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Minerals, Volume 7, Issue 12 (December 2017)

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Cover Story (view full-size image) Tellurium (Te) enrichment has been identified in Mid-Jurassic pyritic coals at Brora, Scotland, [...] Read more.
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Open AccessArticle Visible Light Enhanced Extracellular Electron Transfer between a Hematite Photoanode and Pseudomonas aeruginosa
Minerals 2017, 7(12), 230; doi:10.3390/min7120230
Received: 23 October 2017 / Revised: 19 November 2017 / Accepted: 20 November 2017 / Published: 23 November 2017
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Abstract
Exploring the interplay between sunlight, semiconducting minerals, and microorganisms in nature has attracted great attention in recent years. Here we report for the first time the investigation of the interaction between a hematite photoelectrode and Pseudomonas aeruginosa PAO1 under visible light irradiation. Hematite
[...] Read more.
Exploring the interplay between sunlight, semiconducting minerals, and microorganisms in nature has attracted great attention in recent years. Here we report for the first time the investigation of the interaction between a hematite photoelectrode and Pseudomonas aeruginosa PAO1 under visible light irradiation. Hematite is the most abundant mineral on earth, with a band gap of 2.0 eV. A hematite electrode was electrochemically deposited on fluorine-doped tin oxide (FTO). It was thoroughly characterized by environmental scanning electron microscopy (ESEM), Raman, and UV–Vis spectroscopy, and its prompt response to visible light was determined by linear sweep voltammetry (LSV). Notably, under light illumination, the hematite electrode immersed in a live cell culture was able to produce 240% more photocurrent density than that in the abiotic control of the medium, suggesting a photoenhanced extracellular electron transfer process occurring between hematite and PAO1. Different temperatures of LSV measurements showed bioelectrochemical activity in the system. Furthermore, I–t curves under various conditions demonstrated that both a direct and an indirect electron transferring process occurred between the hematite photoanode and PAO1. Moreover, the indirect electron transferring route was more dominant, which may be mainly attributed to the pyocyanin biosynthesized by PAO1. Our results have expanded our understanding in that in addition to Geobacter and Shewanella it has been shown that more microorganisms are able to perform enhanced extracellular electron transfer with semiconducting minerals under sunlight in nature. Full article
(This article belongs to the Special Issue Environmental Mineralogy)
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Open AccessArticle Tellurium Enrichment in Jurassic Coal, Brora, Scotland
Minerals 2017, 7(12), 231; doi:10.3390/min7120231
Received: 31 October 2017 / Revised: 20 November 2017 / Accepted: 21 November 2017 / Published: 23 November 2017
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Abstract
Mid-Jurassic pyritic coals exposed at the village of Brora, northern Scotland, UK, contain a marked enrichment of tellurium (Te) relative to crustal mean, average world coal compositions and British Isles Carboniferous coals. The Te content of Brora coal pyrite is more than one
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Mid-Jurassic pyritic coals exposed at the village of Brora, northern Scotland, UK, contain a marked enrichment of tellurium (Te) relative to crustal mean, average world coal compositions and British Isles Carboniferous coals. The Te content of Brora coal pyrite is more than one order of magnitude higher than in sampled pyrite of Carboniferous coals. The Te enrichment coincides with selenium (Se) and mercury (Hg) enrichment in the rims of pyrite, and Se/Te is much lower than in pyrites of Carboniferous coals. Initial pyrite formation is attributed to early burial (syn-diagenesis), with incorporation of Te, Se, Hg and lead (Pb) during later pyrite formation. The source of Te may have been a local hydrothermal system which was responsible for alluvial gold (Au) in the region, with some Au in Brora headwaters occurring as tellurides. Anomalous Te is not ubiquitous in coal, but may occur locally, and is detectable by laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS). Full article
(This article belongs to the Special Issue Toxic Mineral Matter in Coal and Coal Combustion Products)
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Open AccessArticle Possible Involvement of Permian Phosphoria Formation Oil as a Source of REE and Other Metals Associated with Complex U-V Mineralization in the Northern Bighorn Basin?
Minerals 2017, 7(12), 232; doi:10.3390/min7120232
Received: 15 August 2017 / Revised: 13 November 2017 / Accepted: 14 November 2017 / Published: 23 November 2017
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Abstract
The origin of V, U, REE and other metals in the Permian Phosphoria Formation have been speculated and studied by numerous scientists. The exceptionally high concentrations of metals have been interpreted to reflect fundamental transitions from anoxic to oxic marine conditions. Much of
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The origin of V, U, REE and other metals in the Permian Phosphoria Formation have been speculated and studied by numerous scientists. The exceptionally high concentrations of metals have been interpreted to reflect fundamental transitions from anoxic to oxic marine conditions. Much of the oil in the Bighorn Basin, is sourced by the Phosphoria Formation. Two of the top 10 producing oil fields in Wyoming are located approximately 50 km west of two abandoned U-V mining districts in the northern portion of the basin. These fields produce from basin margin anticlinal structures from Mississippian age reservoir rock. Samples collected from abandoned U-V mines and prospects hosted in Mississippian aged paleokarst in Montana and Wyoming have hydrocarbon residue present and contain anomalous high concentrations of many metals that are found in similar concentrations in the Phosphoria Formation. As, Hg, Mo, Pb, Tl, U, V and Zn, often metals of environmental concern occur in high concentrations in Phosphoria Formation samples and had values ranging from 30–1295 ppm As, 0.179–12.8 ppm Hg, 2–791 ppm Mo, <2–146 ppm Pb, 10–490 ppm Tl, 907–86,800 ppm U, 1240–18,900 ppm V, and 7–2230 ppm Zn, in mineralized samples from this study. The REE plus Y composition of Madison Limestone- and limestone breccia hosted-bitumen reflect similar patterns to both mineralized samples from this study and to U.S. Geological Survey rock samples from studies of the Phosphoria Formation. Geochemical, mineralogical and field data were used to investigate past theories for mineralization of these deposits to determine if U present in home wells and Hg content of fish from rivers on the proximal Crow Indian Reservation may have been derived from these deposits or related to their mode of mineralization. Full article
(This article belongs to the Special Issue Mineral Resources and the Environment)
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Open AccessArticle A 3D Geological Model of a Vein Deposit Built by Aggregating Morphological and Mineral Grade Data
Minerals 2017, 7(12), 234; doi:10.3390/min7120234
Received: 29 August 2017 / Revised: 17 October 2017 / Accepted: 22 November 2017 / Published: 26 November 2017
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Abstract
The objective of this study was to establish a methodology for building a 3D geological model of a mineral vein deposit, encompassing morphology and wolframite content. The available data set includes stope data (vein thickness and wolframite quantity) and borehole data (vein thickness
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The objective of this study was to establish a methodology for building a 3D geological model of a mineral vein deposit, encompassing morphology and wolframite content. The available data set includes stope data (vein thickness and wolframite quantity) and borehole data (vein thickness and wolframite modal classes). The data captured from boreholes and stopes differ in terms of their spatial distribution and clustering as well as the size and shape of each sample. Therefore, a specific methodology was designed to combine these two sources of information. The morphology model mapped vein thickness as a vein proportion variable, by applying a two-phase Direct Sequential Simulation (DSS) locally conditioned to borehole data. Regarding the evaluation of wolframite content, the variables are unable to be related directly to each other and are non-co-located. Therefore, a proximity study was made using DSS to build local conditional cumulative histograms (by borehole class and by mine level). The final model of wolframite quantity was generated using Probability Field Simulation. The proposed approach considers the initially identified problems, allowing the mineral potential of the deposit to be quantified by integrating the results of the two independent methodologies. Full article
(This article belongs to the Special Issue Geological Modelling)
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Open AccessArticle Influence of Froth Height on Column Flotation of Kaolin Ore
Minerals 2017, 7(12), 235; doi:10.3390/min7120235
Received: 17 October 2017 / Revised: 9 November 2017 / Accepted: 22 November 2017 / Published: 26 November 2017
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Abstract
The influence of the froth height in the reverse flotation of kaolinitic ore was analyzed based on the recovery by entrainment and by true flotation of iron, titanium and manganese oxides (FeO, TiO2 and MnO). Also, the influence of the particle size
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The influence of the froth height in the reverse flotation of kaolinitic ore was analyzed based on the recovery by entrainment and by true flotation of iron, titanium and manganese oxides (FeO, TiO2 and MnO). Also, the influence of the particle size in the drainage process was analyzed. The recovery by entrainment and by true flotation of the three oxides is inversely proportional to the froth height. The entrained particles are drained more easily in the froth phase than the floated particles since they are not attached to the bubbles. The recovery by entrainment and drainage of the entrained material is similar for the three oxides. However, the recovery by true flotation and drainage of the floated material is different for the three oxides. FeO has the lowest recovery, as a consequence of the minor contribution of its hydrophobic minerals, while MnO has the greatest recovery values. For the entrained material, the finest fraction is entrained more easily, but it is also drained more easily, meaning these particles have more mobility in the froth zone. For the true floated material, the finest fraction is drained more easily, indicating the greater mobility of these particles in the froth; however, the coarsest fraction is drained more easily than the two intermediate fractions, indicating the weaker attachment of the larger particles to the bubbles. Full article
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Open AccessArticle New Insights into the Adsorption of Oleate on Cassiterite: A DFT Study
Minerals 2017, 7(12), 236; doi:10.3390/min7120236
Received: 31 October 2017 / Revised: 19 November 2017 / Accepted: 24 November 2017 / Published: 27 November 2017
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Abstract
A new understanding of the adsorption mechanism of oleate on cassiterite surfaces is presented by density functional theory (DFT) calculations. Various convergence tests were conducted to optimize the parameter settings for the rational simulation of cassiterite bulk unit cell and surface slabs. The
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A new understanding of the adsorption mechanism of oleate on cassiterite surfaces is presented by density functional theory (DFT) calculations. Various convergence tests were conducted to optimize the parameter settings for the rational simulation of cassiterite bulk unit cell and surface slabs. The calculated surface energies of four low-index cassiterite cleavage planes form an increasing sequence of (110) < (100) < (101) < (001), demonstrating (110) is the most thermodynamically stable surface of cassiterite. The interaction strengths of the oleate ion (OL), OH, and H2O on the SnO2 (110) face are in the order of H2O < OH < OL, which reveals that the OL is able to replace the adsorbed H2O and OH on the mineral surfaces. Mulliken population calculations and electron density difference analysis show that electrons transfer from the Sn atoms on the cassiterite (110) surface to the O atoms offered by carboxyl groups of oleate during the interaction. The populations of newly formed O1–Sn1 and O2–Sn2 bonds are 0.30 and 0.29, respectively, indicating that these two bonds are of a very low covalency. Density of states analysis reveals that the formation of an O1–Sn1 bond mainly results from the 5s and 5p orbitals of the Sn1 atom and the 2p orbital of the O1 atom. Full article
(This article belongs to the Special Issue Molecular Simulation of Mineral-Solution Interfaces)
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Open AccessArticle Mineral Sequestration of Carbon Dioxide in Circulating Fluidized Bed Combustion Boiler Bottom Ash
Minerals 2017, 7(12), 237; doi:10.3390/min7120237
Received: 11 September 2017 / Revised: 3 November 2017 / Accepted: 27 November 2017 / Published: 29 November 2017
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Abstract
This paper investigates the mineral sequestration of carbon dioxide in circulating fluidized bed combustion (CFBC) boiler bottom ash. CFBC bottom ash, which originated from two sources, was prepared along with pulverized coal-fired (PC) boiler bottom ash as a control. These ashes were exposed
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This paper investigates the mineral sequestration of carbon dioxide in circulating fluidized bed combustion (CFBC) boiler bottom ash. CFBC bottom ash, which originated from two sources, was prepared along with pulverized coal-fired (PC) boiler bottom ash as a control. These ashes were exposed to accelerated carbonation conditions at a relative humidity of 40% and 100%, in order to investigate the effects of humidity on the carbonation kinetics of the bottom ash. The obtained results showed that not only lime but other calcium-bearing phases (gehlenite, wollastonite, and brownmillerite) in CFBC bottom ash participated in the mineral carbonation reaction. In particular, these phases underwent hydration in a wet carbonation environment, whereby the carbon dioxide uptake and capacity of CFBC bottom ash are significantly enhanced. This study may have important implications, demonstrating the feasibility of carbon dioxide sequestration and recycling of CFBC boiler bottom ash. Full article
(This article belongs to the Special Issue Carbon Capture and Storage via Mineral Carbonation)
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Open AccessArticle Geostatistical Methodology to Characterize Volcanogenic Massive and Stockwork Ore Deposits
Minerals 2017, 7(12), 238; doi:10.3390/min7120238
Received: 27 October 2017 / Revised: 20 November 2017 / Accepted: 27 November 2017 / Published: 30 November 2017
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Abstract
The Zambujal ore deposit, Neves-Corvo mine, is a zoned volcanogenic sulfide deposit of copper and zinc, with massive ores at the top and stockwork ores at the bottom. Metal grades are strongly zoned by ore types. The main methodology hereby proposed combines geostatistical
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The Zambujal ore deposit, Neves-Corvo mine, is a zoned volcanogenic sulfide deposit of copper and zinc, with massive ores at the top and stockwork ores at the bottom. Metal grades are strongly zoned by ore types. The main methodology hereby proposed combines geostatistical techniques so that an improved stochastic geological model of the Zambujal deposit encompassing morphology and grades is presented. The model of the morphology was made in two main steps. First, a 3D solid of the boundaries was created and then a 3D grid model of the local sulfide proportion was simulated. This latter variable was modeled by using rock specific gravity as a proxy. After that, a conditional grid model of relative copper grades, i.e., recalculated metal grades assuming only the sulfide content, is also simulated in accordance with the morphology. At the end, the new tool, metal tonnage cut-off surface, is proposed, which combines copper grades within massive ores and stockwork ores. To validate the results found, the global tonnages of copper obtained by Ordinary Kriging and the proposed methodology are compared. Full article
(This article belongs to the Special Issue Geological Modelling)
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Open AccessArticle Discovery of a Novel Cationic Surfactant: Tributyltetradecyl-Phosphonium Chloride for Iron Ore Flotation: From Prediction to Experimental Verification
Minerals 2017, 7(12), 240; doi:10.3390/min7120240
Received: 28 October 2017 / Revised: 24 November 2017 / Accepted: 28 November 2017 / Published: 2 December 2017
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Abstract
In this work, tributyltetradecyl-phosphonium chloride (TTPC), has been first introduced to be a novel and efficient cationic surfactant for cationic reverse flotation separation of quartz from magnetite. The first-principles density functional theory calculations, Zeta potential measurements and adsorption isotherm measurements consistently predict that
[...] Read more.
In this work, tributyltetradecyl-phosphonium chloride (TTPC), has been first introduced to be a novel and efficient cationic surfactant for cationic reverse flotation separation of quartz from magnetite. The first-principles density functional theory calculations, Zeta potential measurements and adsorption isotherm measurements consistently predict that TTPC may be a promising collector that is better than dodecyl triethyl ammonium chloride (DTAC), based on the facts that TTPC and DTAC both prefer to physically adsorb on the quartz surface owing to electrostatic force, but the active part (P+(C4H9)3) of TTPC takes much more positive charges than that (N+(CH3)3) of DTAC. The micro-flotation and Bench-scale flotation results further verify that TTPC presents a stronger collecting power and much better selectivity for iron ore reverse flotation in comparison to the conventional collector DTAC. Furthermore, the corresponding adsorption mechanism of TTPC on the quartz have also been investigated in detail. This work might show a good example to discover a potential candidate collector by analogy with a known excellent collector based on reasonable prediction. Full article
(This article belongs to the Special Issue Flotation Chemistry)
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Open AccessArticle Indicator Variograms as an Aid for Geological Interpretation and Modeling of Ore Deposits
Minerals 2017, 7(12), 241; doi:10.3390/min7120241
Received: 1 November 2017 / Revised: 28 November 2017 / Accepted: 30 November 2017 / Published: 5 December 2017
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Abstract
Geostatistics offers a set of methods for modeling, predicting, or simulating geological domains in space. In addition of being an input of some of these methods, indicator direct and cross-variograms convey valuable information on the geometry of the domain layouts and on their
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Geostatistics offers a set of methods for modeling, predicting, or simulating geological domains in space. In addition of being an input of some of these methods, indicator direct and cross-variograms convey valuable information on the geometry of the domain layouts and on their contact relationships, in particular, on the surface area of a domain boundary, on the surface area of the contact between two domains, on the propensity for a domain to be in contact with, or separated from, another domain, and on the minimum and maximum distances between points from two domains. Accordingly, the indicator variograms inferred from sparse sampling data can be used to determine whether or not an interpreted model of the subsurface is consistent with the sampling information. The previous concepts are illustrated through a case study corresponding to a porphyry copper deposit. Full article
(This article belongs to the Special Issue Geological Modelling)
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Open AccessArticle Selective Recovery of Mushistonite from Gravity Tailings of Copper–Tin Minerals in Tajikistan
Minerals 2017, 7(12), 242; doi:10.3390/min7120242
Received: 31 October 2017 / Revised: 1 December 2017 / Accepted: 4 December 2017 / Published: 7 December 2017
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Abstract
Tajikistan has abundant copper–tin resources. In this study, mineralogical analysis of copper–tin ores from the Mushiston deposit of Tajikistan indicates that tin mainly occurred in mushistonite, cassiterite, and stannite, while copper mainly occurred in mushistonite, malachite, azurite, and stannite. The total grades of
[...] Read more.
Tajikistan has abundant copper–tin resources. In this study, mineralogical analysis of copper–tin ores from the Mushiston deposit of Tajikistan indicates that tin mainly occurred in mushistonite, cassiterite, and stannite, while copper mainly occurred in mushistonite, malachite, azurite, and stannite. The total grades of tin (Sn) and copper (Cu) were 0.65% and 0.66%, respectively, and the dissemination size of copper–tin minerals ranged from 4 μm to over 200 μm. Coarse particles of copper–tin minerals were partially recovered by shaking table concentrators with a low recovery rate. Based on the mineralogical analysis, flotation recovery was used for the first time on the fine particles of copper–tin minerals, including mushistonite, from shaking table tailings. Single factor flotation experiments, open circuit flotation tests, and closed circuit flotation tests were performed to determine the optimized flotation conditions. Results indicated that benzohydroxamic acid (C6H5CONHOH) and lead nitrate could effectively recover the mushistonite, cooperating with other depressants. The final concentrate contained 13.28% Sn, with a recovery rate of 61.56%, and 18.51% Cu, with a recovery rate of 86.52%. This method proved effective for the exploitation and use of this type of copper–tin resource in Tajikistan. Full article
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Open AccessArticle Joint Application of Fractal Analysis and Weights-of-Evidence Method for Revealing the Geological Controls on Regional-Scale Tungsten Mineralization in Southern Jiangxi Province, China
Minerals 2017, 7(12), 243; doi:10.3390/min7120243
Received: 27 October 2017 / Revised: 5 December 2017 / Accepted: 6 December 2017 / Published: 11 December 2017
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Abstract
The Southern Jiangxi Province (SJP) hosts one of the best known districts of tungsten deposits in the world. Delineating spatial complexities of geological features and their controls on regional-scale tungsten mineralization by using an integrated fractal and weights-of-evidence (WofE) method can provide insights
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The Southern Jiangxi Province (SJP) hosts one of the best known districts of tungsten deposits in the world. Delineating spatial complexities of geological features and their controls on regional-scale tungsten mineralization by using an integrated fractal and weights-of-evidence (WofE) method can provide insights into the understanding of ore genesis and facilitate further prospecting in this area. The box-counting fractal analysis shows that most of the tungsten occurrences are distributed in regions with high fractal dimensions of faults and fault intersections, suggesting ore-forming favorability of areas with highly complex structural patterns. The WofE-derived indices are employed to quantitatively measure the controls of analyzed features on mineralization, which illustrate that tungsten anomalies, faults, Yanshanian granites, and manganese anomalies have high contrast values, implying a spatially strong correlation of these features with tungsten occurrences. In particular, high manganese anomalies in host rock may provide a novel indication for mineral prospecting in this area. A predictive map is extracted based on the combination of fractal and WofE results, providing intuitive guides for future prospectivity in this area. Regions identified by high posterior probability in conjunction with high fractal dimensions of both faults and fault intersections are evaluated as the most favorable targets. Full article
(This article belongs to the Special Issue Geological Modelling)
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Open AccessArticle Separation Mechanism of Fatty Acids from Waste Cooking Oil and Its Flotation Performance in Iron Ore Desiliconization
Minerals 2017, 7(12), 244; doi:10.3390/min7120244
Received: 16 October 2017 / Revised: 29 November 2017 / Accepted: 5 December 2017 / Published: 12 December 2017
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Abstract
Using the mixed fatty acids (MFA) produced by waste cooking oil as flotation collectors directly, the flotation effect is usually not satisfactory, especially at lower temperature, which may be due to the presence of large amounts of saturated fatty acids. In this study,
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Using the mixed fatty acids (MFA) produced by waste cooking oil as flotation collectors directly, the flotation effect is usually not satisfactory, especially at lower temperature, which may be due to the presence of large amounts of saturated fatty acids. In this study, waste cooking oil was separated into saturated fatty acids (SFA) and unsaturated fatty acids (UFA). The separation mechanism was studied by molecular simulation based on quantum and molecular mechanics. SFA and UFA were analyzed by iodine value, melting point measurement and Fourier transform infrared (FT-IR) spectroscopy to check the result of the separation. The micro-flotation and bench-scale flotation tests were performed to investigate the flotation differences between SFA and UFA. The results showed that the poor flotation performance of waste cooking oil was due to the large amount of SFA in presence. If the SFA was separated out, the TFe grade and recovery of the flotation concentrates would be increased by 4.09 and 2.70 percentage points, respectively and the SiO2 grade would be 4.03 percentage points lower at the same time. This study would provide technical supports and theoretical guidance for the waste cooking oil application in the field of mineral processing. Full article
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Open AccessArticle Anomalously High Cretaceous Paleobrine Temperatures: Hothouse, Hydrothermal or Solar Heating?
Minerals 2017, 7(12), 245; doi:10.3390/min7120245
Received: 1 November 2017 / Revised: 9 December 2017 / Accepted: 9 December 2017 / Published: 13 December 2017
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Abstract
Elevated surface paleobrine temperatures (average 85.6 °C) are reported here from Cretaceous marine halites in the Maha Sarakham Formation, Khorat Plateau, Thailand. Fluid inclusions in primary subaqueous “chevron” and “cumulate” halites associated with potash salts contain daughter crystals of sylvite (KCl) and carnallite
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Elevated surface paleobrine temperatures (average 85.6 °C) are reported here from Cretaceous marine halites in the Maha Sarakham Formation, Khorat Plateau, Thailand. Fluid inclusions in primary subaqueous “chevron” and “cumulate” halites associated with potash salts contain daughter crystals of sylvite (KCl) and carnallite (MgCl2·KCl·6H2O). Petrographic textures demonstrate that these fluid inclusions were trapped from the warm brines in which the halite crystallized. Later cooling produced supersaturated conditions leading to the precipitation of sylvite and carnallite daughter crystals within fluid inclusions. Dissolution temperatures of daughter crystals in fluid inclusions from the same halite bed vary over a large range (57.9 °C to 117.2 °C), suggesting that halite grew at different temperatures within and at the bottom of the water column. Consistency of daughter crystal dissolution temperatures within fluid inclusion bands and the absence of vapor bubbles at room temperature demonstrate that fluid inclusions have not stretched or leaked. Daughter crystal dissolution temperatures are reproducible to within 0.1 °C to 10.2 °C (average of 1.8 °C), and thus faithfully document paleobrine conditions. Microcrystalline hematite incorporated within halite crystals also indicate high paleobrine temperatures. We conclude that halite crystallized from warm brines rich in K-Mg-Na-Cl; sylvite and carnallite daughter crystals were nucleated during cooling of the warm brines sometime after deposition. Hothouse, hydrothermal, and solar-heating hypotheses are compared to explain the anomalously high surface paleobrine temperatures. Solar radiation stored in shallow density stratified brines is the most plausible explanation for the observed paleobrine temperatures and the progressively higher temperatures downward through the paleobrine column. The solar-heating hypothesis may also explain high paleobrine temperatures documented from fluid inclusions in other ancient halites. Full article
(This article belongs to the Special Issue Fluid Inclusions: Study Methods, Applications and Case Histories)
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Open AccessArticle Fe–Ti(–V) Oxide Deposits of the Kunene Anorthosite Complex (SW Angola): Mineralogy and Thermo-Oxybarometry
Minerals 2017, 7(12), 246; doi:10.3390/min7120246
Received: 25 October 2017 / Revised: 10 December 2017 / Accepted: 12 December 2017 / Published: 14 December 2017
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Abstract
The Kunene Intrusive Complex (KIC), in NW Namibia and SW Angola, is one of the largest Proterozoic anorthosite massif-type exposures in the world. A geochemical, mineralogical and petrological study of four Fe–Ti(–V) oxide bodies located in the understudied Angolan part of the KIC
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The Kunene Intrusive Complex (KIC), in NW Namibia and SW Angola, is one of the largest Proterozoic anorthosite massif-type exposures in the world. A geochemical, mineralogical and petrological study of four Fe–Ti(–V) oxide bodies located in the understudied Angolan part of the KIC has been performed. The massive Fe–Ti(–V) oxide bodies, locally apatite-rich (nelsonites), are lenticular or dike-like. They consist mostly of titaniferous magnetite, ilmenite and minor aluminous spinel, apatite, olivine and graphite. Titaniferous magnetite displays a wide variety of subsolvus features, including aluminous spinel–magnetite–ulvöspinel exsolutions and ilmenite (Trellis) exsolutions. This work estimated the composition of the titaniferous magnetite prior to the exsolution, in order to calculate the temperature and oxygen fugacity of the different lithologies of each ore body. The thermo-oxybarometry results obtained range from 600 °C to 820 °C and fO2 from 10−24.7 to 10−14.7. These values do not correspond to magmatic crystallization in equilibrium, but to a later re-equilibration. In addition, the mineralogical and geochemical results indicate that the studied ore bodies contain economic reserves of Ti, V, and possibly of P and REE. Full article
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Open AccessArticle Effect of Flowing Water on Sr Sorption Changes of Hydrous Sodium Titanate
Minerals 2017, 7(12), 247; doi:10.3390/min7120247
Received: 10 November 2017 / Revised: 4 December 2017 / Accepted: 11 December 2017 / Published: 14 December 2017
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Abstract
Radioactive contaminated water has been generated at the Fukushima Daiichi Nuclear Power station (F1NPS). Hydrous sodium titanate (SrTreat®) is able to remove radioactive Strontium (Sr) from this water. Knowing the amount of radioactive nuclides in the used as-received SrTreat® is
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Radioactive contaminated water has been generated at the Fukushima Daiichi Nuclear Power station (F1NPS). Hydrous sodium titanate (SrTreat®) is able to remove radioactive Strontium (Sr) from this water. Knowing the amount of radioactive nuclides in the used as-received SrTreat® is important for effective disposal and deposition of the F1NPS waste. This study investigated changes in the ability of SrTreat® to sorb Sr, and to understand the causes of changes in the sorbing. An investigation of the Sr sorption ability of SrTreat® is important for calculating the initial radioactive inventory of used SrTreat®. This study carries out Sr sorption studies with acid-base titrations and X-ray photoelectron spectroscopy (XPS) to characterize the properties. After exposure to simulated treated water for 99 h, the surface structure of the SrTreat® was changed, and the percentage of sorbed Sr and the buffer capacity for protons decreased. When the amount of radioactive nuclides contained in the used SrTreat® is calculated from the sorption data of the as-received SrTreat®, the radioactive Sr content will be overestimated with a concomitant increase in the deposition and disposal costs of the used SrTreat®. Full article
(This article belongs to the Special Issue Environmental Mineralogy)
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Open AccessArticle Vesuvianite from the Somma-Vesuvius Complex: New Data and Revised Formula
Minerals 2017, 7(12), 248; doi:10.3390/min7120248
Received: 2 December 2017 / Revised: 12 December 2017 / Accepted: 14 December 2017 / Published: 16 December 2017
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Abstract
At present, the vesuvianite group of minerals consists of eight members, six of which are distinguished by the dominant cation in the Y1(A,B) five-coordinated site. We investigated two vesuvianite samples from the type locality by electron microprobe analysis, Mössbauer and infrared spectroscopy,
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At present, the vesuvianite group of minerals consists of eight members, six of which are distinguished by the dominant cation in the Y1(A,B) five-coordinated site. We investigated two vesuvianite samples from the type locality by electron microprobe analysis, Mössbauer and infrared spectroscopy, TGA/DSC, MAS NMR, single-crystal and powder X-ray diffraction. The crystal structures of these samples (# 27844 and 51062 from the Vesuvius collection, Fersman Mineralogical Museum, Moscow) have been refined to R1 = 0.027 and R1 = 0.035, respectively. Both samples have the space group P4/nnc; a = 15.5720(3) and 15.5459(3), c = 11.8158(5) and 11.7988(4), respectively. In both samples low-occupied T1 and T2 sites are populated by minor B and Al, which agrees with their high-temperature origin. According to our experimental results, the general revised crystal-chemical formula of vesuvianite can be written as VII−IXX19VY1VIY12(Z2O7)4(ZO4)10(W)10, where X are seven- to nine-coordinated sites of Ca with minor Na, K, Fe2+ and REE impurities; VY has a square pyramidal coordination and is occupied predominantly by Fe3+ with subordinate Mg, Al, Fe2+ and Cu2+; VIY has octahedral coordination and is predominantly occupied by Al with subordinate Mg, Fe2+, Fe3+, Mn2+, Mn3+, Ti, Cr and Zn; ZO4 = SiO4, sometimes with subordinate AlO4 and/or (OH)4, and W = OH, F, with minor O and Cl. The idealized charge-balanced formula of the vesuvianite end-member without subordinate cations is Ca19Fe3+(Al10Me2+2)(Si2O7)4(SiO4)10O(OH)9, where Ме = Fe2+, Mg2+, Mn2+. Full article
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Open AccessArticle Effect of Intercalation Agents on Morphology of Exfoliated Kaolinite
Minerals 2017, 7(12), 249; doi:10.3390/min7120249
Received: 17 November 2017 / Revised: 12 December 2017 / Accepted: 14 December 2017 / Published: 16 December 2017
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Abstract
Kaolinite intercalation compounds were prepared by intercalating fatty acids and quaternary ammonium salts into kaolinite layers, using methanol-grafted kaolinite as the precursor. Meanwhile, massive lamellas were exfoliated during the intercalation process. The interlayer structure, chemical bonding and morphology of kaolinite before and after
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Kaolinite intercalation compounds were prepared by intercalating fatty acids and quaternary ammonium salts into kaolinite layers, using methanol-grafted kaolinite as the precursor. Meanwhile, massive lamellas were exfoliated during the intercalation process. The interlayer structure, chemical bonding and morphology of kaolinite before and after intercalation were characterized in detail. As the alkyl chain length increases, the basal spacing of kaolinite increases gradually. The morphology analysis indicated that the ionic type of intercalation agent has a more important influence on the morphology change of kaolinite than their alkyl chain length. The initial kaolinite layers were mostly transformed into nanoscrolls in the product intercalated with stearyl trimethyl ammonium chloride (STAC). The present study demonstrates the arrangement model of intercalated molecules between kaolinite layers using X-ray diffraction (XRD) in conjunction with Fourier transform infrared (FTIR) and stereochemical calculation. On the basis of a probed arrangement model, the mechanism of effect of the alkyl chain length and ionic type of intercalation agent on the morphology of exfoliated kaolinite is suggested. Full article
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Open AccessArticle Chemical Force Microscopy Study on the Interactions of COOH Functional Groups with Kaolinite Surfaces: Implications for Enhanced Oil Recovery
Minerals 2017, 7(12), 250; doi:10.3390/min7120250
Received: 10 November 2017 / Revised: 5 December 2017 / Accepted: 12 December 2017 / Published: 19 December 2017
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Abstract
Clay–oil interactions play a critical role in determining the wettability of sandstone oil reservoirs, which, in turn, governs the effectiveness of enhanced oil recovery methods. In this study, we have measured the adhesion between –COOH functional groups and the siloxane and aluminol faces
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Clay–oil interactions play a critical role in determining the wettability of sandstone oil reservoirs, which, in turn, governs the effectiveness of enhanced oil recovery methods. In this study, we have measured the adhesion between –COOH functional groups and the siloxane and aluminol faces of kaolinite clay minerals by means of chemical force microscopy as a function of pH, salinity (from 0.001 M to 1 M) and cation identity (Na+ vs. Ca2+). Results from measurements on the siloxane face show that Ca2+ displays a reverse low-salinity effect (adhesion decreasing at higher concentrations) at pH 5.5, and a low salinity effect at pH 8. At a constant Ca2+ concentration of 0.001 M, however, an increase in pH leads to larger adhesion. In contrast, a variation in the Na+ concentration showed less effect in varying the adhesion of –COOH groups to the siloxane face. Measurements on the aluminol face showed a reverse low-salinity effect at pH 5.5 in the presence of Ca2+, whereas an increase in pH with constant ion concentration resulted in a decrease in adhesion for both Ca2+ and Na+. Results are explained by looking at the kaolinite’s surface complexation and the protonation state of the functional group, and highlight a more important role of the multicomponent ion exchange mechanism in controlling adhesion than the double layer expansion mechanism. Full article
(This article belongs to the Special Issue Organo-Mineral Interactions)
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Open AccessArticle LA-ICP-MS U-Th-Pb Dating and Trace Element Geochemistry of Allanite: Implications on the Different Skarn Metallogenesis between the Giant Beiya Au and Machangqing Cu-Mo-(Au) Deposits in Yunnan, SW China
Minerals 2017, 7(12), 251; doi:10.3390/min7120251
Received: 30 October 2017 / Revised: 13 December 2017 / Accepted: 15 December 2017 / Published: 19 December 2017
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Abstract
The giant Beiya Au skarn deposit and Machangqing porphyry Cu-Mo-(Au) deposit are located in the middle part of the Jinshajiang–Ailaoshan alkaline porphyry metallogenic belt. The Beiya deposit is the largest Au skarn deposit in China, whilst the Machangqing deposit comprises a well-developed porphyry-skarn-epithermal
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The giant Beiya Au skarn deposit and Machangqing porphyry Cu-Mo-(Au) deposit are located in the middle part of the Jinshajiang–Ailaoshan alkaline porphyry metallogenic belt. The Beiya deposit is the largest Au skarn deposit in China, whilst the Machangqing deposit comprises a well-developed porphyry-skarn-epithermal Cu-Mo-(Au) mineral system. In this paper, we present new allanite U-Th-Pb ages and trace element geochemical data from the two deposits and discuss their respective skarn metallogenesis. Based on the mineral assemblage, texture and Th/U ratio, the allanite from the Beiya and Machangqing deposits are likely hydrothermal rather than magmatic. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) allanite U-Th-Pb dating has yielded Th-Pb isochron ages of 33.4 ± 4.6 Ma (MSWD = 0.22) (Beiya) and 35.4 ± 9.8 Ma (MSWD = 0.26) (Machangqing), representing the retrograde alteration and magnetite skarn mineralization age of the two deposits. The Beiya and Machangqing alkali porphyry-related mineralization are synchronous and genetically linked to the magmatic hydrothermal activities of the Himalayan orogenic event. Major and trace element compositions reveal that the Beiya allanite has higher Fe3+/(Fe3+ + Fe2+) ratios, U content and Th content than the Machangqing allanite, which indicate a higher oxygen fugacity and F content for the ore-forming fluids at Beiya. Such differences in the ore-forming fluids may have contributed to the different metallogenic scales and metal types in the Beiya and Machangqing deposit. Full article
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Open AccessReview Advances and Opportunities in Ore Mineralogy
Minerals 2017, 7(12), 233; doi:10.3390/min7120233
Received: 28 October 2017 / Revised: 19 November 2017 / Accepted: 22 November 2017 / Published: 24 November 2017
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Abstract
The study of ore minerals is rapidly transforming due to an explosion of new micro- and nano-analytical technologies. These advanced microbeam techniques can expose the physical and chemical character of ore minerals at ever-better spatial resolution and analytical precision. The insights that can
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The study of ore minerals is rapidly transforming due to an explosion of new micro- and nano-analytical technologies. These advanced microbeam techniques can expose the physical and chemical character of ore minerals at ever-better spatial resolution and analytical precision. The insights that can be obtained from ten of today’s most important, or emerging, techniques and methodologies are reviewed: laser-ablation inductively-coupled plasma mass spectrometry; focussed ion beam-scanning electron microscopy; high-angle annular dark field scanning transmission electron microscopy; electron back-scatter diffraction; synchrotron X-ray fluorescence mapping; automated mineral analysis (Quantitative Evaluation of Mineralogy via Scanning Electron Microscopy and Mineral Liberation Analysis); nanoscale secondary ion mass spectrometry; atom probe tomography; radioisotope geochronology using ore minerals; and, non-traditional stable isotopes. Many of these technical advances cut across conceptual boundaries between mineralogy and geochemistry and require an in-depth knowledge of the material that is being analysed. These technological advances are accompanied by changing approaches to ore mineralogy: the increased focus on trace element distributions; the challenges offered by nanoscale characterisation; and the recognition of the critical petrogenetic information in gangue minerals, and, thus the need to for a holistic approach to the characterization of mineral assemblages. Using original examples, with an emphasis on iron oxide-copper-gold deposits, we show how increased analytical capabilities, particularly imaging and chemical mapping at the nanoscale, offer the potential to resolve outstanding questions in ore mineralogy. Broad regional or deposit-scale genetic models can be validated or refuted by careful analysis at the smallest scales of observation. As the volume of information at different scales of observation expands, the level of complexity that is revealed will increase, in turn generating additional research questions. Topics that are likely to be a focus of breakthrough research over the coming decades include, understanding atomic-scale distributions of metals and the role of nanoparticles, as well how minerals adapt, at the lattice-scale, to changing physicochemical conditions. Most importantly, the complementary use of advanced microbeam techniques allows for information of different types and levels of quantification on the same materials to be correlated. Full article
(This article belongs to the Special Issue Fundamentals and Frontiers in Mineralogy)
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Open AccessReview Abundance, Distribution, and Modes of Occurrence of Uranium in Chinese Coals
Minerals 2017, 7(12), 239; doi:10.3390/min7120239
Received: 27 October 2017 / Revised: 28 November 2017 / Accepted: 29 November 2017 / Published: 1 December 2017
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Abstract
Due to its environmental and resource impacts, the geochemistry of uranium in coal is of both academic and practical significance. In order to give a comprehensive summary about the geochemistry of uranium in coals, the abundance, distribution, and modes of occurrence of uranium
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Due to its environmental and resource impacts, the geochemistry of uranium in coal is of both academic and practical significance. In order to give a comprehensive summary about the geochemistry of uranium in coals, the abundance, distribution, and modes of occurrence of uranium in Chinese coals were reviewed in this paper. Although some coals from southwestern and northwestern China are significantly enriched in uranium, the common Chinese coals are of a comparable uranium concentration to the world coals. The roof and floor rocks, and parting of coalbeds, or coal benches that are close to the surrounding rock are favorable hosts for uranium in one coalbed. The uranium concentrations in coals of different ages decrease in this order, e.g., Paleogene and Neogene > Late Permian > Late Triassic > Late Carboniferous and Early Permian > Late Jurassic and Early Cretaceous > Early and Middle Jurassic. Uranium in Chinese coals is mainly associated with organic matter, and is correspondingly enriched in subbituminous coal and lignite. Full article
(This article belongs to the Special Issue Toxic Mineral Matter in Coal and Coal Combustion Products)
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