Artifacts made of durable materials, such as stone, can provide valuable clues to reconstruct the past. Marble sourcing, in particular,provides information about contact, trade, and other activities in the greater Mediterranean area. The Worcester Art Museum of Massachusetts (WAM) initiated a provenance study by requesting that an analysis of several marble artifacts occur at the University of South Florida's Archaeological Science Laboratory. The 55 marble samples used in this study are from the Worcester Art Museum's collection of Antioch mosaics. Positive results might reveal: 1) preferred sources of tesserae, 2) information about trade of specialized stone, 3) changes in preferred sources during different chronological periods, and 4) workshop preferences. The requested analysis had two objectives. First, once the provenance of the materials is determined, then the results could reveal meaning behind the images contained within the mosaic floor. Second, the results could reveal new trade routes in the Mediterranean. The first step in this analysis was X-ray diffraction (XRD),which differentiates dolomite and calcite marbles. The second step used stable isotope ratio analysis (SIRA), which measures carbon-13 and oxygen-18 isotopic ratios. These two steps have helped to identify Mediterranean marble sources in previous studies. Most of the ancient Mediterranean marble sources have been identified. They have different isotopic values and other characteristics that allow for differentiation. Only one source of dolomite marble exists, which is located in the eastern Mediterranean. It has been identified through XRD in previous studies. Many of the calcite marble sources have different carbon and oxygen isotopic values, which were provided from the SIRA. Those marble artifacts with overlapping carbon and oxygen values can be further analyzed using archaeological, historical, and other information and by using other scientific techniques including cathodoluminescence, electron paramagnetic resonance, and strontium isotope analysis. This thesis discusses the methods used to prepare the samples and analysis conduction; it also discusses the results of the analyses, and presents interpretations regarding the provenance and trade of the marble used for mosaics at Antioch. The results of the SIRA and XRD analysis showed that the materials used for mosaic tesserae come from a variety of sources. Although no definitive matches were found, the results provide the basis for the collection of a colored marble database of sources and artifacts.

La tesi indaga la produzione e la messa in opera delle tessere musive e dei sectilia parietali in paste vitree in epoca tardoantica e altomedievale, studiando in particolare il caso di Milano. Nella prima parte viene esaminato il processo di produzione del vetro musivo, poco noto nella documentazione edita, ma estremamente fecondo per la ricostruzione degli scambi commerciali e culturali del periodo esaminato. Con vari strumenti (etnoarcheologia, ricettari, analisi archeometriche, resti archeologici, fonti economiche, stime quantitative, documentazione di restauro) vengono rintracciati gli indicatori di riconoscibilità di un atelier che produce piastre musive colorate e a foglia d’oro, i marker di cronologia, provenienza e tecnologia ottenibili dalle analisi chimiche sul vetro musivo e l’esito materiale dei gesti eseguiti da chi mette in opera rintracciabili sui frammenti. Nella seconda parte sono affrontate le problematiche specifiche del caso milanese. In particolare viene riconsiderata l’ipotesi dell’esistenza di una bottega milanese per la realizzazione e la posa di tessellata vitrea. A fronte di una bibliografia contraddittoria sulla datazione e il contesto culturale in seno a cui sarebbero nate queste competenze, vengono valutati i resti archeologici di decorazioni musive parietali (lacerti e tessere sciolte) e vengono caratterizzati con analisi archeometriche. Viene così determinata la diffusione dell’arte, contestualizzato quanto ancora conservato e stabilito quali apporti commerciali e culturali ha comportato la realizzazione dei mosaici milanesi. I resti archeologici, le fonti letterarie, le attestazioni iconografiche, le analisi archeometriche, pur nella loro difficile lettura, permettono di riconoscere tre momenti di diffusione dell’arte musiva: l’età tardo-imperiale, l’età gota e i secoli finali dell’altomedioevo. Per ogni periodo vengono analizzati tre casi significativi: la basilica di San Lorenzo (fine IV-inizi V sec.), il battistero di San Giovanni alle Fonti (fine V-VI sec.) e la basilica di Sant’Ambrogio (V-VI e X sec.). La ricerca contribuisce a diverse problematiche aperte: la tecnologia del vetro, gli elementi di continuità e innovazione rispetto alle tecniche romane, la decorazione parietale dei monumenti milanesi, le scelte dei committenti che hanno finanziato gli edifici, l’investimento necessario, le relazioni intraprese per realizzare le opere. / The thesis studies the production and layout of wall mosaic tesserae and of glass paste sectilia in late antique and early medieval times, focusing in particular on the case of Milan. The first part examines the productive process of glass mosaics to reconstruct the commercial and cultural exchanges of the studied period. Different tools (ethnoarchaeology, technical recipes, archaeometric analyses, archaeological remains, economic sources, quantitative estimates, restoration reports) are used to track the indicators of a workshop producing coloured and gold-leaf mosaic plates, to identify the markers of mosaic glass history and technology from chemical analysis, and to detect the material results on the remains of the actions performed by the craftsmen. The second part investigates the specific issues of the case of Milan. In particular, it reconsiders the hypothesis of the existence of a Milanese workshop that manufactures and lays out glass tesserae, approached so far in a contradictory literature in term of chronology and cultural framework. The archaeological remains, literary sources, iconographic testimonies, and archaeometric analyses, despite their difficult interpretation, allow identifying three stages of diffusion of mosaic art in Milan: the late Imperial age, the age of the Goths, and the final centuries of the Early Middle Ages. Three significant cases are analyzed for each of these periods: the Basilica of San Lorenzo (late 4th-early 5th c.), the baptistery of San Giovanni alle Fonti (end 5th-6th c.) and the Basilica of Sant’Ambrogio (5th-6th and 10th c.). This research contributes to the state of several open questions: the technology of glass, the preserved or innovative features with respect to Roman techniques, the mural decoration of Milanese buildings, the choices of the customers who have financed the buildings, the investment required, the social and commercial relations established in order to carry out the works.