BYZANTINE GLASS MOSAICS EXCAVATED FROM THE “CROSS CHURCH”, JERASH, JORDAN: AN ARCHAEOMETRICAL INVESTIGATION

Abstract

The finding of considerable remains of glass mosaic floors, together with great stone mosaic floors dated back to Byzantine period ( 6th to 7th century A.D) from the Cross Church at the Jerash/Jerasa archaeological site in northern Jordan represented a strange phenomenon (glass mosaic). The chemical analysis of ancient glass mosaic tesserae can provide important information regarding the manufacturing technology of the glass mosaic made during a specific period. The aim of this study is to characterize the chemical and technological aspects of Byzantine glasses excavated from this main archaeological site. For this purpose, a considerable group of glass tesserae of different colours were collected and analyzed by XRF spectroscopy. XRD spectroscopy was used to identify the crystalline phases of glass tesserae and mineralogically to characterize the underlying lime mortar. All samples were investigated by optical microscopy. The results of chemical analyses indicated that the glass tesserae show a clear difference in chemical composition. The majority of the glass tesserae are compositionally homogeneous and belongs to the so-called natron-based silica–soda–lime glass type, whereas some samples are of relatively high level content of lead and aluminium. The tesserae colorants and opacifiers also are varied. Microscopic examination show obvious formal differences among glass tesserae samples.