Through the assistance of trace element and petrographic analyses on 14 samples of mortar aggregates from Roman monuments, including the Porticus Aemilia, the Temple of Concordia, the Temple of the Dioscuri, Temple B and other structures of the Area Sacra di Largo Argentina, and the Villa di Livia, we establish the source area and we investigate the chronological employment of the volcanic materials used in ancient Rome's masonry. In contrast to previous inferences, the petrochemical data presented here show that systematic exploitation of the local ‘Pozzolane Rosse’ pyroclastic deposit has occurred since the early development of concrete masonry, at the beginning of the second century bc, through the early Imperial age. Subsequently, exploitation was extended to the overlying Pozzolane Nere and Pozzolanelle deposits. Only during the early phase of development of the concrete masonry in Rome, volcaniclastic sediments outcropping near the construction sites were mixed with the sieved remains of the tuff employed as the coarse aggregate, to produce the fine aggregate. The results of the study on the investigated monuments suggest the possibility of establishing the chronological identification of three different types of mortars, as a function of the composition of the volcanic material employed in the fine aggregate, which, when implemented by future studies, may contribute to the dating of monuments and archaeological structures.

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We use trace element discrimination diagrams to provide a geochemical fingerprint for Tufo Lionato, the volcanic rock most commonly used in the ancient Roman dimension stone technique. Based on the comparison of their geochemical signatures, we identify different rock facies of Tufo Lionato employed since the fourth to third centuries and through the second century bce in the construction of the temples of the Area Sacra di Largo Argentina. These rock facies correspond to two previously identified building stones: Aniene Tuff and Monteverde Tuff, named after their supposed source areas located in the Aniene River Valley and in the homonymous locality of the Tiber River Valley, respectively. However, the results of our study demonstrate previous misidentification of these volcanic rocks in the different construction phases of Temple C, providing a revision of the dating system currently accepted for the diffusion of Tufo Lionato architecture. We show that the Aniene facies has been exploited since the end of the fourth century bce and that it was employed along with Tufo Giallo della Via Tiberina in the podium and staircase of Temple C, whereas observations at Largo Argentina suggest that the ‘Monteverde Tuff’ was only sporadically used in the early phases of the dimension stone construction technique.

Identification of the volcanic material (pozzolan) stored in a Roman ship of the fourth to third century bce, wrecked in the ancient harbour of Pisa (central Italy), was based on ratios of selected trace elements. The compositions of the major volcanic products erupted by the volcanoes of the Roman province, including the volcanic districts of Latium (Vulsini, Vico, Monti Sabatini and the Alban Hills) and Campania (Roccamonfina, the Phlegraean Fields, Ischia, Procida and Vesuvius) are compared with the pozzolan from the Pisa ship. Superposition of the Zr/Y, Nb/Y and Nb/Zr ratios of the pyroclastic material from the wrecked ship (computed from the published literature) allows correlation with the products of the Onano eruption from the Vulsini Volcanic District. The Vulsini rocks outcrop extensively in a sector drained by the hydrographic network of the Fiora River, which has been a well‐developed commercial water trade route since Etruscan times, with a river port and a sea port connected to the important town of Vulci, and, since 273 bce, part of the larger Roman harbour system of Cosa.

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