The present research explores the potential of manganese oxide waste ore in energy storage applications, focusing on supercapacitors. The investigation assesses the electrochemical capabilities of natural manganese oxides obtained from the Drama region, which has been the main mining center of Greece for manganese ore, especially that of battery-grade quality. Samples were collected from abandoned mining sites in the Kato Nevrokopi area, Drama. The structure and composition of the manganese minerals were determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Electrochemical tests involved the preparation of electrodes using natural nsutite and heat-treated nsutite (hausmannite). Then, the designed electrodes were subjected to cyclic voltammetry tests and charge–discharge measurements. The hausmannite electrode exhibited a higher specific capacitance of 667 F/g at a current density of 0.2 A/g, and the electrode material retained 98.3% of its initial capacitance after 1000 cycles. This study provides new perspectives on simple and efficient methods for transforming natural nsutite material from mining waste to hausmannite with greater structural homogeneity and better electrochemical behavior.

Strategic metals are indispensable for meeting the needs of modern society. It is then necessary to reassess the potential of such metals in Europe. For the exploration of strategic metals, portable XRF (X-Ray Fluorescence) and LIBS (Laser Induced Breakdown Spectroscopy) are powerful techniques allowing their multi-elementary analysis. This paper presents a database providing more than 2000 pXRF data and more than 4000 pLIBS spectra acquired on minerals from the Mineralogy and Petrology Museum of National and Kapodistrian University of Athens (NKUA), selected based on their potential in bearing strategic metals. The combination of these two portable techniques, along with expanding dataset on strategic metal-rich minerals, provides valuable insights into strategic metal affinities and demonstrates the effectiveness of portable tools for exploring strategic raw materials. Indeed, such database allows to strengthen the knowledge on strategic metals by producing statistic and chemometric analyses (e.g., boxplot, PCA, PLS) on their distribution.

The manganese deposits at the Kato Nevrokopi area are located in the Drama Basin (Northern Greece) and belong to the Rhodope Metamorphic Province. The deposits were previously exploited for several supergene Mn-oxide ore bodies of massive, battery-grade nsutite, spatially associated with fault zones in the vicinity of Oligocene granitic intrusions. We conducted detailed geological, mineralogical, and geochemical investigations at the Mavro Xylo deposit, which led to the identification of Ag-rich Mn-Zn±Pb vein-type mineralization. The studied paragenesis appears to have developed during two hydrothermal stages: stage I, characterized by the mineral assemblage rhodonite–quartz–rhodochrosite–pyrophanite–pyrite–galena–Te bearing argentite–sphalerite–wurtzite–alabandite, and stage II, dominated by Ag-rich, Mn-Zn±Pb oxides in the form of fracture-fills along a high-angle NE-SW fault zone in brecciated marbles. Bulk analyses of the stage-II oxide assemblage yielded concentrations of Ag up to 0.57 wt.%. In the veins, wurtzite is present in bands, succeeded by manganese oxides, while calcite and quartz are the main gangue minerals. We placed particular emphasis on the occurrence of Ag in high concentrations within distinct manganese oxides. Major silver carriers include Zn-bearing todorokite, chalcophanite, and hydrous Pb-Mn oxide. The vein-type mineralization at Mavro Xylo shares many characteristics with other intermediate-sulfidation epithermal precious metal-rich deposits associated with high Mn concentrations. The evolution of the mineral paragenesis indicates a change in the physicochemical attributes of the ore-forming fluids, from initially reducing (stage I) to oxidizing (stage II). Although the origin of the initial ore-forming fluid remains to be constrained, the above redox change is tentatively attributed to the increasing incursion of meteoric waters over time.

Manganese oxide minerals have a remarkable range of applications. This investigation delves into their potential utility in energy storage, particularly as supercapacitors. The study centers on natural manganese oxides sourced from the Drama region (Greece), evaluating their electrochemical promise and devising strategies for addressing the remediation of mining waste sites. Samples were collected from abandoned mining sites at Kato Nevrokopi area, Drama region. Techniques such as X-ray diffraction (XRD) were employed to probe the structural characteristics of the minerals. Electrochemical studies involved the preparation of electrodes using natural and heat-treated nsutite (hausmannite). Then, the designed electrodes were subjected to cyclic voltammetry tests and charge-discharge measurements. Results showed superior electrochemical performance for the hausmannite-based electrode due to its greater structural homogeneity.

In situ analysis techniques of ore and drill core samples provide fast results that can be used to facilitate the decision-making process during the geochemical exploration of ore deposits. This study applies the use of two portable devices, pXRF and Laser-Induced Breakdown Spectroscopy (pLIBS), to a small manganese oxide deposit situated in the Rhodope metamorphic complex, Kato Nevrokopi, northern Greece. The study provides an example of exploration of a variety of manganese minerals, including Mn-oxides, Mn-carbonates, and Mn-silicates. It tests the accuracy of mineral identification using these two techniques. The application of pXRF helped in the elemental identification of critical trace metals in certain Mn minerals and showed that there is Ag enrichment in the ore, which is associated with the mineral hetaerolite (ZnMn₂O₄). From the LIBS analysis, it can be seen that Mn minerals with different Mn valences (+2, +3, and +4) display distinct spectra. This observation will be further examined by expanding the sampling pool of the spectra of manganese oxides. It is postulated that the presence of trace elements in Mn minerals may differ according to the valence of the Mn, which in turn affects the LIBS signals of the sample.