Exploring grain sizing of sedimentary calcareous rocks using Raman spectroscopy

In the present work, the intensity variations of the Raman signal and associated background intensities of calcareous materials as a function of their grain sizes has been investigated. According to previous literature studies, the present work shows that Raman signal and associated background intensities contain information on the average grain size of the calcareous rock under investigation, and for the first time, it explores the possibility to achieve corresponding quantitative data. The availability of a method which can allow extracting quantitative information on the average grain size from Raman spectra could be very useful for quick assays along the whole lime production chain. To explore this possibility, a set of sedimentary calcareous rock samples from various Italian quarries were petrographically classified and then subjected to Raman spectroscopy (785 nm), along with corresponding pellets and crystalline calcite powder samples. A repeatable behaviour of the Raman signal and background intensities on grain and particle sizes were achieved, and hence, the possibility to derive semi-quantitative information on the latter from the measurement of the former was demonstrated. The encouraging results achieved can be exploitable in the field of the lime industry, as well in a variety of scientific contexts and other material production chains.