Conference Agenda

Typically, ceramic samples are analyzed mineralogically after firing, with in situ bulk sample analyses already representing a significant advancement. High-Temperature Raman Imaging takes this a step further: It is the only method enabling spatially resolved investigation of ceramic samples at the micrometer scale at temperatures exceeding 1000 °C. This technique allows real-time observation of phase transformations, kinetic processes, and reaction fronts, eliminating the need to quench samples, thus preserving intermediate phases.
In this study, we demonstrate the method’s capability to track dynamic processes in complex systems, such as the CaO-Al₂O₃-SiO₂ system. Through hyperspectral Raman images, we visualize phase evolution and reaction kinetics. For instance, the γ- to β-Ca₂SiO₄ transition occurred ~290°C below the accepted critical temperature, highlighting the method’s sensitivity to rapid, localized changes.
By combining high spatial resolution with classical least squares fitting, relative phase proportions and reaction front migrations are quantified, offering unprecedented insights into high-temperature reactions. This approach both advances the fundamental understanding of mineral transformations and provides practical implications for optimizing material performance in industrial applications. Thus, High Temperature Raman Imaging is an indispensable tool for mineralogists and applied geoscientists.

Some of the most homogeneous natural K-feldspars like the ones from Itrongahy (Madagascar) and Volkesfeld (Germany) contain up to 2.5wt% Fe2O3, where the Fe3+ replaces the aluminum on the tetrahedral sites. Some of the vibrational modes of feldspars are considerably affected in vibrational frequency by a mass increase in the substitution of Al by heavier elements [1]. How is the Raman scattering intensity affected by the larger number of electrons of Fe3+? We report measured Raman spectra of synthetic and natural iron-rich feldspars with Fe/(Al+Fe) molar ratio between 0 and 0.59. The synthetic feldspars have been previously characterized by EPMA and XRD [2]. Ab initio spectral calculations complement our measurements. We discuss the correlation between Fe/(Al+Fe) molar ratio, band shifts and band intensities with respect to the question whether this information be used to learn about iron in other feldspars.
[1] Aliatis I., Lambruschi E., Mantovani L., Bersani D., Andò S., Gatta G.D., Gentile P., Salvioli-Mariani E., Prencipe M., Tribaudino M., Lottici P.P. (2015) A comparison between ab initio calculated and measured Raman spectrum of triclinic
albite (NaAlSi3O8). Journal of Raman Spectroscopy 46, 501-508, doi: 10.1002/jrs.4670

[2] Taroev V., Göttlicher J., Kroll H., Kashaev A., Suvorova L., Pentinghaus H., Bernotat-Wulf H., Breit U., Tauson V., and Lashkevich V. (2008) Synthesis and structural state of K-feldspars in the system K[AlSi3O8]-K[FeSi3O8]. European Journal of Mineralogy 20, 635-651, doi: 10.1127/0935-1221/2008/0020-1840

The combination of X-ray fluorescence (XRF) and Laser-Induced Breakdown Spectroscopy (LIBS) enables comprehensive geochemical analysis, combining well established procedures for main elements and a procedure for light elements such as lithium (Li), which cannot be detected by XRF. This study presents optimized fused bead preparation methods suitable for combined wave length dispersive XRF–LIBS (handheld-LIBS in our case) analysis of geological materials. Fused beads were produced using sodium tetraborate (Na₂B₄O₇) as flux from certified reference materials and Li-bearing ores. To ensure effective laser–sample interaction for LIBS, two approaches were evaluated: (1) addition of CuO as a coloring agent and (2) mechanical surface roughening by lapping. While CuO-doped beads allowed sufficient laser coupling, their application was limited by uncertainties in copper oxidation state and concentration control. In contrast, surface-roughened beads provided stable LIBS performance without introducing contamination, as verified by XRF measurements before and after treatment. Micro-XRF mapping confirmed a high degree of elemental homogeneity within the fused beads, also at spatial scales relevant for LIBS analysis. Calibration of both XRF and LIBS systems demonstrated the feasibility of the combined analytical workflow. The results indicate that surface-modified fused beads represent a simple and robust preparation strategy for integrated XRF–LIBS analysis. This approach enables accurate determination of major elements by XRF alongside reliable quantification of lithium and other light elements by LIBS, offering significant potential for geochemical and mineralogical applications.

Venus is often referred to as Earth’s twin given their similarity in size and density. However, with an atmosphere predominately comprised of CO₂, a thick cloud layer and high temperature and pressure surface conditions (~460°C and 90 bars, respectively), observing and analysing the surface of Venus requires a unique approach. Upcoming missions to Venus, including VERITAS (NASA) and EnVision (ESA), will be equipped with near-infrared (NIR) spectrometers that will collect emissivity measurements in six bandwidths to determine the type of materials present at Venus’ surface. In anticipation of these missions, this work measured the emissivity of basalt and its alteration products (calcite and anhydrite) at high temperatures with the aim to determine the extent alteration impacts emissivity values and to what degree basalt alteration is distinct from felsic rock emissivity. High temperature (~380-500°C) emissivity measurements were collected at the Planetary Spectroscopy Laboratory (PSL) at DLR, Berlin, for a range of alkaline basalt and calcite and/or anhydrite mixtures (50% or 10% basalt) with grains sizes of 250-300 µm or 300-355 μm. A basalt slab and a glass made from the basalt were also measured. The results of this work show that the presence of alteration materials does lower the emissivity of the basalt following a nonlinear relationship between mixture proportions and emissivity value. Distinguishing mixture proportions of basalt to alteration products is difficult given a lack of distinct features in the six observable bandwidths. However, these mixtures have emissivity values distinct from both felsic and unaltered basalt rocks.

In our laboratory, X-ray diffraction (XRD) analyses are routinely conducted on samples with masses of only a few milligrams, often containing amorphous components, which need to be preserved in an uncontaminated state for subsequent additional analyses. Conventional sample preparation methods, such as dusting powder onto glass slides or onto a flat zero-background holder (ZBH) using vacuum grease or adhesive tape, were not suitable, due to the resulting amorphous background and the risk of sample contamination. Likewise the ZBH without vacuum grease proved ineffective, as it could not retain the powder while tilting the sample in the θ–2θ diffractometer. In the absence of a capillary measurement system, a grazing-incidence X-ray diffraction (GIXRD) approach was implemented. The geometry includes a rotating sample holder, equatorial Soller slits, and a flat graphite monochromator. The sample was gently sprinkled on an ungreased ZBH and incidence angles ranging from 0.5° to 3° were evaluated. The clean ZBH proved capable of retaining the sample when rotated at 10 rpm. A relatively large divergence slit (0.3°) was employed to maintain a reasonable analysis time (6 seconds acquisition per 0.03° step in 2θ). The method is demonstrated here through its application to mineralized deposits above the water line in a high-pressure reactor where the reaction of crushed basalt with CO₂-enriched water and a head-space of supercritical CO₂ was investigated after 30 days at 150 °C and 70 bar.

Post-mining environments are complex systems where geological, hydrological, ecological and infrastructural processes interact across different spatial and temporal scales. Their monitoring requires methods capable of capturing spatial heterogeneity, temporal change and material-specific information. Spectral sensing technologies, including UAV-based multispectral imaging, VNIR hyperspectral sensing in the 500–1000 nm range, field observations and complementary thermal measurements, offer new opportunities to support smarter monitoring strategies in landscapes shaped by mining legacies.

This contribution explores different post-mining scenarios, including mine-affected waters, exposed mineral surfaces, mine residues, vegetation patterns and corrosion phenomena on industrial heritage structures. By combining UAV observations with calibration targets, in-situ measurements and complementary environmental or geochemical information, the research aims to improve the interpretation of spectral and spatial patterns in complex post-mining settings.

A central focus is placed on the development of reproducible preprocessing and quality-control frameworks, including dark current correction, empirical line calibration, spectral smoothing, reflectance validation and metadata documentation. These workflows are being implemented as open and reusable processing tools, including a publicly available GitHub repository, to transform raw sensor data into comparable products across sensors, sites, acquisition campaigns and environmental conditions.

The contribution discusses both the challenges and opportunities of spectral sensing technologies for smart post-mining monitoring, highlighting their potential to connect field-scale observations, environmental interpretation and decision-support. In this way, spectral sensing can contribute to more systematic, reproducible and application-oriented monitoring of post-mining environments.

This study utilizes high-resolution airborne hyperspectral imagery from NASA’s Next Generation Advanced Visible/Infrared Imaging Spectrometer (AVIRIS-NG) to map the environmental impact of the Rio Tinto mining district in southwestern Spain. As a world-class polymetallic sulfide deposit with a mining history spanning millennia, the region is characterized by extensive sulfide-bearing waste, tailings, and flooded pits. These materials generate severe acid mine drainage (AMD), making the Rio Tinto River one of the most acidic and metal-polluted fluvial systems globally. To characterize this contamination, AVIRIS-NG radiance data were processed into surface reflectance using the Fast Line-of-sight Atmospheric Analysis of Hypercubes (FLAASH) model. Spectral mixture analysis was subsequently employed to identify secondary minerals, which exhibit diagnostic reflectance features caused by electronic and vibrational transitions in iron, water, and hydroxyl groups. The analysis successfully mapped a diverse suite of minerals, including jarosite, goethite, hematite, melanterite, rozenite, copiapite, and gypsum, alongside metal sulfate hydrates, sericite, and kaolinite. Results indicate that acid waters are prevalent in tailings ponds and the main river channel. Jarosite, goethite, and hematite were identified as the dominant indicators of active AMD generation across waste-covered areas. Additionally, the detection of ephemeral minerals like melanterite and its dehydration product, rozenite, provides specific insights into localized geochemical conditions. These high-fidelity mapping results offer a comprehensive spatial overview of mineralogical indicators, providing a critical baseline for environmental monitoring and the remediation of fluvial networks impacted by historical and modern mining activities.