Mortars and stone materials of the Ipogeo di Caivano, a 1st century A. D. funerary monument in the Naples National Archaeological Museum C. Colella, M. de’ Gennaro, O. Marino, M. Colella, P. Cappelletti, A. Colella Centro di Eccellenza “Restituzione computerizzata di manoscritti e di monumenti della pittura antica”, Università Federico II, Napoli Abstract Within a research plan, aiming to obtain a computer-aided restitution of the Ipogeo di Caivano, a funerary monument of Roman age, located in the Archaeological Museum of Naples, this investigation reports the archaeometric characterisation of mortars and stone materials, in view of a restoration project which can not be delayed yet. Through chemical, X-ray diffraction, optical and electronic microscope and thermal analyses of samples, suitably collected from the indoor and outdoor walls of the monument, the constitution of mortars and stone materials was completely disclosed, pointing out, in particular, the composition of the plasters, either under a qualitative or, in some selected cases, also under a quantitative profile (aggregate/binder ratio). It is of particular interest the discovery that dolomite (most probably coming from a deposit in Bellona, Caserta) was used as aggregate in the finishing layer of the indoor plasters, namely the substrate for the pictorial works. Keywords: hypogeum, ancient mortars, aggregates, dolomite, Bellona stone, stone materials. 1 Introduction The Ipogeo di Caivano is a funerary monument, built in the last decades of the 1st century A.D., discovered accidentally in 1923 in the territory of Caivano (some 15 km north of Naples) during some excavation works. Some years later, to preserve the monument from damages of environmental origin and/or vandalism, it was decided to transfer it into the Naples Archaeological Museum. This was made in 1929, when the hypogeum was excavated, sectioned in parts, having care to recover the plasters with frescoes, and reassembled in a courtyard of the museum. To better control the effects of the rising dump and water vapour condensation, the hypogeum, which is partly buried, was isolated from the underlying soil by interposition of a lead plate and laterally by the construction of an air space. Nevertheless, after more than seventy years have passed, the injuries of time are evident, as the monument appears notably damaged. The major problems consist in the detachment of plaster and colour fragments in several points with the irremediable lost of parts of frescoes. Restoration is therefore urgently needed to avoid any further decay. The archaeometric study of the monument and the diagnostics of the damages have been entrusted to the Centro di eccellenza per la restituzione computerizzata di manoscritti e di monumenti della pittura antica