Objective: To evaluate the influence of fine and ultrafine particles (also called mud) on the flotation of a sulfide gold ore from the Nova Xavantina Mine, located in the state of Mato Grosso, assessing recovery and gold content in the generated concentrate. Theoretical Framework: Gold ore processing presents specific characteristics that differentiate it from other mineral commodities. Sulfide gold ore processing routes may involve, in addition to comminution, concentration steps that exploit differentiating physical and physicochemical properties, such as the difference in specific gravity and hydrophobicity (natural or induced) between the gold-bearing minerals and the gangue minerals. The physical and surface properties of fine particles impose a series of limitations on flotation performance, especially when they coexist with coarse particles. Method: The methodology comprised the collection of samples at the ERO Brasil Nova Xavantina mineral processing plant, carried out by company employees, followed by preparation, chemical characterization (XRF and Fire Assay), granulometric analysis (wet sieving), mineralogical analysis (XRD), and image analysis (SEM/EDS). The ore sample was classified by hydrocycloning to generate three samples with different granulometric distributions, which were subjected to flotation tests in a bench-scale mechanical cell, in rougher and scavenger stages, varying the percentage of solids and pH. Results and Discussion: The sample tested was composed mainly of quartz and pyrite, which explains its high Si and Fe contents. Granulometric analysis indicated a large presence of fine particles (92.53% passing through the 25 µm mesh). Flotation tests indicate that the slime significantly influences the Au content and recovery, thus affecting the selectivity of flotation. The best results were obtained for hydrocyclone overflow samples with 10% solids. Research Implications: The results obtained contribute to the optimization of gold ore processing, typically sulfide ores, assisting in operational decision-making in plants facing problems related to high fines content in the ore, with direct impacts on recovery and Au content. Originality/Value: This work investigated experimentally the effect of slurries on the flotation of sulfide gold ore from a real industrial circuit, providing technical support for improving mineral processing routes and operational practices.

ABSTRACT The ability to economically oxidise ores using high-shear reactors presents an opportunity to increase gold recovery from refractory sulphide ores without resorting to costly oxidative treatments. This study provides the first integrated laboratory-to-pilot validation of Aachen pre-oxidation applied to the treatment of medium-grade double-refractory gold ores within a carbon-in-leach circuit. The effects of the high-shear reactor on oxygen transfer, leaching kinetics, cyanide consumption, preg-robbing behaviour, and its synergy with fine grinding were quantitatively assessed under industrial conditions. Laboratory-scale tests demonstrated that Aachen pre-oxidation improved gold recovery by 4–6% while reducing cyanide consumption by 8–11%. Following these promising laboratory results, a pilot-scale Aachen reactor was tested on site. Dissolved oxygen increased from 6–8 mg/L to 21–32 mg/L, resulting in accelerated leaching kinetics and lower cyanide consumption. For the KD sample, characterised by high preg-robbing tendencies and gold encapsulation in sulphides, gold recovery was improved by 5% at plant granulometry and by 11% after regrinding. For the KLK sample, where gold is locked in sulphide minerals, the application of Aachen pre-oxidation, with and without grinding, showed only a 1% improvement. Furthermore, the Aachen pre-oxidation mechanism resulted in a significant 10% reduction in NaCN consumption across both samples.

Everything people say and write about themselves isn't true. However, it's there, like grains of precious metal in gold ore. And if we imagine that someday (and perhaps this is happening right now) our biological population will be studied by truly independent researchers, they will rely on the facts of human history, not on our self-assessments.

The economic viability of marginal gold reserves remains a major challenge in the final stages of mining operations, particularly when constrained by underground mining methods. This study investigates a strategic transition from underground to open-pit mining to enhance the economic potential of marginal gold deposits and extend the overall life of mine. Focusing on a gold mine approaching depletion, the research evaluates the technical, economic, and operational implications of converting the mining method to access previously uneconomic ore zones. A comparative analysis was carried out between underground and open-pit scenarios using parameters such as stripping ratio, recovery factor, cut-off grade, and Net Present Value (NPV). A sensitivity analysis was also conducted to assess the influence of gold price, mining cost, and ore grade on project feasibility and risk. The results demonstrate that transitioning to open-pit mining significantly increases recoverable reserves by reclassifying marginal zones as economically viable, leading to improved project NPV and extended life of mine. In addition to economic benefits, the transformation supports operational continuity and improved resource utilization. Nevertheless, geotechnical stability, environmental management, and regulatory compliance remain critical aspects to be addressed in implementing such a transition.

Organic anion transporter 1 (OAT1) is a mechanism for uptake of mercuric-cyanide complexes into proximal tubular cells.

Na 2 CO 3 reduces Fe(OH) 3 formation via soluble complexation, while CMC-Na disperses existing aggregates. Both inhibited secondary encapsulation, raising gold leaching efficiency from 88.31% to 93.95% and 92.47%, respectively.

This study deal with a method for gold recovery from printed circuit boards (PCBs) obtained from WEEE collected in Burkina Faso. After grinding PCB samples and leaching with aqua regia, a solution rich in metal ions were obtained, containing notably 6.04 μg/g of gold, a concentration roughly 200 times higher than that of conventional gold ores. The study focused on the selective adsorption of Au3+ ions using a magnetic Fe-BTC/PpPDA MOF composite. This MOF exhibited a microporous microstructure (iodine index of about 2543.2 mg/g) and a point of zero charge (pHpzc) of 5.6, promoting electrostatic interactions in an acidic environment. Batch tests demonstrated highly efficient and selective gold adsorption, with a recovery rate exceeding 98%. The Fe-BTC/PpPDA material also enables the reduction of Au3+ ions to metallic gold, catalyzed by the amine and hydroxyl groups in the structure. After desorption of gold-loaded composite a magnetic separation allowed a good regeneration of the adsorbent, with a recovery rate of 89% after a second cycle. Infrared spectroscopy analyses confirmed the involvement of N-H and O-H functions in the adsorption and reduction mechanism of gold ions.

This research was conducted in Bungkuk Durian Village due to the presence of reserves of gold ore where there were nearly 23,227,517 tonness in South Kalimantan Provunce, one of which was in Bungkuk Durian Village, Batu Ampar District, Tanah Laut Regency. There are various ways to get the desired gold, one of which is by using a gold rock rolling tool or known as a drum tool. This research is a qualitative descriptive study using a case study approach with 6 research subjects consisiting of 2 drum equipment owners, 2 gold mining land owners and 2 subordinates or labor contractor. The research was carried out through observation, interviews, and documentation through the process of collecting data and analyzing the data with descriptive data analysis. The results of this study indicate that two groups led by the owners of drum tools where in the agreement was made verbally, before the agreement took place the parties already knew where the land was and what tools would later be used in grinding gold rock, is these collaborations the paties use cooperation contracts (musyarakah mudharabah) with different variastions or types. In addition, in the implementation of the cooperation contract there is a mistake in terms of practice where the loss should be borne jointly propotionally as long as the loss is not caused by the capital manager but what happens in the field is that the loss will only be borne by the owner of the equipment, regardless of sincerity. The owners of drum equipment because they have obtained permission from the land owner, so that this collaborative practice is categorized as syirkah fasid, namely syirkah namely one of the conditions is not fulfilled

The article presents the new characteristic data on magmatism at the Vetrensky gold ore field in the Upper Kolyma basin. The authors give the first information on the composition and elements in impurities, and try to estimate the U-Pb age by the extracted zircons. They also demonstrate features that permit to distinguish the studied magmatic bodies as a special complex of presumably Early Cretaceous age, which is close to that of the gold mineralization.

Screening is a critical link in the separation of gold ores. However, issues such as the agglomeration of material masses and screen aperture blinding often lead to low screening precision and poor desliming performance, severely impacting the efficiency of subsequent crushing processes. To address these challenges, this paper proposes a rigid–flexible coupled screening method for viscous and moist gold ores. The time-frequency response characteristics of the screen surface motion were investigated, the influence of processing capacity and moisture content on screening performance was analyzed, and an industrial performance evaluation of the rigid–flexible coupled screen surface was conducted. Laboratory and industrial test results demonstrate that the rigid–flexible coupled screen surface exhibits a periodic, non-regular waveform with a maximum peak vibration intensity of 14.79 g. Screening efficiency is synergistically inhibited by moisture content and processing capacity. When the ore moisture content is below 3% and the processing capacity ranges from 15 to 22.5 t/(h·m2), the screening efficiency can exceed 85%. Compared with conventional screen surfaces, the implementation of the rigid–flexible coupled screen surface achieved a desliming efficiency of 91%, a maximum processing capacity in the crushing stage of 380 tons per hour, a nearly 12% improvement in the screening efficiency of the closed-circuit checking process for crushed products, and an approximately 8% reduction in the circulating load ratio of the crushing circuit. These enhancements collectively ensure the stable operation of both the screening and crushing processes.

The progressive depletion of high-grade ore bodies has shifted attention toward the exploitation of lower-grade deposits as viable sources of value. In recent years, there has been growing emphasis on mining and processing methods that incorporate sustainability by addressing both environmental and socio-economic considerations. To maximize resource recovery, integrated strategies that combine exploration, grade control drilling, mine planning, and processing are essential. Within this framework, particle sorting has emerged as an effective coarse separation method that can upgrade low-grade feed prior to the more energy-demanding milling and subsequent processing stages. Incorporating screening before particle sorting not only assists in identifying the distribution of metals but also determines the most suitable particle size ranges for sorting performance. This study reports on the applicability of sensor-based sorting technologies to low-grade gold and nickel ores from Australia, with a focus on grade deportment by particle size. The results demonstrate that substantial upgrading of low-grade ores is possible, achieving 70%–80% metal recovery within approximately 30%–40% of the original mass through the use of induction and XRT sensors. Overall, the findings indicate that both induction and XRT sorting methods are broadly effective across ore types, offering enhanced upgrading capability and improved processing efficiency.

The area of disturbed lands that have lost their original economic value is the most important indicator of industrial impact, since they are ecologically dangerous and cause significant economic damage. In the structure of disturbed lands, 67 % are violations during the development of mineral deposits. At present, statistical provision with data on disturbed lands is limited by the problem of the lack of statistical reporting by municipalities. The assessment of the nature of disturbed lands at the local level carried out using two methods: automatic software and manual image interpretation, showed that the dynamics of disturbed lands for individual deposits is smoother, more logical and explainable than for the regions of their location, which most likely confirms the low quality of statistics in this area. Analysis of space images showed that the greatest destructive impact on the environment occurs at the time of waste rock storage, as well as in the process of expanding the zone of active raw material extraction. According to the results of the analysis of the selected space images, the highest rate of increment of disturbed lands is characterized by large and old oil fields (an average of 10 % per year) and coal mining with an average annual increment of over 5 % even for a new deposit. Next comes the mining of gold and iron ore. Deposits located in more northern regions increase disturbed lands with greater intensity. In terms of the overall scale of disturbed land increment, only half of the deposits under consideration did not exceed the average Russian increment rate of 6.2 %. Large and old deposits mostly exceed the average annual values. The largest excesses were observed in the Khanty-Mansiysk Autonomous Okrug and Kemerovo Oblast, which is quite significant, since these regions specialize in oil (Khanty-Mansiysk Autonomous Okrug) and coal (Kemerovo Region) production.

Abstract Processing of high-grade gold ores is uncommon, so extraction is currently carried out using conventional methods, with cyanide as the agent due to its high selectivity and stability. Despite its popularity, this process presents environmental risks, which have led to the implementation of alternative lixiviants such as thiourea, which allows gold extraction in less time than cyanide. Gold leaching with thiourea is an interesting alternative; however, it can degrade irreversibly if the system’s potential is not controlled. This study examines the effect of oxalate as an additive to control the oxidation potential and improve gold recovery by regulating Fe and Cu ions that consume thiourea during acidic leaching at room temperature. While oxalate enhanced gold extraction, it interfered with the determination of thiourea concentration by iodate titration. The use of Zn 2+ reduces this interference by masking oxalate as a ZnC 2 O 4 in an acidic medium. Graphical abstract

The morphology, chemical composition, and ore and heavy-mineral associations of gold from placers in the Ursky ore cluster and the less-studied Kasminsko–Chesnokovsky prospective area in northeastern Salair indicate numerous and diverse primary sources, as well as the presence of gold in intermediate reservoirs. Gold with a fineness of 970–1000‰ is predominantly hypergenically altered. The placers have formed primarily from quartz, quartzcarbonate, and quartz–(carbonate)–sulfide veins and stockworks of the main gold mineralization stage, including mineralization superimposed on barite-polymetallic ores with fine and finely dispersed gold in the Ursky ore cluster, and on basic dikes. Another source of gold is metasomatite (carbonate–mica, quartzite, and quartz–albite–epidote rocks with rutile), which either accompanies gold ore bodies or is indirectly associated with them. Differences in the typomorphic properties of the placer gold are due to varying contributions from these primary sources. In the placers of the upper reaches of the Ur and Zvonchikha rivers, the source is likely gold mineralization predominantly superimposed on basic dikes. This gold exhibits high fineness (>910‰) and contains copper impurities (up to 1–6 wt.%), as well as an inclusion of Pd telluride in one instance. Quartzite is another potential source of Au (as observed at the Kopna deposit). In the lower part of the Ur River placer, the fineness of Au and the proportion of copper-bearing gold decrease, while gold with mercury impurities is more frequently encountered. The gold mineralization here is probably superimposed on polymetallic mineralization or localized within rocks of the Pecherkinsky complex. The presence of gold with fineness below 820‰ (as at the Iyunsky deposit) indicates polymetallic gold-bearing mineralization. Sources for the gold in the Chesnokovka and Kurnichikha river placers, besides mineralization associated with basic dikes, include mineralization characterized by gold with a fineness of 820–910‰ (including rather small and fine gold), which typically contains mercury impurities. These could be quartz veins and metasomatites developed in terrigenous rocks of the Suenginsky Formation, known within the area. Inclusions in gold from placers of the Kasminsko–Ursky ore district are represented by minerals from sulfide ores, metasomatites, and weathering crusts. Unlike gold from the Ursky ore cluster, gold from the Kasminsko–Chesnokovsky area contains no inclusions of copper minerals (chalcopyrite, bornite, covellite, and tennantite), which are common in pyrite-polymetallic ores. The typomorphic properties of gold from the Aprelsky deposit reflect multiple sources, including quartz veins, metasomatites in rocks of the Pecherkinsky Formation, and possibly mineralization superimposed on polymetallic ores. The sources of gold for the Khristinovskaya Yama placer are likely diverse and similar to those for the Ur and Zvonchikha river placers. An isoferroplatinum grain from the Khristinovskaya Yama placer can be classified as the Vilyui type.

Abstract The State of Sinaloa, in Mexico, has significant gold deposits, which are exploited by artisanal miners using mercury. This process is dangerous, inefficient, and restricted, limiting gold recovery (30%) and excluding the extraction of silver and other metals present in the ore. This study presents an alternative method for recovering gold and silver. The ore in this region exhibits refractory characteristics that hinder its metallurgical processing, such as the presence of montmorillonite, a clay with high adsorption capacity. Gold recovery with cyanide reaches 76% and presents high consumption of leaching reagents (78% for cyanide). However, the use of thiourea in the presence of peroxide and oxalate improves the gold recovery to 98% and increases the process efficiency. However, silver recovery remains low owing to the refractory nature of the ore. Addition of oxalate reduces the consumption of leaching agents, and the peroxide acts as an oxidizing agent for gold extraction. Graphical Abstract

This study examines two hypotheses: (i) Geogenic metal(loid)s in the Geita region contribute to high cancer rates. (ii) Poor waste management in artisanal and small-scale gold mining (ASGM) activities increases the mobility of carcinogenic metal(loid)s, thereby increasing health risks. Using pollution and ecological risk indices, this study evaluated the contamination of toxic metal(loid)s and assessed their associated carcinogenic risks. The findings reveal that As, Cr, and Ni pose significant threats, with Cr exceeding the unacceptable carcinogenic risk level (1 × 10-4) for both adults and children. The mean concentrations of As and Ni in both topsoil and subsoil exceed Tanzania's agricultural soil standards. Moreover, pollution indices, including the enrichment factor, geo-accumulation index, and contamination factor, confirm the high pollution levels of these metal(loid)s. The results further reveal that Cr and Ni are geogenic, originating from the weathering of mafic rocks within the Geita Greenstone Belt, while As is predominantly associated with gold ores. One of the five analyzed gold ores had a pH of 3.01 and As concentration of 99.3mg/kg, while some tailings exhibited a pH of 9.3 and As concentration of 11.2mg/kg. Under neutral conditions, As concentrations ranged from 0.05mg/kg to 2.39mg/kg, indicating a significant variation. This suggests that some gold ores in Geita are acid-forming, while certain tailings are alkaline. Consequently, the mobility of toxic metal(loid)s is enhanced by both acid and alkaline drainage. These findings support both hypotheses. Assessing acid mine drainage in ASGM sites should be prioritized globally to reduce associated health risks.

The hydrocyclone is currently the most commonly used classification device in gold ore processing. However, its efficiency is limited by both its operating principles and structural design, making further improvement in classification performance difficult. In recent years, high-frequency vibrating screens—capable of precisely classifying particles based on their geometric size—have played an increasingly important role in efficient classification. Despite these advantages, there is ongoing debate about their application in classifying gold ores, which are often compositionally complex. To address this issue, this study established a pilot-scale experiment platform to assess the classification performance of high-frequency vibrating screens with gold ore. The results were then compared to those obtained using hydrocyclones. In addition, flotation tests were conducted to examine the relationship between the particle size distribution produced by high-frequency screens and flotation performance. This approach provides a comprehensive evaluation of the potential advantages of high-frequency vibrating screens in processing complex gold ores.

Abstract The Witwatersrand Basin, accounting for one-third of all gold ever mined, hosts both free milling and refractory ores, with the Vaal and Crystalkop reefs at Kopanang Gold Mine serving as examples of the latter. Traditionally, gold ores from the basin are classified as free milling, with cyanidation providing high recovery rates. Achieving higher recovery rates of gold ore is crucial for maximising resource utilisation, reducing waste, and enhancing the profitability and sustainability of gold mining in South Africa amidst declining ore grades. Refractory gold in reefs can be trapped within sulphides or silicates, necessitating additional processing steps. This study investigates the mineralogy of these reefs, emphasising their refractory nature and the challenges they pose to gold recovery. Detailed mineralogical and geochemical analyses were conducted using optical petrography under reflected light, X-ray diffraction (XRD), mineral liberation analysis (MLA), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), and X-ray fluorescence (XRF). The Vaal and Crystalkop reefs predominantly host native gold associated with pyrite and pyrrhotite, with the Vaal Reef exhibiting a notably higher association with sulphides compared to the Crystalkop Reef. Both reefs also contain a relatively high proportion of liberated gold. Leaching tests revealed that, although the final 24-hour gold recoveries were similar at 82.1% for the Vaal Reef and 82.8% for the Crystalkop Reef, the Crystalkop Reef demonstrated a more gradual and stable recovery curve over time. This suggests that gold in the Crystalkop Reef is released more predictably during cyanidation, indicating more favourable leaching kinetics and potentially less variability due to mineralogical locking. The findings demonstrate that most of the inaccessible gold within the Vaal Reef ore is associated with sulphide minerals, while the Crystalkop Reef’s silicate-locked gold presents additional challenges for recovery. Despite the higher gold grade in the profile of the Crystalkop Reef, its moderate recovery rate is attributed to the difficulty of leaching silicate-bound gold. The study confirms the refractory nature of these ores and the need for tailored processing methods to improve recovery to >90%. When comparing the gold recovery rates and grades from the current study to those of a previous study on ores from both reefs, significant regional variability is evident in both parameters. This variability highlights the limitations of generalisations and underscores the need for further research on reefs from the basin. These results highlight the importance of understanding ore-specific mineralogy to optimise metallurgical processes, offering insights into improving recovery rates for refractory gold ores in the Klerksdorp goldfield and the Witwatersrand Basin.

Refractory gold and silver ores present significant challenges because precious metals are encapsulated within sulfide matrices, severely limiting extraction by conventional cyanidation. In this study, a pyritic concentrate from the Bacis Mine (Durango, Mexico) was characterized and subjected to two oxidative pretreatments—roasting and alkaline pressure oxidation—before cyanidation. X-ray diffraction confirmed pyrite to be the dominant phase, with quartz and minor carbonates contributing to the material’s refractory character. Roasting at 550 °C achieved gold and silver extraction of 80% and 70%, respectively, which improved to 89% Au and 74% Ag with the addition of hydrogen peroxide. In contrast, alkaline pressure oxidation at 150 °C and 1 MPa O2 yielded the highest extraction of 92% for Au and 76% for Ag at 1 h. Thermodynamic analysis using the Fe–S Pourbaix diagram at 80 °C supported these experimental results, showing the destabilization of FeS2 under oxidizing and moderately alkaline conditions. Overall, this study demonstrates that alkaline pressure oxidation is a technically efficient and environmentally favorable pretreatment for refractory gold ores.

Relevance. The metallogeny of the Yenisei Ridge has established a high degree of age correlation between the stages of its lithospheric evolution, expressed in granitoid magmatism, and all the milestones of the gold-ore process. At the same time, modern scientific and industrial literature contains significantly divergent taxonomic categories for describing granitoid magmatism in the Yenisei Ridge and, in particular, within the Verkhne-Yenashiminsky Ore Cluster. Such discrepancies create significant difficulties and generate uncertainty in classification, dating, and genetic attribution of individual complexes to specific geodynamic events. As a result, it becomes considerably problematic to trace the connection between the metallogenic development of specific areas and ore clusters with the granitoid magmatism manifested in their vicinity. In this regard, an urgent task is the analysis of existing classification schemes with subsequent certification of granitoid massifs based on the following factual foundation: available data on petrographic composition and geochronology, and the characteristics of their manifestation in radiogeochemical fields, reported here for the first time. Aim. Radiogeochemical certification of the granitoid massifs of the Verkhne-Yenashiminsky Ore Cluster based on airborne gamma-ray spectrometric survey data. Methods. Analysis of complex geological and geophysical materials using radiogeochemical indicators. Results and conclusions. The paper introduces the detailed description of the currently existing classifications of granitoid magmatism in the Trans-Angara region and their correlation with each other. Based on the analysis of airborne gamma-ray spectrometric data, a contrasting radiogeochemical difference was established between the Verkhne-Yenashiminsky Ore Cluster granitoids formed in different geodynamic settings: rift-related complexes (Glushikhinsky, Gurakhinsky) and late-collisional Kalamin-type granitoids. An intermediate position between them is occupied by the granitoids of the Ayakhtinsky complex, which have the most controversial interpretation of their nature. The authors identified high post-magmatic mobility of radioactive elements (U, Th, K), especially for the rift-related complexes. It was established that airborne gamma-ray spectrometry is an effective method for differentiating granitoid complexes. The wide radiogeochemical diversity of the Verkhne-Yenashiminsky Ore Cluster granitoids reflects the complex, multi-stage geodynamic evolution of the region and is an indicator of its high metallogenic potential.