Minerals

13 pages, 4132 KiB

Open AccessArticle

Density Functional Theory and Atomic Force Microscopy Study of Oleate Functioned on Siderite Surface

by Lixia Li, Chen Zhang, Zhitao Yuan, Haiqing Hao and Chenyang Zhao

Minerals 2018, 8(1), 33; https://doi.org/10.3390/min8010033 - 21 Jan 2018

Cited by 14 | Viewed by 5041

Efficiently discovering the interaction of the collector oleate and siderite is of great significance for understanding the inherent function of siderite weakening hematite reverse flotation. For this purpose, investigation of the adsorption behavior of oleate on siderite surface was performed by density functional [...] Read more.

Efficiently discovering the interaction of the collector oleate and siderite is of great significance for understanding the inherent function of siderite weakening hematite reverse flotation. For this purpose, investigation of the adsorption behavior of oleate on siderite surface was performed by density functional theory (DFT) calculations associating with atomic force microscopy (AFM) imaging. The siderite crystal geometry was computationally optimized via convergence tests. Calculated results of the interaction energy and the Mulliken population verified that the collector oleate adsorbed on siderite surface and the covalent bond was established as a result of electrons transferring from O1 atoms (in oleate molecule) to Fe1 atoms (in siderite lattice). Therefore, valence-electrons’ configurations of Fe1 and O1 changed into 3d^6.514s^0.37 and 2s^1.832p^4.73 from 3d^6.214s^0.31 and 2s^1.83p^4.88 correspondingly. Siderite surfaces with or without oleate functioned were examined with the aid of AFM imaging in PeakForce Tapping mode, and the functioned siderite surface was found to be covered by vesicular membrane matters with the average roughness of 16.4 nm assuring the oleate adsorption. These results contributed to comprehending the interaction of oleate and siderite. Full article

► Show Figures

Figure 1

18 pages, 12162 KiB

Open AccessArticle

Dating Ore Deposit Using Garnet U–Pb Geochronology: Example from the Xinqiao Cu–S–Fe–Au Deposit, Eastern China

by Yu Zhang, Yongjun Shao, Rongqing Zhang, Dengfeng Li, Zhongfa Liu and Huayong Chen

Minerals 2018, 8(1), 31; https://doi.org/10.3390/min8010031 - 19 Jan 2018

Cited by 41 | Viewed by 7664

Abstract

The large Xinqiao Cu–S–Fe–Au deposit in the Tongling ore district, Eastern China, is characterized by a large-scale stratiform orebody, in which garnet is widely distributed as the main gangue mineral associated with mineralization. Xinqiao garnet can be divided into early (Grt1) and late [...] Read more.

The large Xinqiao Cu–S–Fe–Au deposit in the Tongling ore district, Eastern China, is characterized by a large-scale stratiform orebody, in which garnet is widely distributed as the main gangue mineral associated with mineralization. Xinqiao garnet can be divided into early (Grt1) and late (Grt2) generations based on extensive back-scattered electron (BSE) imaging observations. Laser ablation (LA)-ICP-MS trace element and U–Pb isotope composition analyses indicate that uranium occurs homogeneously within the Xinqiao garnet, and Grt1 and Grt2 have weighted average ²⁰⁷Pb-corrected ²⁰⁶Pb/²³⁸U ages of 137.0 ± 7.8 Ma (Mean standard weighted deviation (MSWD) = 4.9) and 129.6 ± 7.1 Ma (MSWD = 1.6), respectively, similar to the zircon U–Pb age (139.6 ± 1.5 Ma) of the Jitou intrusion. These garnet U–Pb ages, combined with the low MnO content and various Y/Ho ratios, suggest that the Xinqiao garnet is likely to have a magmatic hydrothermal replacement origin associated with the Jitou stock. Based on previous studies of the Xinqiao deposit, we infer that the Xinqiao stratiform orebody may have formed from the Early Cretaceous magmatic hydrothermal fluids associated with the Jitou stock, and may have been generated by the Early Cretaceous tectono-thermal event in Eastern China. Full article

► Show Figures

Graphical abstract

10 pages, 344 KiB

Open AccessEditorial

Acknowledgement to Reviewers of Minerals in 2017

by Minerals Editorial Office

Minerals 2018, 8(1), 30; https://doi.org/10.3390/min8010030 - 19 Jan 2018

Viewed by 3200

Abstract

Peer review is an essential part in the publication process, ensuring that Minerals maintains high quality standards for its published papers [...]
Full article

16 pages, 5445 KiB

Open AccessArticle

Thermal Stability of Woolly Erionite-K and Considerations about the Heat-Induced Behaviour of the Erionite Group

by Paolo Ballirano, Alessandro Pacella, Andrea Bloise, Matteo Giordani and Michele Mattioli

Minerals 2018, 8(1), 28; https://doi.org/10.3390/min8010028 - 19 Jan 2018

Cited by 23 | Viewed by 3671

Abstract

The thermal behavior of a woolly erionite-K sample (Lander County, NV, USA), chemical formula (Ca_2.03Na_0.73K_2.52Mg_0.26)[Al_8.22Si_27.78O_71.80]·35.94H₂O, was investigated in the 303–1173 K thermal range by in situ X-ray [...] Read more.

The thermal behavior of a woolly erionite-K sample (Lander County, NV, USA), chemical formula (Ca_2.03Na_0.73K_2.52Mg_0.26)[Al_8.22Si_27.78O_71.80]·35.94H₂O, was investigated in the 303–1173 K thermal range by in situ X-ray powder diffraction. Present data suggest a general thermally-induced volume contraction whose magnitude increases as

\frac{S i}{S i + A l}

ratio becomes smaller. An inverse correlation between

\frac{S i}{S i + A l}

ratio and T_dehydr is observed because higher

\frac{S i}{S i + A l}

ratio values are associated to lower dehydration temperatures. A positive dependence exists between

\frac{S i}{S i + A l}

ratio and T_break. A higher Si content results in a greater thermal stability, in agreement with the general trend observed in zeolites. On the contrary, no correlation has been found between T_break and weighted ionic potential (Z/r)_wt as suggested by reference data. Heating produces a general depletion of the Ca1, Ca2, Ca3, and K1 sites, which is counterbalanced by an increase of the K2 site scattering, even though the latter is not populated at RT. No “internal ion exchange” mechanism was apparently acting in the present sample differently from other erionite samples analysed in the past. At 303 K approximately 20 e⁻ allocated at the OW H₂O sites might be assigned to (extra-framework) EF cations. Such fraction increases due to their migration from the extra-framework cation sites following the same mechanism reported in reference data. Full article

(This article belongs to the Special Issue Natural Zeolites)

► Show Figures

Figure 1

15 pages, 6096 KiB

Open AccessArticle

Following the Amphibolite to Greenschist Metamorphic Path through the Structural Parameters of Spinels from Amsaga (Mauritania)

by Davide Lenaz, Henrik Skogby, Nicola Rigonat and Julien Berger

Minerals 2018, 8(1), 27; https://doi.org/10.3390/min8010027 - 18 Jan 2018

Cited by 5 | Viewed by 5040

Abstract

We investigated the crystal and structural behavior of several Cr-bearing spinels from the Archean chromitites of Amsaga (Mauritania). The chemical and structural data testified a retrograde metamorphism from amphibolite to greenschist facies, witnessed by relative changes in the amount of all the major [...] Read more.

We investigated the crystal and structural behavior of several Cr-bearing spinels from the Archean chromitites of Amsaga (Mauritania). The chemical and structural data testified a retrograde metamorphism from amphibolite to greenschist facies, witnessed by relative changes in the amount of all the major oxides (Cr, Al, Mg, Fe²⁺, Fe³⁺), the relative proportion of Fe³⁺/Fe_tot as well as the structural parameters, including the cell edge and the oxygen coordinate. The general agreement between electron microprobe and Mössbauer data indicates that the analyzed spinels are stoichiometric. The structural data revealed that the oxygen positional parameter of amphibole-bearing samples is the highest observed among Cr-bearing spinels with similar Cr# and Mg#. Consequently, it is suggested that a structural study of detrital Cr-spinels could be important in discriminating an amphibole-chromitite source from an ophiolite source. Full article

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

► Show Figures

Figure 1

20 pages, 14072 KiB

Open AccessArticle

Sb-Bi Alloys and Ag-Cu-Pb-Sb-Bi Sulphosalts in the Jialong Cu-Sn Deposit in North Guangxi, South China

by Jianping Liu, Weikang Chen and Qingquan Liu

Minerals 2018, 8(1), 26; https://doi.org/10.3390/min8010026 - 16 Jan 2018

Cited by 4 | Viewed by 5745

Abstract

Although native bismuth is a relatively common mineral, native antimony is less abundant, and Sb-Bi alloys are relatively rare phases in Nature. Sb-Bi alloys and Ag-Cu-Pb-Sb-Bi sulphosalts have been discovered in the Jialong vein-type Cu-Sn deposit in North Guangxi, South China. The Jialong [...] Read more.

Although native bismuth is a relatively common mineral, native antimony is less abundant, and Sb-Bi alloys are relatively rare phases in Nature. Sb-Bi alloys and Ag-Cu-Pb-Sb-Bi sulphosalts have been discovered in the Jialong vein-type Cu-Sn deposit in North Guangxi, South China. The Jialong deposit is hosted by schist within the contact zone of a Neoproterozoic granite. Four stages of ore formation are recognised, with the Sb-Bi alloy- and sulphosalt-bearing assemblage formed during the third stage. Sulphosalts include Pb-Bi-Ag sulphosalts (pavonite), Sb-Bi sulphosalts (tintinaite, terrywallaceite), and Sb sulphosalt (ullmanite, freibergite, bournonite). Grains of Sb-Bi alloy measure 2–20 μm in diameter, show rounded margins and occur together with galena along the edges or internal fissures of sulphosalts. The Sb-Bi alloys do not coexist with bismuthinite, BiS (an unnamed mineral), or with native bismuth. Two phases of Sb-Bi alloys are identified based on back-scattered electron image observations and electron microprobe analysis. The textural and thermodynamic relationships indicate that Phase I was formed before Phase II. Phase I contains high Sb (69.15–80.12 wt %) and lower Bi (18.01–27.85 wt %), while Phase II contains low Sb (0.89–25.24 wt %) and high Bi (72.95–98.89 wt %). Cooling in the range of 270–400 °C and decreasing sulphur fugacity promote precipitation of Sb-Bi alloys and sulphosalts during the late stage of incursion of Sb- and Bi-bearing magmatic hydrothermal fluids. Full article

► Show Figures

Figure 1

14 pages, 5508 KiB

Open AccessArticle

Efficient Extraction of Vanadium from Vanadium–Titanium Magnetite Concentrate by Potassium Salt Roasting Additives

by Renmin Li, Tao Liu, Yimin Zhang, Jing Huang and Chengbao Xu

Minerals 2018, 8(1), 25; https://doi.org/10.3390/min8010025 - 15 Jan 2018

Cited by 31 | Viewed by 6166

Abstract

In this paper, potassium salt roasting additives were applied to extract vanadium from vanadium–titanium magnetite concentrate. Meanwhile, the mechanisms of potassium salt roasting and acid leaching kinetics were investigated. The results indicate that potassium salt roasting additives are more efficient than sodium and [...] Read more.

In this paper, potassium salt roasting additives were applied to extract vanadium from vanadium–titanium magnetite concentrate. Meanwhile, the mechanisms of potassium salt roasting and acid leaching kinetics were investigated. The results indicate that potassium salt roasting additives are more efficient than sodium and calcium salt and that K₂SO₄ works best. Under certain conditions (a dosage of K₂SO₄ of 4 wt %, a roasting temperature of 900 °C, a roasting time of 1 h, a leaching temperature of 95 °C, a sulfuric acid concentration of 10% (v/v), and a leaching time of 1.5 h with a liquid to solid ratio of 3 mL/g) the vanadium leaching efficiency reached 71.37%, an increase of 30.20% compared to that of blank roasting. Additionally, XRD and related SEM-EDS analyses indicated that K₂SO₄ fully destroyed the structure of vanadium-bearing minerals such as magnetite, and promoted the generation of soluble KVO₃ to inhibit the formation of insoluble Ca(VO₃)₂ in the roasting process. Furthermore, it promoted the dissolution of sphene and the release of its vanadium in the leaching process, which increased the vanadium leaching efficiency significantly. Meanwhile, leaching kinetics analyses showed that the leaching process was controlled by internal diffusion; the apparent activation energy decreased from 37.43 kJ/mol with blank roasting to 26.31 kJ/mol with potassium salt roasting. The reaction order, with regards to the sulfuric acid concentration, decreased from 0.6588 to 0.5799. Therefore, potassium salt roasting could improve mineral activity, accelerating the leaching process and reducing the dependence on high temperature and high acidity. Full article

► Show Figures

Figure 1

12 pages, 11684 KiB

Open AccessArticle

Vanadium Bioleaching Behavior by Acidithiobacillus ferrooxidans from a Vanadium-Bearing Shale

by Dunpei Wei, Tao Liu, Yimin Zhang, Zhenlei Cai, Jingtao He and Chengbao Xu

Minerals 2018, 8(1), 24; https://doi.org/10.3390/min8010024 - 15 Jan 2018

Cited by 20 | Viewed by 5629

Abstract

This study investigated bioleaching behavior of vanadium from a vanadium-bearing shale using Acidithiobacillus ferrooxidans (A. ferrooxidans). Results showed a maximum recovery of 62% vanadium in 1.2-day bioleaching, which was 22.45% higher than the controls. Then, the vanadium leaching efficiency decreased significantly, [...] Read more.

This study investigated bioleaching behavior of vanadium from a vanadium-bearing shale using Acidithiobacillus ferrooxidans (A. ferrooxidans). Results showed a maximum recovery of 62% vanadium in 1.2-day bioleaching, which was 22.45% higher than the controls. Then, the vanadium leaching efficiency decreased significantly, only 24% of that was obtained on the tenth day. The vanadium extraction in 1.2 days was mainly attributed to the dissolution of vanadium in free oxides of shale. Fe³⁺ produced by A. ferrooxidans promoted the dissolution process. X-ray diffraction (XRD) patterns of the leached residues confirmed the generation of jarosite. SEM-EDS analysis of the residues indicated that jarosite adsorbed on the shale and inhibited the further dissolution of vanadium. The relevance of V, Fe, S, O was quite good in the energy disperse X-ray spectrometry (EDS) element mapping of jarosite, and acid-washing of the jarosite resulted in 31.6% of the vanadium in the precipitates desorption, indicating that the decrease of vanadium leaching efficiency in bioleaching process was caused by both adsorption and co-precipitation with jarosite. Full article

(This article belongs to the Collection Bioleaching)

► Show Figures

Figure 1

16 pages, 4125 KiB

Open AccessArticle

Factors to Enable Crystallization of Environmentally Stable Bioscorodite from Dilute As(III)-Contaminated Waters

by Masahito Tanaka and Naoko Okibe

Minerals 2018, 8(1), 23; https://doi.org/10.3390/min8010023 - 15 Jan 2018

Cited by 23 | Viewed by 3916

Abstract

Applicability of the bioscorodite method (use of the thermo-acidophilic Fe(II)-oxidizing archaeon Acidianus brierleyi for arsenic (As) oxidation and immobilization at 70 °C) was tested for synthetic copper refinery wastewaters of a wide range of dilute initial As(III) concentrations ([As(III)]_ini = 3.3–20 mM) [...] Read more.

Applicability of the bioscorodite method (use of the thermo-acidophilic Fe(II)-oxidizing archaeon Acidianus brierleyi for arsenic (As) oxidation and immobilization at 70 °C) was tested for synthetic copper refinery wastewaters of a wide range of dilute initial As(III) concentrations ([As(III)]_ini = 3.3–20 mM) with varying initial [Fe(II)]/[As(III)] molar ratios ([Fe(II)]_ini/[As(III)]_ini = 0.8–6.0). Crystallization of scorodite (FeAsO₄·2H₂O) tends to become increasingly challenging at more dilute As(III) solutions. Optimization of conditions such as initial pH, seed feeding and initial [Fe(II)]/[As(III)] molar ratio was found critical in improving final As removal and product stability: Whilst setting the initial pH at 1.2 resulted in an immediate single-stage precipitation of crystalline bioscorodite, the initial pH 1.5 led to a two-stage As precipitation (generation of brown amorphous precursors followed by whitish crystalline bioscorodite particles) with a greater final As removal. The formation process of bioscorodite precipitates differed significantly depending on the type of seed crystals fed (bio- versus chemical- scorodite seeds). Feeding the former was found effective not only in accelerating the reaction, but also in forming more recalcitrant bioscorodite products (0.59 mg/L; Toxicity Characteristic Leaching Procedure (TCLP) test). Under such favorable conditions, 94–99% of As was successfully removed as crystalline bioscorodite at all dilute As(III) concentrations tested by setting [Fe(II)]_ini/[As(III)]_ini at 1.4–2.0. Providing an excess Fe(II) (closer to [Fe(II)]_ini/[As(III)]_ini = 2.0) was found beneficial to improve the final As removal (up to 98–99%) especially from more dilute As(III) solutions. Full article

► Show Figures

Figure 1

17 pages, 3871 KiB

Open AccessReview

The Proterozoic Vazante Hypogene Zinc Silicate District, Minas Gerais, Brazil: A Review of the Ore System Applied to Mineral Exploration

by Gema R. Olivo, Lena V. S. Monteiro, Fernando Baia, Paul Slezak, Igor Carvalho, Neil A. Fernandes, Gustavo D. Oliveira, Basilio Botura Neto, Alexandra McGladrey, Adalene M. Silva, Márcia A. Moura and Daniel Layton-Matthews

Minerals 2018, 8(1), 22; https://doi.org/10.3390/min8010022 - 15 Jan 2018

Cited by 12 | Viewed by 7191

Abstract

The Proterozoic Vazante zinc silicate district in Minas Gerais, Brazil, hosts world-class hypogene willemite deposits in dolomitic rocks interbedded with siliciclastic rocks deposited in subtidal to supratidal environments. Willemite ore bodies are structurally controlled along regional NE-trending structures which are interpreted as being [...] Read more.

The Proterozoic Vazante zinc silicate district in Minas Gerais, Brazil, hosts world-class hypogene willemite deposits in dolomitic rocks interbedded with siliciclastic rocks deposited in subtidal to supratidal environments. Willemite ore bodies are structurally controlled along regional NE-trending structures which are interpreted as being active during the Neoproterozoic Brasiliano orogeny. The hydrothermal alteration is characterized by an early stage of Fe-dolomite, which replaced the host dolomitic rocks, followed by precipitation of minor sphalerite and then hematite and willemite. Elements commonly enriched in the zinc ore include As, Ba, Be, Bi, Cd, Co, Fe, Ge, In, Mo, Ni, Sb, Se, U, V and W. Mineralogical, fluid inclusion and isotopic data indicates that mixing of S-poor metalliferous saline fluids with meteoric water favored the formation of willemite ore. Carbonaceous phyllites from the underlying thick siliciclastic sequence show evidence of early enrichment in zinc (and ore-related metals) and remobilization, respectively, prior to and during the Brasiliano orogenic event. This unit is interpreted as a possible source of ore-related elements. It is proposed that during the Brasiliano orogeny, hot (T > 170 °C) saline fluids (>15 wt % eq. NaCl) leached metals from siliciclastic source rocks and precipitated willemite ore in the overlying dolomitic sequence along structures that favored mixing with oxidizing meteoric water. Full article

(This article belongs to the Special Issue Geology and Mineralogy of Zn-Pb Nonsulfide Deposits)

► Show Figures

Figure 1

9 pages, 2859 KiB

Open AccessArticle

Liquid Cell Transmission Electron Microscopy and the Impact of Confinement on the Precipitation from Supersaturated Solutions

by Roland Kröger and Andreas Verch

Minerals 2018, 8(1), 21; https://doi.org/10.3390/min8010021 - 15 Jan 2018

Cited by 29 | Viewed by 5547

Abstract

The study of nucleation and growth from supersaturated ion solutions is a key area of interest in biomineralization research and beyond with high-resolution in situ imaging techniques such as liquid cell transmission electron microscopy (LCTEM) attracting substantial attention. However, there is increasing experimental [...] Read more.

The study of nucleation and growth from supersaturated ion solutions is a key area of interest in biomineralization research and beyond with high-resolution in situ imaging techniques such as liquid cell transmission electron microscopy (LCTEM) attracting substantial attention. However, there is increasing experimental evidence that experiments performed with this technique differ from those performed in bulk solutions due to the spatial restriction, which is a prerequisite for LCTEM to provide electron transparent samples. We have performed 2D Finite Elements (FE) simulations to study the impact of confinement on the steady state concentration profiles around a nanoparticle in a supersaturated solution of the constituent ions. We find that confinement below a critical value significantly reduces the concentration of available ions in solutions and hence the stability of the precipitates. These findings could explain the necessity to substantially increase ion activities of Ca²⁺ and CO₃²⁻ to induce precipitation in LCTEM. Full article

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

► Show Figures

Figure 1

13 pages, 6275 KiB

Open AccessArticle

Recovery and Purification of Tin from Tailings from the Penouta Sn–Ta–Nb Deposit

by Félix Antonio López, Irene García-Díaz, Olga Rodríguez Largo, Francisco García Polonio and Teresa Llorens

Minerals 2018, 8(1), 20; https://doi.org/10.3390/min8010020 - 12 Jan 2018

Cited by 39 | Viewed by 10568

Abstract

A concentrate obtained from mining tailings containing mainly cassiterite and columbotantalite was reduced for the production of tin metal. The compounds CaCO₃, Na₂CO₃, K₂CO₃, and borax were used as fluxes in the pyrometallurgical [...] Read more.

A concentrate obtained from mining tailings containing mainly cassiterite and columbotantalite was reduced for the production of tin metal. The compounds CaCO₃, Na₂CO₃, K₂CO₃, and borax were used as fluxes in the pyrometallurgical reduction smelting process, and graphite was employed as the reducing agent. The greatest recovery of Sn (>95%) was obtained when using CaCO₃ as the flux; the purity of Sn was 96%. A slag equivalent to 25% of the mass of the initial concentrate was produced during the recovery of the Sn. This contained 45% Nb₂O₅ and Ta₂O₅, adding extra value to the mine tailings. The tin metal ingot was purified by electrorefining involving a tin and H₂SO₄ electrolyte solution and a 101.9 A/m² current applied for 148 h. Under these conditions, 90 wt % of the Sn in the ingot was recovered at a purity of 99.97%. Full article

(This article belongs to the Special Issue Minerals in Mine Wastes: Contributions to the Circular Economy)

► Show Figures

Figure 1

9 pages, 2618 KiB

Open AccessArticle

Different Conditions of Formation Experienced by Iron Meteorites as Suggested by Neutron Diffraction Investigation

by Francesco Grazzi, Antonella Scherillo, Vanni Moggi-Cecchi, Marco Morelli, Giovanni Pratesi and Stefano Caporali

Minerals 2018, 8(1), 19; https://doi.org/10.3390/min8010019 - 12 Jan 2018

Cited by 2 | Viewed by 3920

Abstract

In this communication, we report the results of a preliminary neutron diffraction investigation of iron meteorites. These planetary materials are mainly constituted by metallic iron with variable nickel contents, and, owing to their peculiar genesis, are considered to offer the best constrains on [...] Read more.

In this communication, we report the results of a preliminary neutron diffraction investigation of iron meteorites. These planetary materials are mainly constituted by metallic iron with variable nickel contents, and, owing to their peculiar genesis, are considered to offer the best constrains on the early stages of planetary accretion. Nine different iron meteorites, representative of different chemical and structural groups, thought to have been formed in very different pressure and temperature conditions, were investigated, evidencing variances in crystallites size, texturing, and residual strain. The variability of these parameters and their relationship, were discussed in respect to possible diverse range of petrological conditions, mainly pressure and cooling rate, experienced by these materials during the crystallization stage and/or as consequence of post accretion events. Full article

(This article belongs to the Special Issue High Pressure Minerals)

► Show Figures

Figure 1

10 pages, 2391 KiB

Open AccessArticle

Breakage Characteristics of Heat-Treated Limestone Determined via Kinetic Modeling

by Hoon Lee, Kwanho Kim, Jeongyun Kim, Kwangsuk You and Hansol Lee

Minerals 2018, 8(1), 18; https://doi.org/10.3390/min8010018 - 12 Jan 2018

Cited by 8 | Viewed by 4321

Abstract

In recent years, heat treatment has attracted attention as a means to improve the color sorting technology with the aim of improving the quality of low-grade limestone. The crucial stage in this technique is to evaluate the breakage characteristics of the sample materials [...] Read more.

In recent years, heat treatment has attracted attention as a means to improve the color sorting technology with the aim of improving the quality of low-grade limestone. The crucial stage in this technique is to evaluate the breakage characteristics of the sample materials after color sorting. In this study, the breakage characteristics of samples showing color differences after heat treatment and of the original raw material were investigated using a laboratory ball mill. The grinding was characterized using the population balance model. Specific rates of breakage and the primary breakage distribution were experimentally determined by first-order kinetic plots and the BII method. The breakage parameters were also back-calculated by employing a simplex method. Grinding of the three materials indicated first-order kinetics, and the experimental results were well described by the model with parameters obtained by back-calculating. Full article

(This article belongs to the Special Issue Mineral Resources and the Environment)

► Show Figures

Figure 1

14 pages, 8897 KiB

Open AccessArticle

Effect of Mica and Hematite (001) Surfaces on the Precipitation of Calcite

by Huifang Xu, Mo Zhou, Yihang Fang and H. Henry Teng

Minerals 2018, 8(1), 17; https://doi.org/10.3390/min8010017 - 12 Jan 2018

Cited by 27 | Viewed by 7795

Abstract

The substrate effect of mica and hematite on the nucleation and crystallization of calcite was investigated using scanning electron microscope (SEM), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD) methods. On mica, we found, in the absence of Mg²⁺, the substrates’ [...] Read more.

The substrate effect of mica and hematite on the nucleation and crystallization of calcite was investigated using scanning electron microscope (SEM), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD) methods. On mica, we found, in the absence of Mg²⁺, the substrates’ (001) surfaces with hexagonal and pseudo-hexagonal two-dimensional (2-D) structure can affect the orientation of calcite nucleation with calcite (001) ~// mica (001) and calcite (010) ~// mica (010) to be the major interfacial relationship. On hematite, we did not observe frequent twinning relationship between adjacent calcite gains, but often saw preferentially nucleation of calcite at surface steps on hematite substrate. We suggest that calcite crystals initially nucleate from the Ca²⁺ layers adsorbed on the surfaces. The pseudo-hexagonal symmetry on mica (001) surface also leads to the observed calcite (001) twinning. A second and less common orientation between calcite {104} and mica (001) was detected but could be due to local structure damage of the mica surface. Results in the presence of Mg²⁺ show that the substrate surfaces can weaken Mg toxicity to calcite nucleation and lead to a higher level of Mg incorporation into calcite lattice. Full article

(This article belongs to the Special Issue Fundamentals and Frontiers in Mineralogy)

► Show Figures

Graphical abstract

11 pages, 2544 KiB

Open AccessArticle

Influence of the Interaction between Sphalerite and Pyrite on the Copper Activation of Sphalerite

by Bo Yang, Xiong Tong, Zhuoyue Lan, Yiqi Cui and Xian Xie

Minerals 2018, 8(1), 16; https://doi.org/10.3390/min8010016 - 12 Jan 2018

Cited by 14 | Viewed by 4984

Abstract

In this paper, the effect of pyrite on the activation of sphalerite was investigated by micro-flotation, copper adsorption experiments, X-ray photoelectron spectroscopy (XPS), and electrochemical measurement. The micro-flotation test results showed that the recovery and flotation rate of sphalerite with copper sulphate as [...] Read more.

In this paper, the effect of pyrite on the activation of sphalerite was investigated by micro-flotation, copper adsorption experiments, X-ray photoelectron spectroscopy (XPS), and electrochemical measurement. The micro-flotation test results showed that the recovery and flotation rate of sphalerite with copper sulphate as activator and butyl xanthate as collector were significantly decreased with the increasing content of pyrite in pulp. Cu²⁺ adsorption results indicated that the adsorption of Cu²⁺ on the sphalerite surface were decreased when pyrite was present in the pulp. XPS surface analysis demonstrated that the proportion of Cu⁺ species increased in the activation products on the sphalerite surface, but the total atomic concentration of Cu atom was decreased. Linear voltammetry measurement suggested that the current density of Cu⁺ species oxidizing to Cu²⁺ species was increased when sphalerite was electrically contacted with pyrite, which confirmed the increased proportion of Cu⁺ species on Cu-activation sphalerite surface when contacting with pyrite. These results indicated that there is not only a competitive adsorption for cupric ions (Cu²⁺), but the galvanic interaction between sphalerite and pyrite also has a significant influence on the copper activation of sphalerite. Full article

(This article belongs to the Special Issue Flotation Chemistry)

► Show Figures

Figure 1

15 pages, 3823 KiB

Open AccessCase Report

Multi-Stage Flotation for the Removal of Ash from Fine Graphite Using Mechanical and Centrifugal Forces

by Xiangning Bu, Tuantuan Zhang, Yaoli Peng, Guangyuan Xie and Erdong Wu

Minerals 2018, 8(1), 15; https://doi.org/10.3390/min8010015 - 11 Jan 2018

Cited by 41 | Viewed by 6597

Abstract

Graphite ore collected from Hunan province, south China was characterized by chemical analysis, X-ray diffraction, and optical microscopy. Rougher and multi-stage flotation tests using a mechanical flotation cell and a flotation column containing an additional centrifugal force field were carried out to promote [...] Read more.

Graphite ore collected from Hunan province, south China was characterized by chemical analysis, X-ray diffraction, and optical microscopy. Rougher and multi-stage flotation tests using a mechanical flotation cell and a flotation column containing an additional centrifugal force field were carried out to promote its grade and economic value. In rougher flotation, both the mechanical flotation cell and flotation column reduced the ash content of the graphite ore from 15.43% to 10.8%, while the yield of the flotation column (91.41%) was much higher than that of the mechanical flotation cell (50%). In the presence of hydrophobic graphite, the seriously entrained gangue restricted further improvement in the quality and economic value of the graphite ore. Therefore, multi-stage flotation circuits were employed to diminish this entrainment. Multi-stage flotation circuits using the two flotation devices further decreased the ash content of the graphite ore to ~8%, while the yield when using the flotation column was much higher than that obtained from the mechanical flotation cell employed. On the other hand, the ash removal efficiency of the flotation column was 3.82-fold higher than that observed for the mechanical flotation cell. The Cleaner 3 flotation circuit using the flotation column decreased the ash content in graphite from 15.43% to 7.97% with a yield of 77.53%. Full article

(This article belongs to the Special Issue Flotation Chemistry)

► Show Figures

Graphical abstract

17 pages, 1535 KiB

Open AccessArticle

Relating Topological and Electrical Properties of Fractured Porous Media: Insights into the Characterization of Rock Fracturing

by Delphine Roubinet, James Irving and Philippe A. Pezard

Minerals 2018, 8(1), 14; https://doi.org/10.3390/min8010014 - 10 Jan 2018

Cited by 18 | Viewed by 4469

Abstract

Numerous laboratory and field experiments suggest that electrical properties of fractured rocks may provide critical information regarding the topological properties of the underlying fracture networks. However, a lack of numerical studies dedicated to realistic fractured media prevents us from assessing, in a systematic [...] Read more.

Numerous laboratory and field experiments suggest that electrical properties of fractured rocks may provide critical information regarding the topological properties of the underlying fracture networks. However, a lack of numerical studies dedicated to realistic fractured media prevents us from assessing, in a systematic manner, the relationships between electrical and topological properties in complex domains for which a representative elementary volume may not exist. To address this issue, we conduct an extended numerical analysis over a large range of realistic fractured porous media with an explicit description of the fractures that takes into account the fracture–matrix interactions. Our work shows that the fracture density determines the suitability of Archie’s law for describing effective electrical properties with complex behavior associated with small fracture densities. In particular, for fracture networks at the percolation threshold surrounded by a low-porosity matrix, the effective petrophysical relationships are impacted by the assumed fracture-length distribution and the exchange of electric current between the fractures and surrounding matrix. These results help in understanding experimental observations that were difficult to explain so far, suggesting that the effective electrical properties of fractured rock may be used to obtain insights into the properties of their geological structures. Full article

(This article belongs to the Special Issue Geological Modelling)

► Show Figures

Figure 1

25 pages, 8057 KiB

Open AccessArticle

C–O Stable Isotopes Geochemistry of Tunisian Nonsulfide Zinc Deposits: A First Look

by Hechmi Garnit, Maria Boni, Giuliana Buongiovanni, Giuseppe Arfè, Nicola Mondillo, Michael Joachimski, Salah Bouhlel and Giuseppina Balassone

Minerals 2018, 8(1), 13; https://doi.org/10.3390/min8010013 - 9 Jan 2018

Cited by 11 | Viewed by 6298

Abstract

A preliminary C–O stable isotopes geochemical characterization of several nonsulfide Zn-Pb Tunisian deposits has been carried out, in order to evidence the possible differences in their genesis. Nonsulfide ores were sampled from the following deposits: Ain Allegua, Jebel Ben Amara, Jebel Hallouf (Nappe [...] Read more.

A preliminary C–O stable isotopes geochemical characterization of several nonsulfide Zn-Pb Tunisian deposits has been carried out, in order to evidence the possible differences in their genesis. Nonsulfide ores were sampled from the following deposits: Ain Allegua, Jebel Ben Amara, Jebel Hallouf (Nappe Zone), Djebba, Bou Grine, Bou Jaber, Fedj el Adoum, Slata Fer (Diapir Zone), Jebel Ressas, Jebel Azreg, Mecella (North South Axis Zone), Jebel Trozza, Sekarna (Graben Zone). After mineralogical investigation of selected specimens, the C–O stable isotopic study was carried out on smithsonite, hydrozincite, cerussite and calcite. The data have shown that all the carbonate generations in the oxidized zones of Ain Allegua and Jebel Ben Amara (Nappe Zone), Bou Jaber, Bou Grine and Fedj el Adoum (Diapir Zone), Mecella and Jebel Azreg (North South Zone) have a supergene origin, whereas the carbonates sampled at Sekarna (Graben Zone) (and in limited part also at Bou Jaber) precipitated from thermal waters at moderately high temperature. Most weathering processes that controlled the supergene alteration of the Zn-Pb sulfide deposits in Tunisia had probably started in the middle to late Miocene interval and at the beginning of the Pliocene, both periods corresponding to two distinct tectonic pulses that produced the exhumation of sulfide ores, but the alteration and formation of oxidized minerals could have also continued through the Quaternary. The isotopic characteristics associated with the weathering processes in the sampled localities were controlled by the different locations of the sulfide protores within the tectonic and climatic zones of Tunisia during the late Tertiary and Quaternary. Full article

(This article belongs to the Special Issue Geology and Mineralogy of Zn-Pb Nonsulfide Deposits)

► Show Figures

Figure 1

13 pages, 15667 KiB

Open AccessArticle

Silica Colloid Ordering in a Dynamic Sedimentary Environment

by Moritz Liesegang and Ralf Milke

Minerals 2018, 8(1), 12; https://doi.org/10.3390/min8010012 - 7 Jan 2018

Cited by 7 | Viewed by 6600

Abstract

The formation of ordered particle arrays plays an essential role in nanotechnology, biological systems, and inorganic photonic structures in the geosphere. Here, we show how ordered arrays of amorphous silica spheres form in deeply weathered lithologies of the Great Artesian Basin (central Australia). [...] Read more.

The formation of ordered particle arrays plays an essential role in nanotechnology, biological systems, and inorganic photonic structures in the geosphere. Here, we show how ordered arrays of amorphous silica spheres form in deeply weathered lithologies of the Great Artesian Basin (central Australia). Our multi-method approach, using optical and scanning electron microscopy, X-ray microdiffraction, Raman spectroscopy, and electron probe microanalysis, reveals that particle morphologies trace the flow of opal-forming colloidal suspensions and document syn- and post-depositional deformation. The micromorphology of amorphous silica pseudomorphs suggests that the volume-preserving replacement of non-silicate minerals proceeds via an interface-coupled dissolution precipitation process. We conclude that colloid flow and post-depositional shearing create but also destroy natural photonic crystals. Contrary to previous studies, our results indicate that purely gravitational settling/ordering is the exception rather than the rule during the formation of three-dimensional periodic sphere arrays in the highly dynamic colloidal suspensions of chemically weathered clastic sediments. Full article

(This article belongs to the Special Issue Mineralogy of Quartz and Silica Minerals)

► Show Figures

Figure 1

16 pages, 5458 KiB

Open AccessArticle

Natural and Modified Zeolite—Alginate Composites. Application for Removal of Heavy Metal Cations from Contaminated Water Solutions

by Milan Kragović, Snežana Pašalić, Marija Marković, Marija Petrović, Blagoje Nedeljković, Miloš Momčilović and Marija Stojmenović

Minerals 2018, 8(1), 11; https://doi.org/10.3390/min8010011 - 6 Jan 2018

Cited by 53 | Viewed by 7378

Abstract

In present paper, the influence of the initial pH and concentration of Pb²⁺ on its adsorption by the natural (NZA) and Fe(III)-modified zeolite-alginate beads (FeA) was studied. Results showed that modification of the starting materials have a positive effect on their adsorption [...] Read more.

In present paper, the influence of the initial pH and concentration of Pb²⁺ on its adsorption by the natural (NZA) and Fe(III)-modified zeolite-alginate beads (FeA) was studied. Results showed that modification of the starting materials have a positive effect on their adsorption capacities (102 and 136 mg/g for the NZA and FeA, respectively). After encapsulation, the mechanism of lead adsorption by both adsorbents was changed and ion exchange dominates. The best adsorption was achieved for initial pH > 3.8. Cation exchange capacity, structural properties, and hydrophobicity of samples were also determined, and the presence of the alginate has no significant influence on investigated properties of samples. Experiments on wastewater from tailings of lead and zinc mine Grot, Serbia, showed that after treatment with both adsorbents, the content of the most abundant heavy metals (Pb, Zn, Hg, and Mn) significantly decreased. Full article

(This article belongs to the Special Issue Selected Papers from the 6th International Symposium on Mining and Environmental Protection)

► Show Figures

Figure 1

18 pages, 4178 KiB

Open AccessArticle

Immobilisation of Platinum by Cupriavidus metallidurans

by Gordon Campbell, Lachlan MacLean, Frank Reith, Dale Brewe, Robert A. Gordon and Gordon Southam

Minerals 2018, 8(1), 10; https://doi.org/10.3390/min8010010 - 5 Jan 2018

Cited by 11 | Viewed by 6693

Abstract

The metal resistant bacterium Cupriavidus metallidurans CH34, challenged with aqueous platinous and platinic chloride, rapidly immobilized platinum. XANES/EXAFS analysis of these reaction systems demonstrated that platinum binding shifted from chloride to carboxyl functional groups within the bacteria. Pt(IV) was more toxic than Pt(II), [...] Read more.

The metal resistant bacterium Cupriavidus metallidurans CH34, challenged with aqueous platinous and platinic chloride, rapidly immobilized platinum. XANES/EXAFS analysis of these reaction systems demonstrated that platinum binding shifted from chloride to carboxyl functional groups within the bacteria. Pt(IV) was more toxic than Pt(II), presumably due to the oxidative stress imparted by the platinic form. Platinum immobilisation increased with time and with increasing concentrations of platinum. From a bacterial perspective, intracellular platinum concentrations were two to three orders of magnitude greater than the fluid phase, and became saturated at almost molar concentrations in both reaction systems. TEM revealed that C. metallidurans was also able to precipitate nm-scale colloidal platinum, primarily along the cell envelope where energy generation/electron transport occurs. Cells enriched in platinum shed outer membrane vesicles that were enriched in metallic, colloidal platinum, likely representing an important detoxification strategy. The formation of organo-platinum compounds and membrane encapsulated nanophase platinum, supports a role for bacteria in the formation and transport of platinum in natural systems, forming dispersion halos important to metal exploration. Full article

(This article belongs to the Special Issue Geomicrobiology and Biogeochemistry of Precious Metals)

► Show Figures

Figure 1

20 pages, 6055 KiB

Open AccessArticle

Heap Leaching: Modelling and Forecasting Using CFD Technology

by Diane McBride, James Gebhardt, Nick Croft and Mark Cross

Minerals 2018, 8(1), 9; https://doi.org/10.3390/min8010009 - 3 Jan 2018

Cited by 23 | Viewed by 9776

Abstract

Heap leach operations typically employ some form of modelling and forecasting tools to predict cash flow margins and project viability. However, these vary from simple spreadsheets to phenomenological models, with more complex models not commonly employed as they require the greatest amount of [...] Read more.

Heap leach operations typically employ some form of modelling and forecasting tools to predict cash flow margins and project viability. However, these vary from simple spreadsheets to phenomenological models, with more complex models not commonly employed as they require the greatest amount of time and effort. Yet, accurate production modelling and forecasting are essential for managing production and potentially critical for successful operation of a complex heap, time and effort spent in setting up modelling tools initially may increase profitability in the long term. A brief overview of various modelling approaches is presented, but this paper focuses on the capabilities of a computational fluid dynamics (CFD) model. Advances in computational capability allow for complex CFD models, coupled with leach kinetic models, to be applied to complex ore bodies. In this paper a comprehensive hydrodynamic CFD model is described and applied to chalcopyrite dissolution under heap operating conditions. The model is parameterized against experimental data and validated against a range of experimental leach tests under different thermal conditions. A three-dimensional ‘virtual’ heap, under fluctuating meteorological conditions, is simulated. Continuous and intermittent irrigation is investigated, showing copper recovery per unit volume of applied leach solution to be slightly increased for pulse irrigation. Full article

(This article belongs to the Special Issue Heap Leaching: The State-of-the-Art)

► Show Figures

Figure 1

10 pages, 6053 KiB

Open AccessArticle

Metal Recovery from the Mobile Phone Waste by Chemical and Biological Treatments

by Yumi Kim, Hyunhee Seo and Yul Roh

Minerals 2018, 8(1), 8; https://doi.org/10.3390/min8010008 - 2 Jan 2018

Cited by 30 | Viewed by 7555

Abstract

Recycling electronic waste is an important subject not only from the point of view of waste treatment, but also regarding the recovery of valuable metals. This research examined the stepwise recovery of metals in mobile phone waste using chemical treatment via pH swing [...] Read more.

Recycling electronic waste is an important subject not only from the point of view of waste treatment, but also regarding the recovery of valuable metals. This research examined the stepwise recovery of metals in mobile phone waste using chemical treatment via pH swing and the biological method using biomineralization. In chemical treatment, the metal fraction attached to the printed circuit board (PCB) and camera parts were separated from the mobile phone waste and were then pulverized into particles with a size less than ~2 mm. The metal fraction was dissolved in aqua regia, and the pH of the solution was increased to 10.5 by adding NH₄OH. The first precipitate was iron oxide, produced by raising the pH to 3.1~4.2 with NH₄OH. Sequentially, copper chloride and rare earth-metal complex were produced at pH 5.7~7.7 and 8.3~10.5, respectively. In the biological method, the filtrate at pH 7.7 was added to a metal-reducing bacteria growth medium as a precursor. After two weeks of incubation, rhodochrosite and calcite were precipitated as nano-sized minerals. The results indicate that effective metal recovery of mobile phone waste is feasible using chemical and biological treatments, and the recovered metals and rare earth metals can be recycled into raw materials for various industries. Full article

(This article belongs to the Special Issue Environmental Mineralogy)

► Show Figures

Graphical abstract

10535 KiB

Open AccessArticle

Geological Modelling and Validation of Geological Interpretations via Simulation and Classification of Quantitative Covariates

by Amir Adeli, Xavier Emery and Peter Dowd

Minerals 2018, 8(1), 7; https://doi.org/10.3390/min8010007 - 29 Dec 2017

Cited by 29 | Viewed by 6605

Abstract

This paper proposes a geostatistical approach for geological modelling and for validating an interpreted geological model, by identifying the areas of an ore deposit with a high probability of being misinterpreted, based on quantitative coregionalised covariates correlated with the geological categories. This proposal [...] Read more.

This paper proposes a geostatistical approach for geological modelling and for validating an interpreted geological model, by identifying the areas of an ore deposit with a high probability of being misinterpreted, based on quantitative coregionalised covariates correlated with the geological categories. This proposal is presented through a case study of an iron ore deposit at a stage where the only available data are from exploration drill holes. This study consists of jointly simulating the quantitative covariates with no previous geological domaining. A change of variables is used to account for stoichiometric closure, followed by projection pursuit multivariate transformation, multivariate Gaussian simulation, and conditioning to the drill hole data. Subsequently, a decision tree classification algorithm is used to convert the simulated values into a geological category for each target block and realisation. The determination of the prior (ignoring drill hole data) and posterior (conditioned to drill hole data) probabilities of categories provides a means of identifying the blocks for which the interpreted category disagrees with the simulated quantitative covariates. Full article

(This article belongs to the Special Issue Geological Modelling)

► Show Figures

Figure 1

5524 KiB

Open AccessArticle

Natural Radioactivity of Intrusive-Metamorphic and Sedimentary Rocks of the Balkan Mountain Range (Serbia, Stara Planina)

by Sanna Masod Abdulqader, Boris Vakanjac, Jovan Kovačević, Zorana Naunovic and Nevena Zdjelarević

Minerals 2018, 8(1), 6; https://doi.org/10.3390/min8010006 - 29 Dec 2017

Cited by 7 | Viewed by 6678

Abstract

Stara Planina (also known as the Balkan mountain range) is known for numerous occurrences and deposits of uranium and associated radionuclides. It is also famous for its geodiversity. The geologic framework is highly complex. The mountain is situated between the latitudes of 43° [...] Read more.

Stara Planina (also known as the Balkan mountain range) is known for numerous occurrences and deposits of uranium and associated radionuclides. It is also famous for its geodiversity. The geologic framework is highly complex. The mountain is situated between the latitudes of 43° and 44° N and the longitudes from 22°16′ to 23°00′ E. Uranium exploration and radioactivity testing on Stara Planina began back in 1948. Uranium has also been mined in the zone of Kalna, within the Janja granite intrusive. The naturally radioactive geologic units of Stara Planina are presented in detail in this paper. The main sources of radioactivity on Stara Planina can be classified as: 1. Granitic endogenous—syngenetic–epigenetic deposits and occurrences; 2. Metamorphogenic—syngenetic; and 3. Sedimentary, including occurrences of uranium deposition and fluctuation caused by water in different types of sedimentary rocks formed in a continental setting, which could be classified under epigenetic types. The area of Stara Planina with increased radioactivity (higher than 200 cps), measured by airborne gamma spectrometry, is about 380 square kilometers. The highest values of measured radioactivity and uranium grade were obtained from a sample taken from the Mezdreja uranium mine tailing dump, where ²²⁶Ra measures 2600 ± 100 Bq/kg and the uranium grade is from 76.54 to 77.65 ppm U. The highest uranium (and lead) concentration, among all samples, is measured in graphitic schist with high concentrations of organic (graphitic) material from the Inovska Series—99.47 ppm U and 107.69 ppm Pb. Thorium related radioactivity is the highest in granite samples from the Janja granite in the vicinity of the Mezdreja granite mine and the Gabrovnica granite mine tailing dump, and it is the same—250 ± 10 Bq/kg for ²³²Th, while the thorium grade varies from 30.82 to 60.27 ppm Th. In gray siltstones with a small amount of organic material, the highest radioactivity is related to potassium—2080 ± 90 Bq/kg for ⁴⁰K. Full article

(This article belongs to the Special Issue Selected Papers from the 6th International Symposium on Mining and Environmental Protection)

► Show Figures

Figure 1

4410 KiB

Open AccessArticle

The Petrography, Mineralogy and Geochemistry of Some Cu- and Pb-Enriched Coals from Jungar Coalfield, Northwestern China

by Dongna Liu, Anchao Zhou, Fangui Zeng, Fenghua Zhao and Yu Zou

Minerals 2018, 8(1), 5; https://doi.org/10.3390/min8010005 - 27 Dec 2017

Cited by 5 | Viewed by 5060

Abstract

The petrological, geochemical, and mineralogical composition of the Carboniferous-Permian coal deposit in the Jungar coalfield of inner Mongolia, Northwestern China, were investigated using optical microscopy and field emission scanning electron microscopy in conjunction with an energy-dispersive X-ray spectrometer (SEM-EDX), as well as X-ray [...] Read more.

The petrological, geochemical, and mineralogical composition of the Carboniferous-Permian coal deposit in the Jungar coalfield of inner Mongolia, Northwestern China, were investigated using optical microscopy and field emission scanning electron microscopy in conjunction with an energy-dispersive X-ray spectrometer (SEM-EDX), as well as X-ray powder diffraction, X-ray fluorescence, and inductively coupled plasma mass spectrometry. The Jungar coal is of high volatile C/B bituminous quality with 0.58% vitrinite reflectance and has a low sulfur content of 0.70% on average. Inertinite (mineral-free basis) generally dominates in coal from the lower part of the Shanxi formation, and vitrinite is the major maceral assemblage in the coal from the Taiyuan formation, which exhibits forms suggesting variation in the sedimentary environment. The Jungar coal is characterized by higher concentrations of copper (Cu) in No. 6 coal, at 55 μg/g, and lead (Pb) in No. 4 coal at 42 μg/g. Relative to the upper continental crust, the rare earth elements (REE) in the coal are characterized by light and medium–heavy REE enrichment. The minerals in the Jungar coal are mainly kaolinite, dickite, pyrite, calcite, siderite, quartz, and, to a lesser extent, gypsum and K-feldspar. The enrichment and occurrence of the trace elements, and of the minerals in the coal, are attributed to the fragmental parent rock during diagenesis and coalification. The main elements with high enrichment factors, Cu and Pb, overall exhibit a notably inorganic sulfide affinity and a weak organic affinity. Primary and epigenetic sedimentary environment and the lithology of the terrigenous parent rock are the key factors that influence the occurrence and formation of Cu and Pb in coal. The depositional environment is more influential in the formation of Cu than Pb in coal. Lead is more easily affected by the terrigenous factors than Cu when they are under a similar depositional environment. Full article

(This article belongs to the Special Issue Mineral Resources and the Environment)

► Show Figures

Graphical abstract

2652 KiB

Open AccessArticle

Co-Bioleaching of Chalcopyrite and Silver-Bearing Bornite in a Mixed Moderately Thermophilic Culture

by Congren Yang, Fen Jiao and Wenqing Qin

Minerals 2018, 8(1), 4; https://doi.org/10.3390/min8010004 - 26 Dec 2017

Cited by 19 | Viewed by 5912

Abstract

Chalcopyrite and bornite are two important copper minerals, and they often coexist. In this study, the co-bioleaching of chalcopyrite and silver-bearing bornite by mixed moderately thermophilic culture at 50 °C was investigated. The bioleaching results show that the extraction percentage of Cu for [...] Read more.

Chalcopyrite and bornite are two important copper minerals, and they often coexist. In this study, the co-bioleaching of chalcopyrite and silver-bearing bornite by mixed moderately thermophilic culture at 50 °C was investigated. The bioleaching results show that the extraction percentage of Cu for co-bioleaching of chalcopyrite (Ccp) and silver-bearing bornite (Bn) (Ccp/Bn = 3:1) was 94.6%. Compared to bioleaching of chalcopyrite or silver-bearing bornite alone, the Cu extraction percentage was greatly enhanced when they were bioleached together. The leaching residues were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Silver-bearing bornite dissolved preferentially compared to chalcopyrite, due to galvanic interactions. Simultaneously, Ag⁺ was released from the silver-bearing bornite into solution. Ag₂S formed on the surface because Cu and Fe in the chalcopyrite were replaced by Ag⁺, accelerating chalcopyrite dissolution and enrichment of Ag on the surface of the chalcopyrite. Full article

(This article belongs to the Collection Bioleaching)

► Show Figures

Figure 1

20667 KiB

Open AccessArticle

Integrated 3D Geological Modeling to Gain Insight in the Effects of Hydrothermal Alteration on Post-Ore Deformation Style and Strain Localization in the Flin Flon Volcanogenic Massive Sulfide Ore System

by Ernst Schetselaar, Doreen Ames and Eric Grunsky

Minerals 2018, 8(1), 3; https://doi.org/10.3390/min8010003 - 25 Dec 2017

Cited by 7 | Viewed by 6357

Abstract

3D geological modeling of lithogeochemical and geological data provides insight into the role of the sulfide ore horizon and associated footwall hydrothermal alteration in localizing shear strain in the Flin Flon volcanogenic massive sulfide deposits, Canada, as deformation evolved from brittle-ductile to ductile [...] Read more.

3D geological modeling of lithogeochemical and geological data provides insight into the role of the sulfide ore horizon and associated footwall hydrothermal alteration in localizing shear strain in the Flin Flon volcanogenic massive sulfide deposits, Canada, as deformation evolved from brittle-ductile to ductile regimes during collisional stages of the 1.9–1.8 Ga Trans-Hudson orogeny. 3D spatial characterization of hydrothermal alteration based on the Ishikawa index (AI) and normative corundum percentages outline sericite + chlorite-rich high strain zones, consisting of Al-enriched and Na-depleted felsic and mafic volcanic rocks in the footwall of the sulfide ore horizon. The hydrothermal vent complex, from which these sheared alteration zones originated, was stacked together with the ore horizon by W-vergent thrust faults during an early collisional deformation regime, imbricating molasse-type clastic sediments with the ore-hosting volcanic and volcaniclastic rocks of the Flin Flon arc assemblage. Chlorite-rich planar zones marked by high values of the Carbonate–chlorite–pyrite index (CCPI) are laterally more extensive and outline a later system of ductile shear zones, in which phyllosilicates, quartz and chalcopyrite in stringer zones localized shear strain and enhanced transposition of the hydrothermal vent stockwork. The contrasting deformation styles of these two thrusting events and their localization within the ore horizon and hydrothermal vent stockwork have important implications for vectoring towards undiscovered ore in this mature mining camp that are possibly also relevant to other strongly deformed VMS ore systems. Full article

(This article belongs to the Special Issue Geological Modelling)

► Show Figures

Figure 1

2062 KiB

Open AccessArticle

Hydrometallurgical Processing Technology of Titanomagnetite Ores

by Victor Ivanovich Sachkov, Roman Andreevich Nefedov, Vladislav Viktorovich Orlov, Rodion Olegovych Medvedev and Anna Sergeevna Sachkova

Minerals 2018, 8(1), 2; https://doi.org/10.3390/min8010002 - 24 Dec 2017

Cited by 22 | Viewed by 11270

Abstract

In this paper, we study the possibility of obtaining iron and titanium-vanadium concentrates with highest contents of iron and titanium, respectively, through hydrometallurgical processing of the titanomagnetite ores of the Chineisk deposit. We varied two key parameters to determine the efficiency of the [...] Read more.

In this paper, we study the possibility of obtaining iron and titanium-vanadium concentrates with highest contents of iron and titanium, respectively, through hydrometallurgical processing of the titanomagnetite ores of the Chineisk deposit. We varied two key parameters to determine the efficiency of the process: (a) concentration of leaching solution (ammonium fluoride); and (b) acidity of solution. Ammonium fluoride concentration was varied from 0.08 mol/L to 4.2 mol/L with the other fixed parameters. It was shown that optimum ammonium fluoride concentration for leaching the ore is 0.42 mol/L; at these concentrations iron and titanium contents are about 62.8 wt % and 3.5 wt % in solid phase, respectively. The acidity of solution was changed by adding of hydrofluoric acid with varied concentration (from 0.86 mol/L to 4.07 mol/L) to ammonium fluoride solution with fixed concentration of 0.42 mol/L. The best results (degree of titanium extraction = 63.7%) were obtained when using a solution of hydrofluoric acid with concentration 4.07 mol/L. In this case, the addition of acid makes it possible to increase the Fe/Ti ratio by 3.4 times in comparison with the original ore. Thus, we conclude that acidity and the concentration of ammonium fluoride solution significantly influences the selectivity of the hydrometallurgical process. Full article

► Show Figures

Figure 1

Journal Menu

Journal Browser

Minerals, Volume 8, Issue 1 (January 2018) – 31 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI