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Minerals, Volume 11, Issue 2 (February 2021) – 135 articles

Cover Story (view full-size image): Digital rock physics allows determining macroscopic rock behavior based on a microscale representation. The accuracy of property prediction depends on the quality of the microtomographic images. This study presents a process-based method to reconstruct the full 3D microstructure of three reservoir sandstones, including grain deposition and diagenetic cementation. It enables efficiently generating synthetic sandstone samples comprising the microstructural complexity of natural rocks and considering any desired size, sorting, and shape of grains. In view of a virtual laboratory, these samples can be further altered to examine the impact of geochemical alterations or fracturing on various petrophysical correlations, which is of particular relevance for a sustainable exploration and utilization of the geological subsurface. View this paper
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Article
Scale-Up of Decanter Centrifuges for the Particle Separation and Mechanical Dewatering in the Minerals Processing Industry by Means of a Numerical Process Model
Minerals 2021, 11(2), 229; https://doi.org/10.3390/min11020229 - 23 Feb 2021
Cited by 1 | Viewed by 979
Abstract
Decanter centrifuges are frequently used for thickening, dewatering, classification, or degritting in the mining industry and various other sectors. Their use in an industrial process chain requires a sufficiently accurate prediction of the product and the machine behaviour. For this purpose, experiments on [...] Read more.
Decanter centrifuges are frequently used for thickening, dewatering, classification, or degritting in the mining industry and various other sectors. Their use in an industrial process chain requires a sufficiently accurate prediction of the product and the machine behaviour. For this purpose, experiments on a smaller pilot-scale are carried out for scale-up of a decanter centrifuge, which is usually a major challenge. Predicting the process behaviour of decanter centrifuges from laboratory tests is rather difficult. Basically, there are two common ways of scale-up: First, via analytical methods and the law of similarity, which often requires an enormous experimental effort. Second, using numerical models, which demands a mathematically and physically precise description of the multiple processes running simultaneously in such machines. This article provides an overview of both methods for scale-up of a decanter centrifuge. The concept of a previous developed numerical approach is introduced. Pros and cons of both scale-up methods are compared and further discussed. Experiments on lab-scale, pilot-scale, and industrial-scale decanter centrifuges with two different finely dispersed calcium carbonate water suspensions were carried out and simulations were done to investigate and prove the scale-up capability and transferability of the numerical approach. Full article
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Article
High Temperature Sulfate Minerals Forming on the Burning Coal Dumps from Upper Silesia, Poland
Minerals 2021, 11(2), 228; https://doi.org/10.3390/min11020228 - 23 Feb 2021
Viewed by 668
Abstract
The subject of this work is the assemblage of anhydrous sulfate minerals formed on burning coal-heaps. Three burning heaps located in the Upper Silesian coal basin in Czerwionka-Leszczyny, Radlin and Rydułtowy near Rybnik were selected for the research. The occurrence of godovikovite, millosevichite, [...] Read more.
The subject of this work is the assemblage of anhydrous sulfate minerals formed on burning coal-heaps. Three burning heaps located in the Upper Silesian coal basin in Czerwionka-Leszczyny, Radlin and Rydułtowy near Rybnik were selected for the research. The occurrence of godovikovite, millosevichite, steklite and an unnamed MgSO4, sometimes accompanied by subordinate admixtures of mikasaite, sabieite, efremovite, langbeinite and aphthitalite has been recorded from these locations. Occasionally they form monomineral aggregates, but usually occur as mixtures practically impossible to separate. The minerals form microcrystalline masses with a characteristic vesicular structure resembling a solidified foam or pumice. The sulfates crystallize from hot fire gases, similar to high temperature volcanic exhalations. The gases transport volatile components from the center of the fire but their chemical compositions are not yet known. Their cooling in the near-surface part of the heap results in condensation from the vapors as viscous liquid mass, from which the investigated minerals then crystallize. Their crystallization temperatures can be estimated from direct measurements of the temperatures of sulfate accumulation in the burning dumps and studies of their thermal decomposition. Millosevichite and steklite crystallize in the temperature range of 510–650 °C, MgSO4 forms at 510–600 °C and godovikovite in the slightly lower range of 280–450 (546) °C. These values are higher than those previously reported. Full article
(This article belongs to the Special Issue Formation of Sulfate Minerals in Natural and Industrial Environments)
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Article
Quantitative Expression of the Burial Phenomenon of Deep Seafloor Manganese Nodules
Minerals 2021, 11(2), 227; https://doi.org/10.3390/min11020227 - 23 Feb 2021
Cited by 2 | Viewed by 850
Abstract
Manganese (polymetallic) nodules on the deep seafloor in the open ocean have attracted great interest because of their economic potential. Visual data on nodules found on the deep seafloor such as photographs and videos have increased exponentially with the recent progress of related [...] Read more.
Manganese (polymetallic) nodules on the deep seafloor in the open ocean have attracted great interest because of their economic potential. Visual data on nodules found on the deep seafloor such as photographs and videos have increased exponentially with the recent progress of related technologies. These data are expected to reflect useful information for estimating these mineral resources, as well as understanding their geological origin. Although the size, number, and coverage of manganese nodules have been measured in seafloor images, the burial of such nodules has not been sufficiently examined. This paper focuses on mathematical expression of the burial of the manganese nodules and attempts to quantitatively elucidate relations among burial degree and nodule geological parameters. The results, that is, a dataset obtained by calculations of relations among parameters, are also utilized for considerations of quantitative expression of burial. These considerations are expected to contribute to a better understanding of the geological origin of manganese nodules. Full article
(This article belongs to the Special Issue Exploration of Polymetallic Nodules)
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Article
Re-Os Age and Stable Isotope (O-H-S-Cu) Geochemistry of North Eastern Turkey’s Kuroko-Type Volcanogenic Massive Sulfide Deposits: An Example from Cerattepe-Artvin
Minerals 2021, 11(2), 226; https://doi.org/10.3390/min11020226 - 23 Feb 2021
Viewed by 832
Abstract
The eastern Pontide tectonic belt (EPTB) contains greater than 350 identified Kuroko type volcanogenic massive sulfide deposits/mineralization/occurrences (VMSD). The deposits are associated with Late Cretaceous felsic volcanics consisting mainly of dacitic and rhyolitic lavas and pyroclastics that outcrop within a narrow zone running [...] Read more.
The eastern Pontide tectonic belt (EPTB) contains greater than 350 identified Kuroko type volcanogenic massive sulfide deposits/mineralization/occurrences (VMSD). The deposits are associated with Late Cretaceous felsic volcanics consisting mainly of dacitic and rhyolitic lavas and pyroclastics that outcrop within a narrow zone running parallel to the eastern Black Sea coast and represent the axial zone of a paleo-magmatic arc. The Cerattepe deposit is the second-largest and is a hybrid VMS system with some epithermal features. To date, no geochemical research constrains the origin and timing of mineralization in the Cerattepe VMS deposit. Here, we provide Cu, O, H and S, isotope analysis of ores and alteration minerals to understand the hydrothermal history of the deposit and date the massive ore with Re-Os geochronology. Secondary weathering mobilized and redistributed metals in the deposit. The copper isotope signatures of shallow ores in the gossan follow patterns resulting from oxidative weathering of copper minerals with gossan Fe oxides of δ65Cu = −2.59‰, enrichment zone copper sulfide of d65Cu = +2.23 and +1.73‰, and primary ores of δ65Cu = +0.71 and +0.41‰. At the boundary of the enrichment zone, further cycling and migration of enrichment zone copper are evidenced by two samples having larger ranges of the δ65Cu = +3.59‰, and −2.93‰. Evidence for a magmatic source for fluids and S are evidenced by the O and H isotope values from quartz veins (δ18O = +7.93‰ to +10.82‰, and δD = −78‰ and −68‰) and sulfides that possess δ34S ratios of –5 and 0‰ from drill core samples. 187Os/188Os–187Re/188Os ratios from drill core sulfide samples of Cerattepe VMS deposit yields a 62±3 Ma isochron age and a highly radiogenic Os initial ratio. This age is compatible with silicate alteration ages from a proximal deposit and clearly shows mineralization occurs at a much younger time than previously proposed for VMS mineralization in the eastern Pontides. The new Re-Os age and source of Os imply that mineralization in the area occurs at a distinctly younger interval in the back-arc basin and metals could be sourced from the surrounding host rocks. Full article
(This article belongs to the Special Issue Mineral Deposits of the Balkan Peninsula and Western Turkey)
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Article
Experimental Study of Pt Solubility in the CO-CO2 Fluid at Low fO2 and Subsolidus Conditions of the Ultramafic-Mafic Intrusions
Minerals 2021, 11(2), 225; https://doi.org/10.3390/min11020225 - 23 Feb 2021
Cited by 3 | Viewed by 872
Abstract
The solubility of Pt in CO-CO2 fluid was studied experimentally at P = 50–200 MPa and T = 950 °C. A mixture of MgC2O4 and MgCO3 was used as a source of the fluid. Upon the reaction of [...] Read more.
The solubility of Pt in CO-CO2 fluid was studied experimentally at P = 50–200 MPa and T = 950 °C. A mixture of MgC2O4 and MgCO3 was used as a source of the fluid. Upon the reaction of the Pt capsule walls and the fluid, a carbonyl of platinum is formed. The use of the high-temperature quartz ceramics as a fluid trap avoids the effect of mechanical contamination with Pt from the eroded capsule walls. The total content of platinum in the porous fluid traps was measured by the Electrothermal Atomic Absorption (ET-AAS) method. In some experiments, the local analysis of traps was carried out by the Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) method. The composition of fluid in bubbles captured in an albite glass trap was studied by micro-Raman spectroscopy. On the capsule walls and MgO, Pt “whiskers” of submicron diameter were observed, which were formed as a product of carbonyl decomposition during quenching. About 5–15% of carbonyl withstands quenching resulting in 1.5 to 2 ppm Pt soluble in acetone (runs at P = 200 MPa) in a quartz glass trap. The amount of Pt soluble in acetone from the capsule walls corresponds to a concentration of up to 8 ppm in the fluid. A high content of soluble Pt of 2000–3000 ppm was determined in a carbon coated MgO matrix. Our study demonstrated that the solubility of Pt in the CO-CO2 fluid is 15–150 ppm, presumably in the form of Pt3(CO)62− under conditions corresponding to the conditions of the subsolidus stage of layered ultramafic-mafic and ultramafic-alkaline intrusions formation. Our preliminary data showed that this solubility will increase with the addition of water at low fO2. Full article
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Article
Characteristics of Metals Leached from Waste Printed Circuit Boards Using Acidithiobacillus ferrooxidans
Minerals 2021, 11(2), 224; https://doi.org/10.3390/min11020224 - 22 Feb 2021
Cited by 1 | Viewed by 820
Abstract
The aim of this study was to compare leaching characteristics of metals from printed circuit boards (PCBs), taken from waste electrical and electronic equipment in the presence and in the absence of the iron-oxidizing bacteria, Acidithiobacillus ferrooxidans. A. ferrooxidans not only increases the [...] Read more.
The aim of this study was to compare leaching characteristics of metals from printed circuit boards (PCBs), taken from waste electrical and electronic equipment in the presence and in the absence of the iron-oxidizing bacteria, Acidithiobacillus ferrooxidans. A. ferrooxidans not only increases the leached concentration of Cu from the PCBs, but also inhibits the components of the 0K medium and leached Cu from forming precipitates such as libethenite (Cu2(PO4)(OH)), thereby assisting Cu recovery from the PCBs. In addition, the leached concentration of Pb from PCBs decreased in the presence of A. ferrooxidans, due to Pb forming amorphous precipitates. It is expected that Pb is not highly toxic to A. ferrooxidans. Consequently, A. ferrooxidans can be used as a cost-effective and environmentally friendly way to leach out valuable metals from PCBs as low-grade urban ore. Full article
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Article
The Late Triassic Molasse Deposits in Central Jilin Province, NE China: Constraints on the Paleo-Asian Ocean Closure
Minerals 2021, 11(2), 223; https://doi.org/10.3390/min11020223 - 22 Feb 2021
Viewed by 662
Abstract
This paper presents a new detailed study including zircon U-Pb-Hf isotopic, whole-rock geochemical and Sr-Nd isotopic analyses of conglomerate and granitic pebbles from the molasse deposits in central Jilin Province, NE China. These data are used to better constrain the Late Permian–Triassic tectonic [...] Read more.
This paper presents a new detailed study including zircon U-Pb-Hf isotopic, whole-rock geochemical and Sr-Nd isotopic analyses of conglomerate and granitic pebbles from the molasse deposits in central Jilin Province, NE China. These data are used to better constrain the Late Permian–Triassic tectonic evolution regarding particularly the final closure of the Paleo-Asian Ocean (PAO) along the Changhun-Yanji suture (CYS). Zircon U-Pb data indicate that the granitic pebbles formed in the end-Permian (254–253 Ma). The youngest detrital zircon age of 231 Ma from the conglomerate, and presence of the overlying Upper Triassic Sihetun Formation suggests that the molasse deposits on the Jin′gui Island formed during the Late Triassic. The end-Permian granitic rocks display high SiO2 (66.07–74.77 wt %), with low MgO (0.55–2.05 wt %) and Mg# (31.61–43.64) values, together with depleted Hf and Nd isotopic values (εHf(t) = +1.61 to +11.62; εNd(t) = +3.3 to +4.2; (87Sr/86Sr)i = 0.706458–0.706842) and juvenile second-stage Hf model ages (1148–512 Ma), suggesting that they were probably generated by the partial melting of a Meso-Neoproterozoic juvenile metabasaltic lower crust. They are characterized by enrichments in large ion lithophile elements (LILEs) and depletions in high field strength elements (HFSEs), with affinities to igneous rocks forming in a subduction-related setting. This, combined with regional coeval subduction-related magmatic rocks, indicates that the PAO still existed along the CYS. In addition, the identification of Late Triassic molasse deposits on the Jin′gui Island in this study, coupled with occurrences of many Early Triassic syn-collisional granitoids along the CYS, indicates that the final closure of the PAO took place prior to the Late Triassic. Full article
(This article belongs to the Special Issue Isotope Dating and Geochemistry of Granite)
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Article
A Combined Soda Sintering and Microwave Reductive Roasting Process of Bauxite Residue for Iron Recovery
Minerals 2021, 11(2), 222; https://doi.org/10.3390/min11020222 - 22 Feb 2021
Cited by 1 | Viewed by 746
Abstract
In this study an integrated process is presented as a suitable method to transform Fe3+ oxides present in bauxite residue into magnetic oxides and metallic iron through a microwave roasting reduction, avoiding the formation of hercynite (FeAl2O4). In [...] Read more.
In this study an integrated process is presented as a suitable method to transform Fe3+ oxides present in bauxite residue into magnetic oxides and metallic iron through a microwave roasting reduction, avoiding the formation of hercynite (FeAl2O4). In the first step, all the alumina phases were transformed into sodium aluminates by adding sodium carbonate as a flux to BR and then leached out through alkali-leaching to recover alumina. Subsequently, the leaching residue was mixed with carbon and roasted by using a microwave furnace at the optimum conditions. The iron oxide present in the sinter was converted into metallic iron (98%). In addition, hercynite was not detected. The produced cinder was subjected to a wet high intensity magnetic separation process to separate iron from the other elements. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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Article
Analysis of the Effect of Payment Mechanism on Exploitation of Polymetallic Nodules in the Area
by , , , and
Minerals 2021, 11(2), 221; https://doi.org/10.3390/min11020221 - 21 Feb 2021
Cited by 1 | Viewed by 743
Abstract
The international seabed area (i.e., the “Area”) is rich in mineral resources. According to the United Nations Convention on the Law of the Sea (UNCLOS) and the relevant implemented agreements, in 2012, the International Seabed Authority (ISA) began to develop the regulations for [...] Read more.
The international seabed area (i.e., the “Area”) is rich in mineral resources. According to the United Nations Convention on the Law of the Sea (UNCLOS) and the relevant implemented agreements, in 2012, the International Seabed Authority (ISA) began to develop the regulations for the exploitation of mineral resources in the Area. The most important part of the regulations involves determining the distribution of benefits from the exploitation of mineral resources in the Area between the ISA and the contractors. The establishment of a financial model to evaluate the economic benefits and compare the distribution scheme was the basic method relied on in the current study of payment mechanism. According to the characteristics of the exploitation project of mineral resources in the Area, the discounted cash flow method was selected to construct the financial model. Taking China’s deep-sea mineral resources development project in the Area as the background, the main parameters of the model were determined. A comparative study of similar financial models with Massachusetts Institute of Technology (MIT) and other foreign countries was carried out, in addition to a sensitivity analysis of parameters. On the basis of the assurance that the contractor’s internal rate of return was not lower than the level of the land mining enterprise, the financial model was used to calculate the internal rate of return and the revenue of royalty under different payment mechanisms and rates. The advantages and disadvantages of different payment mechanisms in the exploitation of mineral resources in the area were analyzed. Lastly, the possible impacts of deep-sea polymetallic nodule mining on Terrestrial metal markets were highlighted. Full article
(This article belongs to the Special Issue Exploration of Polymetallic Nodules)
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Article
Enriched Co-Treatment of Pharmaceutical and Acidic Metal-Containing Wastewater with Nano Zero-Valent Iron
Minerals 2021, 11(2), 220; https://doi.org/10.3390/min11020220 - 20 Feb 2021
Cited by 2 | Viewed by 937
Abstract
Among traditional hazardous waste sources, pharmaceutical-containing wastewater and acidic mine drainage need treatment to preserve the expected water supply quality. A nano zero-valent iron (nZVI)-enriched treatment of these two streams is evaluated for simultaneous removal of various heavy metal ions, organic pollutants, sulfates, [...] Read more.
Among traditional hazardous waste sources, pharmaceutical-containing wastewater and acidic mine drainage need treatment to preserve the expected water supply quality. A nano zero-valent iron (nZVI)-enriched treatment of these two streams is evaluated for simultaneous removal of various heavy metal ions, organic pollutants, sulfates, the efficiency of the treatment system, and separation of reaction products in the fluidized-bed reactor. The reactor packed with silica sand was inoculated with sludge from an anaerobic digester, then 1–3 g/L of nZVI slurry added to cotreat a hospital feed and acid mine wastewater at 5:2 v/v. The biotreatment process is monitored through an oxidation–reduction potential (Eh) for 90 days. The removal pathway for the nZVI used co-precipitation, sorption, and reduction. The removal load for Zn and Mn was approximately 198 mg Zn/g Fe and 207 mg Mn/g Fe, correspondingly; achieving sulfate (removal efficiency of 94% and organic matter i.e., chemical oxygen demand (COD), biological oxygen demand (BOD), dissolved organic carbon (DOC), total dissolved nitrogen (TDN) reduced significantly, but ibuprofen and naproxen achieved 31% and 27% removal, respectively. This enriched cotreatment system exhibited a high reducing condition in the reactor, as confirmed by Eh; hence, the nZVI was dosed only a few times in biotreatment duration, demonstrating a cost-effective system. Full article
(This article belongs to the Special Issue Treatment, Beneficiation, and Valorization of Acid Mine Drainage)
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Article
Soil Biochemical Indicators and Biological Fertility in Agricultural Soils: A Case Study from Northern Italy
Minerals 2021, 11(2), 219; https://doi.org/10.3390/min11020219 - 20 Feb 2021
Cited by 2 | Viewed by 762
Abstract
Industrial farming without considering soil biological features could lead to soil degradation. We aimed to evaluate the biochemical properties (BPs) and biological fertility (BF) of different soils under processing tomato cultivation; estimate the BF through the calculation of a simplified BF index (BFIs); [...] Read more.
Industrial farming without considering soil biological features could lead to soil degradation. We aimed to evaluate the biochemical properties (BPs) and biological fertility (BF) of different soils under processing tomato cultivation; estimate the BF through the calculation of a simplified BF index (BFIs); determine if the crop was affected by BP and BF. Three farms were individuated in Modena (MO), Ferrara (MEZ) and Ravenna (RA) provinces, Italy. Soil analysis included total and labile organic C, microbial biomass-C (Cmic) and microbial respiration measurements. The metabolic (qCO2), mineralization (qM) and microbial (qMIC) quotients, and BFIs were calculated. Furthermore, plant nutrient contents were determined. The low Cmic content and qMIC, and high qCO2 found in MEZ soils indicate the occurrence of stressful conditions. The high qMIC and qM, and the low qCO2 demonstrated an efficient organic carbon incorporation as Cmic in MO soils. In RA soils, the low total and labile organic C contents limited the Cmic and microbial respiration. Therefore, as confirmed by the BFIs, while MO showed the healthiest soils, RA soils had an inefficient ecophysiological energy state. However, no effects on plant nutrient contents were observed, likely because of masked by fertigation. Finally, BP monitoring is needed in order to avoid soil degradation and, in turn, crop production decline. Full article
(This article belongs to the Special Issue Elemental and Isotope Geochemistry of the Earth’s Critical Zone)
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Article
Three-Dimensional Anisotropic Inversions for Time-Domain Airborne Electromagnetic Data
Minerals 2021, 11(2), 218; https://doi.org/10.3390/min11020218 - 20 Feb 2021
Viewed by 695
Abstract
Rocks and ores in nature usually appear macro-anisotropic, especially in sedimentary areas with strong layering. This anisotropy will lead to false interpretation of electromagnetic (EM) data when inverted under the assumption of an isotropic earth. However, the time-domain (TD) airborne EM (AEM) inversion [...] Read more.
Rocks and ores in nature usually appear macro-anisotropic, especially in sedimentary areas with strong layering. This anisotropy will lead to false interpretation of electromagnetic (EM) data when inverted under the assumption of an isotropic earth. However, the time-domain (TD) airborne EM (AEM) inversion for an anisotropic model has not attracted much attention. To get reasonable inversion results from TD AEM data, we present in this paper the forward modeling and inversion methods based on a triaxial anisotropic model. We apply three-dimensional (3D) finite-difference on the secondary scattered electric field equation to calculate the frequency-domain (FD) EM responses, then we use the inverse Fourier transform and waveform convolution to obtain TD responses. For the regularized inversion, we calculate directly the sensitivities with respect to three diagonal conductivities and then use the Gauss–Newton (GN) optimization scheme to recover model parameters. To speed up the computation and to reduce the memory requirement, we adopt the moving footprint concept and separate the whole model into a series of small sub-models for the inversion. Finally, we compare our anisotropic inversion scheme with the isotropic one using both synthetic and field data. Numerical experiments show that the anisotropic inversion has inherent advantages over the isotropic ones, we can get more reasonable results for the anisotropic earth structures. Full article
(This article belongs to the Special Issue 3D-Modelling of Crustal Structures and Mineral Deposit Systems)
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Article
Kinetic Energy Calculation in Granite Particles Comminution Considering Movement Characteristics and Spatial Distribution
Minerals 2021, 11(2), 217; https://doi.org/10.3390/min11020217 - 20 Feb 2021
Viewed by 605
Abstract
Profound knowledge of the movement characteristics and spatial distribution of the particles under compression during the crushing of rocks and ores is essential to further understanding kinetic energy release law. Various experimental methods such as high-speed camera technology, the coordinate method, and the [...] Read more.
Profound knowledge of the movement characteristics and spatial distribution of the particles under compression during the crushing of rocks and ores is essential to further understanding kinetic energy release law. Various experimental methods such as high-speed camera technology, the coordinate method, and the color tracking method were adopted to improve the understanding of particles’ movement characteristics and spatial distribution in rock comminution. The average horizontal velocities of the four size particles α, β, γ, and δ are statistically calculated. The descending order of the particles’ average velocity is γ, β, α, and δ. In comparison, the descending order of the particles’ kinetic energy is α, β, γ, and δ. Moreover, the contribution of α particles to the total kinetic energy exceeds 70%. The spatial distribution characteristics of coarse and fine particles show different results. The probability of fine particles appearing in the range closer to the center area is greater, while the position of large particles appears to be more random. The color tracking results show that super-large particles generated by crushing are on the specimen’s surface, while small particles are generally produced from inside. The above results indicate a connection between the particle generation mechanism, movement characteristics, and spatial distribution in the comminution process. Full article
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Article
Mineralogical and Chemical Specificity of Dusts Originating from Iron and Non-Ferrous Metallurgy in the Light of Their Magnetic Susceptibility
Minerals 2021, 11(2), 216; https://doi.org/10.3390/min11020216 - 20 Feb 2021
Cited by 2 | Viewed by 763
Abstract
This study aims at detailed characteristics and comparison between dusts from various iron and non-ferrous metal production processes in order to identify individual mineral phases, chemical composition, and their influence on the values of magnetic susceptibility. Various analytical methods used include inductively coupled [...] Read more.
This study aims at detailed characteristics and comparison between dusts from various iron and non-ferrous metal production processes in order to identify individual mineral phases, chemical composition, and their influence on the values of magnetic susceptibility. Various analytical methods used include inductively coupled plasma optical emission spectroscopy, X-ray diffraction, scanning electron microscopy, and Mössbauer spectroscopy integrated with magnetic susceptibility measurements and thermomagnetic analysis. Metallurgical wastes that have arisen at different production stages of iron and non-ferrous steel are subjected to investigation. The analyzed dust samples from the iron and non-ferrous metallurgy differ in terms of magnetic susceptibility as well as their mineral and chemical composition. The research confirmed the presence of many very different mineral phases. In particular, interesting phases have been observed in non-ferrous dust, for example challacolloite, which was found for the first time in the dusts of non-ferrous metallurgy. Other characteristic minerals found in non-ferrous metallurgy dusts are zincite, anglesite, and lanarkite, while dusts of iron metallurgy contain mostly metallic iron and iron-bearing minerals (magnetite, hematite, franklinite, jacobsite, and wüstite), but also significant amounts of zincite and calcite. Full article
(This article belongs to the Special Issue Natural and Technogenic Magnetic Particles in the Environment)
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Article
Gel Formation at the Front of Expanding Calcium Bentonites
Minerals 2021, 11(2), 215; https://doi.org/10.3390/min11020215 - 20 Feb 2021
Cited by 1 | Viewed by 688
Abstract
The removal of potentially harmful radioactive waste from the anthroposphere will require disposal in geological repositories, the designs of which often favour the inclusion of a clay backfill or engineered barrier around the waste. Bentonite is often proposed as this engineered barrier and [...] Read more.
The removal of potentially harmful radioactive waste from the anthroposphere will require disposal in geological repositories, the designs of which often favour the inclusion of a clay backfill or engineered barrier around the waste. Bentonite is often proposed as this engineered barrier and understanding its long-term performance and behaviour is vital in establishing the safety case for its usage. There are many different compositions of bentonite that exist and much research has focussed on the properties and behaviour of both sodium (Na) and calcium (Ca) bentonites. This study focusses on the results of a swelling test on Bulgarian Ca bentonite that showed an unusual gel formation at the expanding front, unobserved in previous tests of this type using the sodium bentonite MX80. The Bulgarian Ca bentonite was able to swell to completely fill an internal void space over the duration of the test, with a thin gel layer present on one end of the sample. The properties of the gel, along with the rest of the bulk sample, have been investigated using ESEM, EXDA and XRD analyses and the formation mechanism has been attributed to the migration of nanoparticulate smectite through a more silica-rich matrix of the bentonite substrate. The migration of smectite clay out of the bulk of the sample has important implications for bentonite erosion where this engineered barrier interacts with flowing groundwater in repository host rocks. Full article
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Review
REEs in the North Africa P-Bearing Deposits, Paleoenvironments, and Economic Perspectives: A Review
Minerals 2021, 11(2), 214; https://doi.org/10.3390/min11020214 - 19 Feb 2021
Cited by 2 | Viewed by 1488
Abstract
A review of the compositional features of Tunisia, Algeria, and Morocco phosphorites is proposed in order to assess and compare the paleoenvironmental conditions that promoted the deposit formation as well as provide information about their economic perspective in light of growing worldwide demand. [...] Read more.
A review of the compositional features of Tunisia, Algeria, and Morocco phosphorites is proposed in order to assess and compare the paleoenvironmental conditions that promoted the deposit formation as well as provide information about their economic perspective in light of growing worldwide demand. Since these deposits share a very similar chemical and mineralogical composition, the attention was focused on the geochemistry of rare earth elements (REEs) and mostly on ΣREEs, Ce and Eu anomalies, and (La/Yb) and (La/Gd) normalized ratios. The REEs distributions reveal several differences between deposits from different locations, suggesting mostly that the Tunisian and Algerian phosphorites probably were part of the same depositional system. There, sub-reducing to sub-oxic conditions and a major REEs adsorption by early diagenesis were recorded. Conversely, in the Moroccan basins, sub-oxic to oxic environments and a minor diagenetic alteration occurred, which was likely due to a different seawater supply. Moreover, the drastic environmental changes associated to the Paleocene–Eocene Thermal Maximum event probably influenced the composition of Northern African phosphorites that accumulated the highest REEs amounts during that span of time. Based on the REEs concentrations, and considering the outlook coefficient of REE composition (Koutl) and the percentage of critical elements in ΣREEs (REEdef), the studied deposits can be considered as promising to highly promising REE ores and could represent a profitable alternative source for critical REEs. Full article
(This article belongs to the Special Issue Feature Papers in Mineral Deposits 2020)
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Article
Mechanical Behavior of Hydroxyapatite-Chitosan Composite: Effect of Processing Parameters
Minerals 2021, 11(2), 213; https://doi.org/10.3390/min11020213 - 19 Feb 2021
Cited by 2 | Viewed by 1114
Abstract
Three-dimensional hydroxyapatite-chitosan (HA-CS) composites were formulated via solid-liquid technic and freeze-drying. The prepared composites had an apatitic nature, which was demonstrated by X-ray diffraction and Infrared spectroscopy analyses. The impact of the solid/liquid (S/L) ratio and the content and the molecular weight of [...] Read more.
Three-dimensional hydroxyapatite-chitosan (HA-CS) composites were formulated via solid-liquid technic and freeze-drying. The prepared composites had an apatitic nature, which was demonstrated by X-ray diffraction and Infrared spectroscopy analyses. The impact of the solid/liquid (S/L) ratio and the content and the molecular weight of the polymer on the composite mechanical strength was investigated. An increase in the S/L ratio from 0.5 to 1 resulted in an increase in the compressive strength for HA-CSL (CS low molecular weight: CSL) from 0.08 ± 0.02 to 1.95 ± 0.39 MPa and from 0.3 ± 0.06 to 2.40 ± 0.51 MPa for the HA-CSM (CS medium molecular weight: CSM). Moreover, the increase in the amount (1 to 5 wt%) and the molecular weight of the polymer increased the mechanical strength of the composite. The highest compressive strength value (up to 2.40 ± 0.51 MPa) was obtained for HA-CSM (5 wt% of CS) formulated at an S/L of 1. The dissolution tests of the HA-CS composites confirmed their cohesion and mechanical stability in an aqueous solution. Both polymer and apatite are assumed to work together, giving the synergism needed to make effective cylindrical composites, and could serve as a promising candidate for bone repair in the orthopedic field. Full article
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Article
Volumetric Quantification and Quality of Water Stored in a Mining Lake: A Case Study at Reocín Mine (Spain)
Minerals 2021, 11(2), 212; https://doi.org/10.3390/min11020212 - 18 Feb 2021
Viewed by 710
Abstract
This study deals with the potential use of water stored in a lake formed by Reocín’s old zinc mine, which has become the second most important reservoir in Cantabria, with a flow of 1300 L s−1. The methodology used is based [...] Read more.
This study deals with the potential use of water stored in a lake formed by Reocín’s old zinc mine, which has become the second most important reservoir in Cantabria, with a flow of 1300 L s−1. The methodology used is based on the hydrogeological and hydrochemical characterization of the area studied. A total of 16 piezometers were installed to monitor the amount and quality of water. Results obtained show a pH close to 8 and iron, manganese, zinc, and sulphate concentrations lower than 0.05 mg L−1, 0.05 mg L−1, 1.063 mg L−1, and 1305.5 mg L−1, respectively. The volume of the water stored in the lake amounts to 34 hm3. Measurements show that Fe, Mn, and Zn concentrations are below the limits acceptable for human consumption, according to the Spanish 0.2, 0.05, and 5.0 mg L−1 standards, respectively, while sulphate greatly exceeds the 250 mg L−1 limit accepted by the norm. Therefore, the water could be apt for human consumption after a treatment appropriate for decreasing the sulphate level by, for example, reverse osmosis, distillation, or ion exchange. Although industrial and energy uses are possible, the lake water could be utilized as a geothermal energy source. The management of the hydric resources generated when a mine is closed could improve the economic and environmental conditions of the zone, with all the benefits it brings about, thus allowing for compensating of the pumping cost that environmental protection entails, creating, at the same time, a new business opportunity for the company that owns the mine. Full article
(This article belongs to the Special Issue Risks Assessment, Management and Control of Mining Contamination)
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Article
Stepwise Utilization Process to Recover Valuable Components from Copper Slag
Minerals 2021, 11(2), 211; https://doi.org/10.3390/min11020211 - 17 Feb 2021
Cited by 2 | Viewed by 891
Abstract
Waste copper slag is a typical hazardous solid waste containing a variety of valuable elements and has not been effectively disposed of so far. In this paper, a stepwise extraction process was proposed to recover valuable elements (copper, iron, lead and zinc) from [...] Read more.
Waste copper slag is a typical hazardous solid waste containing a variety of valuable elements and has not been effectively disposed of so far. In this paper, a stepwise extraction process was proposed to recover valuable elements (copper, iron, lead and zinc) from waste copper slag. The specific procedures are as follows: (1) A flotation process was adopted to enrich copper, and when the copper grade in the flotation concentrate was 21.50%, the copper recovery rate was 77.78%. (2) The flotation tailings were pelletized with limestone, then the green pellets were reduced, and the magnetic separation process was carried out. When the iron and copper grades in the magnetic concentrate were 90.21% Fe and 0.4% Cu, 91.34% iron and 83.41% copper were recovered, respectively. (3) Non-magnetic tailings were mixed with clinker and standard sand to produce common Portland cement. Several products were obtained from the waste copper slag through the proposed process: flotation concentrate, measured 21.50% Cu; magnetic concentrate, containing 90.21% TFe and 0.4% Cu; direct reduction dust, including 65.17% ZnO and 2.66% PbO; common Portland cement for building construction. The comprehensive utilization method for waste copper slag achieved zero tailing and has great potential for practical application. Full article
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Article
Invasive and Non-Invasive Analyses of Ochre and Iron-Based Pigment Raw Materials: A Methodological Perspective
Minerals 2021, 11(2), 210; https://doi.org/10.3390/min11020210 - 17 Feb 2021
Cited by 2 | Viewed by 875
Abstract
Naturally occurring and deeply coloured iron-bearing materials were exploited very early on by human populations. The characterization of these materials has proven useful for addressing several archaeological issues, such as the study of technical behaviors, group mobility, and the reconstruction of cultural dynamics. [...] Read more.
Naturally occurring and deeply coloured iron-bearing materials were exploited very early on by human populations. The characterization of these materials has proven useful for addressing several archaeological issues, such as the study of technical behaviors, group mobility, and the reconstruction of cultural dynamics. However, this work poses some critical methodological questions. In this paper, we will review ochre studies by focusing on the analytical methods employed, the limits of non-invasive methods, as well as examples of some quality research addressing specific issues (raw material selection and provenience, heat treatment). We will then present a methodological approach that aims to identify the instrumental limits and the post-depositional alterations that significantly impact the results of the non-invasive analysis of cohesive ochre fragments from Diepkloof rock Shelter, South Africa. We used ochre materials recuperated in both archaeological and geological contexts, and we compared non-invasive surface analyses by XRD, scanning electron microscopy coupled with dispersive X-ray spectrometry (SEM-EDXS), and particle-induced X-ray emission (PIXE) with invasive analysis of powder pellets and sections from the same samples. We conclude that non-invasive SEM-EDXS and PIXE analyses provide non-representative results when the number of measurements is too low and that post-depositional alterations cause significant changes in the mineralogical and major element composition at the surface of archaeological pieces. Such biases, now identified, must be taken into account in future studies in order to propose a rigorous framework for developing archaeological inferences. Full article
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Article
Genetic Link between Podiform Chromitites in the Mantle and Stratiform Chromitites in the Crust: A Hypothesis
Minerals 2021, 11(2), 209; https://doi.org/10.3390/min11020209 - 16 Feb 2021
Cited by 1 | Viewed by 2024
Abstract
No genetic link between the two main types of chromitite, stratiform and podiform chromitites, has ever been discussed. These two types of chromitite have very different geological contexts; the stratiform one is a member of layered intrusions, representing fossil magma chambers, in the [...] Read more.
No genetic link between the two main types of chromitite, stratiform and podiform chromitites, has ever been discussed. These two types of chromitite have very different geological contexts; the stratiform one is a member of layered intrusions, representing fossil magma chambers, in the crust, and the podiform one forms pod-like bodies, representing fossil magma conduits, in the upper mantle. Chromite grains contain peculiar polymineralic inclusions derived from Na-bearing hydrous melts, whose features are so similar between the two types that they may form in a similar fashion. The origin of the chromite-hosted inclusions in chromitites has been controversial but left unclear. The chromite-hosted inclusions also characterize the products of the peridotite–melt reaction or melt-assisted partial melting, such as dunites, troctolites and even mantle harzburgites. I propose a common origin for the inclusion-bearing chromites, i.e., a reaction between the mantle peridotite and magma. Some of the chromite grains in the stratiform chromitite originally formed in the mantle through the peridotite–magma reaction, possibly as loose-packed young podiform chromitites, and were subsequently disintegrated and transported to a crustal magma chamber as suspended grains. It is noted, however, that the podiform chromitites left in the mantle beneath the layered intrusions are different from most of the podiform chromitites now exposed in the ophiolites. Full article
(This article belongs to the Special Issue Chromite Deposits: Mineralogy, Petrology and Genesis)
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Article
Measurement on Diffusion Coefficients and Isotope Fractionation Factors by a Through-Diffusion Experiment
Minerals 2021, 11(2), 208; https://doi.org/10.3390/min11020208 - 16 Feb 2021
Viewed by 663
Abstract
For radioactive waste disposal, it is important that local groundwater flow is slow as groundwater flow is the main transport medium for radioactive nuclides in geological formations. When the groundwater flow is very slow, diffusion is the dominant transport mechanism (diffusion-dominant domain). Key [...] Read more.
For radioactive waste disposal, it is important that local groundwater flow is slow as groundwater flow is the main transport medium for radioactive nuclides in geological formations. When the groundwater flow is very slow, diffusion is the dominant transport mechanism (diffusion-dominant domain). Key pieces of evidence indicating a diffusion-dominant domain are the separation of components and the fractionation of isotopes by diffusion. To prove this, it is necessary to investigate the different diffusion coefficients for each component and the related stable isotope fractionation factors. Thus, in this study, through-diffusion and effective-porosity experiments were conducted on selected artificial materials and natural rocks. We also undertook measurements relating to the isotope fractionation factors of Cl and Br isotopes for natural samples. For natural rock samples, the diffusion coefficients of water isotopes (HDO and H218O) were three to four times higher than those of monovalent anions (Cl, Br- and NO3), and the isotope fractionation factor of 37Cl (1.0017–1.0021) was slightly higher than that of free water. It was experimentally confirmed that the isotope fractionation factor of 81Br was approximately 1.0007–1.0010, which is equivalent to that of free water. The enrichment factor of 81Br was almost half that of 37Cl. The effective porosity ratios of HDO and Cl were slightly different, but the difference was not significant compared to the ratio of their diffusion coefficients. As a result, component separation was dominated by diffusion. For artificial samples, the diffusion coefficients and effective porosities of HDO and Cl were almost the same; it was thus difficult to assess the component separation by diffusion. However, isotope fractionation of Cl and Br was confirmed using a through-diffusion experiment. The results show that HDO and Cl separation and isotope fractionation of Cl and Br can be expected in diffusion-dominant domains in geological formations. Full article
(This article belongs to the Special Issue Halogen Stable Isotope Studies in Geological Processes)
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Article
Structural and High-Pressure Properties of Rheniite (ReS2) and (Re,Mo)S2
Minerals 2021, 11(2), 207; https://doi.org/10.3390/min11020207 - 16 Feb 2021
Cited by 1 | Viewed by 922
Abstract
Rhenium disulfide (ReS2), known in nature as the mineral rheniite, is a very interesting compound owing to its remarkable fundamental properties and great potential to develop novel device applications. Here we perform density functional theory (DFT) calculations to investigate the structural [...] Read more.
Rhenium disulfide (ReS2), known in nature as the mineral rheniite, is a very interesting compound owing to its remarkable fundamental properties and great potential to develop novel device applications. Here we perform density functional theory (DFT) calculations to investigate the structural properties and compression behavior of this compound and also of the (Re,Mo)S2 solid solution as a function of Re/Mo content. Our theoretical analysis is complemented with high-pressure X-ray diffraction (XRD) measurements, which have allowed us to reevaluate the phase transition pressure and equation of state of 1T-ReS2. We have observed the 1T-to-1T’ phase transition at pressures as low as ~2 GPa, and we have obtained an experimental bulk modulus, B0, equal to 46(2) GPa. This value is in good agreement with PBE+D3 calculations, thus confirming the ability of this functional to model the compression behavior of layered transition metal dichalcogenides, provided that van der Waals corrections are taken into account. Our experimental data and analysis confirm the important role played by van der Waals effects in the high-pressure properties of 1T-ReS2. Full article
(This article belongs to the Special Issue First Principles Calculations of Minerals and Related Materials)
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Article
Secondary Sulfates from the Monte Arsiccio Mine (Apuan Alps, Tuscany, Italy): Trace-Element Budget and Role in the Formation of Acid Mine Drainage
Minerals 2021, 11(2), 206; https://doi.org/10.3390/min11020206 - 15 Feb 2021
Cited by 2 | Viewed by 857
Abstract
A suite of sulfate minerals from the Monte Arsiccio mine (Apuan Alps, Northern Tuscany, Italy), previously identified by using both X-ray diffraction and micro-Raman spectroscopy, was studied through inductively coupled plasma mass spectrometry (ICP-MS), in order to determine their trace-element content. Several elements [...] Read more.
A suite of sulfate minerals from the Monte Arsiccio mine (Apuan Alps, Northern Tuscany, Italy), previously identified by using both X-ray diffraction and micro-Raman spectroscopy, was studied through inductively coupled plasma mass spectrometry (ICP-MS), in order to determine their trace-element content. Several elements (Tl, Rb, As, Sb, Co, Ni, Cu, Zn, and Cr) were found above the detection limits. Among them, some are important from an environmental perspective and may reach relatively high concentrations (e.g., Tl = 1370–2988 μg/g; As = 505–1680 μg/g). Thus, these sulfates may act as transient sinks for some of these potentially toxic elements, as well as for sulfate ions and acidity. Indeed, dissolution experiments revealed the ability of these secondary minerals to produce a significant pH decrease of the solutions, as well as the release of Fe, Al, and K as major ions. This work discusses the relation between the budget of trace elements and the crystal chemistry of sulfate minerals and provides new insights about the environmental role played by the sulfate dissolution in controlling the quality of water in acid mine drainage systems. Full article
(This article belongs to the Special Issue Sulfates: Crystal-Chemistry and Their Geological Significance)
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Article
Characterization of Fines Produced by Degradation of Polymetallic Nodules from the Clarion–Clipperton Zone
Minerals 2021, 11(2), 205; https://doi.org/10.3390/min11020205 - 15 Feb 2021
Cited by 1 | Viewed by 846
Abstract
The discharge of fluid–particle mixture tailings can cause serious disturbance to the marine environment in deep-sea mining of polymetallic nodules. Unrecovered nodule fines are one of the key components of the tailings, but little information has been gained on their properties. Here, we [...] Read more.
The discharge of fluid–particle mixture tailings can cause serious disturbance to the marine environment in deep-sea mining of polymetallic nodules. Unrecovered nodule fines are one of the key components of the tailings, but little information has been gained on their properties. Here, we report major, trace, and rare earth element compositions of <63 μm particles produced by the experimental degradation of two types of polymetallic nodules from the Clarion–Clipperton Zone. Compared to the bulk nodules, the fines produced are enriched in Al, K, and Fe and depleted in Mn, Co, Ni, As, Mo, and Cd. The deviation from the bulk composition of original nodules is particularly pronounced in the finer fraction of particles. With X-ray diffraction patterns showing a general increase in silicate and aluminosilicates in the fines, the observed trends indicate a significant contribution of sediment particles released from the pores and cracks of nodules. Not only the amount but also the composition of nodule fines is expected to significantly differ depending on the minimum recovery size of particles at the mining vessel. Full article
(This article belongs to the Special Issue Exploration of Polymetallic Nodules)
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Article
The Solution Interaction of Tetrathionate Ions and Sodium Isobutyl Xanthate and Its Effect on the Flotation of Galena and Chalcopyrite
Minerals 2021, 11(2), 204; https://doi.org/10.3390/min11020204 - 15 Feb 2021
Viewed by 641
Abstract
Tetrathionates have been found in significantly high concentrations in recycled process waters from massive sulphide ore processing plants. These polythionates react with xanthate added to flotation pulps thus reducing xanthate dosages in solution potentially affecting flotation performance. The current study focused on the [...] Read more.
Tetrathionates have been found in significantly high concentrations in recycled process waters from massive sulphide ore processing plants. These polythionates react with xanthate added to flotation pulps thus reducing xanthate dosages in solution potentially affecting flotation performance. The current study focused on the effect of the tetrathionate-xanthate reaction on sulphide mineral recoveries. Ore dissolution studies confirmed the generation of tetrathionates by copper-lead-zinc ores. In 20 min, the tetrathionates consumed more than half of the xanthate in solution at pH 7. Rest potential measurements and Fourier transform infrared spectroscopy (FTIR) showed that the degree of collector-mineral interactions of xanthate and both galena and chalcopyrite was greatly reduced in the presence of a 2000 mg/L tetrathionate solution. Microflotation tests showed that chalcopyrite recovery was less sensitive to tetrathionates as indicated by small changes in mineral recoveries. Galena was sensitive to the action of tetrathionates on the mineral surface as the galena recovery significantly declined when floated with xanthate as a collector in both a 500 mg/L tetrathionate solution and a 2000 mg/L tetrathionate solution. These fundamental results lay a sound base on which more discussion into the significance and the effect of tetrathionates on flotation performance of sulphide ores can be developed. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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Review
An Overview of the Geochemical Characteristics of Oceanic Carbonatites: New Insights from Fuerteventura Carbonatites (Canary Islands)
Minerals 2021, 11(2), 203; https://doi.org/10.3390/min11020203 - 15 Feb 2021
Cited by 1 | Viewed by 1047
Abstract
The occurrence of carbonatites in oceanic settings is very rare if compared with their continental counterpart, having been reported only in Cape Verde and Canary Islands. This paper provides an overview of the main geochemical characteristics of oceanic carbonatites, around which many debates [...] Read more.
The occurrence of carbonatites in oceanic settings is very rare if compared with their continental counterpart, having been reported only in Cape Verde and Canary Islands. This paper provides an overview of the main geochemical characteristics of oceanic carbonatites, around which many debates still exist regarding their petrogenesis. We present new data on trace elements in minerals and whole-rock, together with the first noble gases isotopic study (He, Ne, Ar) in apatite, calcite, and clinopyroxene from Fuerteventura carbonatites (Canary Islands). Trace elements show a similar trend as Cape Verde carbonatites, almost tracing the same patterns on multi-element and REE abundance diagrams. 3He/4He isotopic ratios of Fuerteventura carbonatites reflect a shallow (sub-continental lithospheric mantle, SCLM) He signature in their petrogenesis, and they clearly differ from Cape Verde carbonatites, i.e., fluids from a deep and low degassed mantle with a primitive plume-derived He signature are involved in their petrogenesis. Full article
(This article belongs to the Special Issue 10th Anniversary of Minerals: Frontiers of Mineral Science)
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Article
Cation Disorder Caused by Olivine-Ringwoodite Phase Transition Mechanism, Possible Explanation for Blue Olivine Inclusion in a Diamond
Minerals 2021, 11(2), 202; https://doi.org/10.3390/min11020202 - 15 Feb 2021
Viewed by 1327
Abstract
Synchrotron X-ray diffraction, as well as visual observations, in a diamond anvil cell (DAC) using soft metal gaskets or slightly reducing gas environment, have revealed that the olivine-ringwoodite transition in olivines of several compositions take place in two steps: step 1: displacive restacking [...] Read more.
Synchrotron X-ray diffraction, as well as visual observations, in a diamond anvil cell (DAC) using soft metal gaskets or slightly reducing gas environment, have revealed that the olivine-ringwoodite transition in olivines of several compositions take place in two steps: step 1: displacive restacking of the oxygen layers, followed by step 2: diffusive reordering of the cations. The initiation of the phase transition was observed at temperatures as low as 200 °C below the reported temperature for the phase transition under hydrostatic conditions. These observations, especially residual disordered cations, have important implications for deep-focus earthquakes, the ability of ringwoodite to host surprising amounts of water, and possibly the observation of a blue olivine inclusion in a natural diamond from Brazil and in a pallasitic meteorite from Russia. Full article
(This article belongs to the Special Issue Structural Characterization of Earth Materials at Extreme Conditions)
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Communication
Gypsum Amendment Induced Rapid Pyritization in Fe-Rich Mine Tailings from Doce River Estuary after the Fundão Dam Collapse
Minerals 2021, 11(2), 201; https://doi.org/10.3390/min11020201 - 14 Feb 2021
Cited by 2 | Viewed by 971
Abstract
Mine tailings containing trace metals arrived at the Doce River estuary, after the world’s largest mine tailings disaster (the Mariana disaster) dumped approximately 50 million m3 of Fe-rich tailings into the Doce River Basin. The metals in the tailings are of concern [...] Read more.
Mine tailings containing trace metals arrived at the Doce River estuary, after the world’s largest mine tailings disaster (the Mariana disaster) dumped approximately 50 million m3 of Fe-rich tailings into the Doce River Basin. The metals in the tailings are of concern because they present a bioavailability risk in the estuary as well as chronic exposure hazards. Trace metal immobilization into sulfidic minerals, such as, pyrite, plays a key role in estuarine soils; however, this process is limited in the Doce River estuarine soil due to low sulfate inputs. Thus, to assess the use of gypsum amendment to induce pyritization in deposited tailings, a mesocosm experiment was performed for 35 days, with vinasse added as carbon source and doses of gypsum (as a sulfate source). Chemical and morphological evidence of Fe sulfide mineral precipitation was observed. For instance, the addition of 439 mg of S led to the formation of gray and black spots, an Fe2+ increase and decrease in sulfides in the solution, an increase in pyritic Fe, and a greater Pb immobilization by pyrite at the end of the experiment. The results show that induced pyritization may be a strategy for remediating metal contamination at the Doce River estuary. Full article
(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)
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Article
Aspects of Estimation and Reporting of Mineral Resources of Seabed Polymetallic Nodules: A Contemporaneous Case Study
Minerals 2021, 11(2), 200; https://doi.org/10.3390/min11020200 - 14 Feb 2021
Cited by 3 | Viewed by 1123
Abstract
Exploration of seabed polymetallic nodules identifies the Clarion Clipperton Zone and the Indian Ocean Nodule Field to be of economic interest. Mineral resource estimation is important to the owner of the resource (all of mankind; and managed by the International Seabed Authority; ISA) [...] Read more.
Exploration of seabed polymetallic nodules identifies the Clarion Clipperton Zone and the Indian Ocean Nodule Field to be of economic interest. Mineral resource estimation is important to the owner of the resource (all of mankind; and managed by the International Seabed Authority; ISA) and to developers (commercial and government groups holding contracts with the ISA). The Committee for Mineral Reserves International Reporting Standards was developed for the land-based minerals industry and adapted in 2015 for ISA-managed nodules. Nodules can be sampled in a meaningful manner using mechanical devices, albeit with minor issues of bias. Grade and moisture content are measured using the established methodology for land-based minerals. Tonnage of resource is determined via the abundance of nodules in kilograms per square metre of seabed. This can be estimated from physical samples and, in some cases, from photographs. Contemporary resource reporting for nodules classify the level of confidence in the estimate, by considering deposit geology, sample geostatistics, etc. The reporting of estimates also addresses reasonable prospects for eventual economic extraction, including factors such as mining technology, the marine environment, metallurgical processing, and metals markets. Other requirements are qualified persons responsible for estimation and reporting, site inspection, and sample chain of custody. Full article
(This article belongs to the Special Issue Exploration of Polymetallic Nodules)
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