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Minerals, Volume 8, Issue 10 (October 2018) – 57 articles

Cover Story (view full-size image): We report, for the first time, the presence of super-reduced (SuR), nominally ultra-high pressure (UHP) and continental crust-derived phases in chromitites from the Caribbean (Mercedita chromitite deposit, eastern Cuba). This assemblage includes moissanite (SiC) hosted in the altered matrix of the chromitite, oriented clinopyroxene and rutile lamellae in chromite, graphite-like amorphous carbon, corundum and SiO2 hosted in healed fractures in chromite grains, and native Cu and Fe-Mn alloys in heavy-mineral concentrates. The origin of this assemblage is discussed and interpreted as related to the alteration (serpentinization) process that affected the deposit at low pressure. View this paper
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2 pages, 171 KiB  
Correction
Correction: Toda, K., et al. Key Factors Affecting Strength Development of Steel Slag-Dredged Soil Mixtures. Minerals 2018, 8(5), 174
by Kanako Toda, Haruna Sato, Nilan Weerakoon, Tsubasa Otake, Satoshi Nishimura and Tsutomu Sato
Minerals 2018, 8(10), 473; https://doi.org/10.3390/min8100473 - 22 Oct 2018
Viewed by 2141
Abstract
The authors wish to make the following corrections to this paper [...] Full article
11 pages, 5022 KiB  
Article
Separation of Oxidized Pyrrhotite from Fine Fraction Serpentine
by Jian Zhou, Yiping Lu and Guozhi Mao
Minerals 2018, 8(10), 472; https://doi.org/10.3390/min8100472 - 22 Oct 2018
Cited by 9 | Viewed by 3825
Abstract
The valuable minerals in copper-nickel sulfide ore can easily be oxidized, leading to the reduction of their flotation recovery and a difficulty in separating them from gangue. In order to solve the problem, the reaction mechanism of the octanohydroxamic acid (OHA) on oxidized [...] Read more.
The valuable minerals in copper-nickel sulfide ore can easily be oxidized, leading to the reduction of their flotation recovery and a difficulty in separating them from gangue. In order to solve the problem, the reaction mechanism of the octanohydroxamic acid (OHA) on oxidized pyrrhotite was revealed through micro-flotation, adsorption tests, zeta potential measurements, and X-ray photoelectron spectroscopy (XPS) analysis. The results show that this is a feasible way to find a suitable collector that can directly react to oxidation products on the surface of pyrrhotite. OHA can efficiently reclaim oxidized pyrrhotite and achieve the selective separation of a pyrrhotite-serpentine mixture in a weak alkaline environment. The adsorption tests, zeta potential measurements, and XPS analyses show that OHA can interact with an oxidized pyrrhotite surface, and the interaction between OHA and serpentine is very weak. The XPS analyses indicate that the OHA collector can chelate with Fe(OH)3 on the surface of oxidized pyrrhotite and form an “O, O” five-ring chelate. At the same time, the OHA collector may compete with the hydroxyl groups of hydrophilic substances on the mineral surface to produce hydrophobic products and reduce the hydrophilic substances on the mineral surface. Full article
(This article belongs to the Special Issue Sustainable Mineral Processing Technologies)
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22 pages, 2792 KiB  
Article
Helium and Argon Isotopes in the Fe-Mn Polymetallic Crusts and Nodules from the South China Sea: Constraints on Their Genetic Sources and Origins
by Yao Guan, Yingzhi Ren, Xiaoming Sun, Zhenglian Xiao and Zhengxing Guo
Minerals 2018, 8(10), 471; https://doi.org/10.3390/min8100471 - 22 Oct 2018
Cited by 3 | Viewed by 4314
Abstract
In this study, the He and Ar isotope compositions were measured for the Fe-Mn polymetallic crusts and nodules from the South China Sea (SCS), using the high temperature bulk melting method and noble gases isotope mass spectrometry. The He and Ar of the [...] Read more.
In this study, the He and Ar isotope compositions were measured for the Fe-Mn polymetallic crusts and nodules from the South China Sea (SCS), using the high temperature bulk melting method and noble gases isotope mass spectrometry. The He and Ar of the SCS crusts/nodules exist mainly in the Fe-Mn mineral crystal lattice and terrigenous clastic mineral particles. The results show that the 3He concentrations and R/RA values of the SCS crusts are generally higher than those of the SCS nodules, while 4He and 40Ar concentrations of the SCS crusts are lower than those of the SCS nodules. Comparison with the Pacific crusts and nodules, the SCS Fe-Mn crusts/nodules have lower 3He concentrations and 3He/4He ratios (R/RA, 0.19 to 1.08) than those of the Pacific Fe-Mn crusts/nodules, while the 40Ar/36Ar ratios of the SCS samples are significantly higher than those of the Pacific counterparts. The relatively low 3He/4He ratios and high 40Ar concentrations in the SCS samples are likely caused by terrigenous detrital input with high radiogenic 4He and 40Ar contents. The SCS crusts and nodules have shorter growth periods, implying that in situ post-formation radiogenic 3He, 4He and 40Ar produced by decay of U, Th and K have no effect on their isotope compositions. Thus, the SCS crusts/nodules inherited the noble gases characteristics of their sources. Helium and Ar isotope compositions in the SCS Fe-Mn crusts and nodules reflect the product of an equilibrium mixture between air-saturated seawater and radiogenic components during their growth, while the partial 3He excess in some SCS samples may represent a little mantle-derived origin. The different He and Ar isotope compositions of the Fe-Mn crusts and nodules between the South China Sea and the Pacific Ocean are due to their different sources and genetic processes. The characteristics of He and Ar isotope compositions in the SCS polymetallic crusts and nodules are similar to the properties of hydrogenetic Fe-Mn oxide/hydroxide precipitates, which reflects mainly the product of an equilibrium mixture between air-saturated seawater and radiogenic components. Full article
(This article belongs to the Special Issue Deep-Sea Minerals and Gas Hydrates)
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43 pages, 56026 KiB  
Article
Gems and Placers—A Genetic Relationship Par Excellence
by Harald G. Dill
Minerals 2018, 8(10), 470; https://doi.org/10.3390/min8100470 - 19 Oct 2018
Cited by 25 | Viewed by 28726
Abstract
Gemstones form in metamorphic, magmatic, and sedimentary rocks. In sedimentary units, these minerals were emplaced by organic and inorganic chemical processes and also found in clastic deposits as a result of weathering, erosion, transport, and deposition leading to what is called the formation [...] Read more.
Gemstones form in metamorphic, magmatic, and sedimentary rocks. In sedimentary units, these minerals were emplaced by organic and inorganic chemical processes and also found in clastic deposits as a result of weathering, erosion, transport, and deposition leading to what is called the formation of placer deposits. Of the approximately 150 gemstones, roughly 40 can be recovered from placer deposits for a profit after having passed through the “natural processing plant” encompassing the aforementioned stages in an aquatic and aeolian regime. It is mainly the group of heavy minerals that plays the major part among the placer-type gemstones (almandine, apatite, (chrome) diopside, (chrome) tourmaline, chrysoberyl, demantoid, diamond, enstatite, hessonite, hiddenite, kornerupine, kunzite, kyanite, peridote, pyrope, rhodolite, spessartine, (chrome) titanite, spinel, ruby, sapphire, padparaja, tanzanite, zoisite, topaz, tsavorite, and zircon). Silica and beryl, both light minerals by definition (minerals with a density less than 2.8–2.9 g/cm3, minerals with a density greater than this are called heavy minerals, also sometimes abbreviated to “heavies”. This technical term has no connotation as to the presence or absence of heavy metals), can also appear in some placers and won for a profit (agate, amethyst, citrine, emerald, quartz, rose quartz, smoky quartz, morganite, and aquamarine, beryl). This is also true for the fossilized tree resin, which has a density similar to the light minerals. Going downhill from the source area to the basin means in effect separating the wheat from the chaff, showcase from the jeweler quality, because only the flawless and strongest contenders among the gemstones survive it all. On the other way round, gem minerals can also be used as pathfinder minerals for primary or secondary gemstone deposits of their own together with a series of other non-gemmy material that is genetically linked to these gemstones in magmatic and metamorphic gem deposits. All placer types known to be relevant for the accumulation of non-gemmy material are also found as trap-site of gemstones (residual, eluvial, colluvial, alluvial, deltaic, aeolian, and marine shelf deposits). Running water and wind can separate minerals according to their physical-chemical features, whereas glaciers can only transport minerals and rocks but do not sort and separate placer-type minerals. Nevertheless till (unconsolidated mineral matter transported by the ice without re-deposition of fluvio-glacial processes) exploration is a technique successfully used to delineate ore bodies of, for example, diamonds. The general parameters that matter during accumulation of gemstones in placers are their intrinsic value controlled by the size and hardness and the extrinsic factors controlling the evolution of the landscape through time such as weathering, erosion, and vertical movements and fertility of the hinterland as to the minerals targeted upon. Morphoclimatic processes take particular effect in the humid tropical and mid humid mid-latitude zones (chemical weathering) and in the periglacial/glacial and the high-altitude/mountain zones, where mechanical weathering and the paleogradients are high. Some tectono-geographic elements such as unconformities, hiatuses, and sequence boundaries (often with incised valley fills and karstic landforms) are also known as planar architectural elements in sequence stratigraphy and applied to marine and correlative continental environments where they play a significant role in forward modeling of gemstone accumulation. The present study on gems and gemstone placers is a reference example of fine-tuning the “Chessboard classification scheme of mineral deposits” (Dill 2010) and a sedimentary supplement to the digital maps that form the core of the overview “Gemstones and geosciences in space and time” (Dill and Weber 2013). Full article
(This article belongs to the Special Issue Mineralogy and Geochemistry of Gems)
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15 pages, 1746 KiB  
Article
Design and Evaluation of an Expert System in a Crushing Plant
by Claudio A. Leiva, Katheryn V. Arcos, Diego A. Poblete, Eduardo A. Serey, Cynthia M. Torres and Yousef Ghorbani
Minerals 2018, 8(10), 469; https://doi.org/10.3390/min8100469 - 19 Oct 2018
Cited by 10 | Viewed by 3921
Abstract
This document presents a proposal for designing an expert system in the Gabriela Mistral Division’s crushing plant belonging to Codelco (Chile) with the objective of maximizing stacked tonnage, allowing the improvement of operational variables that directly interact with the crushing process. In addition, [...] Read more.
This document presents a proposal for designing an expert system in the Gabriela Mistral Division’s crushing plant belonging to Codelco (Chile) with the objective of maximizing stacked tonnage, allowing the improvement of operational variables that directly interact with the crushing process. In addition, this study considers the impact that occurs in both the process and operational continuity regarding the standardization of the system. In the first stage, a survey and analysis of historic operation data was carried out, which allowed the definition of benchmarking indicators. Subsequently, both modalities of operation were compared, monitoring processed tonnage and detentions related to operational failures. As a result, significant differences were observed in the performance of the critical line operating with expert control, with a 55% reduction in the detentions referred to operational failures. Added to this is the benefit of low cost and improved quality as the control provides an analysis of the variables in reduced time intervals, which is superior to human control. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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27 pages, 2918 KiB  
Article
Economic Block Model Development for Mining Seafloor Massive Sulfides
by Maxime Lesage, Cyril Juliani and Steinar L. Ellefmo
Minerals 2018, 8(10), 468; https://doi.org/10.3390/min8100468 - 19 Oct 2018
Cited by 5 | Viewed by 6481
Abstract
To support open-pit studies related to seafloor massive sulfides mining projects, an economic block-model is required. A modular framework is proposed to produce economic block models accommodating various levels of data. The framework is illustrated on a site of interest located on the [...] Read more.
To support open-pit studies related to seafloor massive sulfides mining projects, an economic block-model is required. A modular framework is proposed to produce economic block models accommodating various levels of data. The framework is illustrated on a site of interest located on the Arctic Mid-Ocean Ridge. Random sampling based on literature datasets is performed to assign grades, porosity and grain density to the model. Other required parameters are produced using relationships found in the literature. Revenues are estimated using literature values within a net smelter return methodology. Mining costs are determined using the cost of a mining system and the estimated time required for excavating the ore. The excavating time is assessed through the specific energy for the ore and the mining machines. The specific energy is calculated with a hyperbaric rock-cutting model. An economic block value of each mining block is then provided. The mining block database resulting from the study constitutes a valuable input into further studies on resource development. The framework has also been used to support a sensitivity study. The availability of the marine assets has been found as having the greatest influence on the economic value of the study case. Full article
(This article belongs to the Special Issue Deep-Sea Minerals and Gas Hydrates)
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3 pages, 149 KiB  
Editorial
Editorial for Special Issue “Mineralogy of Quartz and Silica Minerals”
by Jens Götze
Minerals 2018, 8(10), 467; https://doi.org/10.3390/min8100467 - 19 Oct 2018
Cited by 4 | Viewed by 3213
Abstract
Quartz and other silica minerals make up 12. [...] Full article
(This article belongs to the Special Issue Mineralogy of Quartz and Silica Minerals)
20 pages, 5901 KiB  
Article
The Crystal Chemistry of Rathite Based on New Electron-Microprobe Data and Single-Crystal Structure Refinements: The Role of Thallium
by Dan Topa and Uwe Kolitsch
Minerals 2018, 8(10), 466; https://doi.org/10.3390/min8100466 - 18 Oct 2018
Cited by 3 | Viewed by 3500
Abstract
Crystal-structure refinements in space group P21/c were performed on five grains of rathite with different types and degrees of thallium, silver, and antimony substitutions, as well as quantitative electron-microprobe analyses of more than 800 different rathite samples. The results [...] Read more.
Crystal-structure refinements in space group P21/c were performed on five grains of rathite with different types and degrees of thallium, silver, and antimony substitutions, as well as quantitative electron-microprobe analyses of more than 800 different rathite samples. The results of these studies both enlarged and clarified the complex spectrum of cation substitutions and the crystal chemistry of rathite. The [Tl+ + As3+] ↔ 2Pb2+ scheme of substitution acts at the structural sites Pb1, Pb2, and Me6, the [Ag+ + As3+] ↔ 2Pb2+ substitution at Me5, and the Sb-for-As substitution at the Me3 site only. The homogeneity range of rathite was determined to be unusually large, ranging from very Tl-poor compositions (0.16 wt%; refined single-crystal unit-cell parameters: a = 8.471(2), b = 7.926(2), c = 25.186(5) Å, β = 100.58(3)°, V = 1662.4(6) Å3) to very Tl-rich compositions (11.78 wt%; a = 8.521(2), b = 8.005(2), c = 25.031(5) Å, β = 100.56(3)°, V = 1678.4(6) Å3). The Ag content is only slightly variable (3.1 wt%–4.1 wt%) with a mean value of 3.6 wt%. The Sb content is strongly variable (0.20 wt%–7.71 wt%) and not correlated with the Tl content. With increasing Tl content (0.16 wt%–11.78 wt%), a clear increase of the unit-cell parameters a, b, and V, and a slight decrease of c is observed, although this is somewhat masked by the randomly variable Sb content. The revised general formula of rathite may be written as AgxTlyPb16−2(x+y)As16+x+yzSbzS40 (with 1.6 < x < 2, 0 < y < 3, 0 < z < 3.5). Based on Pb–S bond lengths, polyhedral characteristics and Pb-site bond-valence sums, we conclude that the Pb1 site is more affected by Tl substitution than the Pb2 site. When Tl substitution reaches values above 13 wt% (or 3 apfu), a new phase (“SR”), belonging to the rahite group, appears as lamellar exsolution intergrowths with Tl-rich rathite (11.78 wt%). Rathite is found only in the Lengenbach and Reckibach deposits, Binntal, Canton Wallis, Switzerland. Full article
(This article belongs to the Special Issue Thallium: Mineralogy, Geochemistry and Ore Processes)
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14 pages, 8205 KiB  
Case Report
Multi-Analytical Investigation of Stains on Dimension Stones in Master Valentim’s Fountain, Brazil
by Roberto Carlos Da Conceição Ribeiro, Patrícia Marques Ferreira de Figueiredo and Daniel Silva Barbutti
Minerals 2018, 8(10), 465; https://doi.org/10.3390/min8100465 - 18 Oct 2018
Cited by 6 | Viewed by 3204
Abstract
Master Valentim’s fountain has become an important historical patrimony for Brazil, being portrayed by famous artists, among them Jean-Baptiste Debret. In 1938, it was registered as cultural heritage by the Brazilian National Historical and Artistic Heritage Institute (IPHAN), and in 1990 it was [...] Read more.
Master Valentim’s fountain has become an important historical patrimony for Brazil, being portrayed by famous artists, among them Jean-Baptiste Debret. In 1938, it was registered as cultural heritage by the Brazilian National Historical and Artistic Heritage Institute (IPHAN), and in 1990 it was subjected to excavation and restoration works. The fountain was built in Gneiss and Lioz limestone, with metallic plates and mortar connecting the Gneiss blocks. Currently, deteriorations in the fountain stones can be observed, such as light stains and some aesthetic modifications caused by inadequate restorations. Petrography, X-ray fluorescence (XRF), XRD, physical properties, colorimetry, electrical conductivity, inductively coupled plasma optical emission spectrometry (ICP-OES), scanning electron microscopy-energy dispersive X-ray (SEM-EDX), and TGA were performed in order to characterize the Gneiss blocks, the metallic plates, and the stones used in previous restorations, as well as light stains observed on the Gneiss blocks. The petrography and XRD analyses inferred that the light stains may have been caused by the formation of an insoluble salt as a result of the association of the lead from the plates with other elements. The XRD analysis on the light staining area indicated the presence of cerussite (PbCO3) and anglesite (PbSO4), which are the probable cause of the light stains. The SEM-EDX results suggested that sulfur is the main element associated to lead. Full article
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33 pages, 5173 KiB  
Article
Decoding of Mantle Processes in the Mersin Ophiolite, Turkey, of End-Member Arc Type: Location of the Boninite Magma Generation
by Satoko Ishimaru, Yuji Saikawa, Makoto Miura, Osman Parlak and Shoji Arai
Minerals 2018, 8(10), 464; https://doi.org/10.3390/min8100464 - 18 Oct 2018
Cited by 7 | Viewed by 5459
Abstract
The Mersin ophiolite, Turkey, is of typical arc type based on geochemistry of crustal rocks without any signs of mid-ocean ridge (MOR) affinity. We examined its ultramafic rocks to reveal sub-arc mantle processes. Mantle peridotites, poor in clinopyroxene (<1.0 vol.%), show high Fo [...] Read more.
The Mersin ophiolite, Turkey, is of typical arc type based on geochemistry of crustal rocks without any signs of mid-ocean ridge (MOR) affinity. We examined its ultramafic rocks to reveal sub-arc mantle processes. Mantle peridotites, poor in clinopyroxene (<1.0 vol.%), show high Fo content of olivine (90–92) and Cr# [=Cr/(Cr + Al) atomic ratio] (=0.62–0.77) of chromian spinel. NiO content of olivine is occasionally high (up to 0.5 wt.%) in the harzburgite. Moho-transition zone (MTZ) dunite is also highly depleted, i.e., spinel is high Cr# (0.78–0.89), clinopyroxene is poor in HREE, and olivine is high Fo (up to 92), but relatively low in NiO (0.1–0.4 wt.%). The harzburgite is residue after high-degree mantle melting, possibly assisted by slab-derived fluid. The high-Ni character of olivine suggests secondary metasomatic formation of olivine-replacing orthopyroxene although replacement textures are unclear. The MTZ dunite is of replacive origin, resulted from interaction between Mg-rich melt released from harzburgite diapir and another harzburgite at the diapir roof. The MTZ dunite is the very place that produced the boninitic and replacive dunite. The MTZ is thicker (>1 km) in Mersin than in MOR-related ophiolite (mostly < 500 m), and this is one of the features of arc-type ophiolite. Full article
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15 pages, 6310 KiB  
Article
Oxidative Depression of Arsenopyrite by Using Calcium Hypochlorite and Sodium Humate
by Shangyong Lin, Runqing Liu, Yongjie Bu, Chen Wang, Li Wang, Wei Sun and Yuehua Hu
Minerals 2018, 8(10), 463; https://doi.org/10.3390/min8100463 - 18 Oct 2018
Cited by 26 | Viewed by 4113
Abstract
During smelting, arsenic in copper concentrates affects the product quality and causes environmental pollution. Removing arsenic minerals from copper concentrates requires environmental-friendly and cost-effective depressants for flotation separation. Ca(ClO)2 was combined with sodium humate (SH) to improve the flotation separation of chalcopyrite [...] Read more.
During smelting, arsenic in copper concentrates affects the product quality and causes environmental pollution. Removing arsenic minerals from copper concentrates requires environmental-friendly and cost-effective depressants for flotation separation. Ca(ClO)2 was combined with sodium humate (SH) to improve the flotation separation of chalcopyrite from arsenopyrite. Results of single-mineral flotation indicated that combined Ca(ClO)2 and SH significantly inhibited arsenopyrite and exerted a negligible effect on chalcopyrite. The arsenic content in copper concentrates significantly decreased from 63% to 11% in the absence of a depressant and in the presence of Ca(ClO)2 and SH, as proven by the mixed-mineral flotation results. SH can adsorb on both mineral surfaces as indicated by the zeta potential measurements and Fourier transform infrared spectroscopy. However, the presence of Ca(ClO)2 increased the adsorption of arsenopyrite compared with chalcopyrite. The arsenopyrite floatability depressed with the Ca(ClO)2 oxidation and subsequent SH adsorption, as verified by X-ray photoelectron spectroscopy. Results of flotation tests confirmed that the chalcopyrite surface was slightly oxidized, but it remained hydrophobic. The combination of depressants has the potential for industrial application. Full article
(This article belongs to the Special Issue Sustainable Mineral Processing Technologies)
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14 pages, 1293 KiB  
Article
Case Studies for Clean Technology Development in the Chemical Industry Using Zeolite Based Catalysts
by Tatjána Juzsakova, Noor Al-Jammal, Igor Cretescu, Viktor Sebestyén, Cuong Le Phuoc, Endre Domokos, Ákos Rédey and Catalina Daniela Stan
Minerals 2018, 8(10), 462; https://doi.org/10.3390/min8100462 - 17 Oct 2018
Cited by 7 | Viewed by 5164
Abstract
This paper deals with the practical implementation of cleaner technologies in the chemical industry, using two case studies as an illustration. The first case study deals with the removal of NOx and N2O gases over an iron-doped ZSM-5 catalyst developed for [...] Read more.
This paper deals with the practical implementation of cleaner technologies in the chemical industry, using two case studies as an illustration. The first case study deals with the removal of NOx and N2O gases over an iron-doped ZSM-5 catalyst developed for tail gas treatment in nitric acid manufacturing. The aim for this case study was to investigate the efficiency of the zeolitic catalyst in the DeNOx process and to compare its catalytic activity with the conventional vanadia-titania. By the experiments carried out, it can be concluded that the new technological developments could significantly contribute to a decrease in environmental pollution. The second case study focuses on zeolite-based catalysts prepared from zeolitic tuff by the impregnation method, for biodiesel production from waste sunflower vegetable oil. The effects of operating and processing variables such as reaction temperature and time were investigated. The results showed that the highest biodiesel yield was 96.7% at an 11.5 MeOH/oil molar ratio, in the presence of 6.4 wt % catalyst at a 50 °C reaction temperature and reaction time of 2 h. The properties of the biodiesel that was produced, such as the viscosity, meet the required specifications of standard JUS EN14214. The common feature of the two different case studies is that both technologies use zeolite catalysts, namely naturally-occurring zeolitic tuff and synthetic ZSM type zeolite catalyst. The examples shown emphasize the importance of the zeolites in clean chemical technologies, which contribute to the protection of the environment. Full article
(This article belongs to the Special Issue Natural Zeolites)
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10 pages, 1322 KiB  
Article
Synchrotron Radiation XRD Investigation of the Fine Phase Transformation during Synthetic Chalcocite Acidic Ferric Sulfate Leaching
by Chaojun Fang, Shichao Yu, Xingxing Wang, Hongbo Zhao, Wenqing Qin, Guanzhou Qiu and Jun Wang
Minerals 2018, 8(10), 461; https://doi.org/10.3390/min8100461 - 17 Oct 2018
Cited by 12 | Viewed by 4661
Abstract
The fine phase transformation process of chalcocite (Cu2S) leaching in acidic ferric sulfate solution was studied by leaching experiments and synchrotron radiation X-ray diffraction (SRXRD) tests. The results showed that the dissolution process of chalcocite was divided into two stages. In [...] Read more.
The fine phase transformation process of chalcocite (Cu2S) leaching in acidic ferric sulfate solution was studied by leaching experiments and synchrotron radiation X-ray diffraction (SRXRD) tests. The results showed that the dissolution process of chalcocite was divided into two stages. In the first stage, Cu2S was firstly transformed to Cu5FeS4 and Cu2−xS, then the galvanic effect between Cu5FeS4 and Cu2−xS accelerated the dissolution process of Cu1.8S → Cu1.6S → CuS, and finally Cu5FeS4 was also transformed to CuS. While in the second stage, CuS was transformed to elemental sulfur, which formed the passivation layer and inhibited the leaching of chalcocite. Specifically, Cu5FeS4 was detected during the chalcocite leaching process by SRXRD for the first time. This research is helpful for revealing the detailed leaching process of chalcocite. Full article
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21 pages, 4722 KiB  
Article
Mineral Phase-Element Associations Based on Sequential Leaching of Ferromanganese Crusts, Amerasia Basin Arctic Ocean
by Natalia Konstantinova, James R. Hein, Amy Gartman, Kira Mizell, Pedro Barrulas, Georgy Cherkashov, Pavel Mikhailik and Alexander Khanchuk
Minerals 2018, 8(10), 460; https://doi.org/10.3390/min8100460 - 17 Oct 2018
Cited by 11 | Viewed by 4620
Abstract
Ferromanganese (FeMn) crusts from Mendeleev Ridge, Chukchi Borderland, and Alpha Ridge, in the Amerasia Basin, Arctic Ocean, are similar based on morphology and chemical composition. The crusts are characterized by a two- to four-layered stratigraphy. The chemical composition of the Arctic crusts differs [...] Read more.
Ferromanganese (FeMn) crusts from Mendeleev Ridge, Chukchi Borderland, and Alpha Ridge, in the Amerasia Basin, Arctic Ocean, are similar based on morphology and chemical composition. The crusts are characterized by a two- to four-layered stratigraphy. The chemical composition of the Arctic crusts differs significantly from hydrogenetic crusts from elsewhere of global ocean by high mean Fe/Mn ratios, high As, Li, V, Sc, and Th concentrations, and high detrital contents. Here, we present element distributions through crust stratigraphic sections and element phase association using several complementary techniques such as SEM-EDS, LA-ICP-MS, and sequential leaching, a widely employed method of element phase association that dissolves mineral phases of different stability step-by-step: Exchangeable cations and Ca carbonates, Mn-oxides, Fe-hydroxides, and residual fraction. Sequential leaching shows that the Arctic crusts have higher contents of most elements characteristic of the aluminosilicate phase than do Pacific crusts. Elements have similar distributions between the hydrogenetic Mn and Fe phases in all the Arctic and Pacific crusts. The main host phases for the elements enriched in the Arctic crusts over Pacific crusts (Li, As, Th, and V) are the Mn-phase for Li and Fe-phase for As, Th, and V; those elements also have higher contents in the residual aluminosilicate phase. Thus, higher concentrations of Li, As, Th, and V likely occur in the dissolved and particulate phases in bottom waters where the Arctic crusts grow, which has been shown to be true for Sc, also highly enriched in the crusts. The phase distributions of elements within the crust layers is mostly consistent among the Arctic crusts, being somewhat different in element concentrations in the residual phase. Full article
(This article belongs to the Special Issue Deep-Sea Minerals and Gas Hydrates)
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3 pages, 168 KiB  
Editorial
Editorial for Special Issue “Geomicrobiology and Biogeochemistry of Precious Metals”
by Frank Reith and Jeremiah Shuster
Minerals 2018, 8(10), 459; https://doi.org/10.3390/min8100459 - 17 Oct 2018
Cited by 2 | Viewed by 2145
(This article belongs to the Special Issue Geomicrobiology and Biogeochemistry of Precious Metals)
12 pages, 5384 KiB  
Article
Compositional and Textural Variations in Hainite-(Y) and Batievaite-(Y), Two Rinkite-Group Minerals from the Sakharjok Massif, Keivy Alkaline Province, NW Russia
by Ekaterina A. Selivanova, Lyudmila M. Lyalina and Yevgeny E. Savchenko
Minerals 2018, 8(10), 458; https://doi.org/10.3390/min8100458 - 16 Oct 2018
Cited by 5 | Viewed by 2911
Abstract
Compositional and textural variations in the rinkite group, seidozerite supergroup minerals, batievaite-(Y), hainite-(Y) and close to them titanosilicates from the Sakharjok massif were studied. Statistical analysis allowed for defining two major substitution schemes leading to batievaite-(Y) and cation-deficient titanosilicates forming: Ca2+ + [...] Read more.
Compositional and textural variations in the rinkite group, seidozerite supergroup minerals, batievaite-(Y), hainite-(Y) and close to them titanosilicates from the Sakharjok massif were studied. Statistical analysis allowed for defining two major substitution schemes leading to batievaite-(Y) and cation-deficient titanosilicates forming: Ca2+ + Na+ + F ↔ □ + Y3+ + (OH) and Ca2+ + Na+ ↔ □ + REE3+. Batievaite-(Y) and other cation-deficient titanosilicates are the earlier minerals formed by solid state transformation of the primary full-cation phase. Hainite-(Y) is a later mineral. It forms rims around earlier titanosilicates, or, less often, separate crystals. Full article
(This article belongs to the Special Issue Arctic Mineral Resources: Science and Technology)
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13 pages, 3453 KiB  
Article
Carbonaceous Materials in the Longmenshan Fault Belt Zone: 3. Records of Seismic Slip from the Trench and Implications for Faulting Mechanisms
by Jialiang Si, Haibing Li, Li-Wei Kuo, Jyh-Rou Huang, Sheng-Rong Song, Junling Pei, Huan Wang, Lei Song, Jiann-Neng Fang and Hwo-Shuenn Sheu
Minerals 2018, 8(10), 457; https://doi.org/10.3390/min8100457 - 16 Oct 2018
Cited by 9 | Viewed by 3395
Abstract
In recent studies on the recognition of graphitized gouges within the principal slip zone (PSZ) of the Longmenshan fault in China, we proposed that the presence of graphite might be evidence of fault slip. Here, we characterized the clay- and carbonaceous-rich gouges of [...] Read more.
In recent studies on the recognition of graphitized gouges within the principal slip zone (PSZ) of the Longmenshan fault in China, we proposed that the presence of graphite might be evidence of fault slip. Here, we characterized the clay- and carbonaceous-rich gouges of the active fault zone of the Longmenshan fault belt using samples collected from the trench at Jiulong, which was deformed during the 2008 MW-7.9 Wenchuan earthquake, to determine if graphite is present and study both the processes influencing fault behavior and the associated faulting mechanism. Mineralogical and geochemical analyses of the Jiulong trench sample show the presence of a hydrothermal mineral (i.e., dickite) integrated with dramatic relative chemical enrichment and relative depletion within a yellowish zone, suggesting the presence of vigorous high-temperature fluid–rock interactions, which are likely the fingerprint of thermal pressurization. This is further supported by the absence of carbonaceous materials (CMs) given the spectrometric data obtained. Interestingly, the Raman parameters measured near the carbonaceous-rich gouge fall within the recognized range of graphitization in the mature fault zone, implying the origin of a mature fault, as shown in the companion paper. According to both the sharp boundary within the very recent coseismic rupture zone of the 2008 MW-7.9 Wenchuan earthquake and the presence of kinetically unstable dickite, it is strongly implied that the yellow/altered gouge likely formed from a recent coseismic event as aconsequence of hydrothermal fluid penetration. We further surmise that the CM characteristics varied according to several driving reactions, e.g., transient hydrothermal heating versus long-term geological metamorphism and sedimentation. Full article
(This article belongs to the Special Issue Mineralogy of Natural Graphite)
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23 pages, 10887 KiB  
Article
Structural Controls of Ore Mineralization in a Polydeformed Basement: Field Examples from the Variscan Baccu Locci Shear Zone (SE Sardinia, Italy)
by Antonio Funedda, Stefano Naitza, Cristina Buttau, Fabrizio Cocco and Andrea Dini
Minerals 2018, 8(10), 456; https://doi.org/10.3390/min8100456 - 16 Oct 2018
Cited by 22 | Viewed by 5574
Abstract
The Baccu Locci mine area is located in a sector of the Variscan Nappe zone of Sardinia (the Baccu Locci shear zone) that hosts several type of ore deposits mined until the first half of the last century. The orebodies consist of lenses [...] Read more.
The Baccu Locci mine area is located in a sector of the Variscan Nappe zone of Sardinia (the Baccu Locci shear zone) that hosts several type of ore deposits mined until the first half of the last century. The orebodies consist of lenses of Zn–Cu sulphides, once interpreted as stratabound, and Qtz–As–Pb sulphide ± gold veins; the implication of structural controls in their origin were previously misinterpreted or not considered. Detailed field mapping, structural analyses, and ore mineralogy allowed for unraveling how different ore parageneses are superimposed each other and to recognize different relationships with the Variscan structures. The sulphide lenses are parallel to the mylonitic foliation, hosted in the hinges of minor order upright antiforms that acted as traps for hydrothermal fluids. The Qtz–As–Pb sulphide veins crosscut the sulphide lenses and are hosted in large dilatational jogs developed in the hanging wall of dextral-reverse faults, whose geometry is influenced by the attitude of reverse limbs of late Variscan folds. The ores in the Baccu Locci shear zone are best interpreted as Variscan orogenic gold-type; veins display mutual crosscutting relationships with mafic dikes dated in the same district at 302 ± 0.2 Ma, a reliable age for the mineralizing events in the area. Full article
(This article belongs to the Special Issue Structural Control of Mineral Deposits: Theory and Reality)
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24 pages, 5716 KiB  
Article
Rare Earth Elements in Planetary Crusts: Insights from Chemically Evolved Igneous Suites on Earth and the Moon
by Claire L. McLeod and Barry J. Shaulis
Minerals 2018, 8(10), 455; https://doi.org/10.3390/min8100455 - 16 Oct 2018
Cited by 12 | Viewed by 11458
Abstract
The abundance of the rare earth elements (REEs) in Earth’s crust has become the intense focus of study in recent years due to the increasing societal demand for REEs, their increasing utilization in modern-day technology, and the geopolitics associated with their global distribution. [...] Read more.
The abundance of the rare earth elements (REEs) in Earth’s crust has become the intense focus of study in recent years due to the increasing societal demand for REEs, their increasing utilization in modern-day technology, and the geopolitics associated with their global distribution. Within the context of chemically evolved igneous suites, 122 REE deposits have been identified as being associated with intrusive dike, granitic pegmatites, carbonatites, and alkaline igneous rocks, including A-type granites and undersaturated rocks. These REE resource minerals are not unlimited and with a 5–10% growth in global demand for REEs per annum, consideration of other potential REE sources and their geological and chemical associations is warranted. The Earth’s moon is a planetary object that underwent silicate-metal differentiation early during its history. Following ~99% solidification of a primordial lunar magma ocean, residual liquids were enriched in potassium, REE, and phosphorus (KREEP). While this reservoir has not been directly sampled, its chemical signature has been identified in several lunar lithologies and the Procellarum KREEP Terrane (PKT) on the lunar nearside has an estimated volume of KREEP-rich lithologies at depth of 2.2 × 108 km3. This reservoir therefore offers a prospective location for future lunar REE exploration. Within the context of chemically evolved lithologies, lunar granites are rare with only 22 samples currently classified as granitic. However, these extraterrestrial granites exhibit chemical affinities to terrestrial A-type granites. On Earth, these anorogenic magmatic systems are hosts to U-Th-REE-ore deposits and while to date only U-Th regions of enrichment on the lunar surface have been identified, future exploration of the lunar surface and interior may yet reveal U-Th-REE regions associated with the distribution of these chemically distinct, evolved lithologies. Full article
(This article belongs to the Special Issue Mineral Deposits of Critical Elements)
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23 pages, 4818 KiB  
Article
A Geometallurgical Approach to Tailings Management: An Example from the Savage River Fe-Ore Mine, Western Tasmania
by Anita Parbhakar-Fox, John Glen and Bonita Raimondo
Minerals 2018, 8(10), 454; https://doi.org/10.3390/min8100454 - 15 Oct 2018
Cited by 33 | Viewed by 6061
Abstract
At the Old Tailings Dam (OTD), Savage River, Western Tasmania, 38 Mt of pyritic tailings were deposited (1967 to 1982) and have since been generating acid and metalliferous drainage (AMD). Mineral chemistry analysis confirmed high concentrations of refractory cobalt in pyrite (up to [...] Read more.
At the Old Tailings Dam (OTD), Savage River, Western Tasmania, 38 Mt of pyritic tailings were deposited (1967 to 1982) and have since been generating acid and metalliferous drainage (AMD). Mineral chemistry analysis confirmed high concentrations of refractory cobalt in pyrite (up to 3 wt %). This study sought to determine, through a series of bench scale tests, if Co could be liberated using biohydrometallurgical techniques. Four bulk tailings samples were collected across the OTD, from up to 1.5 m depth, targeting three sulphide-bearing facies. The study was conducted in four stages: (1) bacterial adaption using BIOX® bacteria; (2) biooxidation optimization with pH, temperature and Fe medium parameters tested; (3) flotation test work to produce a sulphide concentrate followed by biooxidation; and (4) Fe and Co precipitation tests. The BIOX® culture adapted to the bulk composite (containing 7 wt % pyrite) in ~10 days, with biooxidation occurring most efficiently at pH 1.5–1.6 and 40 °C whilst the Fe medium concentration was identified as a less-controlling parameter. Flotation produced a 71% pyrite concentrate with total oxidation occurring after 14 days of biooxidation with 99% of Co leached. At pH 3, Co was effectively separated from Fe, however Ni and Cu were also present in the pregnant liquor solution and therefore required refining before production of cobalt hydroxide, the intermediate saleable product. This study shows that adopting a geometallurgical approach to tailings characterisation can identify if mine waste has commodity potential and how best to extract it therefore unlocking the potential for unconventional rehabilitation of AMD affected sites. Full article
(This article belongs to the Special Issue Geometallurgy)
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11 pages, 3269 KiB  
Article
Dimension and Crushed Stones Extraction as a Source of Social and Environmental Conflicts in Poland
by Justyna Górniak-Zimroz and Katarzyna Pactwa
Minerals 2018, 8(10), 453; https://doi.org/10.3390/min8100453 - 15 Oct 2018
Cited by 2 | Viewed by 2895
Abstract
Crushed and dimension stones, which include 33 lithological varieties among igneous rocks, metamorphic rocks and sedimentary rocks, are mainly located in the southern and south-western part of Poland. Demand for this group of minerals is continuously high, which results from conducted and planned [...] Read more.
Crushed and dimension stones, which include 33 lithological varieties among igneous rocks, metamorphic rocks and sedimentary rocks, are mainly located in the southern and south-western part of Poland. Demand for this group of minerals is continuously high, which results from conducted and planned infrastructural investments. Mining activity is associated with interference in the natural environment. Negative consequences of exploitation include, among others: Land surface deformations, and the pollution of the soil, air, and water. In many cases, the extraction of minerals also leads to the liquidation of housing and transportation infrastructure located in the mining area, as well as to reducing the value of real estate in the immediate vicinity of the deposit or to increase in the level of stress among local residents, who are exposed to noise, which causes growing social conflicts in areas designated for exploitation. Thus, the awareness of negative effects of undertaking open-cast mining leads to the conflicts between various groups of stakeholders (residents, environmental organizations, mining entrepreneurs). Through the use of multi-criteria evaluation, this article identifies the places of potential social and environmental conflicts resulting from the planned mining activity in three areas of the densest occurrence of the analysed deposits (Lower Silesia Province, Lesser Poland Province and Świętokrzyskie Province). The assessment of lands over the deposits recognized initially and in detail was proposed, determining the degree of their accessibility. Due to the proposed method, it’s possible to obtain results of the classification of each fragment of the analysed deposit, as well as the surroundings of such deposit at any distance from it, within the boundaries of analysed area. Information may be made available to users of the deposits, mining enterprises interested in exploitation of the deposits or administration responsible for issuing decisions regarding concessions for exploitations of the deposits, so that they have knowledge about conflict areas in the region, resulting from the impact of planned mining activity on life and health of the people and on the environment. Full article
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18 pages, 4915 KiB  
Article
Impact of Temperature and Geothermal Gradient on Sandstone Reservoir Quality: the Baiyun Sag in the Pearl River Mouth Basin Study Case (Northern South China Sea)
by Chuan Lei, Jinglan Luo, Xiong Pang, Chi Li, Jiang Pang and Yongkun Ma
Minerals 2018, 8(10), 452; https://doi.org/10.3390/min8100452 - 15 Oct 2018
Cited by 12 | Viewed by 4975
Abstract
Deep-water areas have become a hotspot for global hydrocarbon exploration. In the deep-water area of the Northern South China Sea, a complete set of source rocks, reservoir rocks, and caprock represents a good oil and gas exploration prospect. The Pearl River Mouth basin, [...] Read more.
Deep-water areas have become a hotspot for global hydrocarbon exploration. In the deep-water area of the Northern South China Sea, a complete set of source rocks, reservoir rocks, and caprock represents a good oil and gas exploration prospect. The Pearl River Mouth basin, an important exploration target in this area, has a wide range of geothermal gradients. However, the mechanism by which the geothermal gradient influences reservoir quality remains unclear, which severely restricts future exploration. We observed that the reduction rates in the porosity and permeability with increasing burial depth and stratum temperature are more rapid in high geothermal gradient areas. The stratum temperature affects the process of diagenesis and the reservoir quality by changing the grain compressive strength, solubility, and precipitation of minerals and clay minerals transformations. With a comparison the crustal extensional thinning histories of different geothermal gradient areas, this study elucidates the comprehensive factors controlling the decreases rates of reservoir porosity and permeability. These findings explain the different evolutions of reservoirs in areas with different geothermal gradients. Full article
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15 pages, 10692 KiB  
Article
Application of Depletion Attraction in Mineral Flotation: I. Theory
by Junhyun Choi, Gahee Kim, Sowon Choi, KyuHan Kim, Yosep Han, Scott A. Bradford, Siyoung Q. Choi and Hyunjung Kim
Minerals 2018, 8(10), 451; https://doi.org/10.3390/min8100451 - 14 Oct 2018
Cited by 10 | Viewed by 5237
Abstract
We investigate the role of depletion interactions in the particle–bubble interactions that determine the attachment capability of particles on the bubble surface in flotation. In this article, we propose a theoretical model that explains how this attractive interaction could enhance flotation efficiency. Two [...] Read more.
We investigate the role of depletion interactions in the particle–bubble interactions that determine the attachment capability of particles on the bubble surface in flotation. In this article, we propose a theoretical model that explains how this attractive interaction could enhance flotation efficiency. Two optimum conditions are determined for the concentration and molecular weight of the depletion agent. The optimum concentration can be determined through the extent of surface activity of the depletion agents. The magnitude of the depletion attraction increases as the concentration increases; however, an increase in the concentration simultaneously enhances its surface concentration. The bubble surface adsorption of the depletion agent results in polymer brushes on the bubble surface that produce a large repulsive interaction. In contrast, the optimal molecular weight of the depletion agents is given by the interaction between the depletion agent sizes, which is determined by its molecular weight and Debye length which is determined by the solution ionic strength. We demonstrate that exploiting this depletion interaction could significantly enhance the flotation efficiency and in principal could be used for any particle system. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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11 pages, 2307 KiB  
Article
Application of Depletion Attraction in Mineral Flotation: II. Effects of Depletant Concentration
by Gahee Kim, Junhyun Choi, Sowon Choi, KyuHan Kim, Yosep Han, Scott A. Bradford, Siyoung Q. Choi and Hyunjung Kim
Minerals 2018, 8(10), 450; https://doi.org/10.3390/min8100450 - 14 Oct 2018
Cited by 10 | Viewed by 4124
Abstract
Along with the accompanying theory article, we experimentally investigate the effect of the depletion attraction force on the flotation of malachite. While varying the concentration of the depletion agent (polyethylene glycol), three different systems are studied: pure malachite, pure silica and a 1:1 [...] Read more.
Along with the accompanying theory article, we experimentally investigate the effect of the depletion attraction force on the flotation of malachite. While varying the concentration of the depletion agent (polyethylene glycol), three different systems are studied: pure malachite, pure silica and a 1:1 mass ratio of malachite and silica binary system. We find that the recovery increases significantly as the concentration of the depletion reagents increases for all three systems. However, the recovery suddenly decreases in a certain concentration range, which corresponds to the onset of the decreased surface tension when high concentrations of the depletion agent are used. The decreased surface tension of the air/water interface suggests that the recovery rate is lowered due to the adsorption of the depletion agent to the bubble surface, acting as a polymer brush. We also perform experiments in the presence of a small amount of a collector, sodium oleate. An extremely small amount of the collector (10−10–10−5 M) leads to the increase in the overall recovery, which eventually reaches nearly 100 percent. Nevertheless, the grade worsens as the depletant provides the force to silica particles as well as target malachite particles. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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14 pages, 19168 KiB  
Article
Nöggerathite-(Ce), (Ce,Ca)2Zr2(Nb,Ti)(Ti,Nb)2Fe2+O14, a New Zirconolite-Related Mineral from the Eifel Volcanic Region, Germany
by Nikita V. Chukanov, Natalia V. Zubkova, Sergey N. Britvin, Igor V. Pekov, Marina F. Vigasina, Christof Schäfer, Bernd Ternes, Willi Schüller, Yury S. Polekhovsky, Vera N. Ermolaeva and Dmitry Yu. Pushcharovsky
Minerals 2018, 8(10), 449; https://doi.org/10.3390/min8100449 - 12 Oct 2018
Cited by 16 | Viewed by 4070
Abstract
The new mineral nöggerathite-(Ce) was discovered in a sanidinite volcanic ejectum from the Laach Lake (Laacher See) paleovolcano in the Eifel region, Rhineland-Palatinate, Germany. Associated minerals are sanidine, dark mica, magnetite, baddeleyite, nosean, and a chevkinite-group mineral. Nöggerathite-(Ce) has a color that ranges [...] Read more.
The new mineral nöggerathite-(Ce) was discovered in a sanidinite volcanic ejectum from the Laach Lake (Laacher See) paleovolcano in the Eifel region, Rhineland-Palatinate, Germany. Associated minerals are sanidine, dark mica, magnetite, baddeleyite, nosean, and a chevkinite-group mineral. Nöggerathite-(Ce) has a color that ranges from brown to deep brownish red, with adamantine luster; the streak is brownish red. It occurs in cavities of sanidinite and forms long prismatic crystals measuring up to 0.02 × 0.03 × 1.0 mm, with twins and random intergrowths. Its density calculated using the empirical formula is 5.332 g/cm3. The Vickers hardness number (VHN) is 615 kgf/mm2, which corresponds to a Mohs’ hardness of 5½. The mean refractive index calculated using the Gladstone–Dale equation is 2.267. The Raman spectrum shows the absence of hydrogen-bearing groups. The chemical composition (electron microprobe holotype/cotype in wt %) is as follows: CaO 5.45/5.29, MnO 4.19/4.16, FeO 7.63/6.62, Al2O3 0.27/0.59, Y2O3 0.00/0.90, La2O3 3.17/3.64, Ce2O3 11.48/11.22, Pr2O3 1.04/0.92, Nd2O3 2.18/2.46, ThO2 2.32/1.98, TiO2 17.78/18.69, ZrO2 27.01/27.69, Nb2O5 17.04/15.77, total 99.59/99.82, respectively. The empirical formulae based on 14 O atoms per formula unit (apfu) are: (Ce0.59La0.165Nd0.11Pr0.05)Σ0.915Ca0.82Th0.07Mn0.50Fe0.90Al0.045Zr1.86Ti1.88Nb1.07O14 (holotype), and (Ce0.57La0.19Nd0.12Pr0.05Y0.06)Σ0.99Ca0.79Th0.06Mn0.49Fe0.77Al0.10Zr1.89Ti1.96Nb1.00O14 (cotype). The simplified formula is (Ce,Ca)2Zr2(Nb,Ti)(Ti,Nb)2Fe2+O14. Nöggerathite-(Ce) is orthorhombic, of the space group Cmca. The unit cell parameters are: a = 7.2985(3), b = 14.1454(4), c = 10.1607(4) Å, and V = 1048.99(7) Å3. The crystal structure was solved using single-crystal X-ray diffraction data. Nöggerathite-(Ce) is an analogue of zirconolite-3O, ideally CaZrTi2O7, with Nb dominant over Ti in one of two octahedral sites and REE dominant over Ca in the eight-fold coordinated site. The strongest lines of the powder X-ray diffraction pattern (d, Å (I, %) (hkl)) are: 2.963 (91) (202), 2.903 (100) (042), 2.540 (39) (004), 1.823 (15) (400), 1.796 (51) (244), 1.543 (20) (442), and 1.519 (16) (282), respectively. The type material is deposited in the collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia (registration number 5123/1). Full article
(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)
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17 pages, 4961 KiB  
Article
Re–Os Pyrite Geochronological Evidence of Three Mineralization Styles within the Jinchang Gold Deposit, Yanji–Dongning Metallogenic Belt, Northeast China
by Shun-Da Li, Zhi-Gao Wang, Ke-Yong Wang, Wen-Yan Cai, Da-Wei Peng, Li Xiao and Jie Li
Minerals 2018, 8(10), 448; https://doi.org/10.3390/min8100448 - 12 Oct 2018
Cited by 12 | Viewed by 3534
Abstract
The Jinchang gold deposit is located in the eastern Yanji–Dongning Metallogenic Belt in Northeast China. The orebodies of the deposit are hosted within granite, diorite, and granodiorite, and are associated with gold-mineralized breccia pipes, disseminated gold in ores, and fault-controlled gold-bearing veins. Three [...] Read more.
The Jinchang gold deposit is located in the eastern Yanji–Dongning Metallogenic Belt in Northeast China. The orebodies of the deposit are hosted within granite, diorite, and granodiorite, and are associated with gold-mineralized breccia pipes, disseminated gold in ores, and fault-controlled gold-bearing veins. Three paragenetic stages were identified: (1) early quartz–pyrite–arsenopyrite (stage 1); (2) quartz–pyrite–chalcopyrite (stage 2); and (3) late quartz–pyrite–galena–sphalerite (stage 3). Gold is hosted predominantly within pyrite. Pyrite separated from quartz–pyrite–arsenopyrite cement within the breccia-hosted ores (Py1) yield a Re–Os isochron age of 102.9 ± 2.7 Ma (MSWD = 0.17). Pyrite crystals from the quartz–pyrite–chalcopyrite veinlets (Py2) yield a Re–Os isochron age of 102.0 ± 3.4 Ma (MSWD = 0.2). Pyrite separated from quartz–pyrite–galena–sphalerite veins (Py3) yield a Re–Os isochron age of 100.9 ± 3.1 Ma (MSWD = 0.019). Re–Os isotopic analyses of the three types of auriferous pyrite suggest that gold mineralization in the Jinchang Deposit occurred at 105.6–97.8 Ma (includes uncertainty). The initial 187Os/188Os values of the pyrites range between 0.04 and 0.60, suggesting that Os in the pyrite crystals was derived from both crust and mantle sources. Full article
(This article belongs to the Special Issue Integrated Chronology Studies of Ore Deposits)
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14 pages, 6962 KiB  
Article
Elemental Concentration in Serpentinitic Soils over Ultramafic Bedrock in Sierra Bermeja (Southern Spain)
by Ana Romero-Freire, José Antonio Olmedo-Cobo and José Gómez-Zotano
Minerals 2018, 8(10), 447; https://doi.org/10.3390/min8100447 - 12 Oct 2018
Cited by 5 | Viewed by 3298
Abstract
Although the presence of potentially toxic metals in soils is normally associated with human soil pollution, these elements also appear naturally in environments in which the lithological base contains ultramafic rocks such as peridotites. Serpentinitic soils tend to develop on substrates of this [...] Read more.
Although the presence of potentially toxic metals in soils is normally associated with human soil pollution, these elements also appear naturally in environments in which the lithological base contains ultramafic rocks such as peridotites. Serpentinitic soils tend to develop on substrates of this kind, often containing metals with few or no known biological functions, which in some cases are toxic for most plants. This study assessed the level of potentially toxic metals and other elements in an endorheic basin discovered in Sierra Bermeja (Southern Spain), one of the largest peridotite outcrops on Earth. In this location—of particular interest given that basins of this kind are very rare on peridotites—six geomorphoedaphic sub-units on three different substrates were identified. The distribution of microelements in these sub-units was analyzed, and stratified random sampling was performed to identify the major ions with essential functions for living organisms and the potentially toxic metals. The lowest values for macronutrients appeared in the soils formed on ultramafic materials. When analyzing the load of potentially toxic metals, no significant differences were detected between the soils formed on serpentinite and peridotite substrates, although different values were obtained in the soils formed over acidic rocks. Full article
(This article belongs to the Special Issue Ultramafic Complexes and Related Deposits)
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13 pages, 6233 KiB  
Article
Titanite Ores of the Khibiny Apatite-Nepheline-Deposits: Selective Mining, Processing and Application for Titanosilicate Synthesis
by Lidia G. Gerasimova, Anatoly I. Nikolaev, Marina V. Maslova, Ekaterina S. Shchukina, Gleb O. Samburov, Victor N. Yakovenchuk and Gregory Yu. Ivanyuk
Minerals 2018, 8(10), 446; https://doi.org/10.3390/min8100446 - 12 Oct 2018
Cited by 17 | Viewed by 4574
Abstract
Geological setting and mineral composition of (apatite)-nepheline-titanite ore from the Khibiny massif enable selective mining of titanite ore, and its processing with sulfuric-acid method, without preliminary concentration in flotation cells. In this process flow diagram, titanite losses are reduced by an order of [...] Read more.
Geological setting and mineral composition of (apatite)-nepheline-titanite ore from the Khibiny massif enable selective mining of titanite ore, and its processing with sulfuric-acid method, without preliminary concentration in flotation cells. In this process flow diagram, titanite losses are reduced by an order of magnitude in comparison with a conventional flotation technology. Further, dissolution of titanite in concentrated sulfuric acid produces titanyl sulfate, which, in turn, is a precursor for titanosilicate synthesis. In particular, synthetic analogues of the ivanyukite group minerals, SIV, was synthesized with hydrothermal method from the composition based on titanyl-sulfate, and assayed as a selective cation-exchanger for Cs and Sr. Full article
(This article belongs to the Special Issue Arctic Mineral Resources: Science and Technology)
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11 pages, 3880 KiB  
Article
Stability of Chromium in Stainless Steel Slag during Cooling
by Qing Zhao, Chengjun Liu, Longhu Cao, Xiang Zheng and Maofa Jiang
Minerals 2018, 8(10), 445; https://doi.org/10.3390/min8100445 - 11 Oct 2018
Cited by 24 | Viewed by 3763
Abstract
The chromium elution behavior of stainless steel (SS) slag depends highly on the chromium distribution, and the molten modification process proved to effectively improve the chromium enrichment in stable phases. However, the phase transformation and variation of chromium stability during the subsequent cooling [...] Read more.
The chromium elution behavior of stainless steel (SS) slag depends highly on the chromium distribution, and the molten modification process proved to effectively improve the chromium enrichment in stable phases. However, the phase transformation and variation of chromium stability during the subsequent cooling process is still poorly understood. In this work, the phase composition and chromium distribution of SS slag from different quenching temperatures were experimentally studied, and the stability of chromium-bearing phases was evaluated using standard leaching tests. The results indicated that dicalcium silicate and spinel phases had formed in the molten slag at 1600 °C, while the dicalcium silicate disappeared and the phases of merwinite and melilite precipitated when the temperature decreased from 1600 to 1300 °C (at a rate of 5 °C/min). During this cooling process, the chromium migrated from other phases into the spinel, significantly suppressing the chromium elution. The leaching results also demonstrated that the potential chromium-bearing phases of glass, dicalcium silicate and merwinite are unstable and are presumably the main source of chromium release. The treated SS slag meets the requirements for the utilization of chromium-bearing slag in the cement and brick industries. Full article
(This article belongs to the Special Issue Metallurgical Slags)
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11 pages, 2494 KiB  
Article
Kaolinite Claystone-Based Geopolymer Materials: Effect of Chemical Composition and Curing Conditions
by Pavlína Hájková
Minerals 2018, 8(10), 444; https://doi.org/10.3390/min8100444 - 11 Oct 2018
Cited by 32 | Viewed by 4578
Abstract
This work describes the role of chemical composition and curing conditions in geopolymer strength, leachability of chemical elements and porosity. The study focuses on geopolymer material prepared from calcined kaolinite claystone, which is not studied frequently as a raw material for geopolymer production, [...] Read more.
This work describes the role of chemical composition and curing conditions in geopolymer strength, leachability of chemical elements and porosity. The study focuses on geopolymer material prepared from calcined kaolinite claystone, which is not studied frequently as a raw material for geopolymer production, although it has a high application potential as it is easily commercially available and allows preparation of geopolymers with low viscosity. The composition of geopolymers and their curing methods were selected considering their ease of use in the praxis. Therefore, the potassium water glass itself was used as alkali activator without any KOH or NaOH addition. Chemical composition was changed only by the density of water glass in the range of 1.2 to 1.6 g·cm−3. Geopolymers were cured at a temperature within the range of 5 °C–70 °C to speed up the solidification process as well as by microwave radiation. High compressive strengths were obtained for geopolymers with the highest densities of the water glass (1.5 and 1.6 g·cm−3) in dependence on various curing conditions. Higher strengths were achieved in the case of samples where the solidification was not accelerated. The samples cured at lower temperatures (5 °C) showed lower porosity compared to the other curing types. The lowest leachability of Si and alkalis was reached for the samples with water glass density 1.5 g·cm−3. Full article
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