Precious Metal Ores Research Articles

The resource curse phenomenon in the case of precious metals: A panel evidence from top 19 exporting countries

The theory suggests that a resource curse is more likely for precious products (such as gold, diamond, and silver) than agricultural products. Therefore, based on this theoretical claim, this study aims to analyze the resource curse hypothesis for a panel of the top 19 exporting countries of precious metal ores and concentrates. Based on different panel data models and annual data from 2001 to 2021, we confirm the presence of a resource curse. In addition to labor and capital variables, the model is extended with institutional quality and human capital variables. By doing so, the direct and indirect impacts of institutional quality and human capital on economic growth are analyzed. The results reveal that both variables significantly and positively impact economic growth. In contrast, their indirect impacts are insufficient to reverse the resource curse into a blessing. Finally, some important policy implications are suggested based on the empirical findings, such as the sustainable utilization and management of natural resources and their rents, the regulation of education policies to increase the national human capital stock, and the necessity of increasing the institutional quality level to prevent corruption and rent-seeking behaviors.

EFFECTS OF HEAVY METALS, CONTAINED IN FLOTATION TAILINGS, ON PLANTS USED IN REVEGETATION

During the processing of precious and base metal ores from the Baia Mare mining area, which contained Au, Ag, Cu, Pb and Zn, large amounts of flotation tailings resulted, which were deposited in the Bozânta tailings management facility, located between Săsar and Bozânta Mare villages, 4 km west of Baia Mare. Due to the presence of minerals containing metal sulphides (mainly pyrite), the acid rock drainage (ARD) has become very active, catalysed by iron- and sulphur-oxidizing bacteria, which naturally occur at these sites. Decreasing the surface of the pond as a result of evaporation, combined with the increase of the beach surface and the absence of any protection at the embankment ridge, led to the entrainment of the tailings by wind at considerable distances. They often end up in neighbouring settlements, especially in the two mentioned villages, as a result of prevailing winds from the NE-SW direction. The purpose of the research was to test the resistance of some plant species (Sinapis alba L. – white mustard; Trifolium pratense L. – red clover and Lolium perenne L. – ray grass) to the conditions generated by the tailings on the surface of the depot, in order to create a vegetation cover with a role in diminishing tailings discharges in the adjacent areas. There were tested the effects of the industrial eluate (acid mine water, pH 4.3), obtained from the tailings pond, over seed germination parameters: germination capacity (GC); germinative energy (GE) and relative seed germination (RG). The results of the tests pointed out that the least affected was white mustard: GC – 95.3%; the differences in the values obtained in the control samples and the GE test – 5.3%; the results for RG – 99.3%, confirm that the white mustard seeds were the least influenced by the industrial eluate, followed by ray grass and red clover. In the tests for plant growth on the tailings pond, 5 experimental variants were used: a) soil (S); b) flotation tailings (T); c) mixture of flotation tailings and soil (T+S); d) mixture of flotation tailings and organo-zeolitic material (T+OZ); e) mixture of flotation tailings, organo-zeolitic material and soil (T+OZ+S). It is recommended to use the T+OZ+S mixture on the pond surface and sowing with Sinapis alba and Trifolium pratense. For both species, double seed sowing is recommended.

Colloids and Nanoparticles: Implications for Hydrothermal Precious Metal Ore Formation

Abstract Research on nanoscale processes is expanding in many scientific and technical disciplines, and economic geology is no exception. The idea that colloidal gold particles (or nanoparticles) may have played a significant role in ore formation was initially based on textural evidence from high-grade epithermal veins. More recently, the discovery of gold nanoparticles in some present-day geothermal systems and several orogenic gold deposits suggests that their formation could be a common process in gold-supersaturated hydrothermal solutions. Rare laboratory studies indicate that gold nanoparticles typically aggregate to form dendritic clusters. Over time, these dendrites perhaps can evolve to form coarser-grained crystals as subsequent annealing and recrystallization occurs. Due to the ephemeral nature and later recrystallization of dendrites, evidence of their former existence is commonly obscured. However, newer nanoscale imaging technologies have resulted in an increased recognition of their presence in hydrothermal gold ores, and thus their role in ore-forming processes merits further research. In particular, does their nucleation and deposition lead to forming higher-grade ores?

Quantum-chemical substantiation of collecting properties of acetylene reagents in flotation of sulphide minerals

The paper presents the analysis results of known data and performed adsorption and spectral IR studies of MIG-4E, DMIPEK and DC-80 acetylene reagents in interaction with galena (PbS) and molybdenite (Mo2S) sulphide minerals. The IR spectra analysis of pure reagents and products of their interaction with the surface of sulphide minerals has showed that the adsorption of MIG-4E molecules takes place on the surface of lead sulphides, and DMIPEC molecules are adsorbed on the surface of molybdenite. Quantum-chemical calculations of the total potential energy of the complexes have shown that the complex formed by a molecule of MIG-4E – PbS of (HUMO) complexes by nucleophilic mechanism has 2514.0873 kcal/mol, which is almost an order of magnitude greater than the total potential energy (270.0439 kcal/mol) of MIG-4E – PbS (HUMO) complex formed by electrophilic mechanism. Analysis of the calculated data of the total potential energy of complexes formed by MIG-4E reagent molecules with PbS surface and DMIPEC molecules with Mo2S surface has showed that the total energy of π-complexes formed by reagents by electrophilic mechanism differs by 47.7% among reagent molecules and amounts to 270.0439 kcal/mol for (MIG-4E + PbS) complex, and 141.9386 kcal/mol for (DMIPEC + Mo2S) complex in the (HUMO) state. Such a difference in the values of total energies of the complexes can correlate with the conformational ability of DMIPEC reagent molecules. Usage of acetylene alcohols as additional selective collectors during flotation of a number of non-ferrous and precious metal ores has shown a significant increase in the extraction of target metals, which makes it possible to consider the reagents based on acetylene derivatives as promising for industrial applications.

Magmatic volatiles and platinum-group element mineralization in the Stillwater layered intrusion, U.S.A.

Abstract The activity of volatile-rich fluids may be important in the evolution of basaltic magmatic systems and associated precious metal ore formation. There is evidence for Cl-rich fluids within the Stillwater Complex (Montana, U.S.A.), which have been linked to platinum and palladium mineralization in the economically important Johns-Manville (J-M) Reef ore body. We present the first data set for heavy halogens (Cl, Br, and I) and natural noble gas isotopes in bulk rock and mineral separates from the Peridotite Zone and the Olivine-Bearing Zone I of the Stillwater Complex, including samples from the J-M Reef and G Chromitite bodies. Our data reveal concentrations of 4 to 13 500 ppm for Cl, 26 ppb to 360 ppm for Br, and <1 ppb to 9 ppm I over the whole sample set. Cl, Br, and I correlate well with each other implying a shared process and/or distribution in mineral species. Br/Cl and I/Cl ratios span a range from 0.3 to 35 × 10−3 and 5 to 900 × 10−6 by weight, respectively, encompassing MORB-like to more enriched compositions, particularly for Br/Cl. High-Br/Cl ratios compared to MORB in some Stillwater samples suggest fractionation of halogens during the exsolution of a volatile-rich fluid to explain the most Br-enriched samples. More generally, the presence of minerals such as scapolite, hornblende, and apatite in the most halogen-enriched samples suggests that the halogen-bearing fluids were derived from the cooling of the intrusion rather than late-stage (low-temperature) metamorphism. The combined halogen abundance and noble gas isotope data set imply that crustal contamination may have played a limited role in the crystallization of pegmatoids and the G Chromitite but is not required to account for the halogen budget of the J-M Reef. High-halogen contents in the sulfide-bearing J-M Reef and associated lithologies are consistent with the influence of fluid-related activity during platinum-group element (PGE)-Reef formation, lending weight to the hydromagmatic model for mineralization in the Stillwater intrusion. Our new data also imply chalcophile tendencies of Br and I over Cl in sulfides in natural systems, hinting at the importance of sulfide liquid interaction with halogen-rich fluids in the formation of sulfide-hosted precious metal ore deposits.

Uncertainties in quantitative mineralogical studies using scanning electron microscope-based image analysis

Scanning electron microscope-based automated mineralogy studies are readily associated with quantitative results, providing one of the foundations of geometallurgical studies. Despite the importance of quantitative data for such studies, and efforts to reduce statistical errors, the reporting of uncertainties is rare. This contribution illustrates how bootstrap resampling can be used to provide robust estimates of statistical uncertainties for the modal mineralogy, metal deportment and all relevant textural attributes of a sample or a series of samples. Based on a case study of the Bolcana Au-Cu porphyry deposit in the South Apuseni Mountains, Romania, the impact of insufficient sampling statistics on quantitative mineralogical studies is illustrated. Quantitative analyses of the mineralogy and microfabric of milled ore samples from seven 40 m drill core intervals from the Bolcana Prospect were conducted using a Mineral Liberation Analyser (MLA), complemented by electron probe micro-analysis. Bootstrap resampling was then applied to assess how many grain mount surfaces should be analysed to achieve statistically robust results for both Cu and Au mineralogy, deportment and textural attributes. Despite variable mineralogy, grades and mineralisation styles, estimated statistical uncertainties on Cu deportment are consistently low. In contrast, uncertainties for Au deportment are so high that most reported values for important characteristics are statistically meaningless. This is mainly attributed to the pronounced nugget effect for Au mineralisation, exacerbated by the small sample size analysed by MLA. An unfeasible number of measurements would be necessary to provide robust figures for the deportment of minor/trace elements and minerals, along with other tangible mineralogical properties, such as mineral associations. The results of this case study demonstrate that statistical uncertainties need to be carefully incorporated when considering the results of automated mineralogical studies and their impact on geometallurgical models. This is particularly relevant for studies of precious metal ores.

Application of Magnetization Treatment in Flotation

With the decrease of mineral resources reserves, the characteristics of “poor, fine and miscellaneous” of mineral resources are becoming more and more obvious. People pay more and more attention to the environmental protection. A simple, green and efficient separation process magnetization flotation has been paid more and more attention by mineral processing workers. Based on the analysis and summary of the development process and advantages of magnetic flotation, the application status of magnetic flotation at home and abroad in the processing of ferrous metal ore, non-ferrous metal ore, rare metal ore, precious metal ore, non-metallic ore, coal, etc. Compared with conventional flotation, it is found that the cost of magnetic flotation is lower than that of conventional flotation. Combining theoretical analysis, computer simulation, experiment and advanced detection methods, the mechanism, influencing factors, process and equipment of magnetic flotation are the development trend in the future.

Xanthation of alginate for heavy metal ions removal. Characterization of xanthate-modified alginates and its metal derivatives

Xanthates are widely used in mining industry as collectors for its high affinity towards metal sulfides and precious metal ores. The possibility of using alginate for xanthation has not been explored yet despite the feasibility by the presence of hydroxyl groups alongside the polymeric chains. Therefore, this work aims to evaluate the alginate as a matrix for xanthation and its application on heavy metal ions removal. In order to obtain green materials, important pararmeter were explored such as the effect of reaction time (4–12 h), type of base (NaOH/KOH) and amount of carbon disulfide (2–10%v/v). Xanthated alginates were analyzed by NMR techniques and evidence of β-elimination was detected at 5.45 ppm. Furthermore, the presence of S element was confirmed by EDS mapping technique, while XRD showed a semi-crystalline structure. On the other hand, the chemical shifts of δ(C=S) and ν(C=S) bands were found around 863–805 cm−1 and 662–602 cm−1 respectively. Also, a shoulder at 182 ppm is appreciated by NMR in solid state attributed to CS group. According to FESEM analyses, morphology of xanthated alginates is affected by interaction with heavy metal ions. Finally, suitable materials for the removal of heavy metal ions were established at optimum pH values.

X-ray Photoelectron Spectroscopy in Mineral Processing Studies

Surface phenomena play the crucial role in the behavior of sulfide minerals in mineral processing of base and precious metal ores, including flotation, leaching, and environmental concerns. X-ray photoelectron spectroscopy (XPS) is the main experimental technique for surface characterization at present. However, there exist a number of problems related with complex composition of natural mineral systems, and instability of surface species and mineral/aqueous phase interfaces in the spectrometer vacuum. This overview describes contemporary XPS methods in terms of categorization and quantitative analysis of oxidation products, adsorbates and non-stoichiometric layers of sulfide phases, depth and lateral spatial resolution for minerals and ores under conditions related to mineral processing and hydrometallurgy. Specific practices allowing to preserve volatile species, e.g., elemental sulfur, polysulfide anions and flotation collectors, as well as solid/liquid interfaces are surveyed; in particular, the prospects of ambient pressure XPS and cryo-XPS of fast-frozen wet mineral pastes are discussed. It is also emphasized that further insights into the surface characteristics of individual minerals in technological slurries need new protocols of sample preparation in conjunction with high spatial resolution photoelectron spectroscopy that is still unavailable or unutilized in practice.

Characterization of lithological zones of the Isanlu sheet 225, North Central Nigeria, using aerogeophysical datasets

Gridded aeromagnetic and aeroradiometric datasets of Isanlu sheet 225 were processed and interpreted in order to map the geological structures and characteristic lithology, as well as potential mineral ore zones in the area. Recorded aeromagnetic data were reduced to the magnetic equator before filtering operations which enhanced the magnetic anomalies. Analytic signal map was created, and subsequently a model was generated along a selected profile for better interpretation of the subsurface materials. On the aeroradiometric data were performed both enhancement and statistical operations. The lithological zones were identified. They are metasedimentary rocks, migmatites and igneous rocks occupying varying proportions within the entire area. Some potential radioactive or precious metal ore zones were also localized. A major structure interpreted in the study area trends in the SE–NW direction. Other surface structures were also delineated and general orientation was evaluated. This information may serve as a valuable database for further prospective research and mineral exploration in the region.

Development of explosive breaking principles for the ores prone to overgrinding

In underground mining of valuable non-metallic raw materials, non-ferrous and precious metal ores, the problem of overgrinding of raw materials as a result of blasting operations is quite acute. For ores of nonferrous and precious metals, represented by strong rocks, the effect of increased concentration of ore minerals in small classes of ore is characteristic. Due to the process of segregation of the mass in ore drawing, small fractions accumulate in significant quantities on the lying side of the mine goaf and on the roughness of its surface. Such ore is often simply lost. It is rational to create conditions for reducing the yield of small fractions already at the stage of separating the ore from the array. Therefore, the development of technological methods for managing the quality of mining enterprise products and methods for improving the completeness of extracting mineral reserves is an urgent scientific and technical task. To solve this problem, a number of model and full-scale experiments were conducted to identify the dependence of the nature of destruction on the method and parameters of blasting, followed by statistical evaluation of the results. The principles of determining the parameters of the technology for breaking valuable ores that are prone to overgrinding are established.

Испытания в промышленных условиях центробежной отсадочной машины для гравитационного обогащения руд цветных и благородных металлов

Испытания в промышленных условиях центробежной отсадочной машины для гравитационного обогащения руд цветных и благородных металлов

Geodynamic position of large and super large precious metal and uranium ore districts and nodes in the East Asia

The analysis results of the geophysical, seismic tomography and mineragenic data are presented, revealing the prerequisites for the regular of the location large and unique precious metals and uranium ore nodes of Southeast Russia, East Mongolia and Northern China. Shown that probable causes localization of the world-class ore clusters and districts above a stagnant oceanic slab perimeter are predetermined by concentration of the lower mantle fluid-heat fluxes at the frontal part of the slab and on its flanks, which are represented by sublatitudinal paleotransformal faults.

A Critical Overview of Dithiophosphinate and Dithiophosphate Interactions with Base Metal Sulfides and Precious Metals

Historically, as for most reagents used in flotation, the wide-spread use of dialkyl dithiophosphinates as collectors in practical applications has preceded a detailed scientific understanding of how they work. Dialkyl dithiophosphinates are a technologically and commercially important class of collectors used in the flotation processing of Cu-Au, complex polymetallic, and precious metal ores. Plant usage has demonstrated that dithiophosphinates exhibit higher selectivity and flotation rates for Cu sulfides, galena, and precious metal values in the presence of other gangue sulfides, than the traditionally used collectors such as dialkyl dithiophosphates and xanthates. They also have an attractive health, safety, and environmental (HSE) profile. Although dithiophosphinates received little attention in the past in the flotation research community, recently, there has been significant interest in this chemistry, and numerous studies have been conducted to understand the fundamental interactions of dithiophosphinates with several base metal sulfides and precious metals. A critical overview of fundamental studies, laboratory ore flotation, and plant practice of dithiophosphinates is given in this paper. The findings from these studies are rationalized and explained by drawing on concepts and insights from coordination chemistry. A comparison between the interactions with various minerals and metals of dithiophosphinate and dithiophosphate analogues brings out some of the subtleties that seemingly minor changes in collector chemistry can make. The critical overview and analysis given here is useful in identifying gaps in knowledge regarding this important class of compounds. This in turn can provide a basis for the design of studies to advance our understanding of dithiophosphinate flotation performance.

Imaging high quality conductors at Golden Grove

The success of the DHEM method in detecting the Gossan Valley mineralisation, south of Gossan Hill mine, in 2008/2009 led to the systematic application of the DHEM method across the Golden Grove lease from 2011 to 2014. The method proved successful in identifying several new zones, including the Grassi resource. During these surveys it was noted that the EM method failed to elicit either in-hole or off-hole responses in a number of holes with economic intersections of lead, zinc and precious metal ore. It became clear that not all economic ore zones contained sufficient conductive sulphide to ensure detection using DHEM. This triggered an assessment of available methods to determine if other down-hole technologies could be used to complement the DHEM method. A program of core petrophysic measurements and petro-physical borehole logging led to the realisation that because the host rocks were very resistive there existed sufficient contrast for high frequency EM imaging to be viable. This led to a trial of the Radio Imaging Method at the Xantho resource of the Gossan Hill Mine in December 2016. The results of the trial suggested direct detection of the massive sphalerite ore is possible. Further work is being undertaken to better understand the optimum survey methodology in the Golden Grove Mine environment with a view to providing specific recommendations that if approved will see the use of the method expanded on the mine leases, both at Gossan Hill and Scuddles mines, as well as on the surrounding mine leases

Effective production of sodium isobutyl xanthate using carbon disulfide as a solvent: Reaction kinetics, calorimetry and scale-up

Alkyl xanthates are by far the most widely used collectors in the froth flotation beneficiation of base metal sulfide and precious metal ores. However, the commercial xanthate production process suffers from low yield, low productivity, poor containment and environmental pollution. To address these issues, an effective method was developed for the synthesis of xanthates using carbon disulfide as both a reactant and the solvent. This study involved the optimization of various process parameters, including solvent dosage, temperature, caustic alkali particle size, and agitation speed, to intensify the conversion of sodium isobutyl xanthate (SIBX) and elucidate the reaction kinetics. The results indicated that carbon disulfide leads to a higher yield and better purity than solvents such as dichloromethane, petroleum ether, acetone, and water. Moreover, the addition of solvent allows the synthesis of high-purity xanthates by employing commercial grainy/sheet caustic soda as the raw material without further pulverization. The rate of the xanthation reaction was controlled by the rate of diffusion through the product layer, and the apparent activation energy was calculated to be 15 kJ∙mol−1. In addition, the thermal behavior of xanthate synthesis in a medium was monitored in a 2 L reaction calorimeter (RC1e) under the optimal conditions. Finally, a pilot-plant process was conducted in a 4000 L stainless-steel-jacketed reactor. The results demonstrated that xanthate production using excess carbon disulfide as a self-solvent gave excellent yield (>95%) and purity (>90%), whereas the kneader approach provided SIBX in only a 91% yield and 84% purity. Furthermore, this technology has widespread adaptability for the preparation of C2 to C8 xanthates. Compared with the traditional kneader approach, this new synthesis technology completely eliminates the required pulverization of caustic alkali, intensifies mass and heat transfer via the solvent, raises the productivity and improves the manufacturing environment, offering an effective and promising approach for the clean production of xanthates.

Methods and Equipment for Breaking Down Gold-Containing Concentrates from Lean Ores and Mining Industry Waste

Exhaustion of rich or readily enriched precious metal ores leads to involvement in operation of stubborn ores from which effective extraction of precious metals by traditional methods is impossible. Within stubborn ores, a considerable part of gold is finely associated with sulphide minerals, generally with arsenopyrite and pyrite, and remains inaccessible for leaching even with fi ne comminution. Presence of an active carbonaceous agent occluding cyanide complexes of gold from solutions is another reason for stubbornness of gold-bearing ores. The joint negative effect of both factors on enrichment gives rise to doubly stubborn ores. A reduction in gold extraction indicators during hydrometallurgical processing for ores and concentrates with sorption and active organic carbon is overcome in most cases by using ion-exchange resins and activated carbon, whereas recovery of gold bonded in sulfides requires breakdown of the mineral crystal lattice. For this purpose, oxidizing roasting, and autoclave or bacterial oxidation of sulfides in a pulp are usually applied. The last two methods are now the most widespread. At the same time, roasting gold ores and concentrates is applied at a number of the overseas enterprises. This shows that hightemperature processes remain the main methods for preparing gold-bearing ores and concentrates for leaching. On the basis of results of calculations, research, and design and engineering development, and industrial tests the authors conclude that it is possible to increase extraction of gold and silver in products from the Mai and Badran fields after pyrolysis in a rotary drum furnace. Compared with oxidizing roasting environmental protection issues are resolved. Procedures and production equipment schemes are developed.

Global Se and Te systematics in hydrothermal pyrite from different ore deposits: a review

Pyrite is one of the most important constituents in hydrothermal base and precious metal ores of Carlin-type, epithermal-porphyry and orogenic Au deposits. The trace elements Se and Te are enriched...

Deselenization and detellurization of precious-metal ore concentrates by swelling oxidizing roasting and successive alkaline leaching

A new technique of swelling oxidizing roasting and alkaline leaching was proposed for deselenization and detellurization of precious-metal ore concentrates. Alkali-metal and alkaline-earth-metal chlorides and carbonates were preliminarily selected as swelling agents. The roasting removal rate and alkaline leaching rate of selenium and tellurium were investigated, and NaCl was selected as an appropriate swelling agent. Furthermore, the effects of various factors on the selenium gasification rate and leaching rate of selenium and tellurium were investigated. The results show that the selenium gasification rate reaches 88.41% after swelling oxidizing roasting for 2 h at 510°C using an NaCl dosage coefficient of 100 and a sulfuric acid dosage coefficient of 1.3; the amorphous elemental tellurium is completely transformed into TiO2. The roasted product is subjected to alkaline leaching using a 100 g/L NaOH solution, which results in a selenium leaching rate of 10.51%, a total selenium removal rate of 98.92%, and a tellurium leaching rate of 97.64%. In the alkaline leaching residue, the contents of selenium, tellurium, gold, platinum, and palladium are 0.7825%, 5.492%, 8.333%, 0.2587%, and 1.113%, respectively; the precious metals are enriched approximately sixfold.

Analysis of mineral grades for geometallurgy: Combined element-to-mineral conversion and quantitative X-ray diffraction

Knowledge of the grade of valuable elements and its variation is not sufficient for geometallurgy. Minerals define not only the value of the deposit, but also the method of extraction and concentration. A number of methods for obtaining mineral grades were evaluated with a focus on geometallurgical applicability, precision and trueness. For a geometallurgical program, the number of samples to be analyzed is large, therefore a method for obtaining mineral grades needs to be cost-efficient, relatively fast, and reliable. Automated mineralogy based on scanning electron microscopy is generally regarded as the most reliable method for analyzing mineral grades. However, the method is time demanding and expensive. Quantitative X-ray diffraction has a relatively high detection limit, 0.5%, while the method is not suitable for some base and precious metal ores, it still provides significant details on gangue mineral grades. The application of the element-to-mineral conversion has been limited to the simple mineralogy because the number of elements analyzed limits the number of calculable mineral grades. This study investigates a new method for the estimation of mineral grades applicable for geometallurgy by combining both the element-to-mineral conversion method and quantitative X-ray diffraction with Rietveld refinement. The proposed method not only delivers the required turnover for geometallurgy, but also overcomes the shortcomings if quantitative X-ray diffraction or element-to-mineral is used alone.