The study of glass from the eastern Mediterranean, south Caucasus and east Africa in the late 8th–14th centuries AD: an interdisciplinary approach

This study aims to increase our understanding of middle Byzantine, early Islamic, medieval Georgian and east African glasses in the late 8th – 14th centuries AD using typological, archaeological and scientific approaches. Using EPMA-WDS, 164 glass samples were selected for the chemical analysis: 113 samples come from al-Raqqa in Syria including 76 from the site of Tell Zujaj, 19 from Tell Abu Ali and 17 from Tell Fukhkhar; 9 samples come from Tbilisi in Georgia; 15 samples come from the Pantokrator Church (Zeyrek Camii) in Istanbul; 2 samples from Fustat; 5 samples from Pemba Island in Zanzibar; 6 samples from al-Qadisiyya in Samarra, Iraq; and 14 samples from al-Mina in northern Syria. The results show that natron glasses continued to be used in al-Raqqa, al-Mina in northern Syria and Tbilisi in Georgia during the late 8th – 10th centuries AD. At the same time, four types of plant ash glasses appeared and produced in northern Syria, Egypt, Iraq and Iran: (1) low MgO-high Al2O3 glasses; (2) high MgO-low Al2O3 glasses; (3) low Al2O3-CaO glasses; (3) low Al2O3-MgO-high CaO glasses. By the 11th – 12th centuries AD, plant ash glasses spread from the Middle East to the Byzantine heartland of Turkey, where a type of plant ash glass from Syria, Israel and Lebanon was found in this study, along with mixed natron-plant ash glasses. This study also shows that high alumina glasses from South-East Asia and East Africa were found in Tbilisi in Georgia and Pemba Island in east Africa. Finally, using typological, archaeological and scientific approaches, this study shows that the demise of the natron glass industry and the rise of the plant ash glass industry in the Middle East was deeply affected by the political and economic conditions during the late 8th – 14th centuries AD