## 1 Introduction  
One of the most important issues in the field of cultural heritage is the characterisation of the materials employed for the realisation of paintings of historical and artistic value, since it can provide information on old technological knowledge, for instance, the painting techniques, the capabilities in the supply and production of pigments from raw materials and ancient community connections [1]. Moreover, the study of materials can also allow detecting possible restoration or conservation works, or in some cases, can even provide information on dating and/or authenticity of the artwork [2, 3]. In this context, the application of suitable archaeometric methodologies, aimed at the comprehensive characterisations of pigments and binders used for the realisation of the wall paintings, is of major relevance; indeed, the chemical characterisation of the materials, joined with the information gathered from historical and archaeological studies, can be both the starting point to reach a complete understanding of the piece of art, and more in general, a precious tool available for the art conservators for restoration work. In spite of the numerous studies having as a topic the characterisation of Roman pigments (about 250 papers in the last 20 years), due to the widespread presence of the Roman empire and also the fact that new sites keep coming to light, the investigation of the pigments and of the artists' palettes employed in Roman wall paintings is still an issue of great interest, as also witnessed by the papers published in particular during the last two years. The aim of the present study was the identification of the pigments used to decorate some destroyed Roman building walls, discovered between the Claudio Marcello and the Porta Latina streets in Rome (Monte d'Oro) within a private property. The fragments were rescued in 2013 by the Soprintendenza Archeologica di Roma together with a great number of ceramic shards dating mainly between the 1 st and 2 nd centuries A.D. Unfortunately, the wall painting and stucco fragments, and the pottery, cannot be related to any visible ancient building (probably destroyed in the 1950s) in the surroundings and are therefore to consider contextless. The fragments were in fact collected in a modern pipe trench nearby a private house, where the owners probably tried to hide archaeological material found somewhere in their property. Additionally, for this information gap, the analyses were important to obtain some further data to confirm or disappoint the archaeological interpretation. In the present study, the investigation was carried out on twelve samples chosen within all recorded colour and painting/stucco types (listed in Table 1), dating approximately between the 1 st century B.C. and the 1 st century A.D. The combined use of elemental analysis techniques together with spectroscopic ones represents the methodological approach which is commonly applied to fulfil the comprehensive characterisation of samples, such as Roman frescoes [4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14]. Scanning electron microscopy equipped with an energy dispersive X-ray detector (SEM-EDS), Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) techniques have been employed to establish the painting technique used to decorate the fragments. Among the analytical techniques implemented during this measurement campaign, it is worth noting that Raman spectroscopy has been successfully applied with both a benchtop device and a more versatile portable Raman spectrophotometer. Furthermore, the remarkable analytical results obtained by the portable instrument were really encouraging from the perspective of the in situ application (i.e., directly on the wall paintings) of this powerful and totally non-destructive technique. Among non-destructive measurements, visible reflectance analyses have also been performed.