Thermal shock from high temperatures and prolonged heat exposure can cause irreversible damage to natural stones, underscoring the need for thorough characterisation. This study examines the effects of thermal exposure at 300 °C and 600 °C, temperatures simulating moderate and high thermal shock, on thirteen carbonate lithologies, including limestones, marbles, travertine, and breccia. Key surface properties, colour, gloss, and roughness, are evaluated to quantify aesthetic impacts and understand the underlying chemical and mineralogical processes. FeO-richer stones show significant increases in the a* coordinate (up to Δa* = +34.37) at 300 °C, driven by the transformation of goethite into hematite. In contrast, stones richer in organic matter exhibit marked decreases in lightness (up to ΔL* = −18.78) at 600 °C, due to the transformation of amorphous organic matter into crystalline phases. Porosity plays a critical role at higher temperatures, correlating with higher ΔL* values, since more porous stones enhance heat transfer and promote the combustion of organic matter. Lightness is influenced by both gloss and surface roughness, with gloss having a more pronounced effect on L*. Statistical analyses, including Tukey’s HSD test, reveal significant differences in stone responses to thermal shock, highlighting their varying degrees of thermal susceptibility. Principal Component Analysis (PCA) identifies colour as the main driver of variability, followed by gloss and roughness. These findings provide a predictive framework for assessing the thermal vulnerability of carbonate stones in relation to their residual composition and texture. Such insights support informed decisions in material selection, conservation strategies, and architectural design, thereby enhancing the long-term durability of natural stones in both heritage and contemporary contexts.
