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Minerals, Volume 7, Issue 5 (May 2017) – 21 articles

Cover Story (view full-size image): We quantified the rates of volume reduction of sulfide mineral grains in low grade agglomerated copper bearing ores. Using X-ray tomography to allow non-disrupted column leaching experiments. We determine the heterogeneity in the leaching behaviour, as overall bulk reductions mask significant mm3 to cm3 scale variability in leaching, and so obscures the complex processes operating in real heap-leaching systems and limits our ability to improve leaching protocols. View this paper
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Article
Insights into Ferric Leaching of Low Grade Metal Sulfide-Containing ores in an Unsaturated Ore Bed Using X-ray Computed Tomography
Minerals 2017, 7(5), 85; https://doi.org/10.3390/min7050085 - 22 May 2017
Cited by 10 | Viewed by 2401
Abstract
The distribution of the metal-bearing mineral grains within a particulate ore prepared for leaching, and the impact of this spatial heterogeneity on overall extraction efficiency is of key importance to a mining industry that must continuously target ever-reducing grades and more complex ore [...] Read more.
The distribution of the metal-bearing mineral grains within a particulate ore prepared for leaching, and the impact of this spatial heterogeneity on overall extraction efficiency is of key importance to a mining industry that must continuously target ever-reducing grades and more complex ore bodies. If accessibility and recovery of the target minerals is to be improved, a more detailed understanding of the behaviour of the system must be developed. We present an in situ analysis using X-ray computed tomography to quantify the rates of volume reduction of sulfide mineral grains in low grade agglomerated copper bearing ores during a miniature laboratory scale column leaching experiment. The data shows the scale of the heterogeneity in the leaching behaviour, with an overall reduction of sulphide mineral grains of 50%, but that this value masks significant mm3 to cm3 scale variability in reduction. On the scale of individual ore fragments, leaching efficiency ranged from 22% to 99%. We use novel quantitative methods to determine the volume fraction of the sulfide that is accessible to the leachate solution. Full article
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Article
Geochemistry and Stable Isotopes of Travertine from Jordan Valley and Dead Sea Areas
Minerals 2017, 7(5), 82; https://doi.org/10.3390/min7050082 - 22 May 2017
Cited by 3 | Viewed by 2451
Abstract
Travertine deposits in Deir Alla, Suwayma, and Az Zara areas were investigated. Mineralogy, geochemistry, stable isotopes and age dating indicate the presence of low-Mg calcite, with minor quartz components. The variable isotope (δ13C and δ18O) signatures indicate dependence on [...] Read more.
Travertine deposits in Deir Alla, Suwayma, and Az Zara areas were investigated. Mineralogy, geochemistry, stable isotopes and age dating indicate the presence of low-Mg calcite, with minor quartz components. The variable isotope (δ13C and δ18O) signatures indicate dependence on water temperature and water/rock isotopic exchange. In contrast, the high δ13C values in some travertine samples reflect 12CO2 degassing processes, increased input of 13C-enriched groundwater, and the presence of surface and groundwater hydrological systems. The high δ18O values may be attributed to evaporation effects and low water temperature during the formation of localized travertine. The age of travertine is the Late Pleistocene. Full article
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Article
Kinetic Study of the Leaching of Low-Grade Manganese Ores by Using Pretreated Sawdust as Reductant
Minerals 2017, 7(5), 83; https://doi.org/10.3390/min7050083 - 20 May 2017
Cited by 14 | Viewed by 2121
Abstract
The reductive leaching of manganese from a low-grade manganese oxide ore was investigated by using pretreated sawdust as the reductant in a sulfuric acid medium. The effects of stirring speed, liquid/solid ratio, sawdust/ore mass ratio, sulfuric acid concentration, reaction temperature, and time on [...] Read more.
The reductive leaching of manganese from a low-grade manganese oxide ore was investigated by using pretreated sawdust as the reductant in a sulfuric acid medium. The effects of stirring speed, liquid/solid ratio, sawdust/ore mass ratio, sulfuric acid concentration, reaction temperature, and time on the manganese extraction were examined. It was found that the leaching efficiency is strongly dependent on temperature and acid concentration. The leaching efficiency of manganese reached 94.1% under the optimal conditions: stirring speed of 300 rpm, liquid/solid ratio of 8:1, mass ratio of sawdust to ore 0.25, sulfuric acid concentration of 1 mol/L and a temperature of 363 K for 180 min. The kinetic analysis was carried out based on the shrinking core model, which indicated that the reductive leaching process was controlled by the chemical reaction. The reaction orders with respect to the sulfuric acid concentration and mass ratio of sawdust are 1.66 and 0.57, respectively. The apparent activation energy for the leaching process has been calculated using the Arrhenius expression and was found to be 51.7 kJ/mol. Full article
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Article
Crystal Chemistry and Stability of Hydrated Rare-Earth Phosphates Formed at Room Temperature
Minerals 2017, 7(5), 84; https://doi.org/10.3390/min7050084 - 19 May 2017
Cited by 11 | Viewed by 3239
Abstract
In order to understand the crystal chemical properties of hydrous rare-earth (RE) phosphates, REPO4,hyd, that form at ambient temperature, we have synthesized REPO4,hyd through the interaction of aqueous RE elements (REEs) with aqueous P at room temperature at pH < [...] Read more.
In order to understand the crystal chemical properties of hydrous rare-earth (RE) phosphates, REPO4,hyd, that form at ambient temperature, we have synthesized REPO4,hyd through the interaction of aqueous RE elements (REEs) with aqueous P at room temperature at pH < 6, where the precipitation of RE hydroxides does not occur, and performed rigorous solid characterization. The second experiment was designed identically except for using hydroxyapatite (HAP) crystals as the P source at pH constrained by the dissolved P. Hydrated RE phosphate that precipitated at pH 3 after 3 days was classified into three groups: LREPO4,hyd (La → Gd) containing each REE from La-Gd, MREPO4,hyd (Tb → Ho), and HREPO4,hyd (Er → Lu). The latter two groups included increasing fractions of an amorphous component with increasing ionic radius, which was associated with non-coordinated water. REallPO4,hyd that contains all lanthanides except Pm transformed to rhabdophane structure over 30 days of aging. In the experiments using HAP, light REEs were preferentially distributed into nano-crystals, which can potentially constrain initial RE distributions in aqueous phase. Consequently, the mineralogical properties of hydrous RE phosphates forming at ambient temperature depend on the aging, the pH of the solution, and the average ionic radii of REE, similarly to the well-crystalline RE phosphates. Full article
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Article
Synthesis of Lithium Fluoride from Spent Lithium Ion Batteries
Minerals 2017, 7(5), 81; https://doi.org/10.3390/min7050081 - 17 May 2017
Cited by 13 | Viewed by 3334
Abstract
Lithium (Li) is considered a strategic element whose use has significantly expanded. Its current high demand is due to its use in lithium ion batteries for portable electronic devices, whose manufacture and market are extensively growing every day. These days there is a [...] Read more.
Lithium (Li) is considered a strategic element whose use has significantly expanded. Its current high demand is due to its use in lithium ion batteries for portable electronic devices, whose manufacture and market are extensively growing every day. These days there is a great concern about the final disposal of these batteries. Therefore, the possibility of developing new methodologies to recycle their components is of great importance, both commercially and environmentally. This paper presents results regarding important operational variables for the dissolution of the lithium and cobalt mixed-oxide (LiCoO2) cathodes from spent lithium ion batteries (LIBs) with hydrofluoric acid. The recovery and synthesis of Co and Li compounds were also investigated. The dissolution parameters studied were: temperature, reaction time, solid-liquid ratio, stirring speed, and concentration of HF. The investigated recovery parameters included: pH, temperature, and time with and without stirring. The final precipitation of lithium fluoride was also examined. The results indicate that an increase in the HF concentration, temperature, and reaction time favors the leaching reaction of the LiCoO2. Dissolutions were close to 60%, at 75 °C and 120 min with a HF concentration of 25% (v/v). The recovery of Co and Li were 98% and 80%, respectively, with purities higher than 94%. Co and Li compounds, such as Co3O4 and LiF, were synthesized. Furthermore, it was possible to almost completely eliminate the F ions as CaF2. Full article
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Article
Improvement of Gold Leaching from a Refractory Gold Concentrate Calcine by Separate Pretreatment of Coarse and Fine Size Fractions
Minerals 2017, 7(5), 80; https://doi.org/10.3390/min7050080 - 16 May 2017
Cited by 11 | Viewed by 2110
Abstract
A total gold extraction of 70.2% could only be reached via direct cyanidation from a refractory As-, S- and C-bearing gold concentrate calcine, and the gold extraction varied noticeably with different size fractions. The reasons for unsatisfactory gold extraction from the calcine were [...] Read more.
A total gold extraction of 70.2% could only be reached via direct cyanidation from a refractory As-, S- and C-bearing gold concentrate calcine, and the gold extraction varied noticeably with different size fractions. The reasons for unsatisfactory gold extraction from the calcine were studied through analyses of chemical composition, chemical phase and SEM-EDS of different sizes of particles. It was found that a significant segregation of compositions occurred during the grinding of gold ore before flotation. As a result, for the calcine obtained after oxidative roasting, the encapsulation of gold by iron oxides was easily engendered in finer particles, whilst in coarser particles the gold encapsulation by silicates was inclined to occur likely due to melted silicates blocking the porosity of particles. The improvement of gold leaching from different size fractions was further investigated through pretreatments with alkali washing, acid pickling or sulfuric acid curing-water leaching. Finally, a novel process was recommended and the total gold extraction from the calcine could be increased substantially to 93.6% by the purposeful pretreatment with alkali washing for the relatively coarse size fraction (+37 μm) and sulfuric acid curing–water leaching for the fine size fraction (−37 μm). Full article
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Article
Characterization of Germanium Speciation in Sphalerite (ZnS) from Central and Eastern Tennessee, USA, by X-ray Absorption Spectroscopy
Minerals 2017, 7(5), 79; https://doi.org/10.3390/min7050079 - 16 May 2017
Cited by 19 | Viewed by 2908
Abstract
X-ray absorption near edge structure (XANES) spectroscopy was used on zoned sphalerites (ZnS) from two world-class Mississippi Valley Type deposits, the Central and Eastern Tennessee Mining district, USA, in order to investigate germanium oxidation states. Due to the low germanium concentrations of these [...] Read more.
X-ray absorption near edge structure (XANES) spectroscopy was used on zoned sphalerites (ZnS) from two world-class Mississippi Valley Type deposits, the Central and Eastern Tennessee Mining district, USA, in order to investigate germanium oxidation states. Due to the low germanium concentrations of these samples, it was necessary to perform the X-ray absorption spectroscopy (XAS) in fluorescence mode. The overlapping of the Zn Kβ and Ge Kα emission lines meant that a high energy-resolution was required. This was achieved using crystal analysers and allowed a bandwidth of 1.3 eV to be obtained. Experimental spectra were compared to XANES calculations and three configurations of germanium incorporation into sphalerite were identified. The first two, the most prevalent, show germanium (II) and (IV) surrounded by sulphur atoms in tetrahedral coordination, suggesting the replacement of Zn by Ge. In the third configuration, germanium (IV) is surrounded by oxygen atoms. This third configuration is unexpected for a zinc sulphide mineral and it resembles that of argutite (GeO2). Full article
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Article
An Alternative Source for Ceramics and Glass Raw Materials: Augen-Gneiss
Minerals 2017, 7(5), 70; https://doi.org/10.3390/min7050070 - 15 May 2017
Cited by 4 | Viewed by 2318
Abstract
Due to the depletion of well-known feldspar reserves in the forms of granite, trachyte and pegmatite, many investigations are focused on new and economic alternatives to these resources. Of these, gneiss is a metamorphic rock type, which is characterized by dark and light [...] Read more.
Due to the depletion of well-known feldspar reserves in the forms of granite, trachyte and pegmatite, many investigations are focused on new and economic alternatives to these resources. Of these, gneiss is a metamorphic rock type, which is characterized by dark and light colored minerals including feldspar and quartz. In this study, Augen-Gneiss rock was subjected to flotation tests to produce alkali (Na + Ca) feldspar and quartz concentrates by adapting different flotation conditions with/without hydrofluoric acid (HF). During these tests, the effect of particle size and different reagent combinations were investigated. The results of these tests showed that, in the presence of HF, a saleable feldspar concentrate with 0.04% Fe2O3 content and a saleable quartz concentrate with 98.45% SiO2 content were obtained. Products with similar qualities to a feldspar concentrate with 0.13% Fe2O3 and a quartz concentrate with 92.53% SiO2 content were produced without HF. The results of these tests clearly showed that, compared to other types of origin, saleable quality feldspar and quartz could well be enriched with/without HF from Augen-Gneiss rock. Full article
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Article
Na-Montmorillonite Edge Structure and Surface Complexes: An Atomistic Perspective
Minerals 2017, 7(5), 78; https://doi.org/10.3390/min7050078 - 12 May 2017
Cited by 15 | Viewed by 3353
Abstract
The edges of montmorillonite (MMT) react strongly with metals and organic matter, but the atomic structure of the edge and its surface complexes are not unambiguous since the experimental isolation of the edge is challenging. In this study, we introduce an atomistic model [...] Read more.
The edges of montmorillonite (MMT) react strongly with metals and organic matter, but the atomic structure of the edge and its surface complexes are not unambiguous since the experimental isolation of the edge is challenging. In this study, we introduce an atomistic model of a Na MMT edge that is suitable for classical molecular dynamics (MD) simulations, in particular for the B edge, a representative edge surface of 2:1 phyllosilicates. Our model possesses the surface groups identified through density functional theory (DFT) geometry optimizations performed with variation in the structural charge deficit and Mg substitution sites. The edge structure of the classical MD simulations agreed well with previous DFT-based MD simulation results. Our MD simulations revealed an extensive H-bond network stabilizing the Na-MMT edge surface, which required an extensive simulation trajectory. Some Na counter ions formed inner-sphere complexes at two edge sites. The stronger edge site coincided with the exposed vacancy in the dioctahedral sheet; a weaker site was associated with the cleaved hexagonal cavity of the tetrahedral sheet. The six-coordinate Na complexes were not directly associated with the Mg edge site. Our simulations have demonstrated the heterogeneous surface structures, the distribution of edge surface groups, and the reactivity of the MMT edge. Full article
(This article belongs to the Special Issue Computational Geochemistry)
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Article
Relating the Mineralogical Characteristics of Tampakan Ore to Enargite Separation
Minerals 2017, 7(5), 77; https://doi.org/10.3390/min7050077 - 12 May 2017
Cited by 5 | Viewed by 1866
Abstract
The mineralogical characteristics of enargite-bearing copper ores from the Tampakan deposit have been investigated as the means to understanding the separation of enargite from other copper sulphides (chalcopyrite and bornite). It was found that a separation of these minerals was possible after grinding [...] Read more.
The mineralogical characteristics of enargite-bearing copper ores from the Tampakan deposit have been investigated as the means to understanding the separation of enargite from other copper sulphides (chalcopyrite and bornite). It was found that a separation of these minerals was possible after grinding the ore samples to a P80 of 90 microns; enargite tends to be ground more readily than the other copper sulphide minerals present in ore samples tested, and consequently, it mostly reported to the fine size fractions. Full article
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Article
Indium Mineralization in a Sn-Poor Skarn Deposit: A Case Study of the Qibaoshan Deposit, South China
Minerals 2017, 7(5), 76; https://doi.org/10.3390/min7050076 - 12 May 2017
Cited by 7 | Viewed by 2570
Abstract
Indium (In) is commonly hosted in Sn-rich deposits but rarely reported in Sn-poor deposits. However, an In-rich and Sn-poor skarn deposit, the Qibaoshan Cu-Zn-Pb deposit, has been identified in south China. Geochemical analyses were undertaken on 23 samples representing the following mineral assemblages: [...] Read more.
Indium (In) is commonly hosted in Sn-rich deposits but rarely reported in Sn-poor deposits. However, an In-rich and Sn-poor skarn deposit, the Qibaoshan Cu-Zn-Pb deposit, has been identified in south China. Geochemical analyses were undertaken on 23 samples representing the following mineral assemblages: sphalerite-pyrite, pyrite-chalcopyrite, pyrite-sphalerite-galena-chalcopyrite, pyrite, magnetite-pyrite, and magnetite. The results show that In is richest in the sphalerite-pyrite ores, with concentrations of 28.9–203.0 ppm (average 122.8 ppm) and 1000 In/Zn values of 2.7–10.9 (average 7.0). Other ore types in the Qibaoshan deposit are In poor, whereas all are Sn poor (10 to 150 ppm), with most samples having Sn concentrations of ≤70 ppm. Indium is mainly hosted by sphalerite, as inferred from the strong correlation between In and Zn, and weak correlation between In and Sn. Mineral paragenetic relationships indicate sphalerite formed from late quartz-sulfide stage of mineralization processes. Indium in the Qibaoshan deposit is richer in vein-type orebodies than in lenticular-type orebodies occurring at contact zones between carbonate and quartz porphyry, or in carbonate xenoliths. Igneous intrusions that were Sn poor and emplaced at shallow depths formed the In-rich orebodies of the Qibaoshan deposit. Full article
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Article
An Innovative Support Structure for Gob-Side Entry Retention in Steep Coal Seam Mining
Minerals 2017, 7(5), 75; https://doi.org/10.3390/min7050075 - 11 May 2017
Cited by 33 | Viewed by 2553
Abstract
This study considered longwall working face No. 41101—located in a steeply inclined coal seam at the Awuzisu coal mine in Xinjiang, China—as an example in which macroscopic shear cracks had occurred in the cement-based filling body of the gob-side entry retention structure. A [...] Read more.
This study considered longwall working face No. 41101—located in a steeply inclined coal seam at the Awuzisu coal mine in Xinjiang, China—as an example in which macroscopic shear cracks had occurred in the cement-based filling body of the gob-side entry retention structure. A mechanical model of the support structure for the gob-side entry retention was first established. Then, field observations and laboratory tests were used to obtain the force exerted by the coal wall on the main roof, the relationship between the axial bearing capacity and compression ratio of the rubble inside the gob, the supporting force exerted by the rubble and filling body, and the thrust of the rubble on the filling body. The shear stress experienced by the roadside filling body of the gob-side entry retention in working face No. 41101 was calculated to be 15.89 MPa. To meet the needs of roadside support, an innovative roadside backfill–truss support structure was adopted, with a 60° angle of inclination used for the anchor bolts of the gob-side entry retention structure. In this way, the ultimate shear strength was improved by 107.54% in comparison with the cement-based filling body. Full article
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Article
Synergistic Adsorption and Flotation of New Mixed Cationic/Nonionic Collectors on Muscovite
Minerals 2017, 7(5), 74; https://doi.org/10.3390/min7050074 - 11 May 2017
Cited by 12 | Viewed by 2105
Abstract
The mixed cationic collector cetyltrimethylammonium chloride (CTAC) and nonionic collector octanol (OCT) was found to exhibit a synergistic effect on the flotation and adsorption of muscovite. To understand the underlying synergistic mechanism, flotation, contact angle, surface tension, and adsorption measurements were carried out. [...] Read more.
The mixed cationic collector cetyltrimethylammonium chloride (CTAC) and nonionic collector octanol (OCT) was found to exhibit a synergistic effect on the flotation and adsorption of muscovite. To understand the underlying synergistic mechanism, flotation, contact angle, surface tension, and adsorption measurements were carried out. The results obtained from flotation measurements indicated that the mixed CTAC/OCT exhibits a better collecting ability than CTAC or OCT. The recovery of muscovite with CTAC only rapidly decreased from 97.25% at pH 2.64 to 75.26% at pH 5.82, followed by a flat horizontal at a pH is higher than 6. In contrast, a high recovery of greater than 85% muscovite was observed using mixed CTAC/OCT at α CTAC = 0.67 (the mole ratio of CTAC:OCT = 2:1) over the investigated pH range. From the surface activity parameters (CMC, γ CMC, Γmax, Amin) estimated from surface measurements and interaction parameters (βm, βσ), in addition to the micellar and interfacial compositions ( x 1 m , x 1 σ ) obtained from the theory of regular solutions, a synergistic effect is evident in the mixed micelle and at the water/air interface. Moreover, the mixed CTAC/OCT at α CTAC = 0.67 exhibited the maximum synergistic interaction. The results obtained from surface tension measurements indicated that the mixed CTAC/OCT exhibits considerably higher surface activities compared to single CTAC or OCT. The contact angle results confirmed that the mixed CTAC/OCT is a better collector than the individual CTAC or OCT for the flotation of muscovite. According to the results obtained from adsorption experiments, compared with that of individual CTAC or OCT, the amounts of CTAC and OCT adsorbed on the muscovite surface are considerably increase in the mixed systems because of co-adsorption. Based on these results, the mixed CTAC/OCT exhibits a remarkable synergistic effect during the flotation and adsorption of muscovite. Full article
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Editorial
Editorial for Special Issue “New Insights in Stability, Structure and Properties of Porous Materials”
Minerals 2017, 7(5), 73; https://doi.org/10.3390/min7050073 - 11 May 2017
Viewed by 1536
Abstract
Porous materials (such as zeolites, clay minerals, and assemblies of oxide nanoparticles) are of great importance for the progress in many technological and environmental fields, such as catalysis, adsorption, separation, and ion exchange, because of their unique pore topologies, tunable structures, and the [...] Read more.
Porous materials (such as zeolites, clay minerals, and assemblies of oxide nanoparticles) are of great importance for the progress in many technological and environmental fields, such as catalysis, adsorption, separation, and ion exchange, because of their unique pore topologies, tunable structures, and the possibility of introducing active reaction sites.[...] Full article
Article
Resource and Reserve Calculation in Seam-Shaped Mineral Deposits; A New Approach: “The Pentahedral Method”
Minerals 2017, 7(5), 72; https://doi.org/10.3390/min7050072 - 10 May 2017
Cited by 3 | Viewed by 10464
Abstract
In recent years, the introduction of specific software for the evaluation of geological resources and mineral reserves has increased significantly thanks to the use of block models capable of working with large databases and applicable to virtually all types of deposits. It is [...] Read more.
In recent years, the introduction of specific software for the evaluation of geological resources and mineral reserves has increased significantly thanks to the use of block models capable of working with large databases and applicable to virtually all types of deposits. It is only in layered, tabular-shaped deposits where the use of block models poses certain drawbacks, not only in terms of visual representation but also during the process of interpolation. Other calculation methods for tabular bodies such as sections, polygons, and triangles work with 2D projections but not with 3D. The “Pentahedral” method described here is undoubtedly an innovative method that allows work to always be conducted in 3D, providing a fairly accurate representation of tabular bodies and making it possible to carry out calculations of resources and reserves using any interpolation method. It is demonstrated with figures and tables of the Carlés mineral deposit, a well-developed exoskarn gold deposit in northwestern Spain (Asturias) where the authors have worked extensively. The pentahedral method takes into account not only geological and stratigraphic data from the model interpolation, but also mining concepts such as “minimum thickness,” related to the minimum seam size that can be economically and technically mined, and “overbreak,” related to the dilution effect that appears during the mining process due to over-excavation. Full article
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Article
Grade Distribution Modeling within the Bauxite Seams of the Wachangping Mine, China, Using a Multi-Step Interpolation Algorithm
Minerals 2017, 7(5), 71; https://doi.org/10.3390/min7050071 - 09 May 2017
Cited by 4 | Viewed by 2306
Abstract
Mineral reserve estimation and mining design depend on a precise modeling of the mineralized deposit. A multi-step interpolation algorithm, including 1D biharmonic spline estimator for interpolating floor altitudes, 2D nearest neighbor, linear, natural neighbor, cubic, biharmonic spline, inverse distance weighted, simple kriging, and [...] Read more.
Mineral reserve estimation and mining design depend on a precise modeling of the mineralized deposit. A multi-step interpolation algorithm, including 1D biharmonic spline estimator for interpolating floor altitudes, 2D nearest neighbor, linear, natural neighbor, cubic, biharmonic spline, inverse distance weighted, simple kriging, and ordinary kriging interpolations for grade distribution on the two vertical sections at roadways, and 3D linear interpolation for grade distribution between sections, was proposed to build a 3D grade distribution model of the mineralized seam in a longwall mining panel with a U-shaped layout having two roadways at both sides. Compared to field data from exploratory boreholes, this multi-step interpolation using a natural neighbor method shows an optimal stability and a minimal difference between interpolation and field data. Using this method, the 97,576 m3 of bauxite, in which the mass fraction of Al2O3 (Wa) and the mass ratio of Al2O3 to SiO2 (Wa/s) are 61.68% and 27.72, respectively, was delimited from the 189,260 m3 mineralized deposit in the 1102 longwall mining panel in the Wachangping mine, Southwest China. The mean absolute errors, the root mean squared errors and the relative standard deviations of errors between interpolated data and exploratory grade data at six boreholes are 2.544, 2.674, and 32.37% of Wa; and 1.761, 1.974, and 67.37% of Wa/s, respectively. The proposed method can be used for characterizing the grade distribution in a mineralized seam between two roadways at both sides of a longwall mining panel. Full article
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Article
Synthesis of Ultramarine from Reservoir Silts
Minerals 2017, 7(5), 69; https://doi.org/10.3390/min7050069 - 07 May 2017
Cited by 5 | Viewed by 2411
Abstract
Ultramarine blue was synthesized by using reservoir silts as a major raw material to replace traditional kaolin clay. The reservoir silts were pretreated to collect the fines, in which the main mineral composition is illite clay. The fine part was mixed with sodium [...] Read more.
Ultramarine blue was synthesized by using reservoir silts as a major raw material to replace traditional kaolin clay. The reservoir silts were pretreated to collect the fines, in which the main mineral composition is illite clay. The fine part was mixed with sodium carbonate, sulfur, and activated carbon, and calcined at 800°C for 8 h. The products were examined by X-ray powder diffraction (XRD) and a scanning electron microscope (SEM) to identify the mineral phases and particle morphology. The color characteristics were measured according to the CIELab system. Brilliant blue ultramarine powders were successfully synthesized with a chroma of 52.4, which is competitive with the commercial ultramarine. Full article
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Article
Origin of the El Dragón Selenium Mineralization, Quijarro Province, Potosí, Bolivia
Minerals 2017, 7(5), 68; https://doi.org/10.3390/min7050068 - 29 Apr 2017
Cited by 12 | Viewed by 3055
Abstract
A re-examination of the El Dragón vein-type Se deposit using polarized light microscopy and scanning-electron microscopy combined with electron-microprobe analyses revealed the following results: the detection of (a) petříčekite, krut’aite and penroseite close to endmember composition; (b) a yet unknown mineral of the [...] Read more.
A re-examination of the El Dragón vein-type Se deposit using polarized light microscopy and scanning-electron microscopy combined with electron-microprobe analyses revealed the following results: the detection of (a) petříčekite, krut’aite and penroseite close to endmember composition; (b) a yet unknown mineral of the ideal composition CuNi2Se4; (c) intermediate members of the vaesite-pyrite solid-solution series; and (d) a mineral with a composition intermediate between athabascaite and its yet unknown S-equivalent, Cu4S5. Triggered by volcanic-hydrothermal activities around the Porco caldera, formation of the mineralization involved five episodes of fault formation and re-opening, fluid-mediated metal mobilization, metalliferous fluid infiltration, and mineral precipitation, re-deposition, and alteration that probably extended from 12 Ma until today. The origin of the Se-vein was accomplished by the multiple injection of highly oxidized, metal-rich fluids into a fault at the interface between black shale and siltstone. These low-T solutions (estimated max. temperature 100 °C, max. pressure 1 bar) possessed high to exceptionally Se fugacities (log fSe2 fluctuating between of −14.5 and −11.2) that prevailed for most of the evolution of the deposit, only interrupted once, during the episode of deposition of sulfides of Cu and Fe and resulting partial alteration of the pre-existing selenides. Formation of end-member krut’aite and native selenium implies a minimum log fSe2 of −11.2 at the final stage of vein formation. The likely source of Se and the accompanying metals (Cu, Ag, Ni, Co, Au, Pb, Hg, Cd, Fe and Bi) is the neighboring Kupferschiefer-type (possibly Devonian) black shale rich in framboidal pyrite, Cu-sulfide aggregates, and organic matter. Deposition of Se-minerals occurred where the oxidized metal-bearing solutions became in contact with a reductant, associated with the reduction of mobile selenate to immobile selenide or elemental Se. Full article
(This article belongs to the Special Issue Se-Bearing Minerals: Structure, Composition, and Origin)
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Article
Improved Modeling of the Grinding Process through the Combined Use of Matrix and Population Balance Models
Minerals 2017, 7(5), 67; https://doi.org/10.3390/min7050067 - 29 Apr 2017
Cited by 15 | Viewed by 2779
Abstract
The mechanistic approach has proven so far to be flexible and successful for simulation of the grinding process. The basic idea underlying mechanistic models, namely the matrix and population balance models, is based on the identification of natural events during grinding. Since each [...] Read more.
The mechanistic approach has proven so far to be flexible and successful for simulation of the grinding process. The basic idea underlying mechanistic models, namely the matrix and population balance models, is based on the identification of natural events during grinding. Since each model has its own capabilities and limitations, their combined use may offer additional advantages on this aspect. In this study, the matrix model and the selection function, namely the probability of breakage of the population balance model, were combined through a MATLAB code to predict the size distribution of the grinding products of quartz, marble, quartzite and metasandstone. The modeling results were in very good agreement with the particle size distributions obtained after grinding the feeds in a ball mill. Full article
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Article
Pore Structure Characterization of Shale Using Gas Physisorption: Effect of Chemical Compositions
Minerals 2017, 7(5), 66; https://doi.org/10.3390/min7050066 - 28 Apr 2017
Cited by 16 | Viewed by 2184
Abstract
In this study, the pore structure characteristics of Canadian Horn River basin shales with various chemical compositions were evaluated using gas physisorption analyses. The samples used in this research were obtained from two different regions (shallow and deep regions) of rock cuttings during [...] Read more.
In this study, the pore structure characteristics of Canadian Horn River basin shales with various chemical compositions were evaluated using gas physisorption analyses. The samples used in this research were obtained from two different regions (shallow and deep regions) of rock cuttings during the drilling of the shale gas field located in Horn River basin. The pore size, specific surface area, total pore volume, micropore surface area, and micropore volume of the shale samples were measured using both nitrogen and CO2. The results indicated that the pore size was not a function of chemical composition, while distinct trends were observed for other macroscopic and microscopic pore-related properties. In particular, the greatest specific surface area and total pore volume were observed for silica-rich carbonate shales, while clay-rich siliceous shales exhibited the greatest micropore volume and micropore surface area. The trends clearly suggested that macroscopic and microscopic pore-related properties of the Canadian Horn River basin shales were closely related to their chemical composition. Furthermore, a stronger correlation was observed between the quartz content and the micropore-related physical properties of shales (i.e., the micropore surface area and micropore volume) in comparison to other properties. Full article
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Article
Ambient Temperature Flotation of Sedimentary Phosphate Ore Using Cottonseed Oil as a Collector
Minerals 2017, 7(5), 65; https://doi.org/10.3390/min7050065 - 26 Apr 2017
Cited by 15 | Viewed by 2290
Abstract
The mid-low grade sedimentary phosphate ore, abundant in silicate and carbonate gangue minerals, exhibits a poor processability. It is conventionally enriched using high temperature flotation to remove silicate gangues with fatty acid as a collector. Cottonseed oil has been proved to be an [...] Read more.
The mid-low grade sedimentary phosphate ore, abundant in silicate and carbonate gangue minerals, exhibits a poor processability. It is conventionally enriched using high temperature flotation to remove silicate gangues with fatty acid as a collector. Cottonseed oil has been proved to be an efficient collector for achieving ambient temperature flotation of the sedimentary phosphate ore used in this study. Flotation kinetics was investigated to ascertain the excellent collecting performance of cottonseed oil, as compared with oleic acid, and the phosphate flotation fitted well with the first-order flotation model. Based on the analysis of flotation reagent effect on the direct flotation process using the response surface methodology (RSM), a closed circuit of direct-reverse flotation for stepwise removing silicate and carbonate gangues from the sedimentary phosphate ore was established. Consequently, a required high quality of phosphate concentrate containing 30.16% P2O5 was obtained, with a recovery of 90.90%. Scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) of the flotation products confirmed that the majority of silicate and carbonate gangues were effectively removed from the concentrate products. Full article
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