Transitions in Islamic plant-ash glass vessels: on-site chemical analyses conducted at the Raya/al-Tur area on the Sinai Peninsula in Egypt

This study focuses on the chemical composition of Islamic plant-ash glass (dated from the 9th to 11th centuries) excavated from the Raya/al-Tur area on the South Sinai in Egypt. Plant-ash glass objects from the Raya site were classified into three compositional types based on on-site chemical analyses with a portable X-ray fluorescence spectrometer. Based on typological characteristics and chemical composition comparisons with contemporary glass objects from other Islamic sites, one hypothesis holds that plant-ash glass objects produced in the Syria–Palestine or Mesopotamian regions could have been imported to Raya during the 9th to 10th centuries. In particular, some colorless glass vessels with a high magnesium/calcium ratio were noted to exhibit post-Sassanian cut decorations. Conversely, most of the bluish-green plant-ash glass objects from the Monastery of Wadi al-Tur near the Raya site exhibited relatively high levels of aluminum, titanium, iron, and lead. These pieces were likely produced during the Fatimid period (late 10th to 12th centuries), and based on their elemental composition, possibly originated in Egypt. The present work provides a greater understanding of chronological changes in post-9th century Islamic plant-ash glasses and the development of social and commercial networks within the Middle Eastern area.