill grinding on the [...] Read more.

Since the particle size, shape, specific surface area, and purity of the ground calcium carbonate (GCC) decide its usability in the paper, paint, and plastic industries, the effect of grinding is important. However, the effect of stirred and ball mill grinding on the particle shape of GCC by dynamic image analysis (DIA) is still lacking in the literature. Therefore, the aim of this study is to compare the aspect ratio at the same fineness (d97 = 50 μm) and evaluate other properties such as color, and surface area of GCC particles by stirred and ball mill grindings. DIA results showed that particles produced by the ball mill had higher aspect ratio values than those by the stirred mill. This was attributed to the impact, and attrition breakage modes produced by the ball and stirred mill, respectively. This conclusion is supported by XRD and SEM. Finally, the results related to physical properties such as aspect ratio, surface area, and whiteness are discussed depending on the usage area of GCC. Full article

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

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18 pages, 3239 KiB

Open AccessEditor’s ChoiceArticle

CO₂ Dipole Moment: A Simple Model and Its Implications for CO₂-Rock Interactions

by Massimo Calcara and Matteo Caricaterra

Minerals 2023, 13(1), 87; https://doi.org/10.3390/min13010087 - 6 Jan 2023

Cited by 6 | Viewed by 25011

Abstract

CO₂ is a widespread fluid naturally occurring within the Earth crust or injected in deep strata for technological issues such as Carbon Capture and Storage (CCS). At STP conditions, CO₂ is a gas, with a net zero dipole moment. Growing pressures [...] Read more.

CO₂ is a widespread fluid naturally occurring within the Earth crust or injected in deep strata for technological issues such as Carbon Capture and Storage (CCS). At STP conditions, CO₂ is a gas, with a net zero dipole moment. Growing pressures produce an increase in its density. The reduced intermolecular distance causes a variation in the molecular structure, due to the intensification of mutual interactions. Some published spot data reveal the departure from the planarity of the bond angle while others provide few values of the CO₂ dipole moment. Based on a small amount of literature-measured angle values, it was possible first to extrapolate a correlation between bond angle and density (R² = 0.879). By fixing the partial charges distribution, we present a simple model that allows the calculation of the CO₂ dipole moment directly from the geometry of the molecule, in the range of 179–162 degrees, 1-degree step. Results give values up to about 1 D. Being aware that this model is qualitative, it gives, however, an explanation of the experimental reactivity, and it also provides a valid tool in identifying zones in the crust where these reactions are likely to occur efficiently. Finally, we hypothesise the role of dry CO₂ in the carbonate formation through the interactions with the basalts. Full article

(This article belongs to the Special Issue CO₂ Geological Storage: Fluid–Rock Interactions and Geochemical Modeling)

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18 pages, 1485 KiB

Open AccessFeature PaperEditor’s ChoiceReview

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 56 | Viewed by 13547

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

(This article belongs to the Special Issue Towards a Sustainable Management of Mine Wastes: Reprocessing, Reuse, Revalorization and Repository, Volume II)

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81 pages, 10617 KiB

Open AccessFeature PaperEditor’s ChoiceReview

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 114 | Viewed by 23304

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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22 pages, 7975 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Melt Composition and Phase Equilibria in the Eclogite-Carbonate System at 6 GPa and 900–1500 °C

by Anton Shatskiy, Altyna Bekhtenova, Anton V. Arefiev and Konstantin D. Litasov

Minerals 2023, 13(1), 82; https://doi.org/10.3390/min13010082 - 5 Jan 2023

Cited by 5 | Viewed by 2107

Abstract

Melting phase relations in the eclogite-carbonate system were studied at 6 GPa and 900–1500 °C. Starting mixtures were prepared by blending natural bimineral eclogite group A (Ecl) with eutectic Na-Ca-Mg-Fe (N2) and K-Ca-Mg-Fe (K4) carbonate mixtures (systems Ecl-N2 and Ecl-K4). In the Ecl-N2 [...] Read more.

Melting phase relations in the eclogite-carbonate system were studied at 6 GPa and 900–1500 °C. Starting mixtures were prepared by blending natural bimineral eclogite group A (Ecl) with eutectic Na-Ca-Mg-Fe (N2) and K-Ca-Mg-Fe (K4) carbonate mixtures (systems Ecl-N2 and Ecl-K4). In the Ecl-N2 system, the subsolidus assemblage is represented by garnet, omphacite, eitelite, and a minor amount of Na₂Ca₄(CO₃)₅. In the Ecl-K4 system, the subsolidus assemblage includes garnet, clinopyroxene, K₂Mg(CO₃)₂, and magnesite. The solidus of both systems is located at 950 °C and is controlled by the following melting reaction: Ca₃Al₂Si₃O₁₂ (Grt) + 2(Na or K)₂Mg(CO₃)₂ (Eit) = Ca₂MgSi₃O₁₂ (Grt) + [2(Na or K)₂CO₃∙CaCO₃∙MgCO₃] (L). The silica content (in wt%) in the melt increases with temperature from < 1 at 950 °C to 3–7 at 1300 °C, and 7–12 at 1500 °C. Thus, no gradual transition from carbonate to kimberlite-like (20–32 wt% SiO₂) carbonate-silicate melt occurs even as temperature increases to mantle adiabat. This supports the hypothesis that the high silica content of kimberlite is the result of decarbonation at low pressure. As temperature increases from 950 to 1500 °C, the melt Ca# ranges from 58–60 to 42–46. The infiltration of such a melt into the peridotite mantle should lower its Ca# and causes refertilization from harzburgite to lherzolite and wehrlitization. Full article

(This article belongs to the Special Issue Kimberlites and Related Rocks: New Insight into Petrogenesis and Diamond Potential of Deeply-Derived Mantle Magmas)

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22 pages, 9486 KiB

Open AccessEditor’s ChoiceArticle

Stable Carbon and Oxygen Isotopic Features of Banded Travertines from the Xiagei Fissure Ridge System (Shangri-La, China)

by Yaxian You, Huaguo Wen, Lianchao Luo, Zhipeng Lu and Liang Li

Minerals 2023, 13(1), 76; https://doi.org/10.3390/min13010076 - 3 Jan 2023

Cited by 2 | Viewed by 2210

Abstract

Banded travertines are important parts of fissure ridge systems, but studies on geochemical characterization of banded travertines are limited. This study investigated the lithofacies and stable carbon and oxygen isotopic features of banded travertines from Xiagei (southwestern China) to examine their formation mechanisms. [...] Read more.

Banded travertines are important parts of fissure ridge systems, but studies on geochemical characterization of banded travertines are limited. This study investigated the lithofacies and stable carbon and oxygen isotopic features of banded travertines from Xiagei (southwestern China) to examine their formation mechanisms. Petrographic analyses of the banded travertines revealed two lithotypes: thick-laminated palisade crystalline crust and thin-laminated composite crystalline crust. δ¹³C and δ¹⁸O of the Xiagei banded travertines range from 2.82‰ to 4.50‰ V-PDB, and from −25.86‰ to −20.90‰ V-PDB. Parent CO₂ evaluation shows that the Xiagei banded travertines mainly received CO₂ from the decarbonation of marine carbonates, but the contributions of magmatic CO₂ and the dissolution of marine carbonates are also unneglectable. Significantly, the magmatic-derived CO₂ might indicate that the delamination of the lithosphere along with the asthenosphere upwelling could be taking place in the eastern Tibetan plateau. Paleotemperature calculation shows that the Xiagei travertines were precipitated from moderate- to high-temperature hot springs (44.3 to 86.8 °C). Interestingly, the thick-laminated palisade crystalline crust and thin-laminated composite crystalline crust display calculated paleotemperature between 66.6 and 86.8 °C and between 56.6 and 77.7 °C, respectively, reflecting the great role of water temperature in controlling the lithofacies of banded travertines. A comparison between the banded travertines at Xiagei and other areas also shows temperature is a non-negligible factor controlling banded travertine precipitation. However, this does not mean that water temperature is the decisive controlling factor and more studies on banded travertines are still indispensable to disclose the potential factors controlling the factors/processes affecting banded travertine lithofacies. This study provides a good example for understanding the relationship between lithofacies and stable isotopic geochemical characteristics of travertine deposits. Full article

(This article belongs to the Special Issue Geochemistry of Travertines and Calcareous Tufas)

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31 pages, 8188 KiB

Open AccessEditor’s ChoiceArticle

Investigating the Capabilities of Various Multispectral Remote Sensors Data to Map Mineral Prospectivity Based on Random Forest Predictive Model: A Case Study for Gold Deposits in Hamissana Area, NE Sudan

by Abdallah M. Mohamed Taha, Yantao Xi, Qingping He, Anqi Hu, Shuangqiao Wang and Xianbin Liu

Minerals 2023, 13(1), 49; https://doi.org/10.3390/min13010049 - 28 Dec 2022

Cited by 12 | Viewed by 3819

Abstract

Remote sensing data provide significant information about surface geological features, but they have not been fully investigated as a tool for delineating mineral prospective targets using the latest advancements in machine learning predictive modeling. In this study, besides available geological data (lithology, structure, [...] Read more.

Remote sensing data provide significant information about surface geological features, but they have not been fully investigated as a tool for delineating mineral prospective targets using the latest advancements in machine learning predictive modeling. In this study, besides available geological data (lithology, structure, lineaments), Landsat-8, Sentinel-2, and ASTER multispectral remote sensing data were processed to produce various predictor maps, which then formed four distinct datasets (namely Landsat-8, Sentinel-2, ASTER, and Data-integration). Remote sensing enhancement techniques, including band ratio (BR), principal component analysis (PCA), and minimum noise fraction (MNF), were applied to produce predictor maps related to hydrothermal alteration zones in Hamissana area, while geological-based predictor maps were derived from applying spatial analysis methods. These four datasets were used independently to train a random forest algorithm (RF), which was then employed to conduct data-driven gold mineral prospectivity modeling (MPM) of the study area and compare the capability of different datasets. The modeling results revealed that ASTER and Sentinel-2 datasets achieved very similar accuracy and outperformed Landsat-8 dataset. Based on the area under the ROC curve (AUC), both datasets had the same prediction accuracy of 0.875. However, ASTER dataset yielded the highest overall classification accuracy of 73%, which is 6% higher than Sentinel-2 and 13% higher than Landsat-8. By using the data-integration concept, the prediction accuracy increased by about 6% (AUC: 0.938) compared with the ASTER dataset. Hence, these results suggest that the framework of exploiting remote sensing data is promising and should be used as an alternative technique for MPM in case of data availability issues. Full article

(This article belongs to the Special Issue Multispectral Remote Sensing Satellite Data for Mineral and Hydrocarbon Exploration: Big Data Processing and Deep Fusion Learning Techniques)

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17 pages, 5133 KiB

Open AccessEditor’s ChoiceArticle

Simple and Rapid Synthesis of Organically Modified Natural Acid Clay for the Adsorption of Anionic and Cationic Dyes

by Tomohiro Iwasaki

Minerals 2023, 13(1), 41; https://doi.org/10.3390/min13010041 - 27 Dec 2022

Cited by 6 | Viewed by 3194

Abstract

A simple method for organically modifying a natural acid clay (Japanese acid clay) rapidly with alkylamine has been developed. Japanese acid clay mainly consists of acidic montmorillonite and was successfully modified with decylamine in water at room temperature for a short time period [...] Read more.

A simple method for organically modifying a natural acid clay (Japanese acid clay) rapidly with alkylamine has been developed. Japanese acid clay mainly consists of acidic montmorillonite and was successfully modified with decylamine in water at room temperature for a short time period (10 min) using an ultrasonic bath without any pretreatments. The structure of the modified clay changed from exterior surface modification to intercalation with an increase in the decylamine content. The equilibrium adsorption capacity for the anionic dye methyl orange (MO) increased with increasing decylamine content. The adsorption kinetics and isotherm were well described by the pseudo-second-order and Langmuir models, respectively. Better MO adsorption was obtained under the conditions of high dosage, low pH value, and low temperature. The adsorbent was also found to have good adsorption for not only MO but also other anionic dyes (Congo red and eosin Y) and cationic dyes (methylene blue, crystal violet, and rhodamine B). In particular, the decylamine-intercalated clay adsorbent exhibited a high level of adsorption capacity for Congo red and crystal violet. The results demonstrate that the synthesis process can provide a simple and cost-effective organoclay as an adsorbent with high performance for the removal of anionic and cationic dyes. Full article

(This article belongs to the Special Issue Raw and Organically Modified Clays and Their Various Application)

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12 pages, 2665 KiB

Open AccessEditor’s ChoiceArticle

The Earliest Generation of Diamond: The First Find of a Diamond Inclusion in Kimberlitic Olivine

by Lyudmila Pokhilenko, Nikolay Pokhilenko, Vladimir Malkovets and Taisia Alifirova

Minerals 2023, 13(1), 36; https://doi.org/10.3390/min13010036 - 26 Dec 2022

Viewed by 5458

Abstract

Today, it is known that the majority of diamonds are crystallized mostly from a metasomatic agent close in the main characteristics to carbonatite melts acting upon mantle rocks, and therefore, diamonds are located in the interstitial space of these rocks. So far, diamond [...] Read more.

Today, it is known that the majority of diamonds are crystallized mostly from a metasomatic agent close in the main characteristics to carbonatite melts acting upon mantle rocks, and therefore, diamonds are located in the interstitial space of these rocks. So far, diamond has never been found included in other kimberlitic or xenolithic minerals. We have found a diamond inclusion inside the kimberlitic olivine grain, which is the first find of its kind. The diamond crystal is to have been captured by the growing olivine at quite high temperatures (more than 1400 °C) early in the history of the cratonic lithospheric mantle formation. The event had taken place long before the depleted peridotite cooled down to the temperature of the Middle Archean cratonic geotherm corresponding to the diamond stability field at depths where carbonatite melts can react with depleted peridotite, making it a diamond-bearing rock. On the one hand, this find provides evidence that diamonds can crystallize from the high-temperature silicate melt with some carbonate component. On the other hand, the diamond was found coexisting with a sulfide inclusion in the same olivine, i.e., crystallization from a sulfide melt may be another way of diamond formation. Full article

(This article belongs to the Special Issue Kimberlites and Related Rocks: New Insight into Petrogenesis and Diamond Potential of Deeply-Derived Mantle Magmas)

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13 pages, 1672 KiB

Open AccessFeature PaperEditor’s ChoiceReview

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 16 | Viewed by 2712

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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23 pages, 60457 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Multi-Dimensional Data Fusion for Mineral Prospectivity Mapping (MPM) Using Fuzzy-AHP Decision-Making Method, Kodegan-Basiran Region, East Iran

by Ali Shabani, Mansour Ziaii, Mehrdad Solimani Monfared, Adel Shirazy and Aref Shirazi

Minerals 2022, 12(12), 1629; https://doi.org/10.3390/min12121629 - 17 Dec 2022

Cited by 18 | Viewed by 2933

Abstract

Analyzing and fusing information layers of exploratory parameters is a crucial stride for increasing the accuracy of pinpointing mineral potential zones in the reconnaissance stage of mineral exploration. Remote sensing, geophysical, geochemical, and geology data were analyzed and fused for identify metallic mineralization [...] Read more.

Analyzing and fusing information layers of exploratory parameters is a crucial stride for increasing the accuracy of pinpointing mineral potential zones in the reconnaissance stage of mineral exploration. Remote sensing, geophysical, geochemical, and geology data were analyzed and fused for identify metallic mineralization in the Kodegan-Basiran region (East Iran). Landsat 7 Enhanced Thematic Mapper Plus (ETM⁺), aeromagnetic data, geological data, and geochemical stream sediment samples were utilized. The study area contains some copper indices and mines. Thus, the main focus of this study was identifying the zones with high potential for metallic copper mineralization. A two-stage methodology was implemented in this study: First, extraction of the exploratory parameters related to metallic mineralization and second is data fusion by the hybrid fuzzy-analytic hierarchy process (Fuzzy-AHP) method. Hydrothermal alterations and iron oxides in the area were mapped by applying the optimum index factor (OIF), band ratio (BR), and least squared fit (LS-Fit) to ETM⁺ data. Intrusive masses were positioned as one of the effective parameters in identifying metallic mineralization zones using the gradient tensor method to assess aeromagnetic data. In order to determine the threshold concentration and the location of mineralization anomalies, the K-means clustering algorithm, vertical geochemical zonality (Vz) index, as well as concentration-area (C-A) multi fractal and singularity analysis were implemented on the geochemical data. In conclusion, the potential zones of metallic mineralization in the Kodegan-Basiran region were displayed in a mineral prospectivity map (MPM) derived from the Fuzzy-AHP decision-making method. Finally, to validate the prospectivity map of metallic mineralization, a control area was selected and surveyed by collecting mineralogical, petrological, and stream sediment samples. Field works confirmed the mineralization of Cu and Fe sulfides, oxides, and hydroxides. The high potential areas identified in the MPM can be considered as targets for future Cu exploration in the Kodegan-Basiran area. Full article

(This article belongs to the Special Issue AI-Based GIS for Pinpointing Mineral Deposits)

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11 pages, 2341 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

In Situ Raman Spectroscopy and DFT Studies of the Phase Transition from Zircon to Reidite at High P–T Conditions

by Yue Gao, Zhi Zheng, Xia Zhao, Yuegao Liu, Jiangzhi Chen, Yan Li, Mengjun Xiong, Xiaotao Zu and Shenghua Mei

Minerals 2022, 12(12), 1618; https://doi.org/10.3390/min12121618 - 15 Dec 2022

Cited by 3 | Viewed by 2239

Abstract

Zircon (ZrSiO₄) provides a good pressure-holding environment for ultra-high-pressure metamorphic minerals during crust exhumation due to its high incompressibility and chemical stability. At high pressure, the zircon can transform to reidite. Previous studies show much higher phase-transition pressures at room temperature [...] Read more.

Zircon (ZrSiO₄) provides a good pressure-holding environment for ultra-high-pressure metamorphic minerals during crust exhumation due to its high incompressibility and chemical stability. At high pressure, the zircon can transform to reidite. Previous studies show much higher phase-transition pressures at room temperature than those at high temperature (>1000 K) due to kinetic hindrance. To further investigate the kinetics of the zircon–reidite phase transition at relatively low temperatures, the phase boundary at 298–800 K was determined using a diamond anvil cell combined with in situ Raman spectra. The results show that reidite becomes thermodynamically more stable compared with zircon at 8 GPa at room temperature, and the slope of the phase boundary at 298–800 K abruptly differs from that of previous studies at 1100–1900 K. Compared with the equilibrium phase boundary calculated by the density functional theory, it indicates that the kinetic effect of the zircon–reidite phase transition is obvious, and there exists a sufficiently large energy driving force provided by an overpressure to overcome the activation energy barrier below a critical temperature of approximately 880 K. The temperature dependence of overpressure is about 0.023 GPa/K. Full article

(This article belongs to the Special Issue High-Pressure Physical and Chemical Behaviors of Minerals and Rocks)

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17 pages, 2612 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Comparative Life Cycle Assessment of Conventional and Dry Stack Tailings Disposal Schemes: A Case Study in Northern China

by Kun Wang, Zheng Zhang, Liyi Zhu, Xiuzhi Yang, Miao Chen and Chao Yang

Minerals 2022, 12(12), 1603; https://doi.org/10.3390/min12121603 - 14 Dec 2022

Cited by 4 | Viewed by 2747

Abstract

Alternative tailings disposal technologies can be effective solutions to mining waste safety and environmental problems. The current decision-making processes for tailings disposal schemes lack consideration of environmental impacts. Based on a case study of an open-pit iron mine in northern China, this study [...] Read more.

Alternative tailings disposal technologies can be effective solutions to mining waste safety and environmental problems. The current decision-making processes for tailings disposal schemes lack consideration of environmental impacts. Based on a case study of an open-pit iron mine in northern China, this study adopted the life cycle assessment (LCA) method to compare the environmental impacts of three tailings disposal schemes of conventional slurry disposal technology (CSDT), dry stack disposal technology (DSDT) by belt conveyance and DSDT by truck transport. The results indicated that (1) the environmental impacts of the CSDT scheme were lowest under the premise that water consumption was ignored; (2) the environmental impacts of the DSDT scheme by belt conveyance mainly originated from its transport process, indicating that the tailings storage facilities (TSFs) site planning could be crucial in design decision making; (3) the environmental impacts of the DSDT scheme by truck transport mainly originated from the energy consumption of dry stacking equipment; and (4) the DSDT scheme by truck transport was eventually found to be preferable and implemented in the case study, after comprehensively considering the LCA results, TSF safety and remaining capacity, and social and policy uncertainties. It is therefore recommended to conduct LCA of environmental impacts in the decision-making process for the sustainable design of TSFs. Full article

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

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29 pages, 10190 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Exploring Platinum Speciation with X-ray Absorption Spectroscopy under High-Energy Resolution Fluorescence Detection Mode

by Clément Laskar, Elena F. Bazarkina, Maria A. Kokh, Jean-Louis Hazemann, Stéphane Foulon, Olivier Leynaud, Elsa Desmaele and Gleb S. Pokrovski

Minerals 2022, 12(12), 1602; https://doi.org/10.3390/min12121602 - 13 Dec 2022

Cited by 3 | Viewed by 4022

Abstract

Critical to interpreting platinum chemical speciation using X-ray absorption spectroscopy (XAS) is the availability of reference spectra of compounds with known Pt redox and coordination. Here we compare different techniques for Pt L_III-edge X-ray absorption near edge structure (XANES) and extended [...] Read more.

Critical to interpreting platinum chemical speciation using X-ray absorption spectroscopy (XAS) is the availability of reference spectra of compounds with known Pt redox and coordination. Here we compare different techniques for Pt L_III-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectral regions for a large set of Pt-O-Cl-S reference compounds of known structures. The measurements were conducted in HERFD (high-energy resolution fluorescence detection, high-resolution or HR) mode, as well as in two conventional modes such as transmission (TR) and nominal-resolution total fluorescence yield (TFY or NR). Samples analyzed here included Pt⁰ (TR), Pt^IIS (HR), Pt^IVS₂ (TR), K₂Pt^IICl₄ (HR + TR), K₂Pt^IVCl₆ (HR + TR), Pt^IVO₂ (HR + TR), C₆H₁₂N₂O₄Pt^II (HR + TR), and aqueous solutions of K₂Pt^IICl₄ and H₂Pt^IVCl₆ (NR + TR), as well as (NH₄)₂Pt^IV(S₅)₃ (HR + TR). XANES spectra in HERFD mode offer a better energy resolution than in conventional modes, allowing a more accurate identification of Pt redox state and coordination geometry. EXAFS spectra in all three modes for a given compound yield identical within errors values of Pt-neighbor interatomic distances and mean square relative displacement (MSRD, σ²) parameters. In contrast, both TR and NR spectra on the one hand and HR spectra on the other hand yield distinct amplitude reduction factor (S₀²) values, 0.76 ± 0.04 and 0.99 ± 0.07 (1 standard error), respectively. This study contributes to the development of an open-access XAS database SSHADE. Full article

(This article belongs to the Special Issue Electron Microbeam and X-ray Techniques: Advances and Applications)

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12 pages, 1997 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Chenowethite, Mg(H₂O)₆[(UO₂)₂(SO₄)₂(OH)₂]·5H₂O, a New Mineral with Uranyl-Sulfate Sheets from Red Canyon, Utah, USA

by Anthony R. Kampf, Jakub Plášil, Travis A. Olds, Chi Ma and Joe Marty

Minerals 2022, 12(12), 1594; https://doi.org/10.3390/min12121594 - 12 Dec 2022

Cited by 3 | Viewed by 2056

Abstract

The new mineral chenowethite, Mg(H₂O)₆[(UO₂)₂(SO₄)₂(OH)₂]·5H₂O, was found in efflorescence crusts on tunnel walls at the Blue Lizard, Green Lizard and Markey uranium mines in Red Canyon, San [...] Read more.

The new mineral chenowethite, Mg(H₂O)₆[(UO₂)₂(SO₄)₂(OH)₂]·5H₂O, was found in efflorescence crusts on tunnel walls at the Blue Lizard, Green Lizard and Markey uranium mines in Red Canyon, San Juan County, Utah, USA. The crystals are long, thin blades up to about 0.5 mm long, occurring in irregular sprays and subparallel groups. Chenowethite is pale green yellow. It has white streak, vitreous to silky luster, brittle tenacity, splintery and stepped fracture and two cleavages: {010} perfect and {001} good. It has a hardness (Mohs) of about 2 and is nonfluorescent in both long- and short-wave ultraviolet illumination. The density is 3.05(2) g/cm³. Optically, crystals are biaxial (−) with α = 1.530(2), β = 1.553(2) and γ = 1.565(2) (white light). The 2V is 72(2)° and dispersion is r > v (slight). The optical orientation is X = b, Y = a, Z = c and the mineral exhibits weak pleochroism in shades of pale green yellow: X < Y < Z. The Raman spectrum is consistent with the presence of UO₂²⁺, SO₄²⁻ and OH^–/H₂O. The empirical formula from electron microprobe analysis and arranged in accordance with the structure is (Mg_0.71Fe²⁺_0.09Co_0.05Ni_0.04)_∑0.89(H₂O)₆[(UO₂)₂(SO₄)₂(OH)₂]·[(H₂O)_4.78(NH₄)_0.22]_∑5.00. Chenowethite is orthorhombic, space group Cmcm; the unit-cell parameters are a = 6.951(2), b = 19.053(6), c = 16.372(5) Å, V = 2168.19(7) Å³ and Z = 4. The crystal structure of chenowethite (R₁ = 0.0396 for 912 I > 2σI reflections) contains [(UO₂)₂(SO₄)₂(OH)₂]²⁻ sheets that are topologically equivalent to those in deliensite, feynmanite, greenlizardite, johannite, meitnerite and plášilite. Full article

(This article belongs to the Special Issue The Crystal Chemistry and Mineralogy of Critical Metals)

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15 pages, 5848 KiB

Open AccessEditor’s ChoiceArticle

Interaction between PEO and Kaolinite in Flocculating: An Experimental and Molecular-Simulation Study

by Xin Tian, Xiaomin Ma, Xianshu Dong, Yuping Fan, Ming Chang and Na Li

Minerals 2022, 12(12), 1585; https://doi.org/10.3390/min12121585 - 10 Dec 2022

Cited by 1 | Viewed by 1886

Abstract

In this paper, the flocculation properties of polyethylene oxide (PEO) on kaolinite and the mechanism of adsorption on kaolinite anisotropic substrates were explored. As revealed by the experimental results, the settling rate and removal rate of kaolinite increased with increasing PEO concentration, but [...] Read more.

In this paper, the flocculation properties of polyethylene oxide (PEO) on kaolinite and the mechanism of adsorption on kaolinite anisotropic substrates were explored. As revealed by the experimental results, the settling rate and removal rate of kaolinite increased with increasing PEO concentration, but too high PEO concentration would cause the small particles to stabilize and become difficult to settle. Furthermore, to probe deep into the interactions between PEO and kaolinite anisotropic substrates, the morphology of adsorbed PEO, interfacial adsorption structure, and dynamic behavior of water molecules were determined by quartz crystal microbalance with dissipation (QCM-D) and molecular dynamics (MD) simulations. The adsorption amount of PEO on different mineral surfaces is in the order of kaolinite > alumina > silica, and the thickness of the adsorption structure formed by alumina is greater than that of silica. As illustrated by the MD simulation results, the adsorption of PEO reduces the concentration of water molecules attached to the kaolinite surface. The PEO forms a double-layer adsorption structure on the 001 surface, while forming a tight monolayer adsorption structure on the 00

\bar{1}

surface, weakening the interaction between the surface and the water molecules. The above results demonstrate that the adsorption of PEO effectively weakened the hydration dispersion of kaolinite and promoted the agglomeration of kaolinite particles. Full article

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

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19 pages, 9012 KiB

Open AccessEditor’s ChoiceArticle

Fusion of Multispectral Remote-Sensing Data through GIS-Based Overlay Method for Revealing Potential Areas of Hydrothermal Mineral Resources

by Saad S. Alarifi, Mohamed Abdelkareem, Fathy Abdalla, Ismail S. Abdelsadek, Hisham Gahlan, Ahmad. M. Al-Saleh and Mislat Alotaibi

Minerals 2022, 12(12), 1577; https://doi.org/10.3390/min12121577 - 9 Dec 2022

Cited by 15 | Viewed by 3750

Abstract

Revealing prospective locations of hydrothermal alteration zones (HAZs) is an important technique for mineral prospecting. In this study, we used multiple criteria inferred from Landsat-8 OLI, Sentinel-2, and ASTER data using a GIS-based weighted overlay multi-criteria decision analysis approach to build a model [...] Read more.

Revealing prospective locations of hydrothermal alteration zones (HAZs) is an important technique for mineral prospecting. In this study, we used multiple criteria inferred from Landsat-8 OLI, Sentinel-2, and ASTER data using a GIS-based weighted overlay multi-criteria decision analysis approach to build a model for the delineating of hydrothermal mineral deposits in the Khnaiguiyah district, Saudi Arabia. The utilized algorithms revealed argillic, phyllic, and propylitic alteration characteristics. The HAZs map resulted in the identification of six zones based on their mineralization potential, providing a basis for potential hydrothermal mineral deposit assessment exploration, which was created by the fusion of mineral bands indicators designated very low, low, moderate, good, very good, and excellent and covers 31.36, 28.22, 20.49, 10.99, 6.35, and 2.59%. Based on their potential for hydrothermal mineral potentiality, the discovered zones match gossans related to sulfide mineral alteration zones, as demonstrated by previous studies. Full article

(This article belongs to the Special Issue Multispectral Remote Sensing Satellite Data for Mineral and Hydrocarbon Exploration: Big Data Processing and Deep Fusion Learning Techniques)

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37 pages, 2914 KiB

Open AccessFeature PaperEditor’s ChoiceReview

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 36 | Viewed by 6022

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

(This article belongs to the Special Issue Carbonate Biomineralization, Environmental, and Diagenetic Significance)

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16 pages, 4766 KiB

Open AccessEditor’s ChoiceArticle

Crystal Engineering in Antisolvent Crystallization of Rare Earth Elements (REEs)

by Jonathan Sibanda, Jemitias Chivavava and Alison Emslie Lewis

Minerals 2022, 12(12), 1554; https://doi.org/10.3390/min12121554 - 1 Dec 2022

Cited by 3 | Viewed by 3039

Abstract

Antisolvent crystallization is a separation technology that separates the solute from the solvent by the addition of another solvent, in which the solute is sparingly soluble. High yields are achieved by using higher antisolvent-to-aqueous ratios, but this generates higher supersaturation, which causes excessive [...] Read more.

Antisolvent crystallization is a separation technology that separates the solute from the solvent by the addition of another solvent, in which the solute is sparingly soluble. High yields are achieved by using higher antisolvent-to-aqueous ratios, but this generates higher supersaturation, which causes excessive nucleation. This results in the production of smaller particles, which are difficult to handle in downstream processes. In this work, the effect of varying the organic (antisolvent)-to-aqueous (O/A) ratio and seed loading on the yield, particle size distribution, and morphology of neodymium sulphate product, during its recovery from an aqueous leach solution using antisolvent crystallization, was investigated. A batch crystallizer was used for the experiments, while ethanol was used as an antisolvent. Neodymium sulphate octahydrate [Nd₂(SO₄)₃.8H₂O] seeds were used to investigate the effect of seed loading. It was found that particle sizes increased as the O/A ratio increased. This was attributed to the agglomeration of smaller particles that formed at high supersaturation. An O/A ratio of 1.4 resulted in higher yields and particles with a plate-like morphology. The increase in yield was attributed to the increased interaction of ethanol molecules with the solvent, which reduced the solubility of neodymium sulphate. Increasing the seed loading resulted in smaller particle sizes with narrow particle size distribution and improved filtration performance. This was attributed to the promotion of crystal growth and suppression of agglomeration in the presence of seeds. Full article

(This article belongs to the Special Issue Recent Developments in Mineral Processing at University of Cape Town)

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22 pages, 2710 KiB

Open AccessEditor’s ChoiceArticle

Impacts of Crystalline Host Rock on Repository Barrier Materials at 250 °C: Hydrothermal Co-Alteration of Wyoming Bentonite and Steel in the Presence of Grimsel Granodiorite

by Amber Zandanel, Kirsten B. Sauer, Marlena Rock, Florie A. Caporuscio, Katherine Telfeyan and Edward N. Matteo

Minerals 2022, 12(12), 1556; https://doi.org/10.3390/min12121556 - 1 Dec 2022

Cited by 2 | Viewed by 3201

Abstract

Direct disposal of dual-purpose canisters (DPC) has been proposed to streamline the disposal of spent nuclear fuel. However, there are scenarios where direct disposal of DPCs may result in temperatures in excess of the specified upper temperature limits for some engineered barrier system [...] Read more.

Direct disposal of dual-purpose canisters (DPC) has been proposed to streamline the disposal of spent nuclear fuel. However, there are scenarios where direct disposal of DPCs may result in temperatures in excess of the specified upper temperature limits for some engineered barrier system (EBS) materials, which may cause alteration within EBS materials dependent on local conditions such as host rock composition, chemistry of the saturating groundwaters, and interactions between barrier materials themselves. Here we report the results of hydrothermal experiments reacting EBS materials—bentonite buffer and steel—with an analogue crystalline host rock and groundwater at 250 °C. Experiment series explored the effect of reaction time on the final products and the effects of the mineral and fluid reactants on different steel types. Post-mortem X-ray diffraction, electron microprobe, and scanning electron microscopy analyses showed characteristic alteration of both bentonite and steel, including the formation of secondary zeolite and calcium silicate hydrate minerals within the bentonite matrix and the formation of iron-bearing clays and metal oxides at the steel surfaces. Swelling clays in the bentonite matrix were not quantitatively altered to non-swelling clay species by the hydrothermal conditions. The combined results of the solution chemistry over time and post-mortem mineralogy suggest that EBS alteration is more sensitive to initial groundwater chemistry than the presence of host rock, where limited potassium concentration in the solution prohibits conversion of the smectite minerals in the bentonite matrix to non-swelling clay species. Full article

(This article belongs to the Section Clays and Engineered Mineral Materials)

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14 pages, 528 KiB

Open AccessEditor’s ChoiceArticle

On the Sorption Mode of U(IV) at Calcium Silicate Hydrate: A Comparison of Adsorption, Absorption in the Interlayer, and Incorporation by Means of Density Functional Calculations

by Ion Chiorescu, Alena Kremleva and Sven Krüger

Minerals 2022, 12(12), 1541; https://doi.org/10.3390/min12121541 - 30 Nov 2022

Cited by 7 | Viewed by 2332

Abstract

Calcium silicate hydrate (C-S-H) is the main product of cement hydration and has also been shown to be the main sorbing phase of actinide ions interacting with cement. U(IV) has been chosen as an exemplary actinide ion to study actinide sorption at C-S-H [...] Read more.

Calcium silicate hydrate (C-S-H) is the main product of cement hydration and has also been shown to be the main sorbing phase of actinide ions interacting with cement. U(IV) has been chosen as an exemplary actinide ion to study actinide sorption at C-S-H as U is the main element in highly active radioactive waste and because reducing conditions are foreseen in a deep geological repository for such waste. U(IV) surface adsorption, absorption in the interlayer, and incorporation into the calcium oxide layer of C-S-H has been modeled quantum mechanically, applying a density functional approach. For each sorption mode various sites have been considered and a combined dynamic equilibration and optimization approach has been applied to generate a set of representative stable sorption complexes. At the surface and in the interlayer similar U(IV) hydroxo complexes stabilized by Ca²⁺ ions have been determined as sorbates. Surface adsorption tends to be preferred over absorption in the interlayer for the same type of sites. Incorporation of U(IV) in the CaO layer yields the most favorable sorption site. This result is supported by good qualitative agreement of structures with EXAFS results for other actinides in the oxidation state IV, leading to a new interpretation of the experimental results. Full article

(This article belongs to the Special Issue Mineral-Water Interfaces and Interfacial Reactions with (Radioactive) Contaminants)

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13 pages, 2912 KiB

Open AccessEditor’s ChoiceArticle

Global Trend for Waste Lithium-Ion Battery Recycling from 1984 to 2021: A Bibliometric Analysis

by Yaoguang Guo, Yujing Liu, Jie Guan, Qianqian Chen, Xiaohu Sun, Nuo Liu, Li Zhang, Xiaojiao Zhang, Xiaoyi Lou and Yingshun Li

Minerals 2022, 12(12), 1514; https://doi.org/10.3390/min12121514 - 27 Nov 2022

Cited by 5 | Viewed by 4303

Abstract

With the massive use of lithium-ion batteries in electric vehicles and energy storage, the environmental and resource problems faced by used lithium-ion batteries are becoming more and more prominent. In order to better resource utilization and environmental protection, this paper employs bibliometric and [...] Read more.

With the massive use of lithium-ion batteries in electric vehicles and energy storage, the environmental and resource problems faced by used lithium-ion batteries are becoming more and more prominent. In order to better resource utilization and environmental protection, this paper employs bibliometric and data analysis methods to explore publications related to waste lithium-ion battery recycling from 1984 to 2021. The Web of Science core set from the SCIE online database was used for this article. These findings demonstrate a considerable increase trend in the number of publications published in the subject of recycling used lithium-ion batteries, with a natural-sciences-centric focus. Argonne National Lab, Chinese Academy of Sciences, and China Academic and Scientific Research Center are the top three institutions in terms of quantity of papers published. The affiliated journals corresponding to these three institutions also have high impact factors, which are 106.47, 44.85, and 58.69, respectively. In comparison to comparable institutes in other nations, the American Argonne National Laboratory supports 223 research articles in this area. China and the US make up the majority of the research’s funding. The two key aspects of current lithium-ion battery recycling research are material structure research and environmentally friendly recycling. Nevertheless, high-capacity lithium-ion batteries, waste lithium-ion integrated structures, and gentle recycling of spent lithium-ion batteries will be the major aspects of study in the future. It is hoped that the above analysis can bring new ideas and methods to the field of waste lithium-ion battery recycling and provide a basis for the subsequent research and application of waste lithium-ion battery recycling. Full article

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

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13 pages, 7078 KiB

Open AccessEditor’s ChoiceArticle

Estimation of Final Product Concentration in Metalic Ores Using Convolutional Neural Networks

by Jakub Progorowicz, Artur Skoczylas, Sergii Anufriiev, Marek Dudzik and Paweł Stefaniak

Minerals 2022, 12(12), 1480; https://doi.org/10.3390/min12121480 - 22 Nov 2022

Cited by 1 | Viewed by 1765

Abstract

Although artificial neural networks are widely used in various fields, including mining and mineral processing, they can be problematic for appropriately choosing the model architecture and parameters. In this article, we describe a procedure for the optimization of the structure of a convolutional [...] Read more.

Although artificial neural networks are widely used in various fields, including mining and mineral processing, they can be problematic for appropriately choosing the model architecture and parameters. In this article, we describe a procedure for the optimization of the structure of a convolutional neural network model developed for the purposes of metallic ore pre-concentration. The developed model takes as an input two-band X-ray scans of ore grains, and for each scan two values corresponding to concentrations of zinc and lead are returned by the model. The whole process of sample preparation and data augmentation, optimization of the model hyperparameters and training of selected models is described. The ten best models were trained ten times each in order to select the best possible one. We were able to achieve a Pearson coefficient of R = 0.944 for the best model. The detailed results of this model are shown, and finally, its applicability and limitations in real-world scenarios are discussed. Full article

(This article belongs to the Special Issue Innovative Solutions for Measurements, Modelling and Control in Mineral Processing)

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16 pages, 5484 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Magnetic Nanosorbents Based on Bentonite and CoFe₂O₄ Spinel

by Nataliya Khodosova, Lyudmila Novikova, Elena Tomina, Larisa Belchinskaya, Alexander Zhabin, Nikolay Kurkin, Victoria Krupskaya, Olga Zakusina, Tatiana Koroleva, Ekaterina Tyupina, Alexander Vasiliev and Pavel Kazin

Minerals 2022, 12(11), 1474; https://doi.org/10.3390/min12111474 - 21 Nov 2022

Cited by 6 | Viewed by 2529

Abstract

New magnetic nanocomposite sorbents were obtained by doping natural bentonite with nanosized CoFe₂O₄ spinel (10 and 20 wt.%). Nanocrystals of cobalt ferrite were synthesized by a citrate burning method. The structure and physical-chemical properties of the composites were characterized by [...] Read more.

New magnetic nanocomposite sorbents were obtained by doping natural bentonite with nanosized CoFe₂O₄ spinel (10 and 20 wt.%). Nanocrystals of cobalt ferrite were synthesized by a citrate burning method. The structure and physical-chemical properties of the composites were characterized by XRD, XRF, TEM, BET, FTIR and Faraday balance magnetometry. During the formation of nanocomposites, 10–30 nm particles of cobalt ferrite occupied mainly the interparticle space of Fe-aluminosilicate that significantly changed the particle morphology and composite porosity, but at the same time retained the structure of the 2:1 smectite layer. A combination of two functional properties of composites, adsorption and magnetism has been found. The adsorption capacity of magnetic nanosorbents exceeded this parameter for bentonite and spinel. Despite the decrease in the adsorption volume, pore size and specific surface area of the composite material relative to bentonite, the sorption activity of the composite increases by 12%, which indicated the influence of the magnetic component on the sorption process. FTIR data confirmed the mechanism of formaldehyde sorption by the composite sorbent. The production of a magnetic nanosorbent opens up new possibilities for controlling the sorption processes and makes it possible to selectively separate the sorbent from the adsorption medium by the action of a magnetic field. Full article

(This article belongs to the Special Issue Environmental Applications of Chemically Modified Clay Minerals, Volume II)

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32 pages, 6210 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Prospectivity Mapping of Heavy Mineral Ore Deposits Based upon Machine-Learning Algorithms: Columbite-Tantalite Deposits in West- Central Côte d’Ivoire

by Kassi Olivier Shaw, Kalifa Goïta and Mickaël Germain

Minerals 2022, 12(11), 1453; https://doi.org/10.3390/min12111453 - 17 Nov 2022

Cited by 4 | Viewed by 4526

Abstract

This study aimed to model the prospectivity for placer deposits using geomorphic and landscape parameters. Within a geographic information system (GIS), spatial autocorrelation analysis of 3709 geochemical samples was used to identify prospective and non-prospective targets for columbite-tantalite (Nb-Ta) placer deposits of Hana-Lobo [...] Read more.

This study aimed to model the prospectivity for placer deposits using geomorphic and landscape parameters. Within a geographic information system (GIS), spatial autocorrelation analysis of 3709 geochemical samples was used to identify prospective and non-prospective targets for columbite-tantalite (Nb-Ta) placer deposits of Hana-Lobo (H-L) Geological Complex (West- Central Côte d’Ivoire, West Africa). Based on mineralization system analysis, hydrologic, geomorphologic and landscape parameters were extracted at the locations of the identified targets. Supervised automatic classification approaches were applied, including Random Forest (RF), K-Nearest Neighbors (KNN) and Support Vector Machines (SVM) to find a prospectivity model complex enough to capture the nature of the data. Metrics such as cross-validation accuracy (CVA), Receiver Operating Characteristic (ROC) curves, Area Under Curve (AUC) values and F-score values were used to evaluate the performance and robustness of output models. Results of applying machine-learning algorithms demonstrated that predictions provided by the final RF and KNN models were very close (κ = 0.56 and CVA = 0.69; κ = 0.54 and CVA = 0.68, respectively) and those provided by the SVM models were slightly lower with κ = 0.46 and CVA = 0.63. Independent validation results confirmed the slightly higher performance of both KNN and RF prospectivity models, compared to final SVM. Sensitivity analyses of both KNN and RF prospectivity models for medium and high-grade Nb-Ta deposits show a prediction rate of up to 90%. Full article

(This article belongs to the Special Issue AI-Based GIS for Pinpointing Mineral Deposits)

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21 pages, 7728 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Mineralogical and Geochemical Characteristics of the H-Pit of the Chatree Gold Deposit, Central Thailand: A Case Study for Assessment of Acid Rock Drainage and Heavy Metal Sources

by Sirawit Kaewpaluk, Abhisit Salam, Thitiphan Assawincharoenkij, Takayuki Manaka, Sopit Poompuang and Surachat Munsamai

Minerals 2022, 12(11), 1446; https://doi.org/10.3390/min12111446 - 15 Nov 2022

Cited by 1 | Viewed by 2882

Abstract

H-pit is one of the significant ore lenses of the Chatree mine in Thailand. Au-Ag mineralization mainly occurs as veins, stockworks, and minor breccias hosted by volcanic and volcaniclastic rocks. Disseminated pyrites are commonly present near mineralized veins in the hanging wall zone. [...] Read more.

H-pit is one of the significant ore lenses of the Chatree mine in Thailand. Au-Ag mineralization mainly occurs as veins, stockworks, and minor breccias hosted by volcanic and volcaniclastic rocks. Disseminated pyrites are commonly present near mineralized veins in the hanging wall zone. This study aims to assess the acid rock drainage (ARD) potential and heavy metal content from the H-pit area. The results indicate that hanging wall rock is a potential acid-forming (PAF) material related to disseminated pyrite formed by hydrothermal alteration. In contrast, the footwall and ore zone materials are classified as non-acid forming (NAF). Because the ore zone has calcite in the veins, it may help buffer the material’s acidity. The results of heavy metal analysis reveal that the ore zone has significantly higher contents of As, Cd, Cu, Pb, and Zn than those in the hanging wall and footwall zones. Moreover, the hanging wall and footwall materials have exceeding values for As, Cd, and Zn compared to those in typical igneous rocks. These heavy metals are interpreted to be sourced from (1) the primary composition in base metal sulfides (e.g., Cu, Pb, and Zn), (2) the substitution of trace elements in sulfides (e.g., As and Cd), and (3) the substitution of trace elements in calcite (e.g., Mn), as evidenced in the EPMA results. In conclusion, the hanging wall rocks in this study containing high sulfur in proximity to the ore zone are a PAF material with heavy metal contaminant sources, whereas the footwall and ore zone materials have a lower potential to be such sources at the Chatree mine. Full article

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

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22 pages, 5301 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of Different Dispersants on the Dispersion/Sedimentation Behavior of Halloysite, Kaolinite, and Quartz Suspensions in the Enrichment of Halloysite Ore by Mechanical Dispersion

by Emrah Durgut, Mustafa Cinar, Mert Terzi, Ilgin Kursun Unver, Yildiz Yildirim and Orhan Ozdemir

Minerals 2022, 12(11), 1426; https://doi.org/10.3390/min12111426 - 10 Nov 2022

Cited by 9 | Viewed by 2749

Abstract

In this study, the dispersion properties of pure halloysite, kaolinite, and quartz minerals in halloysite ore were determined in the absence and presence of dispersants (sodium silicate, STPP, SHMP). First of all, the samples were characterized by chemical, mineralogical, BET, FTIR, and TEM [...] Read more.

In this study, the dispersion properties of pure halloysite, kaolinite, and quartz minerals in halloysite ore were determined in the absence and presence of dispersants (sodium silicate, STPP, SHMP). First of all, the samples were characterized by chemical, mineralogical, BET, FTIR, and TEM analyses. Afterward, the physico-chemical properties of these minerals were investigated by zeta potential measurements and dispersion/sedimentation experiments in the absence and presence of the dispersants. The zeta potential measurements showed that the surface charges of all minerals changed from negative to positive as the PH changed from basic to acidic. The presence of dispersants at natural pHs indicated that the mineral surface charges tended to become more negative as the concentration increased in the zeta potential measurements. SHMP showed the most effect on the zeta potential. In the dispersion/sedimentation experiments, settling was slowed down with the use of dispersants. Finally, the dispersion properties of halloysite ore in the presence of dispersants were explored using mechanical dispersion and pulp viscosity experiments based on the amount of material passing to <38 μm size and the chemical changes in the materials. As a result of the mechanical dispersion tests carried out in the presence of dispersants (sodium silicate, STPP, SHMP), 71.3% of the material with 30.8% Al₂O₃ and 50.5% SiO₂ content passed to <38 μm size without using dispersant, and 73.2% of <38 μm sized material with 35.5% Al₂O₃ and 46.1% SiO₂ content was gained in the use of 7.5 kg/ton SHMP, which was determined as the optimum within the scope of the study. In conclusion, dispersant use enhanced the mechanical dispersion effect for plastic clay mineral separation from hard minerals in an aqueous medium. Full article

(This article belongs to the Special Issue Nanotubular and Nanofibrous Clay Minerals)

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14 pages, 5179 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Microbial Mat Stratification in Travertine Depositions of Greek Hot Springs and Biomineralization Processes

by Christos Kanellopoulos, Vasiliki Lamprinou, Artemis Politi, Panagiotis Voudouris, Ioannis Iliopoulos, Maria Kokkaliari, Leonidas Moforis and Athena Economou-Amilli

Minerals 2022, 12(11), 1408; https://doi.org/10.3390/min12111408 - 4 Nov 2022

Cited by 7 | Viewed by 3740

Abstract

The study of microbial mats in extreme environments is of high scientific interest from geological, ecological, and geomicrobiological aspects. These mats represent multilayer bio-structures where each taxonomic group dominates a specific vertical layering distribution resulting from its growth and metabolic activity. In the [...] Read more.

The study of microbial mats in extreme environments is of high scientific interest from geological, ecological, and geomicrobiological aspects. These mats represent multilayer bio-structures where each taxonomic group dominates a specific vertical layering distribution resulting from its growth and metabolic activity. In the present study, microbial mats in a hot spring environment from Aedipsos (Euboea Island, Greece) resulting in the creation of thermogenic travertine, were studied through an interdisciplinary approach. The mineralogical composition was determined by optical microscopy, XRD, and SEM-EDS microanalysis, and the identification of Cyanobacteria was made primarily on morphological characteristics. The main mineral phase in the studied samples is calcite and, to a less extent, aragonite, with several trace elements in the mineral-chemistry composition, i.e., up to 1.93 wt. % MgO, up to 0.52 wt. % SrO, up to 0.44 wt. % Na₂O, up to 0.17 wt. % K₂O, and up to 3.99 wt. % SO₃. The dominant facies are lamination and shrubs, which are the most common among the facies of thermogenic travertines of the area. Several layers were identified, (i) a top mainly abiotic layer consisting of calcium carbonate micritic crystals, (ii) a second biotic layer–the Cyanobacteria layer, dominated by the species Leptolyngbya perforans, (iii) a third biotic layer where Leptolyngbya perforans, Chloroflexus and other bacteria occur, and (iv) a deeper abiotic part with several layers where no photosynthetic microorganisms occur. In the upper layers, nineteen (19) species of Cyanobacteria were identified, classified in the orders Chroococcales (37%), Synechococcales (31%), Oscillatoriales (16%), and Spirulinales (6%). Among the identified Cyanobacteria, there are typical thermophilic and limestone substrate species. These Cyanobacteria are found to participate in the biomineralization and biologically-influenced processes, i.e., (i) filamentous Cyanobacteria are trapping calcium carbonate crystals, and diatoms, (ii) extracellular polymeric substances (EPS) create crystal retention lattice contributing to the biomineralization process, and (iii) filamentous sheaths of Cyanobacteria are calcified, resulting in the creation of calcium carbonate tubes. Full article

(This article belongs to the Special Issue Bio-Geochemistry of Heavy Metals/Metalloids)

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17 pages, 2088 KiB

Open AccessEditor’s ChoiceArticle

Oxidative Dissolution of Low-Grade Ni-Cu Ore and Impact on Flotation of Pentlandite

by Benjamin Musuku, Eija Saari and Olli Dahl

Minerals 2022, 12(11), 1406; https://doi.org/10.3390/min12111406 - 3 Nov 2022

Cited by 3 | Viewed by 2420

Abstract

This paper investigated the effect of mineral surface oxidation on the floatability of Kevitsa low-grade Ni-Cu ore. Physicochemical measurements, ethylene diamine tetra acetic acid (EDTA) extraction, and oxygen uptake experiments were carried out with slurry and recycled process water samples obtained from the [...] Read more.

This paper investigated the effect of mineral surface oxidation on the floatability of Kevitsa low-grade Ni-Cu ore. Physicochemical measurements, ethylene diamine tetra acetic acid (EDTA) extraction, and oxygen uptake experiments were carried out with slurry and recycled process water samples obtained from the Kevitsa Cu-Ni sequential concentrator plant. The pH of recycled process water, copper flotation feed, and nickel flotation feed dropped by 0.7, 0.4, and 0.7 points, respectively, from May to July. The oxygen demand increased from recycled process water to the copper flotation feed, then dropped for the nickel flotation feed. The nickel flotation feed Redox potential (ORP) was lowest for July, while EDTA extractable metals increased from May to July. There was a 20% drop in nickel recoveries from May to July. Based on ORP measurements of the nickel flotation feed, good nickel flotation takes place in a moderately oxidizing (75–170 mV) and alkaline (9.2–9.7 pH) environment. Therefore, the ORP/pH of the nickel flotation feed is important to the nickel flotation. The results showed that at the Kevitsa plant, the grinding process is an electrochemically active environment, which, together with the incoming recycled process water quality, defines the degree of mineral surface oxidation for flotation. The increasing corrosiveness of the recycled process water increased mineral surface oxidation and depressed pentlandite flotation. Laboratory flotation experiments confirmed the observed poor plant flotation response when the corrosiveness of recycled process water increased. Total dissolved solids (TDS) was proven to be a reliable online parameter for the corrosiveness of the recycled process water and was inversely proportional to the pentlandite recovery. The findings of this study may help the plant develop ways to enable a timely response to changes in recycled process water quality to prevent harmful impacts on pentlandite flotation. Full article

(This article belongs to the Special Issue Water within Minerals Processing, Volume II)

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60 pages, 13465 KiB

Open AccessEditor’s ChoiceReview

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 2637

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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11 pages, 10332 KiB

Open AccessEditor’s ChoiceArticle

Methodology and Model to Predict HPGR Throughput Based on Piston Press Testing

by Giovanni Pamparana, Bern Klein and Mauricio Guimaraes Bergerman

Minerals 2022, 12(11), 1377; https://doi.org/10.3390/min12111377 - 29 Oct 2022

Cited by 5 | Viewed by 3458

Abstract

Sizing High-Pressure Grinding Rolls (HPGR) requires a large quantity of material, making it not attractive and costly to be considered for new mining projects regardless of their energy consumption reduction benefits. Ongoing efforts are being made at the University of British Columbia to [...] Read more.

Sizing High-Pressure Grinding Rolls (HPGR) requires a large quantity of material, making it not attractive and costly to be considered for new mining projects regardless of their energy consumption reduction benefits. Ongoing efforts are being made at the University of British Columbia to predict the behaviour of the HPGR using a low quantity of material on a piston-and-die press apparatus. Although the energy requirements and size reduction predictive models are already developed, there is still a need to predict the HPGR throughput on a small-scale test. This paper presents a new model to predict the HPGR throughput based on the previously developed model to predict the operational gap by using less than 2 kg of sample. The throughput model was developed using machine learning techniques and calibrated using pilot-scale HPGR tests and piston press tests. The resulting model has an R² of 0.91 with an average prediction error of ±4.2%. The developed methodology has the potential to fill the gap of the missing throughput model. Further pilot-scale HPGR testing is required to continue validating the model. Full article

(This article belongs to the Special Issue Experimental and Numerical Studies of Mineral Comminution)

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18 pages, 2428 KiB

Open AccessEditor’s ChoiceArticle

A Combined Extended X-ray Absorption Fine Structure Spectroscopy and Density Functional Theory Study of Americium vs. Yttrium Adsorption on Corundum (α–Al₂O₃)

by Nina Huittinen, Sinikka Virtanen, André Rossberg, Manuel Eibl, Satu Lönnrot and Robert Polly

Minerals 2022, 12(11), 1380; https://doi.org/10.3390/min12111380 - 29 Oct 2022

Cited by 2 | Viewed by 2263

Abstract

Adsorption reactions on mineral surfaces are influenced by the overall concentration of the adsorbing metal cation. Different site types (strong vs. weak ones) are often included to describe the complexation reactions in the various concentration regimes. More specifically, strong sites are presumed to [...] Read more.

Adsorption reactions on mineral surfaces are influenced by the overall concentration of the adsorbing metal cation. Different site types (strong vs. weak ones) are often included to describe the complexation reactions in the various concentration regimes. More specifically, strong sites are presumed to retain metal ions at low sorbate concentrations, while weak sites contribute to metal ion retention when the sorbate concentration increases. The involvement of different sites in the sorption reaction may, thereby, also be influenced by competing cations, which increase the overall metal ion concentration in the system. To date, very little is known about the complex structures and metal ion speciation in these hypothetical strong- and weak-site regimes, especially in competing scenarios. In the present study, we have investigated the uptake of the actinide americium on corundum (α–Al₂O₃) in the absence and presence of yttrium as competing metal by combining extended X-ray absorption fine structure spectroscopy (EXAFS) with density functional theory (DFT) calculations. Isotherm studies using the radioactive ¹⁵²Eu tracer were used to identify the sorption regimes where strong sites and weak sites contribute to the sorption reaction. The overall americium concentration, as well as the presence of yttrium could be seen to influence both the amount of americium uptake by corundum, but also the speciation at the surface. More specifically, increasing the Am³⁺ or Y³⁺ concentrations from the strong site to the weak site concentration regimes in the mineral suspensions resulted in a decrease in the overall Am–O coordination number from nine to eight, with a subsequent shortening of the average Am–O bond length. DFT calculations suggest a reduction of the surface coordination with increasing metal–ion loading, postulating the formation of tetradentate and tridentate Am³⁺ complexes at low and high surface coverages, respectively. Full article

(This article belongs to the Special Issue Mineral-Water Interfaces and Interfacial Reactions with (Radioactive) Contaminants)

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18 pages, 3742 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Alkali-Activated Metakaolins: Mineral Chemistry and Quantitative Mineral Composition

by Marta Valášková, Zdeněk Klika, Jozef Vlček, Lenka Matějová, Michaela Topinková, Helena Pálková and Jana Madejová

Minerals 2022, 12(11), 1342; https://doi.org/10.3390/min12111342 - 23 Oct 2022

Cited by 10 | Viewed by 2721

Abstract

The reaction products resulting from the alkali-activation of metakaolin are impacted by the composition of the initial kaolin, and amount of alkali-activated kaolinite and water. The present study focused on analyzing these parameters on the metakaolins calcined at 800 °C from three kaolins, [...] Read more.

The reaction products resulting from the alkali-activation of metakaolin are impacted by the composition of the initial kaolin, and amount of alkali-activated kaolinite and water. The present study focused on analyzing these parameters on the metakaolins calcined at 800 °C from three kaolins, and the metakaolins’ alkali activation for 2, 3 and 28 days. The first objective was to evaluate the mineral chemistry and quantitative mineral phase composition from the bulk chemical analysis using the chemical quantitative mineral analysis (CQMA) procedure and conduct a comparison of the chemistry of the metakaolins after alkali activation for 28 days according to the elements Al, Si, Na and K, using the leaching test in distilled water. The second task was to search for possible relationships between the quantitative number of phases in alkali-activated metakaolins and compressive strength. The main methods used for the characterization of material were X-ray fluorescence, X-ray diffraction, thermal TG/DTA and infrared spectroscopy. Metakaolins alkali activated for 28 days contained crystalline quartz, muscovite, orthoclase, and unreacted metakaolinite contained zeolite A (Z-A), hydrosodalite (HS) and thermonatrite (TN) in the amorphous/weakly crystalline phase. The compressive strengths (CS) from 6.42 ± 0.33 to 9.97 ± 0.50 MPa are related positively to H₂O+ and H₂O bound in HS and TN. Full article

(This article belongs to the Special Issue Development in Geopolymer Materials and Applications)

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