Twenty glass samples collected from four structures at Umm el-Jimal, northeast Jordan were analysed using the Electron Probe Micro-Analysis (EPMA). Except one ash-soda-lime-silica glass, all were natron-soda-lime-silica glasses of Levantine origin. Most of the glasses compositionally resemble glass from the Byzantine tank furnaces at Apollonia-Arsuf (Arsuf), but four with lower lime are closer to Umayyad period production at Bet Eli’ezer (Hadera). The paper presents diagnostic information indicating recycling in a Diagnostic Recycling Table (DRT) in which the analyses are ranked in a descending order of K2O, a key contaminant in the recycling process. This allows the comparison of a range of contaminant elements and it is observed that in general glass contaminated with fuel ash components K2O, P2O5 and CaO are also richer in transition metal oxides CuO, PbO, FeO and MnO, confirming that both sets of elements are important in identifying recycled glass. Chlorine is also identified as a component modified by recycling. The results ascertain that Umm el-Jimal was part of a major system of glass recycling in the Byzantine period, and emphasise the importance of recycled glass in its supply, in spite of its relative proximity to the location of raw glass production on the Syro-Palestinian coast
