Sedimentary basin-hosted manganese oxides may represent an important yet underexplored source of critical metals. Here we present a stratigraphic, textural, mineralogical, and compositional characterization of Mn-oxide nodules, coatings, and veins in the Pisco onshore forearc basin, Peru. The Mn-oxide mineralization is stratabound within marine sandstone, siltstone, and tuff from the Neogene Chilcatay and Pisco formations. X-ray diffraction and electron microprobe analyses identify the Mn oxides as cryptomelane (± hollandite) and todorokite, which cement detrital grains and fossilize biological remains. Bulk chemical analyses of nodules, coatings, and veins reveal significant cobalt enrichment (mean = 0.17 ± 0.15 wt% Co; up to 0.63 wt% Co), corroborated by electron probe microanalysis of individual Mn oxide phases (mean = 0.37 ± 0.33 wt% Co; up to 2.1 wt% Co). The stratigraphic control, biomorphic replacement, mineralogy, and chemical composition collectively indicate a diagenetic origin for the Mn-oxide mineralization. The formation pathway likely involved organic matter decay or brine-hydrocarbon interactions coupled with Mn and Fe reduction, resulting in metal-enriched porewaters that circulated along structures and permeable horizons. Subsequent precipitation under oxygenated conditions occurred during late Pliocene uplift and exposure of the East Pisco Basin. This study demonstrates that diagenetic Mn oxides exposed in onshore basins represent a potential resource for manganese and critical elements such as cobalt.

Municipal Solid Waste Incineration (MSWI) plants pose significant environmental concerns, generating solid by-products, namely Fly Ash (FA) and Bottom Ash (BA). These MSWI residues have received attention due to the presence of valuable elements, Potentially Toxic Elements (PTE), and other contaminants. Radionuclide detection is also critical because they can concentrate in incineration ashes to pose a radiological hazard. Therefore, multi-element and radionuclide analysis was performed on BA and FA, including samples from bag filters containing lime (FAL) and soda (FAS) additives collected from two MSWI plants in northern Italy. BA and FA were sampled in 2013, 2020, 2021, and 2022 for a multi-year assessment, including during the COVID-19 pandemic. Our objectives were to evaluate the potential of elemental flows and radiological impact of the two different MSWI plants. The chemical concentration of 70 elements and the activity of 8 radionuclides were determined using sector Field Inductively Coupled Plasma Mass Spectrometry (ICP-SFMS) and alpha and gamma spectrometry, respectively. Regarding major elements (Fe, Al, Mg, Ti, and P), high mean concentrations were found in BA, followed by FAL and FAS. Notably, in BA samples, Fe, Al, Zn, and Cu averaged 47600, 35300, 4100, and 3500 mg kg−1, respectively, and critical raw materials, namely elements of economic importance such as Mg, P, Ti, and Ba, were concentrated at 16100, 6800, 3500, and 1400 mg kg−1, respectively. The annual flows of elements from MSWI residue streams ranged in the order of 103-104 kg a-1 for Fe, Al, Zn, Cu, Mg and Ti, and the sum of Rare Earth Elements (∑REE) was about hundreds of kg per year. Chondrite-normalized patterns of REE and normalized patterns of selected elements over crustal averages helped to evaluate anthropogenic signals, which enabled us to hypothesise elemental sources related to the input MSW. BA and FA showed a higher content of natural radionuclides than artificial ones. In BA, natural radionuclides, 40K and 210Pb, ranged from 666 to 693 Bq kg−1 and 23.3–48.1 Bq kg−1, respectively. In FA, 40K ranged from 308 to 2198 Bq kg−1 and 210Pb from 17.1 to 534 Bq kg−1. Activity concentration index (ACI) results in all-natural radionuclides below the permissible limit (<1). Still, the significant abundance of 210Pb and 40K, coupled with their complex behaviour, calls for new and continuous evaluation of long-term emissions and the radiological hazard related to MSWI systems. 

Artisanal and small-scale mining (ASM) has emerged as a vital economic lifeline for millions across Africa, Asia, and Latin America, driven by increasing gold prices, global demand, unemployment, and poverty. This sector accounts for approximately 28.9% of Ghana’s GDP and provides a livelihood for nearly 70% of Ghanaians, predominantly those residing in rural areas. However, this sector faces numerous environmental and health challenges, including uncontrolled mine waste disposal, contaminating water and soil with heavy metals. This review critically examines the environmental consequences of ASM waste management, focusing on informal underground tailings disposal. Using a dual-method strategy that combines systematic review and literature analysis, the study synthesizes 110 Scopus-indexed publications (2004–2024) to examine how ASM activities affect the safety, health, and ecosystems of Ghanaian ASM communities. Key findings reveal critical gaps in long-term waste management strategies, inadequate attention to health risks, and a lack of holistic socio-environmental assessments of ASM operations. The study underscores the urgent need for evidence-based interventions, including stricter regulatory enforcement, community-centered remediation, and sustainable livelihood alternatives. By addressing these gaps in Ghana, similar ASM-dependent economies can transform this sector into a force for equitable development without sacrificing environmental integrity or public health. Future research should prioritize cost-effective remediation technologies and policy frameworks that are tailored to the realities of informal mining communities.

Tungsten (W) is an emerging contaminant of concern whose high mobility in the environment is of scientific debate. It is also a critical raw material whose mining is expected to increase. Mine waste management aims to create an anoxic environment of neutral pH to limit sulfide oxidation and acid mine drainage. This study evaluates the stability of W-minerals under such geochemical conditions to develop recommendations for W mine waste management. Intact cores of legacy mine tailings from Morkulltjärnen, Sweden, were collected and analyzed using whole rock geochemistry and XRD. Monolayers with minutes amounts of W were generated by hydroseparation and studied using SEM-EDS, automated mineralogy, and microprobe analysis. Scheelite concentrates from the decommissioned processing plant were analyzed with XRF and 7 step sequential extractions. Groundwater was collected from eight wells in the Morkulltjärnen tailings in 2023 and 2024 and analyzed for 71 elements, anions and chemophysical parameters. This is one of the first field studies presenting mineralogical signs of scheelite weathering with tabular morphology, rod-shaped and porous structure, and loss of W from the crystal lattice, leading to very high concentrations (up to 23 mg/L) of dissolved W in anoxic and alkaline groundwater. This shows that standard mine waste management practices are unsuitable for scheelite, and action is needed to limit W mobilization into the surrounding environment from scheelite-rich tailings. Adsorption onto Fe-(hydr)oxides may be effective for controlling W mobilization from legacy mine waste, but in new mines, sulfides and tungstates should be separated in the processing plant and stored under anoxic and oxic conditions, respectively.

The energy transition, which aims to reduce carbon emissions and to slow down climate change, demands an ever-increasing supply of the so-called “critical metals”. Rare-earth Elements and Yttrium (REY) are among the most critical metals, as they are indispensable in most technologies associated with the generation and storage of renewable energy. In recent years there has been a growing interest in the potential of karst bauxites as nonconventional sources of REY and other critical metals such as Sc and Ga. The Sierra de Bahoruco (SW Dominican Republic) contains the most REY-enriched karst bauxites globally. In view of the high potential for hosting important REY contents, the Dominican Republic government has declared the Reserva Fiscal Ávila (RFA), a state-owned area within the Sierra de Bahoruco for assessment and exploration of its REY resources. In this study, we present the first data on the mineralogy and composition of bauxitic rocks from the RFA. The bauxitic deposits comprise clayey bauxites and Fe-rich bauxites that are composed predominantly of Al-oxyhydroxides (gibbsite, boehmite and nordstrandite), kaolinite and Fe-oxyhydroxides. The bauxites are enriched in REY, with a median value of 1,310ppm and up to 2,542ppm, with a consistent enrichment in Light REE (LREE) and Y compared to Middle REE (MREE) and Heavy REE (HREE). The positive correlation between the contents of REY and Th, and negative correlation with K, makes gamma-ray spectrometry an appropriate tool for the exploration. In addition, bauxitic rocks from the RFA contain significant Sc (up to 105ppm) and Ga (up to 54ppm) contents, and their extraction could potentially represent a substantial economic surplus to the revenue generated solely from the aluminum production.

Due to the lack of pre-mining mineralogical and geochemical data at historic mine sites, evaluation of the pre-mining geochemical baseline condition is required. For this purpose, we reconstructed the pre-mining geochemical baseline for Los Bronces mine (Central Chile) using the Yerba Loca Nature Sanctuary, located 6 km south, as a proximal natural analog where in similar altitudes (4000–4200 m) than in Los Bronces (3600–4000 m), mineralized breccias are currently undergoing natural weathering, leading to acid rock drainage (ARD) with pH values as low as 2.57 with SO4 at 2893 mg/L, Fe at 285 mg/L, Al at 64.4 mg/L, and Cu at 54.4 mg/L during summer. The stream’s pH, initially controlled by jarosite and later by schwertmannite, remains below 3.94, sustaining elevated Cu concentrations. In winter, pH rises towards neutral due to frozen ARD sources at high elevation (>3600 m asl) combined with rainfall-driven dilution in the lower catchment, decreasing metal loads in the streams. Archival data indicates that pre-mining breccias at Los Bronces, with a Cu grade of 1.43 wt%, were composed of 1.43 wt% pyrite, 0.92 wt% chalcopyrite, and other sulfide minerals, leading to significant ARD when weathered. Based on similarities with Yerba Loca and geochemical modeling results, it is inferred that pre-mining drainage at Los Bronces had a pH range of 2.5 to 5 during summer, with likely higher Cu concentrations but similar trace element levels, suggesting a similar annual cycle as today observed at Yerba Loca with a potential increase towards neutral pH in winter.

Uranium (U) release from mining has been typically associated with former U mine sites, but trace U levels in iron or base metal ores can also lead to U mobilization into ground and surface water posing potential risks due to U's chemical toxicity and radioactivity. This study investigates U sources and mobility at an iron ore mine site in Northern Sweden, where U concentrations (median 1.8 μg/l) exceeding the Swedish annual guideline value of 0.17 μg/l have been detected in a river receiving excess process water from the mine site. Drill core samples were characterized to identify the minerals hosting U in the iron ore and sequential extraction tests were conducted on solid samples from the processing plant to assess U mobility potential. Results indicate that, given its low U content, iron ore is not a significant source of the elevated U levels detected in the process water. Thorite, the main U-bearing mineral remains stable under the neutral to alkaline pH conditions in the processing plant. U speciation calculations on process water monitoring data, performed in PHREEQC with the PRODATA thermodynamic database, revealed dominant calcium uranyl carbonate complexes, specifically Ca2UO2(CO3)3 and CaUO2(CO3)32−. Mine water from Leveäniemi and Gruvberget open pits, particularly Leveäniemi, was identified as the main source of U to the process water in the recirculation system. The U in mine water originates from groundwater infiltration into the open pits and leaching of U from the open pit wall rocks. Further investigation of these sources and U's geochemical behavior in mine water before it mixes with process water in the processing plant is crucial for understanding the processes driving elevated downstream U concentrations.

Waste metallurgical slags have shown the potential to serve as a source of critical raw materials. In this study, we examined the extraction of Cu and Zn from a fine-grained copper slag from the Tsumeb smelter (Namibia). A combination of chemical analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and automated mineralogy (autoSEM) was used to determine its elemental and mineralogical composition. Silicate glass was determined as being the most abundant phase (over 90 area %) and the dominant host phase for the target elements (58–70% of the total Cu, over 90% of the total Zn). Based on these results, the reprocessing of the slag by sulfide flotation and subsequent pyrometallurgical treatment would be inefficient. For the extraction of Cu and Zn, a hydrometallurgical approach using acid leaching was proposed. Extraction tests to simulate agitation leaching were carried out by leaching the original fine-grained material in H2SO4 (20, 50, and 100 g/l) at liquid/solid (L/S) ratios of 5, 10, and 20 kg/l and ambient temperature for 1 and 6 h. The extraction efficiencies increased with the increasing acid concentrations, L/S ratios, and leaching time, reaching up to 70% for Cu and 94% for Zn. High extraction efficiencies of As were reached (up to 91%), possibly lowering the environmental hazards posed by the original material.