Editorial for Special Issue “Microanalysis Applied to Mineral Deposits”

The global demand for metals and minerals is increasing—especially for the so-called Critical Raw Materials (CRMs)—nurturing renewed scientific and societal interest into the exploration, extraction, processing, and environmental implications of these materials. From technologies such as electric vehicles, solar panels, and wind turbines to digital infrastructure and defense applications, our modern economy depends on a reliable and constant supply of these materials. Yet, ensuring their availability in an environmentally sustainable and socially responsible manner is one of the most pressing challenges facing the mining and geoscience communities.

In ore deposits, Critical Raw Materials typically occur in trace amounts as by-products in the extraction process of the main commodities. Their efficient recovery is hindered by both complex geochemical behavior and the physical associations with host and gangue minerals. Furthermore, as environmental regulations tighten across jurisdictions, there is growing pressure to improve extraction efficiency while minimizing ecological impact. This necessitates a detailed understanding of the mineralogical and chemical composition of ore deposits—knowledge best gained through advanced microanalytical techniques.

In this Special Issue, Microanalysis Applied to Mineral Deposits we showcase recent innovative research that leverages advanced microanalytical techniques to characterize mineral deposits in ways that directly inform mineral processing, enhance the recovery of economically valuable elements, and contribute to environmental stewardship. From 3D imaging and laser ablation studies to petrographic, spectroscopic, and thermodynamic modeling, the articles in this Issue demonstrate the critical role of microanalysis in modern ore geology.

1. Highlights from the Special Issue

In their contribution, Hunt et al. [1] examine greisen-type ore from Tasmania, Australia, focusing on the mineral zinnwaldite—a lithium-bearing mica with potential as a CRM source. Using electric pulse fragmentation (EPF), they explore an innovative method for reducing excessive fine particle formation, a common issue with traditional comminution methods. The application of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) further reveals the chemical compositional variations within zinnwaldite, distinguishing between vein-hosted and groundmass varieties in terms of their lithium, rubidium, cesium, and rare earth element contents. These insights are not only crucial for resource recovery but also underscore the importance of having a good understanding of the ore mineralogy, textures, and mineral chemistry to optimize the mineral processing technologies and, ultimately, improve metal recoveries.

Akua Abrafi Appiah et al. [2] present a detailed geometallurgical analysis of the Arthur River magnesite deposit in Tasmania, Australia, utilizing scanning electron microscopy (SEM), portable X-ray fluorescence (pXRF), and LA-ICP-MS. Their study differentiates three magnesite ore types based on physical and chemical properties, with significant implications for beneficiation strategy and downstream processing. The identification of magnesium-bearing carbonate gangue minerals (dolomite), along with their association with silicates (quartz and talc), demonstrates the complexity of even seemingly simple ore systems. In this context, microanalysis becomes an essential tool not only for classification of ore types but also for informing processing design and anticipating metallurgical challenges.

In the Xiangshan uranium ore field—China’s largest volcanic-hosted uranium deposit—Yu et al. [3] investigate hydrothermal alteration processes. Employing petrography, Tescan’s Integrated Mineral Analyzer (TIMA), micro-XRF techniques, and mass balance calculations, the study analyses mineralogical changes during hematitization and illitization, revealing fluid compositions favorable for uranium mobility. Their thermodynamic modeling shows how specific alteration assemblages correlate with uranium deposition, offering a predictive framework for exploration and shedding light on the physicochemical pathways governing uranium transport and precipitation.

Zhou et al. [4] focus on the carbonaceous components of the Huangjindong gold deposit in the Jiangnan Orogenic Belt, China. Through petrographic analysis and Raman spectroscopy, they distinguish between the following two types of carbonaceous material (CM): CM1, formed by regional metamorphism, and CM2, a hydrothermal product linked to mineralization. This dual-origin CM plays a multifaceted role in gold deposition—either promoting gold precipitation via redox reactions or enhancing metal absorption and deformation. The study underscores the importance of characterizing also non-metallic phases in an investigation into ore mineralogy, which often mediate key geochemical reactions during ore formation.

Expanding the analytical dimension into three dimensions, Krebbers et al. [5] apply computed tomography (CT) to study scheelite-bearing ores from the Kara Fe-W deposit in Australia. Unlike traditional 2D microscopy, CT enables non-destructive visualization of mineral textures and spatial relationships in 3D. Their findings on scheelite distribution, associated hydrous minerals, and modal mineralogy apply to both genesis interpretation and mineral processing optimization. By quantifying WO₃ grades and grain size distributions, CT acts as a high-resolution bridge between petrology and ore beneficiation strategies.

Next, King et al. [6] utilize electron backscatter diffraction (EBSD) and LA-ICP-MS mapping to study pyrite from the Olympic Dam IOCG deposit—one of the world’s most significant polymetallic resources. Their work uncovers ductile deformation microstructures in pyrite, a feature rarely preserved in brecciated systems. Elemental mapping reveals complex zoning patterns of arsenic, cobalt, and nickel, often associated with strain localization. These microstructures not only inform interpretations of ore genesis and post-ore tectonic history but also have practical implications for mineral processing, as zoning may indicate heterogeneity in trace metal content with direct relevance to CRM recovery and environmental remediation.

Finally, in a hydrothermal synthesis study, Kovalchuk et al. [7] investigate the incorporation of gold and arsenic in pyrite and marcasite under simulated ore-forming conditions (350 °C/500 bar and 490 °C/1000 bar) with salinities ranging from 15 to 35 wt.% NaCl. Using the Electron Probe Micro-Analyzer (EPMA), LA-ICP-MS, and Electron Backscatter Diffraction (EBSD), the study finds that pyrite can host up to 8000 ppm gold and 5 wt.% arsenic, with a strong gold–arsenic correlation. Marcasite, by contrast, shows no such correlation. The results suggest that invisible gold in pyrite is controlled by fluid chemistry and arsenic content, rather than by lattice substitution, refining our understanding of ore-forming processes.

2. The Expanding Role of Microanalysis

Collectively, the contributions included in this Special Issue of Minerals demonstrate that detailed microanalytical approaches in geosciences are far more than academic exercises; they provide possibilities for a more holistic mining process, through optimization of metal recovery from ores and improved understanding of the environmental footprint of mining. Through improved recovery of valuable metals as main commodities (and also as by-products), and better targeting of exploration efforts, or the mitigation of deleterious components, microanalysis is clearly key for unlocking a more modern and environmentally benign way of mining.

Importantly, the diversity of analytical techniques showcased in this Issue—from spectrometry and diffraction to tomography and thermodynamic modeling—illustrates the interdisciplinary nature of mineral deposit studies today. As ore bodies become more complex and environmental expectations rise, these tools will only grow in importance. Equally, the studies highlight the need for cross-disciplinary collaboration between geologists, mineralogists, geochemists, and mining and processing engineers.

In this context, the Editors hope this Special Issue serves as both a resource and an inspiration. The microanalytical insights presented here not only deepen our understanding of mineral deposits but also chart a course toward more efficient, responsible, and informed resource development.