The study of archaeological and architectural geomaterials is fundamental for understanding their origin, composition, degradation processes, and conservation. Recent advancements focus on innovative scientific methods to preserve these materials minimizing damage to artifacts. This work combines two approaches: the application of infrared (IR) spectroscopy for geomaterial characterization and the development of a novel protocol through the use of PCA. IR spectroscopy provides critical insights into mineralogical phases in geomaterials but is often limited by sample complexity, which produce broad and overlapping spectral peaks. Portable IR instruments enable non-invasive, on-site data acquisition, yet their reflectance spectra differ significantly from other modes due to spectral distortions. To overcome these challenges, a chemometric approach is proposed, to detect spectral variations and providing information on raw material, production techniques, and degradation monitoring. Whitin Spoke 5 of PNRR project “CHANGES”, a new protocol is being developed to analyze and interpret geomaterial data. To validate the protocol, various natural and artificial geomaterial samples were exposed to ageing. These were analyzed over time using Fourier transform infrared spectroscopy in external reflection mode (ER-FTIR). ER-FTIR is entirely non-invasive, compared to Attenuated Total Reflectance (FTIR-ATR), and µTransmission (µ-FTIR), making it particularly valuable for Cultural Heritage studies. A multivariate statistical analysis was applied to the spectral data to assess the protocol's efficacy. The comparative spectral analysis also aimed to create a reference database. These advancements improve geomaterials characterization and monitoring, broaden applications in geology and material science, marking a significant step in preserving and understanding Cultural Heritage.