Minerals — Open Access Journal of Mining & Mineral Processing

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 Cu_2−xS, then the galvanic effect between Cu₅FeS₄ and Cu_2−xS accelerated the dissolution process of Cu_1.8S → Cu_1.6S → 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

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

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

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 M_W-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 M_W-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

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

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

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

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

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

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

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

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: (Ce_0.59La_0.165Nd_0.11Pr_0.05)_Σ0.915Ca_0.82Th_0.07Mn_0.50Fe_0.90Al_0.045Zr_1.86Ti_1.88Nb_1.07O₁₄ (holotype), and (Ce_0.57La_0.19Nd_0.12Pr_0.05Y_0.06)_Σ0.99Ca_0.79Th_0.06Mn_0.49Fe_0.77Al_0.10Zr_1.89Ti_1.96Nb_1.00O₁₄ (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) ų. 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

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

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

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

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 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

Modeling ore body in 3D is the basis of digital intelligent mining. However, most existing three-dimensional mining software uses the contour approach that requires too much man–machine interaction and difficult partial updating. Moreover, accounting for uncertainty and low geometric quality picking is very difficult in the direct contour approach. Therefore, an implicit modeling approach to automatically build the three-dimensional model for ore body by means of spatial interpolation directly based on the geological borehole data with Hermite radial basis function (HRBF) algorithm as the core is proposed. Furthermore, in order to solve the problems of weak continuity of models due to the long-distance original boreholes as well as the boundary-point normal solution error, the densification of original borehole data with the virtual borehole as well as the calculation of point-cloud normal direction based on the adjacent hole-drilling method is proposed. The verification of two mine engineering projects and comparison with the explicit modeling results show that this approach could realize the automatic building of three-dimensional models for the ore body with high geometric quality, timely update and accurate results. Full article