Minerals

22 pages, 7506 KiB

Open AccessArticle

Trace Element Analysis of Pyrite from the Zhengchong Gold Deposit, Northeast Hunan Province, China: Implications for the Ore-Forming Process

by Yong-Jun Shao, Wen-Shu Wang, Qing-Quan Liu and Yu Zhang

Minerals 2018, 8(6), 262; https://doi.org/10.3390/min8060262 - 20 Jun 2018

Cited by 35 | Viewed by 7316

Abstract

The Zhengchong gold deposit is located in the central segment of the Jiangnan Orogen in northeastern Hunan Province, South China. The host rocks of this deposit are the Neoproterozoic slates of the Lengjiaxi Group and granodiorite. The structures in the Zhengchong gold deposit [...] Read more.

The Zhengchong gold deposit is located in the central segment of the Jiangnan Orogen in northeastern Hunan Province, South China. The host rocks of this deposit are the Neoproterozoic slates of the Lengjiaxi Group and granodiorite. The structures in the Zhengchong gold deposit are dominated by NE-trending reverse faults, which control the gold-bearing veins. The orebody consists of NE-trending laminated quartz veins and NW-trending quartz veins. The alteration styles include silicification, carbonatization, sulfidation, sericitization and chloritization. The Zhengchong gold mineralization can be divided into four stages: Quartz-pyrite (stage I), quartz-pyrite-arsenopyrite (stage II), quartz-polysulfide (stage III) and quartz-carbonate (stage IV). Three generations of hydrothermal pyrite were identified: Disseminated euhedral to subhedral cubes in altered wall-rock (PyI), euhedral to subhedral cubes inter-grown with arsenopyrite and tetrahedrite in quartz veins and wall-rock (PyII), and euhedral cubes with microinclusions (native gold, galena, sphalerite, chalcopyrite, tetrahedrite, and pyrrhotite) or metasomatic textures in sulfide-rich veins or veinlets (PyIII). PyII and PyIII are arsenian pyrite and represent the main Au-bearing minerals. PyI records the lowest concentrations of Au; PyII and PyIII record similar amounts of Au, Cu, Pb, Zn, and Bi, but PyIII is more enriched in Co, Ni, Te, and Se. The substitution of As, Se and Te for S and that of Co and Ni for Fe occurs by direct-ion exchange. Invisible gold is uniformly distributed within the arsenian pyrite, and visible gold fills microfractures in PyII or occurs as inclusions in PyIII. Co, Ni, Cu exhibit positive correlations with Au and a negative correlation between Au + Cu + Co + Ni and Fe reflect that Fe vacancies may have been a major cause of the precipitation of invisible Au and other metal elements in pyrite structure. There are systematic trace element differences between the three generations of pyrite (PyI, PyII, PyIII). The more Co, Ni and Se, Te substitution that occurred for Fe and S, respectively, the greater the increase in the Co/Ni ratio (<1) and the decrease in the Se/Te ratio (<10) in stage III, indicating that a more reduced, lower-temperature metamorphic hydrothermal fluid was present in stage III. Full article

(This article belongs to the Section Mineral Deposits)

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23 pages, 5044 KiB

Open AccessArticle

(Bio)leaching Behavior of Chromite Tailings

by Viviana Bolaños-Benítez, Eric D. Van Hullebusch, Piet N.L. Lens, Cécile Quantin, Jack Van de Vossenberg, Sankaran Subramanian and Yann Sivry

Minerals 2018, 8(6), 261; https://doi.org/10.3390/min8060261 - 20 Jun 2018

Cited by 17 | Viewed by 7351

Abstract

Chromite beneficiation operations in Sukinda valley (India) produce large amounts of tailings, which are stored in open air. In this study, bioleaching experiments were carried out in batch reactors with Acidithiobacillus thiooxidans or Pseudomonas putida in order to determine the potential leachability of [...] Read more.

Chromite beneficiation operations in Sukinda valley (India) produce large amounts of tailings, which are stored in open air. In this study, bioleaching experiments were carried out in batch reactors with Acidithiobacillus thiooxidans or Pseudomonas putida in order to determine the potential leachability of metals contained in these tailings due to biological activity. Acidic and alkaline pH resulted from the incubation of tailings with A. thiooxidans and P. putida, respectively. Tailings were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM), and chemical extraction of Cr(VI) with KH₂PO₄ was performed. Mineralogical investigations showed that tailings are mainly composed of chromite, hematite, lizardite, chlorite, and goethite, which are all known as Cr-bearing phases. During the leaching with A. thiooxidans and P. putida, total Cr was initially extracted as Cr(VI) due to the presence of phosphates in the medium, and subsequently decreased because of Cr(VI) adsorption and reduction to Cr(III). Reduction was associated with bacterial activity, but also with the presence of ferrous iron. Despite the occurrence of siderophores in the tailings after incubation with P. putida, under acidic conditions, Fe extracted remained higher. Extracted Ni, Mn, and Al concentrations also increased over time. Given the significant amount of chromite tailings produced every year, this study shows that tailings storage and leachability represent a potential source of chromium. However, our findings suggest that the presence of bacterial communities, as well as physicochemical processes, favor Cr(VI) reduction. Full article

(This article belongs to the Collection Bioleaching)

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23 pages, 10817 KiB

Open AccessArticle

Three-D Mineralogical Mapping of the Kovdor Phoscorite–Carbonatite Complex, NW Russia: I. Forsterite

by Julia A. Mikhailova, Gregory Yu. Ivanyuk, Andrey O. Kalashnikov, Yakov A. Pakhomovsky, Ayya V. Bazai, Taras L. Panikorovskii, Victor N. Yakovenchuk, Nataly G. Konopleva and Pavel M. Goryainov

Minerals 2018, 8(6), 260; https://doi.org/10.3390/min8060260 - 20 Jun 2018

Cited by 14 | Viewed by 5176

Abstract

The Kovdor alkaline-ultrabasic massif (NW Russia) is formed by three consequent intrusions: peridotite, foidolite–melilitolite and phoscorite–carbonatite. Forsterite is the earliest mineral of both peridotite and phoscorite–carbonatite, and its crystallization governed evolution of magmatic systems. Crystallization of forsterite from Ca-Fe-rich peridotite melt produced Si-Al-Na-K-rich [...] Read more.

The Kovdor alkaline-ultrabasic massif (NW Russia) is formed by three consequent intrusions: peridotite, foidolite–melilitolite and phoscorite–carbonatite. Forsterite is the earliest mineral of both peridotite and phoscorite–carbonatite, and its crystallization governed evolution of magmatic systems. Crystallization of forsterite from Ca-Fe-rich peridotite melt produced Si-Al-Na-K-rich residual melt-I corresponding to foidolite–melilitolite. In turn, consolidation of foidolite and melilitolite resulted in Fe-Ca-C-P-F-rich residual melt-II that emplaced in silicate rocks as a phoscorite–carbonatite pipe. Crystallization of phoscorite began from forsterite, which launched destruction of silicate-carbonate-ferri-phosphate subnetworks of melt-II, and further precipitation of apatite and magnetite from the pipe wall to its axis with formation of carbonatite melt-III in the pipe axial zone. This petrogenetic model is based on petrography, mineral chemistry, crystal size distribution and crystallochemistry of forsterite. Marginal forsterite-rich phoscorite consists of Fe²⁺-Mn-Ni-Ti-rich forsterite similar to olivine from peridotite, intermediate low-carbonate magnetite-rich phoscorite includes Mg-Fe³⁺-rich forsterite, and axial carbonate-rich phoscorite and carbonatites contain Fe²⁺-Mn-rich forsterite. Incorporation of trivalent iron in the octahedral M1 and M2 sites reduced volume of these polyhedra; while volume of tetrahedral set has not changed. Thus, trivalent iron incorporates into forsterite by schema (3Fe²⁺)_oct → (2Fe³⁺ + □)_oct that reflects redox conditions of the rock formation resulting in good agreement between compositions of apatite, magnetite, calcite and forsterite. Full article

(This article belongs to the Special Issue Arctic Mineral Resources: Science and Technology)

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12 pages, 1698 KiB

Open AccessArticle

Near-Infrared Spectroscopy of Hydrothermal versus Low-Grade Metamorphic Chlorites

by Oscar M. Kamps, Frank J.A. Van Ruitenbeek, Paul R.D. Mason and Freek D. Van der Meer

Minerals 2018, 8(6), 259; https://doi.org/10.3390/min8060259 - 19 Jun 2018

Cited by 5 | Viewed by 5032

Abstract

Although the composition of chlorite group minerals represents a known proxy for conditions in various geological environments, few comparative studies of chlorites from different geological environments have been carried out. In this study, we compare chlorites from a hydrothermal system with those formed [...] Read more.

Although the composition of chlorite group minerals represents a known proxy for conditions in various geological environments, few comparative studies of chlorites from different geological environments have been carried out. In this study, we compare chlorites from a hydrothermal system with those formed under low-grade metamorphic conditions. Both sets of samples were collected from the Pilbara Craton, Western Australia. Near-infrared (NIR) spectroscopy was used to determine if spectral differences record compositional differences between chlorites from the two geological environments. The spectra showed a significant difference in the Mg-OH absorption wavelength, near 2350 nm, with the hydrothermal group showing longer absorption wavelengths than the metamorphic one. A comparison of the spectral data with geochemical analyses showed a relation between the absorption wavelength and the magnesium-to-iron ratio (magnesium number) of chlorite, as well as the bulk rock composition. Metamorphic rocks have a higher magnesium-to-iron ratio than the hydrothermal ones, predominantly explained by differences in the degree of metasomatism. In the hydrothermal system, mass transfer changes the bulk rock composition while for the metamorphic samples the original bulk chemistry determines the current composition of the rock. Full article

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10 pages, 10453 KiB

Open AccessArticle

Pinnoite Deposit in DaQaidam Saline Lake, Qaidam Basin, China: Hydroclimatic, Sedimentologic, and Geochemical Constraints

by JunQing Yu, Rongchang Hong, Chunliang Gao, Aiying Cheng and Lisa Zhang

Minerals 2018, 8(6), 258; https://doi.org/10.3390/min8060258 - 19 Jun 2018

Cited by 7 | Viewed by 3881

Abstract

Mg-borates were traditionally thought to be diagenetic products of other primary borate minerals. Here we report results from the study of pinnoite deposit from DaQaidam saline lake, indicating that pinnoite minerals are primary in origin. Within the detecting limit of X-ray powder diffraction [...] Read more.

Mg-borates were traditionally thought to be diagenetic products of other primary borate minerals. Here we report results from the study of pinnoite deposit from DaQaidam saline lake, indicating that pinnoite minerals are primary in origin. Within the detecting limit of X-ray powder diffraction analysis (XRD) analysis, no other borate minerals than pinnoite are detected from the Mg-borate deposit. The cemented pinnoite orebody shows the sedimentary structure of light-dark lamination couplets, which signal marked seasonal variations in brine chemistry. The scanning electronic microscopy coupled with an energy dispersive X-ray spectrometer (SEM-EDX) examination reveals that all pinnoite minerals displayed euhedral, giving no indication of diagenetic origin. A marked shift in lithology from clastic sediment to evaporitic deposit reflects a critical change in sedimentation regime associated with abrupt changes in hydroclimatic conditions. The deposition of the pinnoite ore-layer containing abundant hydromagnesite marked the beginning of the evaporite formation and the end of the clastic deposition. This suggests that aridification occurred abruptly and the saline lake was much more alkaline than today in the early-stage of the evaporite deposition. The intensified summer evaporation and seasonal variations in water chemistry brought about a shallow to nearly desiccated paleo-lake with pH exceeding 9.3, Mg/Ca ratio >39, and boron concentration >600 mg/L, which favored pinnoite precipitation and the formation of pinnoite deposit in the central DaQaidam saline lake. Full article

(This article belongs to the Special Issue Sedimentary Ore Deposits: Origin, Exploitation, Paleoenvironmental Significance)

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14 pages, 1799 KiB

Open AccessArticle

Potential of Soil, Sludge and Sediment for Mineral Carbonation Process in Selinsing Gold Mine, Malaysia

by Sharifah Nur Munirah Syed Hasan, Faradiella Mohd Kusin, Shamshuddin Jusop and Ferdius Mohamat Yusuff

Minerals 2018, 8(6), 257; https://doi.org/10.3390/min8060257 - 17 Jun 2018

Cited by 19 | Viewed by 6015

Abstract

Soil, sludge and sediment that are rich in alkaline earth silicates play significant roles as passive agents for removing carbon dioxide through mineral carbonation process. This study was conducted to characterize the mineralogical component and chemical composition of gold mining wastes and to [...] Read more.

Soil, sludge and sediment that are rich in alkaline earth silicates play significant roles as passive agents for removing carbon dioxide through mineral carbonation process. This study was conducted to characterize the mineralogical component and chemical composition of gold mining wastes and to identify the availability of natural silicate minerals as a feedstock for the mineral carbonation process. Particle-size distribution analysis was performed, and pH of the soil, sludge, and sediment were determined, whereas the mineralogical component and chemical composition of the samples were also analyzed. Results demonstrated that the presence of sepiolite and chlorite-serpentine in the stockpile and mine tailings can sequester carbon dioxide into magnesium carbonates, while the presence of stilpnomelane in the stockpile can be sequestered into iron carbonate. The presence of large amounts of small-size particles (silt fraction) in sludge (78.23%) at the mine tailings was identified to have higher surface area to absorb carbon dioxide. pH conditions of sludge (pH 7.9) and sediment (pH 8.3) from the mine tailings were favorable to enhance carbonate precipitation. Therefore, gold mine wastes have shown the potential for passive sequestration of carbon dioxide, thus, providing more insights into the enhancement of mineral carbonation process and the potential of natural silicate minerals. Full article

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14 pages, 3426 KiB

Open AccessArticle

Temporal Evolution of Calcite Surface Dissolution Kinetics

by Irshad Bibi, Rolf S. Arvidson, Cornelius Fischer and Andreas Lüttge

Minerals 2018, 8(6), 256; https://doi.org/10.3390/min8060256 - 16 Jun 2018

Cited by 33 | Viewed by 5265

Abstract

This brief paper presents a rare dataset: a set of quantitative, topographic measurements of a dissolving calcite crystal over a relatively large and fixed field of view (~400 μm²) and long total reaction time (

> 6 h

). Using [...] Read more.

This brief paper presents a rare dataset: a set of quantitative, topographic measurements of a dissolving calcite crystal over a relatively large and fixed field of view (~400 μm²) and long total reaction time (

> 6 h

). Using a vertical scanning interferometer and patented fluid flow cell, surface height maps of a dissolving calcite crystal were produced by periodically and repetitively removing reactant fluid, rapidly acquiring a height dataset, and returning the sample to a wetted, reacting state. These reaction-measurement cycles were accomplished without changing the crystal surface position relative to the instrument’s optic axis, with an approximate frequency of one data acquisition per six minutes’ reaction (~10/h). In the standard fashion, computed differences in surface height over time yield a detailed velocity map of the retreating surface as a function of time. This dataset thus constitutes a near-continuous record of reaction, and can be used to both understand the relationship between changes in the overall dissolution rate of the surface and the morphology of the surface itself, particularly the relationship of (a) large, persistent features (e.g., etch pits related to screw dislocations; (b) small, short-lived features (e.g., so-called pancake pits probably related to point defects); (c) complex features that reflect organization on a large scale over a long period of time (i.e., coalescent “super” steps), to surface normal retreat and step wave formation. Although roughly similar in frequency of observation to an in situ atomic force microscopy (AFM) fluid cell, this vertical scanning interferometry (VSI) method reveals details of the interaction of surface features over a significantly larger scale, yielding insight into the role of various components in terms of their contribution to the cumulative dissolution rate as a function of space and time. Full article

(This article belongs to the Special Issue Mineral Surface Reactions at the Nanoscale)

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31 pages, 15014 KiB

Open AccessArticle

A Mosaic of Colors: Investigating Production Technologies of Roman Glass Tesserae from Northeastern Italy

by Sarah Maltoni and Alberta Silvestri

Minerals 2018, 8(6), 255; https://doi.org/10.3390/min8060255 - 16 Jun 2018

Cited by 29 | Viewed by 10070

Abstract

In the current study, a set of 60 glass tesserae from two disrupted Roman mosaics located in Pordenone and Trento (northeastern Italy) are analyzed, with the aim of investigating the coloring and opacification techniques, with a focus on the causes of specific textural [...] Read more.

In the current study, a set of 60 glass tesserae from two disrupted Roman mosaics located in Pordenone and Trento (northeastern Italy) are analyzed, with the aim of investigating the coloring and opacification techniques, with a focus on the causes of specific textural features. All the available colors and textures were selected for archaeometric analyses, in order to guarantee the full characterization of both assemblages and comparisons between the two sites. The applied analytical protocol comprises micro-textural and preliminary chemical characterizations of the tesserae by means of OM and SEM-EDS, mineralogical analysis of the opacifiers by XRD and chemical analysis of the glassy matrices by EPMA; in addition, on specific tesserae, micro-Raman spectroscopy, FORS, and EPR were also performed to clarify the type of opacifer, coloring ion and oxidation state, respectively. Results show that both the base-glass and the coloring/opacification techniques identified are consistent with the presumed Roman dating of the mosaics. All the tesserae are natron-based and chemically comparable with major Roman compositional groups, except for red samples. Antimony-based opacifiers are identified in most of the blue, turquoise, white, yellow and green tesserae, and copper-based opacifiers in the red ones; cobalt and copper are the most frequent ionic colorants used to obtain various shades of blue, turquoise and green colors. Despite the general comparability of both assemblages with the published data on glass tesserae coeval in age, the present study shows differences in the technological solutions used for obtaining the same color, and less common coloring and opacification techniques in three samples from Pordenone. The banded textures of some tesserae were also carefully investigated, and multiple factors influencing the changes in color (different distribution or relative abundance of opacifiers, crystal size, micro-texture, chemical composition of glassy matrix) are identified. Full article

(This article belongs to the Special Issue Mineralogical Applications for Cultural Heritage)

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26 pages, 45973 KiB

Open AccessArticle

Structural Controls on Copper Mineralization in the Tongling Ore District, Eastern China: Evidence from Spatial Analysis

by Tao Sun, Ying Xu, Xuhui Yu, Weiming Liu, Ruixue Li, Zijuan Hu and Yun Wang

Minerals 2018, 8(6), 254; https://doi.org/10.3390/min8060254 - 15 Jun 2018

Cited by 15 | Viewed by 6748

Abstract

Structures exert significant controls on hydrothermal mineralization, although such controls commonly have cryptic expression in geological datasets dominated by 2D maps. Analysis of spatial patterns of mineral deposits and quantification of their correlation with detailed structural features are beneficial to understand the plausible [...] Read more.

Structures exert significant controls on hydrothermal mineralization, although such controls commonly have cryptic expression in geological datasets dominated by 2D maps. Analysis of spatial patterns of mineral deposits and quantification of their correlation with detailed structural features are beneficial to understand the plausible structural controls on mineralization. In this paper, a series of GIS-based spatial methods, including fractal, Fry, distance distribution and weights-of-evidence analyses, were employed to reveal structural controls on copper mineralization in the Tongling ore district, eastern China. The results indicate that Yanshanian intrusions exert the most significant control on copper mineralization, followed by EW-trending faults, intersections of basement faults and folds. The scale-variable distribution patterns of copper occurrences are attributed to the different structural controls operating in the basement and sedimentary cover. In the basement, EW-trending faults serve as pathways for channeling Yanshanian magma from a deep magma chamber to structurally controlled trap zones in the caprocks, imposing an important regional control on the spatial distribution of Cretaceous magmatic-hydrothermal system genetically related to copper mineralization. In the sedimentary cover, bedding-parallel shear zones, formed during the progressive folding and shearing in Indosinian and overprinted by tensional deformation in Yanshanian, act as favorable sites for hosting, focusing and depositing the ore-bearing fluids, playing a vital role in the localization of stratabound deposits at fine scale. Full article

(This article belongs to the Special Issue Structural Control of Mineral Deposits: Theory and Reality)

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13 pages, 6287 KiB

Open AccessArticle

Bio-Minerals Combined with Bacillus cereus for Enhancing the Nitrogen Removal Efficiency under Aerobic Conditions

by Hyunhee Seo and Yul Roh

Minerals 2018, 8(6), 253; https://doi.org/10.3390/min8060253 - 15 Jun 2018

Cited by 5 | Viewed by 3478

Abstract

Nitrogen compounds such as nitrate, nitrite, and ammonium are among the prolonged contaminants in surface water and groundwater worldwide. In this study, we evaluated nitrogen removal efficiency using the combination of biologically synthesized Pd-FeS and Bacillus cereus in comparison between two batch reactors, [...] Read more.

Nitrogen compounds such as nitrate, nitrite, and ammonium are among the prolonged contaminants in surface water and groundwater worldwide. In this study, we evaluated nitrogen removal efficiency using the combination of biologically synthesized Pd-FeS and Bacillus cereus in comparison between two batch reactors, one with a single nitrate (NO₃⁻–N) and the other with a mixed nitrogen (NO₃⁻–N + NO₂⁻–N + NH₄⁺–N) under aerobic conditions. The removal efficiency of NO₃⁻–N by bio-Pd-FeS + Bacillus cereus in a single nitrate reactor showed 100% with a low production (ca. 10%) of NO₂⁻–N and NH₄⁺–N for 5 days and this combination was three-fold more effective than a single application of bio-Pd-FeS and Bacillus cereus respectively. Also, bio-Pd-FeS + Bacillus cereus in the mixed nitrogen (NO₃⁻–N + NO₂⁻–N + NH₄⁺–N) removed 95% NO₃⁻–N, 20% NO₂⁻–N, and 35% NH₄⁺–N, respectively. Since iron and sulfur-based bio-minerals could be reusable in a reducing condition of in-situ and in an oxygen-limited closed condition of ex-situ applications, the results suggested that the combination should get more attention for an efficient eco-friendly sustainable bioremediation technology. Full article

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

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21 pages, 5234 KiB

Open AccessArticle

Contribution of Benthic Processes to the Growth of Ooids on a Low-Energy Shore in Cat Island, The Bahamas

by Giulio Mariotti, Sara B. Pruss, Roger E. Summons, Sharon A. Newman and Tanja Bosak

Minerals 2018, 8(6), 252; https://doi.org/10.3390/min8060252 - 14 Jun 2018

Cited by 25 | Viewed by 5637

Abstract

Ooids are typically found in frequently reworked coastal sediments, and are thought to accrete by inorganic chemical precipitation around moving grains. The high organic content and the presence of biosignatures, however, suggest that ooids interact with benthic microbial communities. Here, we investigate the [...] Read more.

Ooids are typically found in frequently reworked coastal sediments, and are thought to accrete by inorganic chemical precipitation around moving grains. The high organic content and the presence of biosignatures, however, suggest that ooids interact with benthic microbial communities. Here, we investigate the role of benthic processes on ooid growth on a leeward shore of Cat Island, The Bahamas. Polished ooids are present in the surf zone, whereas dull ooids and grapestones are present in microbially colonized sediments seaward of the surf zone. Wave hydrodynamics and sediment transport modeling suggest that microbially colonized sediments are mobilized at monthly time scales. We propose a new conceptual model for both ooids and grapestone. Ooids rest and accrete in the area covered by microbial mats, but are periodically transported to the surf zone where wave abrasion polishes them within days. Ooids are then transported back to microbially colonized areas where the accretion cycle resumes. Ooids too large to be transported become trapped outside the surf zone, exit the “conveyor belt” and become grapestones. The benthic growth mechanism predicts petrographic characteristics that match observations: successive ooid laminae do not thin outward, laminae exhibit irregularities, and some ooids include multiple nuclei. Full article

(This article belongs to the Special Issue Microbialites: Preservation of Extant and Extinct Systems)

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3 pages, 163 KiB

Open AccessEditorial

Editorial for Special Issue “Geochemistry and Mineralogy of Hydrothermal Metallic Mineral Deposits”

by Theodore J. Bornhorst

Minerals 2018, 8(6), 251; https://doi.org/10.3390/min8060251 - 14 Jun 2018

Viewed by 3354

Abstract

The Special Issue of Minerals on Geochemistry and Mineralogy of Hydrothermal Metallic Mineral Deposits presents the results of diverse geochemical and mineralogical research from across the globe[…] Full article

(This article belongs to the Special Issue Geochemistry and Mineralogy of Hydrothermal Metallic Mineral Deposits)

17 pages, 2801 KiB

Open AccessArticle

Effect of Ammonium Chloride on the Efficiency with Which Copper Sulfate Activates Marmatite: Change in Solution Composition and Regulation of Surface Composition

by Shengdong Zhang, Dongxia Feng, Xiong Tong, Bo Yang and Xian Xie

Minerals 2018, 8(6), 250; https://doi.org/10.3390/min8060250 - 13 Jun 2018

Cited by 3 | Viewed by 6808

Abstract

Zinc sulfide minerals are the primary choice for zinc extraction and marmatite is one of the two most common zinc sulphide minerals (sphalerite and marmatite), therefore it is of great significance to study and optimize the flotation of marmatite. To improve the activation [...] Read more.

Zinc sulfide minerals are the primary choice for zinc extraction and marmatite is one of the two most common zinc sulphide minerals (sphalerite and marmatite), therefore it is of great significance to study and optimize the flotation of marmatite. To improve the activation of copper sulfate on marmatite, a method involving the addition of ammonium chloride is devised. The method has been proven to be an effective way of improving the activation efficiency of copper sulfate towards marmatite under alkaline conditions. The strengthening mechanism was studied using micro-flotation, adsorption test, X-ray photoelectron spectroscopy, and by analyzing changes in solution composition. Flotation test results show that the activation effect of the copper sulfate towards marmatite is enhanced with the addition of ammonium chloride. According to the results of the adsorption measurements and X-ray photoelectron spectroscopy analysis, when the marmatite surface is activated using copper sulfate with added ammonia chloride, it adsorbs more copper sulfide and less copper hydroxide and zinc hydroxide. These changes in surface composition are believed to occur via the following process: NH₃(aq) promotes the dissolution of zinc hydroxide and then facilitates the conversion of surface copper hydroxide to copper sulfide. In addition, the occurrence of Cu(NH₃)_n²⁺ can promote the adsorption of copper ions (Cu²⁺ can be stored as Cu(NH₃)_n²⁺ via complexation, and then, when the concentration of copper ions decreases, Cu²⁺ can be released through the decompositionof Cu(NH₃)_n²⁺. Hence, the copper ion concentration can be maintained and this can facilitate the adsorption of Cu²⁺ on marmatite). Based on a comprehensive analysis of all our results, we propose that adding ammonium chloride to the copper sulfate changes the solution components (i.e., the presence of NH₃(aq) and Cu(NH₃)_n²⁺) and then regulates the surface composition of marmatite. The change in surface composition improves the hydrophobicity of mineral surface and this leads to an improvement in activation of marmatite. Full article

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12 pages, 1540 KiB

Open AccessArticle

Raman Micro-Spectroscopy Identifies Carbonaceous Particles Lying on the Surface of Crocidolite, Amosite, and Chrysotile Fibers

by Alessandro Croce, Aldo Arrais and Caterina Rinaudo

Minerals 2018, 8(6), 249; https://doi.org/10.3390/min8060249 - 13 Jun 2018

Cited by 14 | Viewed by 8023

Abstract

Micro-Raman spectroscopy has been applied on UICC (Union for International Cancer Control’s) crocidolite and amosite from South Africa and on UICC chrysotile from Canada. Under Optical Microscope (OM), the surface of the fibers was often characterized by areas, micrometric in size, appearing dark. [...] Read more.

Micro-Raman spectroscopy has been applied on UICC (Union for International Cancer Control’s) crocidolite and amosite from South Africa and on UICC chrysotile from Canada. Under Optical Microscope (OM), the surface of the fibers was often characterized by areas, micrometric in size, appearing dark. The laser beam was successively focused on areas of the same sample showing different optical contrasts. On the bright zones, Raman spectra peculiar for crocidolite, amosite or chrysotile were recorded. When dark areas were optically identified, the laser beam was addressed onto these regions and, in the Raman patterns, in addition to the bands produced by the mineral fiber, bands ascribing to substituted carbonaceous phases were observed. These bands were lying in the 4000–1100 cm⁻¹ spectral range. On the basis of the shape of the bands and their relative intensities, suggestions about the order-disorder of the carbonaceous particles could be proposed, and they appeared more ordered on amosite than on crocidolite and chrysotile. From the exposed data, crocidolite and amosite fibers from South Africa, and chrysotile fibers from Canada, largely used in industry in the past, are characterized by many carbonaceous micrometric particles, lying on the fiber surfaces. Based on the noxiousness of the carbon particles on human health, their presence on asbestos fibers may play a role in increasing the carcinogenic effects of the analyzed fibrous minerals. Full article

(This article belongs to the Special Issue Occurrence, Crystal-Chemistry and Properties of Fibrous Minerals)

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10 pages, 2797 KiB

Open AccessEditor’s ChoiceArticle

Fiemmeite Cu₂(C₂O₄)(OH)₂∙2H₂O, a New Mineral from Val di Fiemme, Trentino, Italy

by Francesco Demartin, Italo Campostrini, Paolo Ferretti and Ivano Rocchetti

Minerals 2018, 8(6), 248; https://doi.org/10.3390/min8060248 - 12 Jun 2018

Cited by 6 | Viewed by 7289

Abstract

The new mineral species fiemmeite, Cu₂(C₂O₄)(OH)₂∙2H₂O, was found NE of the Passo di San Lugano, Val di Fiemme, Carano, Trento, Italy (latitude 46.312° N, longitude 11.406° E). It occurs in coalified woods [...] Read more.

The new mineral species fiemmeite, Cu₂(C₂O₄)(OH)₂∙2H₂O, was found NE of the Passo di San Lugano, Val di Fiemme, Carano, Trento, Italy (latitude 46.312° N, longitude 11.406° E). It occurs in coalified woods at the base of the Val Gardena Sandstone (upper Permian) which were permeated by mineralizing solutions containing Cu, U, As, Pb and Zn. The oxalate anions have originated from diagenesis of the plant remains included in sandstones. The mineral forms aggregate up to 1 mm across of sky blue platelets with single crystals reaching maximum dimensions of about 50 μm. Associated minerals are: baryte, olivenite, middlebackite, moolooite, brochantite, cuprite, devilline, malachite, azurite, zeunerite/metazeunerite, tennantite, chalcocite, galena. Fiemmeite is monoclinic, space group: P2₁/c with a = 3.4245(6), b = 10.141(2), c = 19.397(3) Å, β = 90.71(1)°, V = 673.6(2) Å³, Z = 4. The calculated density is 2.802 g/cm³ while the observed density is 2.78(1) g/cm³. The six strongest reflections in the X-ray powder diffraction pattern are: [d_obs in Å (I)(hkl)] 5.079(100)(020), 3.072(58)(112), 9.71(55)(002), 4.501(50)(022), 7.02(28)(012), 2.686(25)(114). The crystal structure was refined from single-crystal data to a final R₁ = 0.0386 for 1942 observed reflections [I > 2σ(I)] with all the hydrogen atoms located from a Difference–Fourier map. The asymmetric unit contains two independent Cu²⁺ cations that display a distorted square-bipyramidal (4+2) coordination, one oxalate anion, two hydroxyl anions and two water molecules. The coordination polyhedra of the two copper atoms share common edges to form polymeric rows running along [100] with composition [Cu₂(C₂O₄)(OH)₂∙2H₂O]_n. These rows are held together by a well-established pattern of hydrogen bonds between the oxalate oxygens not involved in the coordination to copper, the hydrogen atoms of the water molecules and the hydroxyl anions. Full article

(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)

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24 pages, 9256 KiB

Open AccessArticle

Mineralogy of Platinum-Group Elements and Gold in the Ophiolite-Related Placer of the River Bolshoy Khailyk, Western Sayans, Russia

by Andrei Y. Barkov, Gennadiy I. Shvedov, Sergey A. Silyanov and Robert F. Martin

Minerals 2018, 8(6), 247; https://doi.org/10.3390/min8060247 - 12 Jun 2018

Cited by 18 | Viewed by 6209

Abstract

We describe assemblages of platinum-group minerals (PGM) and associated PGE–Au phases found in alluvium along the River Bolshoy Khailyk, in the western Sayans, Russia. The river drains the Aktovrakskiy ophiolitic complex, part of the Kurtushibinskiy belt, as does the Zolotaya River ~15 km [...] Read more.

We describe assemblages of platinum-group minerals (PGM) and associated PGE–Au phases found in alluvium along the River Bolshoy Khailyk, in the western Sayans, Russia. The river drains the Aktovrakskiy ophiolitic complex, part of the Kurtushibinskiy belt, as does the Zolotaya River ~15 km away, the site of other placer deposits. Three groups of alloy minerals are described: (1) Os–Ir–Ru compositions, which predominate, (2) Pt–Fe compositions of a Pt₃Fe stoichiometry, and (3) Pt–Au–Cu alloys, which likely crystallized in the sequence from Au–(Cu)-bearing platinum, Pt(Au,Cu), Pt(Cu,Au), and PtAuCu₂, to PtAu₄Cu₅. The general trends of crystallization of PGM appear to be: [Os–Ir–Ru alloys] → Pt₃Fe-type alloy (with inclusions of Ru-dominant alloy formed by exsolution or via replacement of the host Pt–Fe phase) → Pt–Au–Cu alloys. We infer that Rh and Co mutually substitute for Fe, not Ni, and are incorporated into the pentlandite structure via a coupled mechanism of substitution: [Rh³⁺ + Co³⁺ + □ → 3Fe²⁺]. Many of the Os–Ir–Ru and Pt–Fe grains have porous, fractured or altered rims that contain secondary PGE sulfide, arsenide, sulfarsenide, sulfoantimonide, gold, Pt–Ir–Ni-rich alloys, and rarer phases like Cu-rich bowieite and a Se-rich sulfarsenide of Pt. The accompanying pyroxene, chromian spinel and serpentine are highly magnesian, consistent with a primitive ultramafic source-rock. Whereas the alloy phases indicate a highly reducing environment, late assemblages indicate an oxygenated local environment leading to Fe-bearing Ru–Os oxide (zoned) and seleniferous accessory phases. Full article

(This article belongs to the Special Issue Platinum-Group Minerals: New Results and Advances in PGE Mineralogy in Various Ni-Cu-Cr-PGE Ore Systems)

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21 pages, 4586 KiB

Open AccessArticle

Hydrothermal Synthesized and Alkaline Activated Carbons Prepared from Glucose and Fructose—Detailed Characterization and Testing in Heavy Metals and Methylene Blue Removal

by Sanja Krstić, Milan Kragović, Maja Pagnacco, Vladimir Dodevski, Branka Kaluđerović, Miloš Momčilović, Ivica Ristović and Marija Stojmenović

Minerals 2018, 8(6), 246; https://doi.org/10.3390/min8060246 - 9 Jun 2018

Cited by 10 | Viewed by 5070

Abstract

In the presented paper, activated carbons were prepared from fructose and glucose, and activating agents (KOH, NaOH, LiOH) by hydrothermal treatment (HTC) treatment. After preparation, samples were characterized in details. Different techniques were used: x-ray powder diffraction analysis, Raman spectral analysis, elemental analysis, [...] Read more.

In the presented paper, activated carbons were prepared from fructose and glucose, and activating agents (KOH, NaOH, LiOH) by hydrothermal treatment (HTC) treatment. After preparation, samples were characterized in details. Different techniques were used: x-ray powder diffraction analysis, Raman spectral analysis, elemental analysis, and determination of textural and morphological properties. Obtained results showed dependence of investigated properties and the nature of precursors (glucose or fructose) as well as the type of hydroxides used as activating agents. After characterization, samples were tested as materials for heavy metals (Pb²⁺, Cd²⁺ and Zn²⁺) and methylene blue removal. Also, adsorption experiments were performed on wastewaters taken from tailings of the lead and zinc mine and kinetic of the methylene blue removal was studied. The factors which distinguished the KOH activated samples were high yield (~14%), content of organic carbon (63–74%), porosity and specific surface area (S_BET ~700–1360 m²/g), a low degree of the crystal phase, indications that potassium ions may be included in heavy metals removal, good removal of the heavy metal ions (~47–59 mg/g for Pb²⁺, ~21–27 mg/g for Cd²⁺ and ~6–10 mg/g for Zn²⁺) and fast (~10–30 min) and good methylene blue (~60–200 mg/g) removal. Full article

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13 pages, 5078 KiB

Open AccessArticle

Selective Liberation of High-Phosphorous Oolitic Hematite Assisted by Microwave Processing and Acid Leaching

by Xianyan Cai, Gongming Qian, Bo Zhang, Qiushi Chen and Chenqiang Hu

Minerals 2018, 8(6), 245; https://doi.org/10.3390/min8060245 - 7 Jun 2018

Cited by 13 | Viewed by 4222

Abstract

The release of valuable minerals from the associated gangues is called liberation. Good liberation is essential to the subsequent separation stage. Selective liberation is advantageous to improve the degree of liberation. Oolitic hematite is one of the typical refractory iron ores in China, [...] Read more.

The release of valuable minerals from the associated gangues is called liberation. Good liberation is essential to the subsequent separation stage. Selective liberation is advantageous to improve the degree of liberation. Oolitic hematite is one of the typical refractory iron ores in China, and its resources are abundant. However, owing to its fine dissemination and complex mineralogical texture, the conventional grinding processes are inefficient in improving the selective liberation of oolitic hematite. In this study, microwave processing and acid leaching were used to assist the liberation of oolitic hematite. The assisted liberation of the oolitic hematite mechanisms of microwave processing and acid leaching were studied by using scanning electron microscope (SEM), X-ray diffraction (XRD), BET specific surface area detection method (BET) and the transflective microscope method. The results indicated that microwave processing can reduce the mechanical strength of oolitic hematite and improve the liberation of hematite, and acid leaching can improve the microwave-assisted liberation efficiency and reduce the content of phosphorus in the grinding product. Compared to direct grinding, the liberation of hematite increased by 54.80% in the grinding product, and especially, the fractions of −0.038-mm and 0.05–0.074 mm increased significantly; however, there was no obvious change in other grain sizes, and the dephosphorization ratio reached 47.20% after microwave processing and acid leaching. After the two stages, the iron grade and recovery of the magnetic separation product increased by 14.26% and 34.62%, respectively, and the dephosphorization ratio reached 88.59%. It is demonstrated that microwave processing and acid leaching comprise an efficient method to improve the liberation of hematite and the dephosphorization ratio of oolitic hematite. The two-stage treatment can achieve selective liberation of oolitic hematite, which is beneficial to the following magnetic separation. Full article

(This article belongs to the Special Issue Process Mineralogy of Critical Metals)

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13 pages, 5108 KiB

Open AccessArticle

Particle-Crushing Characteristics and Acoustic-Emission Patterns of Crushing Gangue Backfilling Material under Cyclic Loading

by Junmeng Li, Yanli Huang, Zhongwei Chen, Meng Li, Ming Qiao and Mehmet Kizil

Minerals 2018, 8(6), 244; https://doi.org/10.3390/min8060244 - 7 Jun 2018

Cited by 41 | Viewed by 4919

Abstract

In solid backfilling coal mining (SBCM), the crushed gangue backfilling material (CGBM) is generally compacted circularly by a compaction machine in order to reduce its compressibility. In this cyclic compaction process, the particles are crushed, which has a significant effect on the deformation [...] Read more.

In solid backfilling coal mining (SBCM), the crushed gangue backfilling material (CGBM) is generally compacted circularly by a compaction machine in order to reduce its compressibility. In this cyclic compaction process, the particles are crushed, which has a significant effect on the deformation resistance of CGBM. However, the deformation resistance of CGBM is critical for controlling overburden strata movement and ground surface subsidence. This study implemented an experimental approach to investigate the particle-crushing characteristics and acoustic-emission (AE) characteristics of CGBM during constant-amplitude cyclic loading (CACL). At the same time, the relationship between particle crushing and AE signals was established. The results showed that the gangue particles were generally in the shape of irregular convex polyhedrons with more edges and angles that were prone to breakage. It also demonstrated that both the crushing ratio (B_g) and the newly produced fine granule content increased with the cyclic loading times. The content of newly generated fine particles can reflect the particle-crushing conditions to a certain extent. What is more, it was found that the CGBM samples exhibited an apparent Felicity effect during CACL, and AE signals were the most active during the first loading cycle. The crushing ratio of CGBM was highly correlated to the AE signals, which indicated that AE signals can be used to reflect the particle-crushing situation of CGBM. This study is of great significance for obtaining an in-depth understanding of the mechanical properties of CGBM, as well as providing guidance for the engineering practice of SBCM. Full article

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

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13 pages, 5666 KiB

Open AccessArticle

Subsidence Management System for Underground Mining

by Lluís Sanmiquel, Marc Bascompta, Carla Vintró and Teresa Yubero

Minerals 2018, 8(6), 243; https://doi.org/10.3390/min8060243 - 7 Jun 2018

Cited by 22 | Viewed by 6273

Abstract

Potash mining is an important economic activity in the north-east of Spain. However, one of the main environmental issues produced for such type of mining is subsidence, which generates horizontal and vertical ground displacements. A Geographic Information System (GIS)-based model is proposed as [...] Read more.

Potash mining is an important economic activity in the north-east of Spain. However, one of the main environmental issues produced for such type of mining is subsidence, which generates horizontal and vertical ground displacements. A Geographic Information System (GIS)-based model is proposed as a management system in a case study with two mines. This system is able to deal with subsidence data and its behavior over time. More than 1300 control points are included in the GIS, with data since 2007. These data processed by the GIS allowed determining the module, sense and direction of the displacements, the sinking velocity and the possible affectation of subsidence to infrastructures and buildings. Hence, the system created can be a useful tool to manage subsidence data, determine its evolution, predict future environmental and social impacts and control corrective measures. Full article

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16 pages, 3401 KiB

Open AccessArticle

Mineralogical and Elemental Composition of Pectinatella magnifica and Its Statoblasts

by Kazue Tazaki, Atsuko Fukuyama, Fumie Tazaki, Masayuki Okuno, Yumiko Hashida, Shozo Hashida, Teruaki Takehara, Keiichi Nakamura and Tomohiro Kato

Minerals 2018, 8(6), 242; https://doi.org/10.3390/min8060242 - 7 Jun 2018

Viewed by 5006

Abstract

Several massive colonies of Pectinatella magnifica have been observed during the summer almost every year since 1974 in agricultural reservoir ponds and lakes with dirty freshwater environments in Ishikawa, Japan, which has posed serious environmental problems on the shores of Hokuriku District. We [...] Read more.

Several massive colonies of Pectinatella magnifica have been observed during the summer almost every year since 1974 in agricultural reservoir ponds and lakes with dirty freshwater environments in Ishikawa, Japan, which has posed serious environmental problems on the shores of Hokuriku District. We collected Pectinatella magnifica during the summer at Kahokugata Lake and Makiyama agricultural reservoir pond in June and July 2016. However, scientific data for the statoblasts of Pectinatella magnifica are limited. Our results for scanning electron microscopy equipped with energy-dispersive spectroscopy (SEM-EDS), inductively coupled plasma-mass spectrometry (ICP-MS), and X-ray powder diffraction (XRD) analyses of Pectinatella magnifica indicated immobilization of the chemical elements that were involved in the mass during the summer. We also reported the characterization of an invasive species of bryozoan (Pectinatella magnifica) in lakes and ponds in Ishikawa, Japan, based on field observations in 2016. We studied the microstructure, mineralogy, chemical composition, and radioactivity associated with these organisms, using a combination of micro-techniques, SEM-EDS, associated with ICP-MS, and XRD. This study aims to illustrate the capability of Pectinatella magnifica to produce minerals within statoblasts and gelatinous material. Obtained results may indicate forming quartz, palygorskite, dolomite, bischofite, pyrolusite, and pyrite, associated with native sulfur and copper in the statoblast. The mass of gelatinous material contains talc and vermiculite as well as non-crystalline phase. The mechanism of biomineral formation has important implications for water–mineral–organism or microorganism interactions both in lower drainage basin systems, such as Kahokugata Lake, and upper water areas, such as Makiyama agricultural reservoir pond. Many types with variety of sizes and shapes of bryozoan (Pectinatella magnifica) were found in lakes and ponds in Japan. The biomineralization systems will be made available for use not only in researching bryozoans (Pectinatella magnifica), but also for environmental change systems from upstream to downstream of the lake. To date, there have been no reports on related electron microscopy observations, including the real-life occurrence of “bioremediation”. These observations could lead to simple methods of removing statoblasts of the invasive alien species Pectinatella magnifica from agricultural and reservoir environments, because there was limited microbial immobilization of the ions during the winter. Full article

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20 pages, 7595 KiB

Open AccessReview

Deformation Processes, Textural Evolution and Weakening in Retrograde Serpentinites

by Cecilia Viti, Cristiano Collettini, Telemaco Tesei, Matthew S. Tarling and Steven A.F. Smith

Minerals 2018, 8(6), 241; https://doi.org/10.3390/min8060241 - 5 Jun 2018

Cited by 34 | Viewed by 9002

Abstract

Serpentinites play a key role in controlling fault rheology in a wide range of geodynamic settings, from oceanic and continental rift zones to subduction zones. In this paper, we provide a summary of the most common deformation mechanisms and frictional strengths of serpentine [...] Read more.

Serpentinites play a key role in controlling fault rheology in a wide range of geodynamic settings, from oceanic and continental rift zones to subduction zones. In this paper, we provide a summary of the most common deformation mechanisms and frictional strengths of serpentine minerals and serpentinites. We focus on deformation mechanisms in retrograde serpentinites, which show a progressive evolution from undeformed mesh and bastite pseudomorphic textures to foliated, ribbon-like textures formed by lizardite with strong crystallographic and shape preferred orientations. We also discuss the possible mechanical significance of anastomosing slickenfibre veins containing ultraweak fibrous serpentines or relatively strong splintery antigorite. Our review and new observations indicate that pressure solution and frictional sliding are the most important deformation mechanisms in retrograde serpentinite, and that they are frictionally weak (μ ~0.3). The mineralogical and microstructural evolution of retrograde serpentinites during shearing suggests that a further reduction of the friction coefficient to μ of 0.15 or less may occur during deformation, resulting in a sort of continuous feedback weakening mechanism. Full article

(This article belongs to the Special Issue Serpentine Group Minerals)

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15 pages, 3303 KiB

Open AccessArticle

Chemical-Petrographic Types and Shock Metamorphism of 184 Grove Mountains Equilibrated Ordinary Chondrites

by Deqiu Dai, Shuang Liu and Xuemei Liu

Minerals 2018, 8(6), 240; https://doi.org/10.3390/min8060240 - 4 Jun 2018

Cited by 3 | Viewed by 3941

Abstract

We reported the petrography and mineral chemistry of 184 equilibrated ordinary chondrites collected from Grove Mountains, Antarctica. The chemical-petrographic types and shock metamorphism degrees of these chondrites were assigned. They were classified into 46 H groups (22 H4, 20 H5, and four H6), [...] Read more.

We reported the petrography and mineral chemistry of 184 equilibrated ordinary chondrites collected from Grove Mountains, Antarctica. The chemical-petrographic types and shock metamorphism degrees of these chondrites were assigned. They were classified into 46 H groups (22 H4, 20 H5, and four H6), 133 L groups (eight L4, 75 L5, and 50 L6), and five LL groups (four LL4 and one LL5). Some of these chondrites could be paired; however, both H and L group meteorites were affected. Further studies such as terrestrial ages and thermal luminescence are required in order to confirm the pairings. The relative abundances of H, L, and LL are different in Grove Mountain meteorites, when compared to those in Transcontinental Ridge meteorites. Based on the shock effects, the shock metamorphism degrees of these chondrites were assigned. Compared to previous studies, the heavily shocked samples of S4 and S5 have a higher fraction (59 out of 184) in Grove Mountain ordinary chondrites. The L group (54 out of 59) is the dominant chemical group in the heavily shocked chondrites, except for five meteorites which belong to the H group. The shock metamorphism degrees of the H and L groups are distinct, which may indicate different surface properties in their parent bodies. In addition, the petrologic types and shock degrees are probably closely related, with the most heavily shocked chondrites observed in types 5 and 6. Full article

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3 pages, 178 KiB

Open AccessEditorial

Editorial for Special Issue “Nucleation of Minerals: Precursors, Intermediates and Their Use in Materials Chemistry”

by Denis Gebauer

Minerals 2018, 8(6), 239; https://doi.org/10.3390/min8060239 - 4 Jun 2018

Cited by 2 | Viewed by 3058

Abstract

n/a Full article

(This article belongs to the Special Issue Nucleation of Minerals: Precursors, Intermediates and Their Use in Materials Chemistry)

16 pages, 3111 KiB

Open AccessArticle

Leaching of Chalcopyrite in Acidified Nitrate Using Seawater-Based Media

by Pía C. Hernández, María E. Taboada, Osvaldo O. Herreros, Teófilo A. Graber and Yousef Ghorbani

Minerals 2018, 8(6), 238; https://doi.org/10.3390/min8060238 - 1 Jun 2018

Cited by 36 | Viewed by 5868

Abstract

The leaching of copper from industrial copper ore with 4.8 wt % chalcopyrite by acidified nitrate with seawater based media was investigated. Water quality (pure water and seawater), temperature (25–70 °C), reagent concentration, and nitrate type (sodium and potassium) were studied variables. Leaching [...] Read more.

The leaching of copper from industrial copper ore with 4.8 wt % chalcopyrite by acidified nitrate with seawater based media was investigated. Water quality (pure water and seawater), temperature (25–70 °C), reagent concentration, and nitrate type (sodium and potassium) were studied variables. Leaching conditions were: 100 g ore/1 L solution; P₈₀ of 62.5 µm; 400 rpm and leaching time, varying between 3 and 7 days. Nitrates in sulfuric acid are known to be good oxidants for sulfide ores. This study showed that up to 80 wt % copper could be extracted at 45 °C in 7 days. In the absence of nitrate, under the same leaching conditions, only a 28 wt % copper extraction was achievable. The extraction rate increased to 97.2 wt % when leach temperature was increased to 70 °C in nitrate-chloride-acid media. The presence of chloride ions also increased the copper extraction rate. The copper extraction achieved in seawater systems were higher than in water systems under the same leaching conditions (increased by an average of 18 wt %). This effect can be attributable to the contribution of chloride that increases proton (H⁺) activity. Full article

(This article belongs to the Special Issue Recent Advances in Hydro- and Biohydrometallurgy)

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12 pages, 4528 KiB

Open AccessArticle

Chemical and Mineralogical Characterization of Recycled Aggregates from Construction and Demolition Waste from Mexico City

by Emiliano Moreno-Pérez, Juan Hernández-Ávila, Yamile Rangel-Martínez, Eduardo Cerecedo-Sáenz, Alberto Arenas-Flores, Ma. Isabel Reyes-Valderrama and Eleazar Salinas-Rodríguez

Minerals 2018, 8(6), 237; https://doi.org/10.3390/min8060237 - 31 May 2018

Cited by 35 | Viewed by 5656

Abstract

In this study, four samples of recycled aggregates from the construction and demolition waste of Mexico City were characterized in order to find innovative uses for these types of materials. Gravel and sand from a recycling plant were analyzed, as well as aggregates [...] Read more.

In this study, four samples of recycled aggregates from the construction and demolition waste of Mexico City were characterized in order to find innovative uses for these types of materials. Gravel and sand from a recycling plant were analyzed, as well as aggregates produced in the laboratory from demolished concrete collected from landfills. The characterization was carried out by means of XRD (X-ray Diffraction), chemical microanalysis (EDS), X-ray fluorescence (XRF), pH measurement, and sieve analysis. The minerals present in the analyzed materials were feldspars, cristobalite and pyroxene, which corresponded to the natural aggregates, as well as variable amounts of calcite, a product of the carbonation of the cement paste adhered to these aggregates, and in a smaller proportion, calcium hemicarboaluminate, rosenhanite, and tobermorite. The quality (amount of cement) of the original concrete has a great influence on the granulometry and the chemical–mineralogical composition of the aggregates, since there will be different quantities and qualities of the cement paste adhered to the aggregates depending on their size. Finally, the pH values measured in all samples fluctuated between 10.15 and 12.08, suggesting that these materials can be used in soil stabilization or in agricultural applications. Full article

(This article belongs to the Special Issue Petrography of Construction Materials: Compositional, Mineralogical and Textural Features)

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11 pages, 1046 KiB

Open AccessArticle

Comparison of Heterotrophic Bioleaching and Ammonium Sulfate Ion Exchange Leaching of Rare Earth Elements from a Madagascan Ion-Adsorption Clay

by Megan J. Barnett, Barbara Palumbo-Roe and Simon P. Gregory

Minerals 2018, 8(6), 236; https://doi.org/10.3390/min8060236 - 30 May 2018

Cited by 38 | Viewed by 7893

Abstract

Rare earth elements (REE) are considered to be a critical resource, because of their importance in green energy applications and the overdependence on Chinese imports. REE rich ion-adsorption deposits (IAD) result from tropical weathering of REE enriched igneous rocks. Commercial REE leaching from [...] Read more.

Rare earth elements (REE) are considered to be a critical resource, because of their importance in green energy applications and the overdependence on Chinese imports. REE rich ion-adsorption deposits (IAD) result from tropical weathering of REE enriched igneous rocks. Commercial REE leaching from IAD, using salt solutions occurs via an ion-exchange mechanism. Bioleaching of IAD by Aspergillus or Bacillus, was compared to Uninoculated Control and Salt leaching (0.5 M ammonium sulfate) over 60 days. Salt leaching was most effective, followed by Aspergillus, Bacillus then Uninoculated Control. Most of the REE and major elements released by Salt leaching occurred before day 3. With bioleaching, REE and major elements release increased with time and had a greater heavy to light REE ratio. Similar total heavy REE release was observed in Salt leaching and Aspergillus (73.1% and 70.7% Lu respectively). In bioleaching experiments, pH was inversely correlated with REE release (R² = 0.947 for Lu) indicating leaching by microbially produced acids. These experiments show the potential for bioleaching of REE from IAD, but dissolution of undesirable elements could cause problems in downstream processing. Further understanding of the bioleaching mechanisms could lead to optimization of REE recovery. Full article

(This article belongs to the Collection Bioleaching)

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14 pages, 2359 KiB

Open AccessArticle

Galvanic Leaching of Seafloor Massive Sulphides Using MnO₂ in H₂SO₄-NaCl Media

by Przemyslaw B. Kowalczuk, Dan Oliric Manaig, Kristian Drivenes, Ben Snook, Kurt Aasly and Rolf Arne Kleiv

Minerals 2018, 8(6), 235; https://doi.org/10.3390/min8060235 - 30 May 2018

Cited by 13 | Viewed by 5518

Abstract

This paper reports the leaching of seafloor massive sulphides (SMS) from the Loki’s Castle area at the Arctic Mid-Ocean Ridge in sulphuric acid with manganese dioxide and sodium chloride. The results presented are of various leaching experiments conducted under different conditions in order [...] Read more.

This paper reports the leaching of seafloor massive sulphides (SMS) from the Loki’s Castle area at the Arctic Mid-Ocean Ridge in sulphuric acid with manganese dioxide and sodium chloride. The results presented are of various leaching experiments conducted under different conditions in order to optimise the dissolution of copper and silver. It was shown that the main copper bearing minerals in the SMS were chalcopyrite and isocubanite, while silver could occur as an admixture in the crystallographic lattice of sulphides or as disseminated micro inclusions. Based on the results, the leaching mechanism was discussed and elucidated. It was shown that the dissolution of the SMS was mainly due to galvanic interactions between the primary marine minerals of SMS and manganese dioxide. Addition of sodium chloride promoted the extraction mechanism. Full article

(This article belongs to the Special Issue Marine Minerals of the Deep Sea: Mineralogy, Crystallography and Their Use for Tailored Processing and Metal Extraction)

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15 pages, 1880 KiB

Open AccessArticle

Femtosecond Laser Ablation-ICP-Mass Spectrometry and CHNS Elemental Analyzer Reveal Trace Element Characteristics of Danburite from Mexico, Tanzania, and Vietnam

by Le Thi-Thu Huong, Laura M. Otter, Michael W. Förster, Christoph A. Hauzenberger, Kurt Krenn, Olivier Alard, Dorothea S. Macholdt, Ulrike Weis, Brigitte Stoll and Klaus Peter Jochum

Minerals 2018, 8(6), 234; https://doi.org/10.3390/min8060234 - 29 May 2018

Cited by 10 | Viewed by 5156

Abstract

Danburite is a calcium borosilicate that forms within the transition zones of metacarbonates and pegmatites as a late magmatic accessory mineral. We present here trace element contents obtained by femtosecond laser ablation-inductively coupled plasma (ICP)-mass spectrometry for danburite from Mexico, Tanzania, and Vietnam. [...] Read more.

Danburite is a calcium borosilicate that forms within the transition zones of metacarbonates and pegmatites as a late magmatic accessory mineral. We present here trace element contents obtained by femtosecond laser ablation-inductively coupled plasma (ICP)-mass spectrometry for danburite from Mexico, Tanzania, and Vietnam. The Tanzanian and Vietnamese samples show high concentrations of rare earth elements (∑REEs 1900 µg∙g⁻¹ and 1100 µg∙g⁻¹, respectively), whereas Mexican samples are depleted in REEs (<1.1 µg∙g⁻¹). Other traces include Al, Sr, and Be, with Al and Sr dominating in Mexican samples (325 and 1611 µg∙g⁻¹, respectively). Volatile elements, analyzed using a CHNS elemental analyzer, reach <3000 µg∙g⁻¹. Sr and Al are incorporated following Ca²⁺ = Sr²⁺ and 2 B³⁺ + 3 O²⁻ = Al³⁺ + 3 OH⁻ + □ (vacancy). REEs replace Ca²⁺ with a coupled substitution of B³⁺ by Be²⁺. Cerium is assumed to be present as Ce⁴⁺ in Tanzanian samples based on the observed Be/REE molar ratio of 1.5:1 following 2 Ca²⁺ + 3 B³⁺ = Ce⁴⁺ + REE³⁺ + 3 Be²⁺. In Vietnamese samples, Ce is present as Ce³⁺ seen in a Be/REE molar ratio of 1:1, indicating a substitution of Ca²⁺ + B³⁺ = REE³⁺ + Be²⁺. Our results imply that the trace elements of danburite reflect different involvement of metacarbonates and pegmatites among the different locations. Full article

(This article belongs to the Special Issue Mineralogy and Geochemistry of Gems)

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22 pages, 9523 KiB

Open AccessArticle

Geophysical Investigation of the Pb–Zn Deposit of Lontzen–Poppelsberg, Belgium

by Maxime Evrard, Gaël Dumont, Thomas Hermans, Michel Chouteau, Olivier Francis, Eric Pirard and Frédéric Nguyen

Minerals 2018, 8(6), 233; https://doi.org/10.3390/min8060233 - 29 May 2018

Cited by 20 | Viewed by 10020

Abstract

The drillhole information from the Lontzen–Poppelsberg site has demonstrated three orebodies and has allowed the estimation of the extension of the lodes, their dip, and the location at the ground surface. The localisation of the lodes makes them excellent targets for further exploration [...] Read more.

The drillhole information from the Lontzen–Poppelsberg site has demonstrated three orebodies and has allowed the estimation of the extension of the lodes, their dip, and the location at the ground surface. The localisation of the lodes makes them excellent targets for further exploration with geophysics. This deposit is classified as a Mississippi Valley Type (MVT) deposit. It consists mainly of Pb–Zn–Fe sulphides that display contrasting values in resistivity, chargeability, density, and magnetic susceptibility, with regards to the sedimentary host rocks. The dipole–dipole direct current (DC) resistivity and induce polarization (IP) profiles have been collected and inverted to successfully delineate the Pb–Zn mineralization and the geological structures. Short-spacing EM34 electromagnetic conductivity data were collected mainly on the top of Poppelsberg East lode and have revealed a conductive body matching with the geologically modelled mineralization. Gravity profiles have been carried out perpendicularly to the lode orientation; they show a strong structural anomaly. High resolution ground magnetic data were collected over the study area, but they showed no anomaly over the ore deposits. The geophysical inversion results are complementary to the model based on drill information, and allow us to refine the delineation of the mineralization. The identification of the geophysical signatures of this deposit permits targeting new possible mineralization in the area. Full article

(This article belongs to the Special Issue Mining and Mineral Exploration Geophysics)

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Minerals, Volume 8, Issue 6 (June 2018) – 42 articles

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