Gangue Minerals Research Articles

Combined effect of magmatic fluid–seawater mixing and host rock alteration on the formation of gold-enriched massive sulfides in the Forecast vent field, southern Mariana Trough

Massive sulfides and sulfide-bearing breccia were collected from the Forecast vent field in the southern Mariana Trough. These samples exhibit varying degrees of hydrothermal alteration and/or mineralization, with the former type having significant enrichments in Au (up to 101 ppm). In this study, detailed analyses of mineralogy, geochemistry, S isotope, and fluid inclusion were conducted to understand the unusual Au-rich mineralization. Mineralogical investigations and geochemical analyses (LA–ICP–MS and EPMA) of dominant sulfide minerals indicate that electrums, the main phase of Au mineralization, are characterized by two different generations based on mineralogical relationships and fineness. Early-stage high fineness electrums (930–981 ‰) are associated with sphalerite under relatively high-temperature fluid conditions, whereas galena is main host mineral related to late-stage low fineness electrums (773–868 ‰). Sphalerite geothermometry (231–264 °C), the occurrence of colloform textured sulfides, and microthermometric characteristics of fluid inclusions (Th = 220–304 °C; Salinity = 1.4–6.6 wt% NaCl equivalent; a general trend of decreasing salinity with decreasing Th) indicate that significant decreases in H2S activity, attributed to seawater dilution and rapid precipitation of sulfide minerals, facilitated the efficient destabilization and deposition of Au transported as sulfide complexes from hydrothermal fluids. In particular, the lower 34S values (+0.2 ‰ to + 1.3 ‰) of sulfides compared to those of arc/back-arc lavas (δ34S = +5‰ to + 11 ‰), along with the prevalence of CO2 in the vapor phase of fluid inclusions, reflect that the significant contribution of magmatic volatile influx supplied most of the sulfur and metals (including Au) to the Forecast hydrothermal fluids. Additionally, the abundance of montmorillonite and varying proportions of sulfide and gangue minerals observed in hydrothermal samples suggest that the chemical buffering of fluids by associated substrates and/or sediments could be another significant factor in promoting Au-rich mineralization. Therefore we conclude that the combination of magmatic fluid–seawater mixing and host rock alteration plays an important role in the formation of Au-enriched massive sulfides in the Forecast vent field.

Mineralogical Insights into PGM Recovery from Middle Group (1–4) Chromite Tailings

Variations in the recovery of platinum group metals (PGMs) are often attributed to mineralogical and other natural ore-type variations. To increase the recovery of PGMs by the flotation process, a comprehensive understanding of gangue and valuable minerals is essential for optimising the extraction and processing of metals. Recoveries may be improved if the questions of how, where, and why losses occur can be answered with a certain degree of confidence. A requirement is the availability of statistically reliable mineralogical data. The PGMs of MG-1–4 chromite tailings dumps of the western limb of the Bushveld complex (BC) were studied in detail to unravel the PGMs and the nature of the platinum group minerals in the sample. Characterisation of the chromite tailings via deportment analysis revealed that the sample contained a significant amount of 3E PGM + Au (Pt, Pd, Ru, and Au) and was concentrated in the -25 µm fraction. The results of automated mineralogical analysis showed that the sample was composed of the PGE-sulphides group, comprising 63.6 vol%, PGE-sulfarsenides 10.4 vol%, PGE-arsenides 1.3 vol%, PGE-bismuth tellurides 3.3 vol%, PGMs-alloy 4.1 vol%, and Laurite comprising 17.3 vol% of the total PGE population. The sample was composed of 66.5 vol% of liberated PGMs, 0.2 vol% attached to liberated BMS, 27.3 vol% of PGMs attached to or locked within silicate or oxide gangue composite particles, 0.2 vol% of PGMs associated with BMS attached to silicate or oxide gangue particles, and a low proportion (5.8 vol%) of PGMs reported being locked within gangue or oxide particles. The majority of PGM grains observed were reported in the fast-floating category (64.4 vol%), 27.6 vol% in the slow-floating 1 category, 2.2 vol% in the slow-floating 2 category, and 5.8 vol% to the non-floating category. The results of the study revealed that the PGMs of MG 1–4 chromite tailings were liberated; however, the low liberation index (<0.2) suggested that a significant portion of PGMs remained trapped within gangue, hindering their recovery. This highlights the need for effective comminution (crushing and grinding) to achieve better liberation. The sample contained fine particles that were more prone to being lost in the tailings and to lowering recovery due to the slimes coating valuable minerals. The recovery of the PGMs from this complex’s polymetallic bodies of low-grade and complex mineralogy will be insufficient with traditional methods and thus innovation is needed. Innovation like advanced comminution, novel flotation equipment or reagents, selective leaching and bioprocessing can overcome these challenges.

Fluid flow in the Katanga Supergroup: From Lufilian brittle tectonic stages to the post-Lufilian period (Democratic Republic of Congo)

The metasedimentary rock succession of the Neoproterozoic-Cambrian Katanga Supergroup in the Central Africa Copperbelt shows evidence of several complex tectonic events. The deformation of this supergroup started from the tectonic inversion at about 570 Ma and lasted up to today, but reached paroxysm at ∼550 Ma. This long period was characterized by folding and faulting throughout multiple compressive and extensional events, which controlled the regional fluid flow on the one hand, and played an important role during formation of the stratiform to stratabound Cu-Co (Ni, U) deposits and the polymetallic Cu-Zn-Pb (Ag, Ge, Mo, Cd) vein type deposits on the other hand. Based on the structural analysis and paleostress reconstruction, coupled with fluid inclusion characterization from mineralized structures in rocks from the Nguba, Kundelungu and Biano Groups, this study demonstrates that the composition of hydrothermal fluids changed during brittle tectonic deformation during the Lufilian orogeny and subsequent uplift and post-Lufilian faulting.During early brittle tectonic deformation along strike slip faults with sinistral and dextral movement related to a NE-SW transpression, the Cu-mineralizing fluid was hypersaline (27.9–31.1 eq. wt% NaCl) with moderate temperatures (Th = 128–216 °C). The subsequent Cu or Cu (Zn, Pb) mineralization formed within an E-W extensional stress regime, related to the late Lufilian orogenic collapse. The fluid inclusions present in the gangue minerals associated with this latter mineralization show a large range in Th (50–264 °C) and salinity (26.7–36.0 eq. wt% NaCl). The decrease in temperature is interpreted to be due to migration of the fluids at shallower depth in the subsurface after uplift and erosion of the orogen. The increased salinity of the fluid is related to the dissolution of evaporites, mainly NaCl. A second H2O-NaCl-CaCl2 fluid with a homogenization temperature below 55 °C has also been found associated with this brittle stage and mineralization phase, but only in rocks belonging to the Kundelungu Group. A third mineralization phase, also characterized by Cu or Cu (Zn, Pb), formed during the post-Lufilian period within a NW-SE transpressional inversion regime. The fluid inclusion in the gangue minerals of this mineralization phase have a smaller range in homogenization temperature (Th = 37–172 °C) and the largest range in salinity (0.71–30 eq. wt% NaCl), compared to the earlier fluid inclusions generations. This large range in salinity may be explained by the mixing of a high salinity fluid, already present during the earlier tectonic stages in the sedimentary basin, with meteoric water. During the more recent rift-related extension, a fluid with again a large and higher range in homogenization temperatures (Th = 47–257 °C) and with a typical low salinity (<10 eq. wt% NaCl) has been recognized in minerals filling NNE-SSW to NE-SW oriented faults and fractures. The upward migration of a relatively low-salinity fluid from deeper parts in the subsurface explains the variation in the temperatures observed with this tectonic event.

A novel surfactant N-hydroxy-9,10-epoxy group-octadecanamide: Part II. Its synthesis and application in flotation separation of spodumene and albite

A novel hydroxamic acid, N-hydroxy-9,10-epoxy group-octadecanamide (N-OH-9,10-O-ODA), was synthesised by modifying the structure of oleic acid. The carboxyl group of oleic acid was converted into an N-hydroxy amide group, and an epoxy group was introduced into its structure. N-OH-9,10-O-ODA was used as a novel collector in the flotation separation of spodumene from one of its associated gangue minerals, specifically albite. N-OH-9,10-O-ODA exhibits remarkable selectivity, with a stronger affinity for collecting spodumene particles compared to albite particles. Zeta potential measurements and X-ray photoelectron spectroscopic analysis reveal that the adsorption quantity of N-OH-9,10-O-ODA on spodumene surface is comparable to that on albite surface. First-principles calculations demonstrate the diverse adsorption configurations of N-OH-9,10-O-ODA on surfaces of spodumene and albite, leading to its distinct collecting abilities for spodumene and albite particles.

Flotation separation mechanism of rutile and chlorite using CMC as depressant

In ores containing rutile, chlorite is the most common silicate gangue mineral. However, the flotation separation of rutile and chlorite has yet to be thoroughly studied. In this study, carboxymethyl cellulose (CMC) was used to depress chlorite when sodium oleate (NaOL) was used as the collector of rutile. The selective depression and its mechanism were investigated through micro-flotation experiments, zeta potential analyses, Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and particle video microscopy (PVM). Single mineral flotation showed selective depression of chlorite by CMC appeared at pH 7, NaOL concentration of 20 mg/L, and CMC concentration of 10 mg/L, when 88.39 % recovery difference between rutile and chlorite was obtained. The most effective concentration of CMC for the artificially mixed ore test was 15 mg/L, resulting in rutile recoveries and grades of 87.78 % and 75.28 % respectively. The results of Zeta, FTIR, and XPS tests indicate that the adsorption of CMC on chlorite surface is attributed to chemical and hydrogen bonding interactions, wherein the OH– and COOH– groups in CMC interact with hydroxyl groups of Fe2+ and Al3+ complexes, thereby diminishing chlorite floatability and impeding subsequent NaOL adsorption. PVM image further elucidates that hydration-repulsion interaction potentials between CMC-absorbed chlorite particles and gas bubbles deter particle adhesion. This markedly reduces chlorite ore carryover on bubble surfaces while minimally impacting rutile. This study can provide a theoretical basis for separating rutile and other vein minerals under the NaOL system.

New Insights into the Depressive Mechanism of Sodium Silicate on Bastnaesite, Parisite, and Fluorite: Experimental and DFT Study

The surface properties of bastnaesite and parisite are similar to their associated gangue mineral, fluorite, which makes the flotation separation of these two rare earth minerals from fluorite one of the industry’s most significant challenges. This study systematically investigates the inhibitory effects and mechanisms of sodium silicate (SS) on bastnaesite, parisite, and fluorite in an octyl hydroxamic acid (OHA) collector system through flotation experiments, various modern analytical methods, and DFT simulations. The flotation test results indicate that the inhibition effects of SS on the three minerals are in the order: fluorite &gt; parisite &gt; bastnaesite. Detection and analysis results indicate that SS forms hydrophilic complexes with Ca atoms on the surfaces of fluorite and parisite, enhancing surface hydrophilicity and inhibiting OHA adsorption, but its impact on bastnaesite is relatively minor. DFT simulation results show that OHA forms covalent bonds with metal ions on mineral surfaces, favoring five-membered hydroxamic-(O-O)-Ce/Ca complexes, and reacts more strongly with Ce atoms than Ca atoms. SS primarily forms covalent bonds with metal atoms on mineral surfaces via the SiO(OH)3− component, and OHA and SS compete for adsorption on the mineral surfaces. OHA has a stronger affinity for bastnaesite, whereas SS shows the highest affinity for fluorite, followed by parisite, and the weakest affinity for bastnaesite.

Minimizing entrainment recovery of ultrafine silicate minerals in pentlandite flotation using carboxymethyl cellulose

The presence of silicate minerals is a common occurrence in various ore types, including nickel sulphide ores. These silicate minerals dilute the grade of flotation concentrates through recovery by entrainment which leads to poor flotation performance and subsequently loss of values. Flotation by entrainment is further enhanced as the particle size of the feed becomes finer. The present work investigates the entrainment characteristics of silicate minerals in the flotation of pentlandite. Within the context of the selective flotation of pentlandite from silicate gangue minerals, the influence of different particle sizes on entrainment flotation was also carried out. PAX was used as a collector for recovering pentlandite, whereas carboxymethyl cellulose (CMC) was employed as a dispersant for the silicate gangue mineral. Microflotation experiment was conducted on a pentlandite-quartz mixture of different particle sizes including − 106 + 75 µm, − 75 + 38 µm, − 38 + 20 µm, and − 20 µm. Electroacoustic zeta potential measurements, Fourier-Transform Infrared (FTIR) Spectroscopy, and Ultraviolet–Visible (UV–Vis) spectroscopy were used to characterise the interaction between pentlandite and quartz and in the presence of PAX and CMC. It was observed during the mixed minerals flotation tests that flotation by entrainment increased with a decrease in feed particle size irrespective of the dosage of CMC. Notwithstanding, the addition of CMC led to notable reduction in entrained silica flotation from 58 % to 38 % in the −20 µm size fraction attributed to improved particle drainage from the froth layer in the presence of CMC. Furthermore, UV–Vis spectroscopy and FTIR results gave further evidence that PAX adsorbed onto pentlandite and quartz minerals surfaces in the presence of CMC, which is consistent with the flotation response observed. Overall, this study confirms entrainment of gangue species is dominant within fine or ultra-fine mineral particles and proposes the use of CMC as a dispersant to limit gangue flotation by entrainment.

Reinforced co-leaching of REEs/Nb/Ti from low-grade concentrate mixture: Decomposition behavior and co-leaching mechanism

Baerzhe ore deposit is rich in such critical elements as rare earth elements (REEs), niobium (Nb), and titanium (Ti). However, in this ore, the REEs/Nb/Ti-bearing minerals are interlocked closely and thus not easily liberated and separated from each other by mineral processing methods. In order to achieve high recoveries of these critical elements, a concentrate mixture of REEs/Nb/Ti minerals can be obtained through gravity/magnetic separation and flotation to discard most of the gangue minerals. And then the Fe2(SO4)3-H2SO4 roasting and H2O leaching of REEs/Nb/Ti from the concentrate mixture by hydrometallurgical method was investigated in this work. The results showed that Nb/Ti-bearing minerals convert to Nb2O4SO4/TiOSO4 in the H2SO4 roasting process and then readily hydrolyze to Nb(OH)5/Ti(OH)4 in the H2O leaching process. When Fe2(SO4)3 is introduced into the H2SO4 roasting process, the solubility and leaching efficiency of Nb/Ti increases significantly by the generation of soluble Fe-Nb/Fe-Ti sulfates and coordination-enhanced leaching of sufficient SO42−. REEs-bearing minerals are still converted to RE2(SO4)3 in the Fe2(SO4)3-H2SO4 roasting, achieving co-leaching of REEs/Nb/Ti during H2O leaching. Under optimal conditions, with a roasting temperature of 300 °C, a mass ratio of H2SO4 to concentrate mixture of 1.0 g/g, a roasting time of 3 h, a mass ratio of Fe2(SO4)3 to concentrate mixture of 0.1 g/g, a leaching temperature of 40 °C, and a leaching time of 3 h, the co-leaching efficiencies of REEs, Nb, and Ti reached 97.76 %, 87.97 %, and 90.82 %, respectively. This new method improves the recovery of REEs/Nb/Ti with good selectivity and relatively low cost, providing a new idea for the efficient exploitation and utilization of low-grade polymetallic ore.

Investigation into the impact of Mn2+ and its interaction with calcite in the flotation of rhodochrosite

The unavoidable Mn2+ ions in pulp were considered in the flotation of rhodochrosite, and its effect and relative interaction mechanism on the floatability of calcite served as a typical gangue mineral were investigated through microflotation tests, zeta potential measurements, SEM-EDS detection, solution chemistry calculation, adsorption experiments, FTIR and XPS analyses. There exhibited a good separation performance of rhodochrosite against calcite with OHA collector, but in the presence of Mn2+ ions, the floatability of calcite was closed to rhodochrosite within a pH of 8.0–10.0, which resulted in the separation difficulty between them. As evidenced, the surface of calcite could be modified by Mn2+ ions, its isoelectric point shifted positively from 8.91 to 10.06, and Mn2+ species detected on calcite surfaces were in close proximity to rhodochrosite. It indicated that MnCO3 precipitates were generated on the surface of calcite. After modified by Mn2+, the calcite surface became more active and obviously increased the adsorption amount of OHA. It was verified from zeta potential and XPS analyses that Mn species on the surface of calcite were active sites for OHA adsorption, likely the hydroxamate group of OHA collector chelated with Mn species to form hydrophobic compounds. As a result, Mn2+ ions in pulp would reduce the flotation selectivity of rhodochrosite from calcite, thus it is necessary to eliminate the disadvantage of Mn2+ for strengthening flotation.

Adsorption behavior and selective regulation of tartaric acid at solid-liquid interface: For ilmenite flotation separation

Ilmenite and its main gangue minerals (titanaugite and forsterite) are challenging to separate due to their similar surface chemical properties. The flotation process is an effective method, and the use of surface modifiers is essential. There is an urgent need to develop more effective and environmentally friendly agents to address the shortcomings of existing surface modifiers and the lack of understanding of the inhibition mechanism. In this work, sodium oleate was used as a collector to investigate the inhibitory effect of tartaric acid (TA) on gangue minerals in ilmenite flotation. This was done through micro-flotation experiments, Zeta potential measurements, x-ray photoelectron spectroscopy (XPS) analysis, solution chemical simulations, molecular dynamics (MD) simulations, and density functional theory (DFT). The results demonstrated a significant decrease in the recovery rates of titanaugite and forsterite after the addition of 1 × 10^4 mol/L TA at pH = 8. TA chemically adsorbs onto the Ca and Mg sites on the surfaces of titanaugite and forsterite through carboxylic acid groups. This impedes the adsorption of anionic collectors due to electrostatic repulsion and steric hindrance, effectively inhibiting gangue minerals and achieving separation from ilmenite.

Valorization of lithium containing slags from pyrometallurgical recycling route of spent lithium-ion batteries: The enrichment of γ-LiAlO2 phase from thermodynamic controlled and modified slags

Pyro-metallurgical processing technology is widely used in the spent lithium-ion batteries recycling to recover valuable metals such as cobalt, nickel and copper, while lithium primarily remains in the slag. The effective valorization of slag, especially lithium recovery, constitutes a significant issue in contemporary pyrometallurgical processes due to the paucity of studies. This paper proposes a novel perspective by defining slag as an aggregate of engineered artificial minerals. Thus, not only the parameters of the beneficiation process can be studied to optimize the separation efficiency during treatment, but also the slag can be re-designed to optimize the carrier minerals of target elements and gangue mineral composition in the initial step with thermodynamic tools. In this paper, the engineering of artificial minerals (EnAM) method was applied to the slag design of the Li2O-CaO-Al2O3-SiO2-MnO system, and an initial attempt was made to apply EnAM method to the flotation study. A flotation study on enrichment effect of the target phase γ-LiAlO2 from thermodynamic controlled slags is conducted.

Mineral chemistry of the Geyer SW tin skarn deposit: understanding variable fluid/rock ratios and metal fluxes

AbstractThe Geyer tin skarn in the Erzgebirge, Germany, comprises an early skarnoid stage (stage I, ~ 320 Ma) and a younger metasomatic stage (stage II, ~ 305 Ma), but yet, the source and distribution of Sn and the physicochemical conditions of skarn alteration were not constrained. Our results illustrate that contact metamorphic skarnoids of stage I contain only little Sn. REE patterns and elevated concentrations of HFSE indicate that garnet, titanite and vesuvianite of stage I formed under rock-buffered conditions (low fluid/rock ratios). Prograde assemblages of stage II, in contrast, contain two generations of stanniferous garnet, titanite-malayaite and vesuvianite. Oscillation between rock-buffered and fluid-buffered conditions are marked by variable concentrations of HFSE, W, In, and Sn in metasomatic garnet. Trace and REE element signatures of minerals formed under high fluid/rock ratios appear to mimic the signature of the magmatic-hydrothermal fluid which gave rise to metasomatic skarn alteration. Concomitantly with lower fluid-rock ratio, tin was remobilized from Sn-rich silicates and re-precipitated as malayaite. Ingress of meteoric water and decreasing temperatures towards the end of stage II led to the formation of cassiterite, low-Sn amphibole, chlorite, and sulfide minerals. Minor and trace element compositions of cassiterite do not show much variation, even if host rock and gangue minerals vary significantly, suggesting a predominance of a magmatic-hydrothermal fluid and high fluid/rock ratios. The mineral chemistry of major skarn-forming minerals, hence, records the change in the fluid/rock ratio, and the arrival, distribution, and remobilization of tin by magmatic fluids in polyphase tin skarn systems.

Water–Rock reactions in the acid leaching of Uranium: Hydrochemical characteristics and reaction mechanisms

Acid in–situ leaching (AISL) mining is used to recover uranium from sandstone using sulphuric acid. However, the evolution of groundwater hydrochemistry, the water–rock reaction mechanisms, and their relationship remain elusive. To effectively address these issues, ore samples were obtained from a sandstone uranium deposit in Inner Mongolia in this work. Soaking tests at different sulphuric acid concentrations were performed to quantify the mining aquifer’s water–rock reaction processes (sulphuric acid and minerals) according to the hydrogeochemical composition analysis and inverse modelling. From our results, it was demonstrated that the water–rock interactions between the sulphuric acid and gangue minerals primarily affect the leachate’s chemical composition. The introduction of sulphuric acid efficiently facilitates the gangue mineral dissolution and the groundwater total dissolved solids (TDS) increases and enhances the formation of uranyl sulphate (predominantly UO2SO4 and UO2(SO4)22– and UO22+, thus stimulating uranium mobility. Mineral precipitation (mirabilite) is primarily responsible for the elevated TDS in the leachate. The leachate’s oxygenation mainly depends on the sulphuric acid concentration and Fe3+ concentration produced by hematite dissolution. During the AISL process, the dissolution of dolomite, calcite, FeO, hematite, pyrite, K–feldspar, anorthite, chlorite, and alunite take place in the groundwater system. In parallel, the precipitation of kaolinite, illite, Ca–Montmorillonite and mirabilite, accompanied by Na–K exchange and Na–Mg exchange occur. The dissolution of dolomite, calcite and illite and Na–Mg exchange mostly affects the hydrochemical evolution, as well as the leachate of Fe mainly from dissolved chlorite. The predominant precipitates were kaolinite and mirabilite, with their precipitation ability increasing with acidity. These findings highlight the importance of clarifying the relationship between the hydrochemical characteristics and the water–rock reaction mechanisms in AISL geochemical processes to elucidate the hydrochemical evolution and mineral corrosion characteristics of ore–bearing aquifers. Finally, K–feldspar, alunite, chlorite, anorthite and dolomite were obtained as the major acid–consuming minerals. Our work provides a novel evaluation method for the prediction of acid consumption that can be used for actual production.

Flotation collector lauryldiethanolamine: Adsorption configuration impact on collecting efficiency

In the reverse flotation separation of apatite and its associated siliceous gangue minerals, the common collector dodecylamine (DDA) exhibits a poor selectivity. To remedy this issue, this study implements a change to DDA molecular structure by integrating two 2-hydroxyethyl groups at the N atom position, ultimately producing a freshly developed collector, lauryldiethanolamine (LDEA). Micro-flotation experiments reveal that, relative to DDA, LDEA showcases an enhanced selectivity in separating apatite from its associated siliceous gangue minerals quartz and K-feldspar through reverse flotation. This difference primarily stems from the weaker collecting ability of LDEA for apatite particles relative to DDA. Nevertheless, zeta potential measurements and X-ray photoelectron spectroscopic tests consistently show that, under identical dosage conditions, LDEA and DDA exhibit similar adsorption quantities on apatite surfaces. This observation implies that factors beyond its adsorption quantities inevitably influence the collecting ability of LDEA for apatite particles. First-principles calculations unveil markedly different adsorption configurations of LDEA and DDA on apatite surfaces, suggesting that the difference in the adsorption configurations of LDEA and DDA accounts for the significant variance in their collecting abilities for apatite particles.

Decoupling the effect of hydraulic oil contamination on the flotation performance of UG2 PGE ore and its interaction with alteration minerals

Oil contamination inadvertently arising from underground mechanised South African platinum mines is known to compromise the subsequent flotation performance. Anecdotal observations suggest that this is further exacerbated in the presence of phyllosilicate alteration minerals. Two ores of varying degrees of alteration from the Bushveld Igneous Complex were utilized in this study to investigate the effects of oil on UG2 platinum group element (PGE) ore flotation and investigate the interaction mechanisms between the oil and phyllosilicate alteration minerals. Mineralogical characterization of the ores indicated a higher percentage of the alteration phyllosilicate minerals in the altered ore (9.2 wt%) in comparison to the normal ore (5.6 wt%); with talc predominating in both ores. Baseline batch flotation test work indicated a reduction of grade with hydraulic oil addition in the normal ore (Pt by 4.5 g/t and Pd by 3.6 g/t), whereas valuable metal grades in the altered ore showed no change. In contrast to the grades, the Pt and Pd recovery dropped by 6 % and 12 %, respectively, in the altered ore floats whereas nearly constant recoveries were obtained for the normal ore as oil concentration increased. The dynamic froth stability and slurry viscosity both increased in the presence of oil and were greater in the altered ore compared to the normal ore. The observed flotation performance of the normal ore was attributed to the increasing froth stability which promoted the recovery of gangue minerals and consequent grade decrease. For the altered ore, the greater increase in the slurry pulp viscosity with oil addition was proposed to lead to poor gas dispersion and reduced interaction between bubbles and particles resulting in the reduction of recovery. The addition of sodium metasilicate successfully mitigated these effects causing a decrease in the viscosity, improvement in particle dispersion and better froth drainage. This study highlighted the potentially harmful effects of oil spillages from mechanised mining and its complex interaction with alteration minerals contained within the ore.

Enhancing flotation separation of fine-grained cassiterite and calcite with cetylpyridine bromide as a dispersant

Calcite is a common gangue mineral in tin ore, which seriously affects the flotation of fine-grained cassiterite. The enhanced flotation separation of fine-grained cassiterite and calcite with cetylpyridine bromide (CPB) as a dispersant were investigated in the study. The CPB significantly improved the flotation separation efficiency of fine-grained cassiterite and calcite, and it exhibited an excellent dispersion effect and relieved the coating phenomenon of calcite particles on the surface of cassiterite particles. The CPB changed the surface potential of cassiterite from negative value to positive value when the pH was in the range of 3.4–11.5. However, regardless of treatment with CPB, the surface potential of calcite was positive when the pH was below 11.5. The O on the surface of cassiterite reacted with CPB, promoting the chemical adsorption of CPB on the surface of cassiterite. There was weak physical adsorption between CPB and calcite. The covering between cassiterite and calcite without CPB was mainly dependent on van der Waals interaction energy and electrostatic interaction energy. When CPB was in the presence, cassiterite and calcite were repelled by the hydrophobic interaction energy and electrostatic interaction energy.

Investigating critical metals Ge and Ga in complex sulphide mineral assemblages using LIBS mapping

Elemental imaging using Laser-Induced Breakdown Spectroscopy (LIBS) mapping is increasingly applied to a wide range of materials. In geomaterials, phase identification and characterization (mineralogy) are crucial for solving a variety of problems in earth sciences and mining industry.Here we applied LIBS mapping to ore samples from the world-class Kipushi deposit, Democratic Republic of Congo, because these ores are known for their great mineral complexity and economic value, especially for their high potential in critical metals such as Ge and Ga.The mineralogy of the samples was reconstructed by combining two approaches: 1) element colocalization in LIBS maps that were selected based on the knowledge of occurring mineral species at the site and 2) correlation maps obtained by applying the Interesting Features Finder (IFF) algorithm. Reconstructed minerals include chalcopyrite, bornite, chalcocite, sphalerite, galena, pyrite, tennantite-(Zn), renierite, tungstenite, betekhtinite, carrollite, gallite, and a series of non-sulphide gangue minerals (quartz, carbonate and clay minerals). SEM-EDS was used to confirm the LIBS-derived mineralogy, especially for sub-pixel inclusions.Among other results, Ge and Ga are hosted as major elements in renierite and gallite, respectively, and also as trace-elements in chalcopyrite, bornite and tungstenite (for Ge), and chalcopyrite, bornite, sphalerite and renierite (for Ga). Particular attention was paid to iron interfering with gallium at 417.20 nm, for which simple background-corrected peak intensities were compared to a more advanced chemometric method (MCR-ALS). All the results were obtained with minimal time and efforts and, while only qualitative in nature, they already provide essential information about ore texture, mineralogical composition and trace-element distribution across the ore.

Gold occurrence in the footwall of the Lappberget Deposit, Garpenberg Mine, Sweden: Implications for recovery efficiency

By-product metals have a significant potential to bring additional economic benefits to mines. However, a detailed characterization of their distribution is generally required to fulfill this potential and should preferably be integrated into a geometallurgical assessment. This contribution presents a detailed mineralogical and textural investigation of gold-bearing phases at the footwall of the Zn–Pb–Ag–(Cu–Au) Lappberget Deposit, Garpenberg Mine, Sweden, using optical microscopy, scanning electron microscope with energy dispersive spectroscopy (SEM-EDS), electron probe microanalysis (EPMA), laser ablation-inductively coupled plasma mass spectrometer (LA-ICPMS), and bulk chemical analysis applied to drill core and Knelson concentrator samples. Gold is a by-product at the Garpenberg mine, but it is unclear how the mineralogy, occurrence, and distribution of gold-bearing phases impact on gold recoveries during mineral processing. Our results show that Au-dominant electrum is the most abundant gold-bearing phase in the footwall of the Lappberget deposit, occurring strongly associated to sulfides in a variety of textures and grain sizes. Electrum grains commonly occur within sulfide borders, as inclusions, intergrowth and overgrowths of chalcopyrite, pyrite, galena, sphalerite, and pyrrhotite. Gangue minerals may also contain disseminated electrum and inclusions. Electrum grain sizes range from ∼5 µm to 300 µm, predominantly below 100 µm. The potential of sulfide lattice-bound invisible gold in the form of solid-solution gold and colloidal gold was also investigated, showing Au depletion within the analyzed sulfide carriers. The analysis of the concentrate samples from the Knelson gravity concentrator showed 584 and 431 ppm of gold content. High degree of liberation is observed among the gold-bearing phases in the concentrate, and gold recovery is highest among fractions coarser than 106 µm mesh. Pyrite and galena are the most abundant minerals in the concentrate samples. The gold-bearing phases were categorized based on its mineralogy, texture, grain size, and association and their influence on gold processing, especially textures and grain size, which implicates its liberation in milling and recovery by the gravity separator.

Visual insights into surface destruction differences of the large flake graphite ground with gangue minerals

In this study, the destruction differences among three levels of large flake graphite (−1.0+0.3, −0.3+0.18, and −0.18+0.15 mm) ground with gangues were investigated. The results revealed that the destruction degree and destruction rate descended with the decrease of graphite flake granularity, and the most severe destruction occurred for −1.0+0.3 mm. The internal microstructure differences of the large flake graphite are precisely the key reason for destruction degree and rate differences. The results of X-ray computed tomography showed that the −1.0+0.3 mm large flake graphite with a high porosity of 12.73 % contained more pores, cracks, and gangues than the −0.18+0.15 mm graphite with a low porosity of 0.097 % from 2D and 3D dimensions. These results indicate that the effective protection of the large flake graphite, particularly the super-large flake graphite (−1.0+0.3 mm), requires timely separation of them from gangues and individual purification to avoid grinding and flotation with fine flake graphite.

Chemical and mineralogical characterisation of Duguri Galena (Bauchi State, Nigeria)

This paper presents a detailed study of Galena samples' chemical and mineralogical properties collected from the Duguri area in Bauchi State, Nigeria. The sample for the research was sourced from Duguri town, Bauchi State, Nigeria. The sourced sample underwent comminution, homogenization, and sampling using the Coning and Quartering method followed by the Jones Riffle sampling method. Chemical analysis results of the crude ore sample showed the presence of Lead oxide (PbO) at an assay of 36.827 %, with Silica as the major gangue mineral present at 45.823 %. The other compounds present in the ore are ZnO (9.656 %), Fe2O3 (8.290 %), Al2O3 (3.409 %), TiO2 (1.072 %), WO3 (0.312 %), and AgO (0.001 %). Mineralogical Characterisation using XRD revealed the phases present in the ore as; Galena (47 %), Cerussite (19.0 %), Quartz (18.8 %), and Gratonite (15 %), hence confirming that the soured ore was Galena (PbS). SEM/EDS results showed the morphology of the sourced sample, containing Lead with other impurities in their quartz form within the ore matrix, with the presence of other elemental constituents (Si, C, and O). Keywords: Galena, Chemical analysis, Mineralogical characterisation, Duguri area, Bauchi State, Nigeria.