This study aims to comprehensively characterize coal extracted from three active mines in northeastern Kazakhstan: Lenin, Saradyr, and Bogatyr. These mines exploit two Carboniferous coal-bearing formations, Dolyn and Karagandy. Dolyn, extracted by the Lenin underground mine at a depth of 700 m, contrasts with Karagandy, extracted at depths up to 260 m in Saradyr and Bogatyr. Six selected samples from the Lenin, Saradyr, and Bogatyr mines underwent various analyses, including proximate and ultimate analyses, elemental analyses (acid digestions with HCl + HNO₃ + HF, ICP-MS), and determination of mineral matter contents (XRD and SEM-EDS). This research aimed to understand the mode of occurrence of minerals and elements, technological and environmental implications of the coal seams extracted from these mines. Results indicate low sulfur and high ash content in the organic matter of all samples. Quartz and kaolinite dominate, with minor euhedral pyrite present in all samples. Framboidal pyrite, iron oxides, and rare earth element (REE)-bearing minerals are exclusively found in Saradyr and Bogatyr samples. Quartz and kaolinite likely reached the peat swamp through detrital processes, while pyrite formation occurred through both syngenetic and epigenetic processes in the coal samples. Ratios like Ce _n /Ce _n , Eu _n /Eu _n , Y _n /Ho _n , and Gd _n /Gd _n suggest REE deposition in anoxic hydrothermal water environments, possibly indicating a tuffaceous origin for the coal samples. Examining the elements’ mode of occurrence suggests their preferential association with mineral matter. Strong positive correlations among elements like Al, K, Na, Ti, Ba, Be, Ni, Cr, Co, Ga, Sc, V, As, Pb, Cu, Zn, and Zr, along with Eu and Sc of the REEs, suggest association with ash yield, consistent with kaolinite and accessory minerals. Comparative analysis of inorganic geochemical composition of coal worldwide reveals notable depletion of major, trace elements, and REEs in samples from all three mines, suggesting limited economic interest. Furthermore, coal samples containing trace elements pose minimal environmental impact.

Rare earth elements (REE) are vital for renewable energy, electronics, and advanced technologies; however, the process-related evolution of REE research has not been systematically quantified. This study conducts the first large-scale bibliometric analysis of 76,768 REE-related publications (1975–2024) from Web of Science, using the Cross-Disciplinary Publication Index (CDPI) and Technology–Economic Linkage Model (TELM). Results reveal three development phases: publication growth from 5000 after 2008, driven by China’s export restrictions and the global clean energy transition; China leads with 24.1% of publications, followed by the U.S. (11.7%) and Germany (6.4%). Interdisciplinary mapping identifies materials science as the central field (CDPI = 0.81) linked to nanotechnology (0.75) and environmental science (0.66). Four thematic clusters dominate: (i) deposit geology, (ii) material applications, (iii) green extraction technologies, and (iv) circular economy strategies. Recent emphasis on sustainable practices and unconventional sources—such as phosphorites, bauxite, coal fly ash, and urban mining—reflects a shift toward green innovation. The findings guide policies to diversify REE supply through unconventional deposits (~50 Mt coal-hosted REE), eco-friendly extraction, and recycling. Future priorities include AI-driven exploration, lifecycle assessment of secondary sources, and stronger global collaboration to secure resilient, sustainable REE supply chains.

Driven by advances in multifunctional materials design, silver halides—both natural (AgCl, AgBr, AgI, and mixed phases such as embolite) and synthetic—have emerged as versatile functional materials characterized by tunable crystallography, phase stability, and compositional variability. This study investigates global research trends, interdisciplinary development, and emerging application areas of silver halides through a bibliometric analysis of 23,841 publications indexed in the Web of Science (1975–2025). CDPI, TELM, VOSviewer, and Excel were employed to evaluate publication growth, disciplinary integration, and thematic evolution. Research output increased markedly after 2005, reaching approximately 700–1000 publications annually during 2020–2025. China (18.3%) and the United States (17.5%) were the leading contributors, while the Chinese Academy of Sciences, Russian Academy of Sciences, and CNRS showed the highest scientific impact. Materials Science Multidisciplinary (CDPI = 0.72), Chemistry Multidisciplinary (0.70), and Physical Chemistry (0.67) exhibited the strongest interdisciplinary integration, whereas Nanoscience and Nanotechnology demonstrated the fastest growth. Keyword co-occurrence analysis identified six major research domains focused on functional materials engineering, including environmental remediation, catalysis, crystal growth, antibacterial materials, interfacial processes, and electroanalytical systems. Recent studies increasingly emphasize structure–property relationships and synthetic control of crystal size, morphology, and surface characteristics to enhance performance in photocatalysis, sensing, antimicrobial coatings, and advanced optical applications. Overall, the results highlight the growing importance of silver halides as strategic functional materials and provide a quantitative framework for future research and technological development. A limitation of this study is its exclusive reliance on the Web of Science database, which may underrepresent relevant publications indexed elsewhere.