Pedra Cabaleira: Characterisation of a Vernacular Building Stone from the Courel Mountains UNESCO Global Geopark

This paper presents the characterisation of Pedra Cabaleira, a historically significant vernacular building stone from the Courel Mountains UNESCO Global Geopark (UGGp), Spain. Pedra Cabaleira presents a noticeable lithological and aesthetic contrast with the predominant lithologies in this UGGp in northwestern Spain. This stone has been historically used in religious and military buildings associated with the Order of Saint John of Jerusalem. This research aims to characterize the mineralogical, petrographic, and petrophysical properties of the stone to contribute to its valorisation as a significant vernacular building material in the context of the Courel Mountains UGGp. Field surveys identified three main lithotypes: a conglomerate (PC-1), a breccia (PC-2), and sandstone beds with intercalated clay-rich layers (PC-3). Analytical techniques included X-ray diffraction, optical petrography, scanning electron microscopy (SEM), mercury intrusion porosimetry, hydric properties, mechanical strength, and salt weathering tests, which revealed significant variations among these lithotypes. The results indicate that the conglomerate and the sandstone beds show the most favourable parameters for construction, with lower microporosity, higher strength, and better durability, while the clay-rich layers within the sandstone show weaker mechanical performance and higher susceptibility to weathering. The study highlights the interplay between geological heritage and built heritage, demonstrating the importance of locally sourced building materials in sustaining historical structures and promoting geotourism in the Courel Mountains UGGp and the potential of this stone to become a Heritage Stone.