Yellow tuff in ancient Pompeii: Implications for construction materials and supply dynamics

The provenance and supply dynamics of building stones represent key issues for understanding construction practices, economic organisation, and resource circulation in the Roman world. In Pompeii, the widespread use of Phlegraean yellow tuff has long raised questions concerning its geological source and procurement system, particularly because of the difficulty in distinguishing between the Neapolitan Yellow Tuff (NYT) and the yellow facies of the Campanian Ignimbrite (CI-LYT). To address this, 50 tuff samples collected from 40 archaeological contexts in Pompeii, spanning both pre- and post-62/63 CE earthquake building phases, were investigated through an integrated analytical approach combining digital and optical microscopy, quantitative X-ray powder diffraction, thermal analysis, vibrational spectroscopy coupled with multivariate statistical analysis, and FESEM-EDS microchemical characterisation of juvenile-clast groundmass glass. The investigated materials exhibit marked textural and mineralogical variability, reflecting differences in depositional facies and post-depositional alteration. Nevertheless, groundmass glass compositions display a geochemical signature that closely matches that of the Neapolitan Yellow Tuff, identifying it as the dominant source of the building stones employed in Pompeii, regardless of chronology or architectural function. These results support a supply-driven procurement model based on the systematic exploitation of NYT deposits and their efficient distribution through the integrated transport network of the Bay of Naples. The extensive use of yellow tuff therefore reflects broader economic, logistical, and organisational strategies that shaped construction activities and resource management in Roman Pompeii.