In several Italian archaeological sites, the presence of the so-called emblemata has been attested to the Republican Roman Age (2nd to 1st century B.C.). They are small mosaics made on a stone or terracotta tray using the opus vermiculatum. This particular technique, which originated in Egypt and/or in Greece during the Hellenistic period (3rd century B.C.), uses very small tesserae (of size less than 0.5 cm) producing a pictorial effect. In the literature, this type of mosaic has been studied from a technical approach only for a small group of mosaics from Greece (Delos, Samos and Rhodes island), while for the Italian area, a project on their archaeometrical and archaeological study is in progress. In a few cases, by observing the surface of the mosaics, it was possible to detect the presence of a painting layer on the mortar. This feature was never reported in the literature, probably because the painted details have survived only in traces, and they are visible only by direct observation. A mosaic from Rome (preserved in site, under the church of St. Susanna), was sampled and analyzed by Raman spectrometry, while two vermiculata mosaics from Privernum (LT) were observed in situ by a portable instrument. Thanks to the characterization, it was possible to observe the use of a luxurious palette of pigments, including cinnabar and Egyptian Blue.
Excavations at the Roman villa of Noheda (Spain) revealed the remains of an exceptionally elaborate fourth-century floor mosaic that contains a surprisingly large number of glass tesserae, representing a broad spectrum of colors. This paper presents the results of the chemical (LA-ICP-MS) and microstructural analyses (SEM-EDS, XRPD) of 420 glass tesserae from these mosaics. The high number of data allowed us to establish the compositional variability and to elucidate questions of supply in relation to a large-scale artistic campaign. The tesserae from Noheda were almost exclusively made from recycled mixed Roman Mn and Sb base glass, thus demonstrating that recycling of Roman base glasses was common practice in the fourth century, occurring on a near industrial scale. It also suggests that the workshops specializing in the production of mosaic tesserae might have been in the western Mediterranean. A limited number of coloring and opacifying additives (Mn, Co, Cu, Sb, Pb) were identified, which resulted in a wide range of hues. These were differentially associated with various trace elements, which implies the use of different raw materials. A sub-set of red, green, and orange tesserae reflect distinct base glass characteristics as well as coloring technologies that point to an Egyptian provenance.
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