Diffuse Reflectance Infrared Spectroscopic Characterization of the Soft Stone of the Berici Hills (Vicenza, Italy) and Classification of Its Main Varieties Using Multivariate Analysis

In this work, the Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectra of 30 specimens of Soft Stone of the Berici Hills (Vicenza, Italy) are analyzed by multivariate tools to characterize their different varieties. This calcareous material shows different characteristics regarding colour, hardness, and type and quantity of included fossils that led to various denominations and classifications. By performing a Principal Component Analysis in the 900–1220 cm−1 spectral range, four main groups could be identified in the dataset investigated: Oligocene stones (White and Coloured Vicenza) and Eocene ones (Yellow and Grey Nanto-like, and Nanto p.d.). The spectral features due to the non-carbonate content of the samples (in particular those of quartz, montmorillonite, kaolinite and sanidine) are discussed and employed to characterize the different groups. An appropriate characterization of the three most represented groups is then proposed by means of a Soft Independent Modelling of Class Analogy (SIMCA). This model also proved useful to get information on the samples left out (the Nanto p.d. sample and the five with hybrid characteristics, Grigio Alpi and Pietra del Mare).