Portable and Benchtop Micro-Raman Spectrometer for Organic Matter Characterization in Rocks: A Comparative Study

Recent technological advances have produced miniaturized, portable Raman spectrometers, enabling direct field analysis, even under challenging conditions or on samples that cannot be removed from the original site, such as confined artifacts or monuments. This study comparatively analyzed portable and high-resolution Raman spectrometers for organic matter (OM) and mineralogical characterization of bulk outcrop rock and thin-section samples from the Tamengo and Bocaina Formations of the Corumbá group in Mato Grosso do Sul, Brazil. The results demonstrate that, despite differences in spectral sensitivity and spatial resolution, the portable Raman spectrometer provides representative average spectra of heterogeneous rock surfaces that are consistent with the average of a spectral map obtained from high-resolution micro-Raman mapping over equivalent areas. Nevertheless, weak or very weak bands are not detectable using a portable instrument. These findings confirm the feasibility of a portable Raman instrument for rapid in situ geological investigations, especially for the preliminary characterization of OM and minerals; however, they underscore the necessity of high-resolution micro-Raman spectrometers for detailed characterization of those samples.