Zanzibar and Indian Ocean trade in the first millennium CE: the glass bead evidence

Marilee Wood,Peter Robertshaw,Nicole Boivin,Mark Horton,Emilio F Orsega,Johannes T Van Elteren,Alison Crowther,Serena Panighello

doi:10.1007/s12520-015-0310-z

Abstract

Recent archaeological excavations at the seventh- to tenth-century CE sites of Unguja Ukuu and Fukuchani on Zanzibar Island have produced large numbers of glass beads that shed new light on the island’s early interactions with the wider Indian Ocean world. A selected sample of the beads recovered was analyzed by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to determine the origins of the glass used to make the beads and potential trade relationships are considered. The data show that two major glass types can be identified: mineral-soda glass, m-Na-Al, produced in Sri Lanka (and possibly South India) and plant ash soda glass. The latter comprises three subtypes: two with low alumina concentrations and different quantities of lime (here designated v-Na-Ca subtypes A and B) and one with high alumina (designated v-Na-Al). The v-Na-Ca subtype A beads are chemically similar to Sasanian type 1 glass as well as Zhizo beads found in southern Africa, while v-Na-Ca subtype B compares reasonably well with glasses from Syria and the Levant. While the mineral-soda beads were made in South Asia, it appears likely that at least some of the plant ash beads were made in South or Southeast Asia from imported raw and/or scrap Middle Eastern glass. In contrast, during this period, all beads imported into southern Africa were made of Middle Eastern glass from east of the Euphrates (v-Na-Ca subtype A) and appear to have arrived on ships from Oman and the Persian Gulf. These data suggest that the two sections of the African coast were engaged in different Indian Ocean trade circuits.

Highlights

In 2011 and 2012, the Sealinks Project undertook excavations at two archaeological sites on Zanzibar that possess evidence for trade contacts with the wider Indian Ocean world in the second half of the first millennium CE
Three basic types of soda-silica glass are represented in the assemblages, one in which the flux used in primary glass manufacture was derived from mineral soda (m-Na-Al) and the other two where the flux was a halophytic plant ash (v-NaCa and v-Na-Al) [the v stands for végétale, French for plant]
The glass beads from Unguja Ukuu and Fukuchani open new insights into Indian Ocean trade to Africa’s eastern seaboard

Summary

Introduction

In 2011 and 2012, the Sealinks Project (www.sealinksproject. com/) undertook excavations at two archaeological sites on Zanzibar that possess evidence for trade contacts with the wider Indian Ocean world in the second half of the first millennium CE. Earlier excavations at the two sites (Horton and Clark 1985; Horton and Middleton 2000; Horton 2015; Juma 2004) provided evidence of Indian Ocean trade, but the Sealinks Project excavations were undertaken with the aim of further refining the chronological parameters for the two sites. Renewed excavation at the two sites was undertaken as part of a systematic study by the Sealinks Project into the trans-oceanic biological exchange that brought a variety of Asian plants and animals to the East African coast in the premodern period (Boivin et al 2013, 2014; Crowther et al 2014, 2015; Helm et al 2012). The rich glass bead assemblage from Zanzibar, the result of more intensive recovery methods than in previous excavations on the island, provides an exceptional opportunity to explore Zanzibar’s connections to the broader Indian Ocean world. We compare the Zanzibar bead assemblages and the trade connections they inform with those in southern Africa during the same period to attempt to discern whether or not the two ends of the eastern African coast were involved in overlapping trade circuits

Methods

Results

Conclusion