Butrint (Albania) between eastern and western Mediterranean glass production: EMPA and LA-ICP-MS of late antique and early medieval finds

In the Late Roman period, the city of Butrint (SW Albania) was one of the most important seaports of the eastern Mediterranean due to its very favourable position and an extended presence of human settlements (from the 5th century BC to the modern age). The city seems to have particularly flourished after being declared a Roman colony under Augustus in 31 BC, but even after the Roman period, Butrint remained a central node in eastern trade routes. During the archaeological campaign of 2011 directed by David Hernandez (University of Notre Dame – US), aimed at identifying the eastern border of the Butrint Roman Forum, several glass artifacts were recovered and dated to the late antique and early medieval period. In this study 33 fragments of glass (32 transparent, 1 opaque) were analysed from different objects (drinking glasses, bowls, etc) mostly dated from the 5th to the 6th centuries AD. The aims of this work are: i) understanding the raw materials, the manufacturing techniques employed for glass production, and their evolution through the time; ii) correctly classifying items of uncertain date; iii) interpreting the economic development and trade models of the area. Chemical analyses were performed by electron microprobe (EMPA) for major and minor elements and by ICP mass spectroscopy (LA-ICP-MS) for trace elements. The chemical results indicate that the samples were produced with natron as fluxing agent. They can be divided, on the basis of the concentrations of Fe, Ti, and Mn, between the two main compositional groups widespread in the Mediterranean from the 4th century onward: HIMT (23 samples), and Levantine I (10 samples). Among the HIMT samples, both “weak” HIMT (13 samples), and “strong” HIMT (10 samples) were identified. This variety of compositions indicates that in Butrint, between the end of the 4th and the end of the 6th century, the glass materials were probably imported from different suppliers