Islamic glass weights from Egypt

Forty-five Islamic glass weights from a private collection were analyzed by non-destructive micro X-ray fluorescence spectroscopy (μ-XRF), with the aim of determining whether an evaporite or sodic ash was used as a source for the introduction of the network modifier in the glass batch. Due to inscriptions or legends impressed on the weights, which were used as reference samples for coinage, thirty-five of them can be dated from the Fatimid age, other three might be assigned to the Mamluk age, while the remaining are of unknown date. Seventeen major, minor and trace elements were determined. The obtained results show that the composition of most of the analysed samples is consistent with a production based on the use of sodic plant ash, due to the relatively high contents of K ₂O (between 1.8 and 4.6 wt.%) and MgO (between 1.9 and 3.9 wt.%). Aluminium and calcium contents mainly range between 1.0 and 3.5 wt.% Al ₂O ₃, and between 5 and 11 wt.% CaO, respectively, while FeO and MnO levels do not generally exceed 1 wt.%, apart from deeply coloured items. As for trace elements, strontium and zirconium contents are mainly lower than 400 and 100 ppm, respectively. Two opaque samples of late Fatimid age feature relatively high lead (some 15 and 4 wt.% PbO) and tin contents (some 8 and 16 wt.% SnO ₂).