Glass groups, glass supply and recycling in late Roman Carthage

Abstract

Carthage played an important role in maritime exchange networks during the Roman and late antique periods. One hundred ten glass fragments dating to the third to sixth centuries CE from a secondary deposit at the Yasmina Necropolis in Carthage have been analysed by electron microprobe analysis (EPMA) to characterise the supply of glass to the city. Detailed bivariate and multivariate data analysis identified different primary glass groups and revealed evidence of extensive recycling. Roman mixed antimony and manganese glasses with MnO contents in excess of 250 ppm were clearly the product of recycling, while iron, potassium and phosphorus oxides were frequent contaminants. Primary glass sources were discriminated using TiO 2 as a proxy for heavy minerals (ilmenite/spinel), Al 2 O 3 for feldspar and SiO 2 for quartz in the glassmaking sands. It was thus possible to draw conclusions about the chronological and geographical attributions of the primary glass types. Throughout much of the period covered in this study, glassworkers in Carthage utilised glass from both Egyptian and Levantine sources. Based on their geochemical characteristics, we conclude that Roman antimony and Roman manganese glasses originated from Egypt and the Levant, respectively, and were more or less simultaneously worked at Carthage in the fourth century as attested by their mixed recycling (Roman Sb-Mn). In the later fourth and early fifth centuries, glasses from Egypt (HIMT) and the Levant (two Levantine I groups) continued to be imported to Carthage, although the Egyptian HIMT is less well represented at Yasmina than in many other late antique glass assemblages. In contrast, in the later fifth and sixth centuries, glass seems to have been almost exclusively sourced from Egypt in the form of a manganese-decolourised glass originally described and characterised by Foy and colleagues (2003). Hence, the Yasmina assemblage testifies to significant fluctuations in the supply of glass to Carthage that require further attention.

Comprehensive Chemical Characterisation of Byzantine Glass Weights

“…The low levels of manganese support a sixth- to seventh-century date for these glasses, because earlier Levantine I assemblages typically contain higher quantities of manganese (e.g. [9, 17, 20, 21, 52, 54–56]). In fact, a substantial number of Byzantine glass weights with a Levantine I composition can be dated to the late sixth and early seventh century CE based on their inscriptions and design (S1 Table).…”

“…Foy-2 as here defined corresponds to the Foy-2 group from Carthage [20] and includes série 2.1 and série 3.2 as originally described by Foy and colleagues [17]. This type of glass has since been variably re-branded HLIMT [55], weak HIMT [57], and HIMT 2 [53, 58].…”

“…This type of glass has since been variably re-branded HLIMT [55], weak HIMT [57], and HIMT 2 [53, 58]. However, it has recently been shown that an association of Foy-2 with HIMT glass is misleading [20, 55, 59–61]. We therefore refer to this group as Foy-2.…”

“…Two Levantine groups (Levantine I & II) tend to have relatively high alumina and lime concentrations, while they are lower in heavy minerals compared to Egyptian glasses (Egypt I & II) (for a comprehensive discussion of the chemical characteristics of these groups see [16]). Even higher quantities of iron, titanium and zirconium oxides characterise the so-called Foy-2 and HIMT ( H igh I ron, M anganese and T itanium) glasses that are believed to have likewise been produced from an Egyptian silica source [15, 17–20]. Large primary glassmaking furnaces have been discovered in Egypt [13] and on the Levantine coast [11, 21], but only the Levantine groups could be unequivocally related to these sites due to the archaeological remains.…”

A Mosaic of Colors: Investigating Production Technologies of Roman Glass Tesserae from Northeastern Italy

“…The reduced compositions are then compared against literature compositional groups for the period of interest; in particular, the main compositional groups dominating the Roman period (1st-3rd century AD) are Sb-colorless, Mn-colorless, Sb/Mn colorless, and unintentionally colored glass. They differ in antimony and manganese contents, being Sb-colorless characterized by high antimony content (Sb 2 O 3 = 0.81 ± 0.16 wt %) and no manganese, Mn-colorless by very high manganese (MnO = 1.41 ± 0.27 wt %) and no antimony, Sb/Mn colorless glass by the presence of both manganese (MnO = 0.41 ± 0.16 wt %) and antimony (Sb 2 O 3 = 0.43 ± 0.15 wt %), and unintentionally colored glass by generally low manganese (MnO < 1 wt %) and negligible antimony [37][38][39]. In addition to different ratios of manganese and antimony, which are not considered in the reduced compositions, the other key characteristics of these groups are the different contents of SiO 2 , Na 2 O, CaO and Al 2 O 3 [37,39]: Sb-colorless glass is characterized by high silica and soda (SiO 2 : 69 ÷ 73 wt %; Na 2 O: 18.5 ÷ 20.5 wt %) and low lime and alumina (CaO: 4 ÷ 5.5 wt % and Al 2 O 3 : 1.6 ÷ 2.2 wt %), Mn-colorless and unintentionally colored glass by low silica and soda (SiO 2 : 67 ÷ 71 wt %; Na 2 O: 14.5 ÷ 17 wt %) and high lime and alumina (CaO: 7 ÷ 9. wt % and Al 2 O 3 : 2.5 ÷ 3 wt %), and Sb/Mn colorless glass by intermediate contents of the above elements (SiO 2 : 68.5 ÷ 71 wt %; Na 2 O: 16.5 ÷ 18.5 wt %; CaO: 5.5 ÷ 7 wt %; Al 2 O 3 : 2 ÷ 2.5 wt %).…”