Early Islamic glass (7th- 10th centuries AD) in Unguja Ukuu, Zanzibar: A microcosm of a globalised industry in the early 'Abbasid period.

Eighty-two glass vessels, recovered from the excavations at the ancient Swahili settlement and port of Unguja Ukuu in Zanzibar, Eastern Africa, were analysed using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The results show that all of the glass samples are soda-lime-silica glass. Fifteen glass vessels belong to the natron glass type and are characterised by low MgO and K2O (<1.50%), suggesting they were made from natron, a mineral flux that was widely used during the Roman period and Late Antiquity. Sixty-seven glass vessels belong to the plant ash glass type, characterised by high magnesia and potash levels (>1.50%), suggesting plant ash was the main alkali flux. Based on the major, minor and trace elements, three different compositional groups were identified for the natron glass and three were identified for the plant ash glass: (1) UU Natron Type 1, (2) UU Natron Type 2, (3) UU Natron Type 3, (4) UU Plant ash Type 1, (5) UU Plant ash Type 2 and (6) UU Plan ash Type 3. Comparison with contemporary Middle Eastern glass groups shows that UU Natron Types 1, 2 and 3 correspond to Egypt II high Na2O, Levantine I and Levantine II respectively, while UU Plant ash Type 1 matches closely with Samarra Group 2. UU Plant ash Types 2 and 3 have unique chemical fingerprints that do not match any of the contemporary plant ash glass groups, but their chemical compositions show some affinity with the old Sassanian plant ash glass, suggesting a possible Mesopotamian provenance. Combined with existing research on early Islamic glass, the authors reveal a complex trading network in the globalisation of Islamic glass, particularly involving glass corresponding to modern Iraq and Syria, in the 7th- 9th centuries AD.

Connected in diversity: Isotopic analysis refines provenance for Islamic plant-ash glass from the eastern Silk Roads.

Our understanding of glass production in Eurasia has been built mostly on evidence from Europe and the Mediterranean. Here, we investigate the occurrence and organization of plant-ash glass production in the eastern continental Islamic region, focusing on an 11th-12th century assemblage unearthed in Shadyakh, Nishapur, Iran. Through Sr-Nd isotope analysis and by examining geochemical contexts and mixing patterns, we find that distinct silica and ash sources originating from Tigris-Euphrates Basin, Central Asia, and potentially Iran were used to make these objects. Zagros-derived silica and Central-Asian-type silica were likely important silica sources for Islamic plant-ash glasses from east of the Tigris. Furthermore, we show that Central Asian glass can be characterized by chemical and isotopic signatures, while Iranian glass may exhibit overlapping signatures with glass from neighboring regions. The plant-ash glass industry in Islamic-period West and Central Asia likely thrived by exploiting and sharing diverse, regionally characteristic raw material sources.

Natron glass beads reveal proto-Silk Road between the Mediterranean and China in the 1st millennium BCE.

Natron-based glass was a vital part of material culture in the Mediterranean and Europe for nearly two millennia, but natron glass found elsewhere on the Eurasian Continent has not received adequate discussion, despite its influence on ancient Asian glass. Here we present a new interpretation of natron glass finds from both the West and the East. After establishing the compositional types and technological sequence of Mediterranean natron glass (eighth-second century BCE) using trace elements, we report the analysis of a mid-1st millennium BCE glass bead from Xinjiang, China, which was likely made with Levantine raw glass, and identify common types of stratified eye beads in Eurasia based on a compositional and typological comparison. Combining these findings, we propose that a considerable number of Mediterranean natron glass products had arrived in East Asia at least by the fifth century BCE, which may have been a contributing factor in the development of native Chinese glass-making. The swift diffusion of natron glass across Eurasia in the 1st millennium BCE was likely facilitated by a three-stage process involving maritime and overland networks and multiple forms of trade and exchange, indicating a highly adaptable and increasingly efficient transcontinental connection along the 'Proto-Silk Road'.

New light on plant ash glass found in Africa: Evidence for Indian Ocean Silk Road trade using major, minor, trace element and lead isotope analysis of glass from the 15th-16th century AD from Malindi and Mambrui, Kenya.

Seventeen glass vessels and twenty glass beads recovered from the excavations at the ancient city of Malindi and the archaeological site of Mambrui in Kenya, east Africa were analysed using electron probe microanalysis (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The results show that all of the glass samples are soda-lime-silica glass. They belong to the high alumina -plant ash glass type, characterised by high alumina and relatively low calcium contents, widely distributed in eastern (10th- 16th centuries AD) and southern Africa (13th - 15th centuries AD), Central Asia (9th- 14th centuries AD) and southeast Asia (12th- 13th centuries AD), made with plant ashes and sands. This is an understudied glass type for which previous research has indicated there were three types. When compared with published research on such glasses using Zr, Ti, Ba, Cr, La, Li, Cs, Na2O, MgO and CaO we have identified at least four different compositional groups of v-Na-Al glass: Types A, B, C and D. By comparing the results with contemporary v-Na-Al glass vessels and beads from Central Asia, Africa, and southeast Asia we show that most of the Malindi and Mambrui glass share similar characteristics to the compositions of Mapungubwe Oblate and some of the Madagascar glass beads from southern Africa. They belong to Type A v-Na-Al glass which is characterised by an elevated level of Ti and Ba and a relatively high ratios of Cr/La, relatively low Zr concentrations and low ratios of Zr/Ti. Differences in Zr, Li, MgO and Na2O concentrations in Type A glass indicates that there are subgroups which might derive from different glass workshop(s) specialising in Type A v-Na-Al glass production. Comparison with the chemical compositions of glass from Ghazni, Afghanistan and Termez, Uzbekistan, and by using lead isotope analysis, we suggest v-Na-Al glass was manufactured in Central Asia and possibly worked into vessels and beads there.

Structure of Ancient Glass by 29 Si Magic Angle Spinning NMR Spectroscopy.

29 Si magic angle spinning (MAS) NMR spectroscopy has been applied for the first time to the structural analysis of ancient glass samples obtained from archaeological excavations. The results show that it is possible to establish the distribution of Si environments in ancient glass by 29 Si MAS NMR, so long as the concentrations of magnetic impurities, such as Mn and Fe oxides, are low. In general, good agreement has been obtained with compositions determined by means of electron probe microanalysis. In addition, the 29 Si MAS NMR data reveal structural differences between glasses manufactured at separate ancient sites.

Tradition and experiment in first millennium a.d. glass production--the emergence of early Islamic glass technology in late antiquity.

Following a brief history of analytical research into ancient glasses, the emergence of early Islamic glasses in the Middle East in late antiquity is discussed. Data sets for Roman and Byzantine glasses are compared to those of the early Islamic period. This is a rare period of technological transition when responses to the "drying up" of the traditional mineral alkali source resulted in experimentation, which can be demonstrated analytically.