Mining, Volume 5, Issue 4 (December 2025) – 9 articles

Varaždin County is rich in mineral resources, attracting considerable investor interest in opening new exploration areas and expanding existing exploitation fields. Since the economic value of mineral resources changes with market conditions, continuous professional assessment is required. Although the proposed methodological framework is broadly applicable to mineral resource management, this case study focuses on the exploitation of construction sand and gravel deposits in Varaždin County. In this way, it addresses the sustainability challenges characteristic of quarry operations rather than large-scale mining projects. The objective of this study was to develop and test a new method for quantifying sustainability indicators in the mineral resource management (spatial, resource-related, environmental, economic, and social sustainability—I_PREGS) and for calculating an aggregated composite index (AK_I) using a pilot project for construction sand and gravel. The research establishes a cause–effect relationship between quantified indicators (I_PREGS) and the newly established aggregated composite index (AK_I). Methodologically, the study applied multivariate analysis to questionnaire data, enabling the selection, weighting, and aggregation of indicators and the design of a conceptual framework for AK_I calculation. The resulting methodology provides an instrument for monitoring and improving sustainable mineral resource management, supporting the objectives of the circular economy. The findings highlight the potential of the AK_I to reduce systemic inefficiencies, guide policy development, and offer a transparent mechanism for assessing both implementation and effectiveness. This significantly improves the current state and strengthens the basis for evidence-based economic policy-making. The case study in Varaždin County further demonstrated that the AK_I not only reproduces administrative decisions with high consistency but also clarifies how applicants should proceed in cases of partial acceptance and how policymakers can interpret conflicting outcomes across different index variants. Full article

The relentless pace of industrialisation and globalisation has precipitated the rapid depletion of surface mineral deposits, presenting a formidable challenge to conventional mining operations and exerting a detrimental impact on their profitability. This depletion, coupled with the escalating demand for minerals, has driven prices to unprecedented highs, thereby inflating operating costs across various industries. Traditional surface and underground mining methods, struggling to meet burgeoning demands, contribute significantly to environmental degradation and substantial energy consumption. In response to these challenges, this study advocates for a paradigm shift from conventional mining methods and mineral resources toward untapped alternatives that hold the potential for enhanced economic viability and sustainability. Utilising environmentally friendly techniques and adopting more economical approaches becomes paramount in addressing the pressing demands of the current era and securing resources for future generations. This short review examines potential alternative mineral resources and the associated mining methods, including fluidised mining, deep-sea mining, brine mining, urban mining, in-situ and heap leaching, and space mining. A meticulous evaluation of the state-of-the-art technologies developed for these unconventional methods is conducted, including an assessment of their respective advantages and disadvantages. Finally, the study deliberates on the prospects of each approach, elucidating their potential contributions to alleviating the global metal crisis. This research provides insights that can inform sustainable mining practices and guide the industry toward a more environmentally responsible and economically viable future. The urgency of such a transition is underscored by the need to address the challenges posed by conventional mining and ensure the availability of mineral resources for generations to come. Full article

This article presents a concept for modernizing the transport system of high-performance coal mines through the transition from traditional monorail to rubber-tyred transport (RTT). The study was conducted based on materials from the V.D. Yalevsky Mine of JSC “SUEK-Kuzbass” with daily longwall output up to 60,000 tons and production capacity up to 10 million tons per year. Analysis of the existing transport system efficiency revealed low equipment utilization rates (52–70%) and significant time losses during shift changeovers (up to 4.3 h/day in development workings). Technical solutions for phased RTT implementation were developed, including six roadway surface scenarios and a fleet composition of 60 specialized equipment units. The research methodology is based on time study observations using the automated “Granch” system, analysis of equipment utilization coefficients, and economic–mathematical modeling using NPV, MIRR, and payback period. The transition to rubber-tyred transport provides a five-fold increase in travel speed (from 4.5 to 25 km/h), reduction in shift changeover time to zero, increase in operating time by 20% in development and 4.5% in extraction, and a reduction in longwall move duration from 173–209 to 88 days. Additional coal production amounts to 6.5 million tons. Economic justification shows NPV of USD 64.2 million with MIRR of 2.4% and a payback period of 4.5 years. Full article

Artisanal and Small-Scale Gold Mining (ASGM) is a primary source of global mercury pollution, creating an urgent need for sustainable, low-cost alternatives to amalgamation. This study investigates the use of cassava wastewater (manipueira), a cyanogenic agricultural byproduct, as a lixiviant for a gold concentrate (14.30–15.87 ppm Au) from an artisanal mine. Two approaches were evaluated: direct leaching with manipueira in natura (250 ppm CN⁻) in single and double 8 h and 12 h cycles, and leaching with a cyanide solution concentrated from dilute manipueira (100 ppm CN⁻) via a simplified air-stripping system. Results were benchmarked against the mine’s amalgamation (44.7% recovery) and 30-day heap leach (75.8% recovery) processes. The most effective method observed was a two-cycle, 8 h leach with manipueira in natura, which achieved a mean gold recovery of $76.75\pm 4.71\%$. This result is comparable to the efficiency of the site’s lengthy heap leach process and suggests a promising, faster, route to eliminating mercury use. Longer (12 h) leaching cycles yielded lower recoveries, suggesting process limitations such as preg-robbing. The cyanide concentration method proved inefficient, recovering a maximum of 12.40% of the available cyanide and resulting in a weaker lixiviant. The findings demonstrate that while direct leaching is a viable alternative to mercury, the inherent instability of manipueira necessitates a focus on developing efficient, controlled systems to extract and concentrate its cyanide content, thereby creating a standardized “green” reagent from a large-volume agricultural waste stream. Full article

In situ uniaxial compressive strength mapping across dykes of different thicknesses within a coal mass and its influence zones at two mines in the Jharia coalfield has been carried out in this study. It provides insight into the manner in which the dyke intrusion altered the adjacent coal mass, leading to the formation of jhama and pulverized zones with modified strength properties. A Digital Schmidt Hammer with an impact energy of 2.207 Nm was used to estimate the in situ uniaxial compressive strength of the coal around the seam–dyke interface in different mines selected for the study. At the first mine, the dyke had a thickness of approximately 15 m, with its influence on the surrounding coal mass extending up to 13.5 m on both sides. Unlike the first mine, the dyke in the second mine was merely 1 m thick, with its effect limited to a zone of around 2.1 m. The average uniaxial compressive strength of unaltered (intact) coal at the studied mines ranged from 31.7 to 38.5 MPa. The zones influenced by the dyke at both mines comprised jhama, which exhibited a 15–18% higher uniaxial compressive strength compared to the surrounding intact coal, and pulverized coal zones, which showed a 46–56% reduction in strength relative to the intact coal. Full article

This study presents the design and validation of an automated skip loading system for vertical shaft hoisting operations, aimed at addressing inefficiencies in current manual systems that contribute to consistent underperformance in meeting daily production targets. Initial assessments revealed a task completion rate of 91.6%, largely due to delays and inaccuracies in manual ore loading and accounting. To resolve these challenges, an automated system was developed using a bin and conveyor mechanism integrated with a suite of industrial automation components, including a programmable logic controller (PLC), stepper motors, hydraulic cylinders, ultrasonic sensors, and limit switches. The system is designed to transport ore from the draw point, halt when one ton is detected, and activate the hoisting process automatically. Digital simulations demonstrated that the automated system reduced loading time by 12% and increased utilization by 16.6%, particularly by taking advantage of the 2 h post-blast idle period. Financial evaluation of the system revealed a positive Net Present Value (NPV) of $1,019,701, a return on investment (ROI) of 69.7% over four years, and a payback period of 2 years and 11 months. The study concludes that the proposed solution significantly improves operational efficiency and recommends further enhancements to the hoisting infrastructure to fully optimize performance. Full article

Organisations are increasingly adopting the Chain of Custody (CoC) standards in the mining industry to enhance the traceability of minerals. It ensures that the minerals they have received are from credible sources and accompanied by verifiable information. However, unlikeother industries such as timber, where the effectiveness and benefits of CoC standards are mainly explored, this study subtly shifts the focus towards identifying strategic opportunities and innovation areas within the CoC standards that could extend beyond traceability. Four CoC standards were selected, and their provisions examined. It was found that implementing these requirements could not only enhance transparency but also support broader sustainability goals across the entire value chain. The study also identifies several challenges that could act as barriers to the CoC system, and these are seen as opportunities for innovative approaches to enhance the effectiveness of the standards. These are labelled as transformative innovation areas, and while they do include blockchains and analytical proof of origin technologies, this study also seeks to advocate for solutions that are more pragmatic and scalable. By identifying opportunities and areas of innovation, the findings will help improve the practical implementation of the standards and suggest areas for future evaluations of effectiveness that could consider aspects beyond traceability, such as sustainability and transparency. Full article

The implementation and application of a safety factor (SF)-based numerical framework in FLAC3D-IMASS (Itasca Model for Advanced Strain Softening) is presented for the evaluation of the short-term stability of unsupported underground excavations in sedimentary rock masses during pillar recovery in bord-and-pillar mining. The stability of underground openings during the initial hours post-excavation must be ensured, as they are not accessed thereafter; therefore, short-term stability assessment is essential. The framework was specifically calibrated to field observations and applied to a case study from an Australian bord-and-pillar mine, focusing on plunge and bellout configurations commonly used during the pillar extraction stage to enhance ore recovery. The modelling approach was integrated with rock mass degradation behavior under static loading conditions and was used to calculate three-dimensional distributions of SF to identify potential failure zones. The results demonstrate that the coal (CO) roof scenario generally maintains structural stability, while the impure coal (Cox) roof scenario is observed to exhibit significant instability, particularly at greater excavation advancement. Among the tested bellout geometries, 8.0 m spans were observed to provide improved performance due to shorter tunnel lengths that enhance confinement and reduce the volume of disturbed rock. Overall, the proposed SF framework effectively captures localized failure mechanisms and is demonstrated as a practical design tool for assessing the short-term stability of unsupported structures during critical stages of underground mining operations. Full article

This paper aims to develop a robust empirical–analytical model using the statistics of mine water level rebound in abandoned mines and the basic physical principles of underground hydraulics. The data collected and treated included the time series of the mine water level for 35 closed and flooded mines from four European countries. Within the developed model, mine water level evolution is governed by an ordinary differential equation with one fitting parameter that depends on the floodable cavity volume in a mine and water inflow before flooding begins. The model assumes that rock properties and residual void distribution are homogeneous, and the mines being flooded are almost isolated hydraulically from the neighboring ones. The exponential formula, as the governing equation solution, was found to be the most suitable for fitting the measurements. The calculated exponential curves allow for excellent or very good fitting of the measured water levels for 17 of 35 mines, and acceptable fitting for 11 mines in terms of minimizing mean-square-root deviation. The proposed approach can be applied to preliminary assessments of mine water level rebound in developing and calibrating sophisticated numerical flow models. Full article