Abstract
Excavations conducted between 2010 and 2012 at Magoro Hill, a site in South Africa’s Limpopo Province frequented or intermittently occupied by African farming communities since the first millennium AD, yielded a substantial glass bead assemblage. A selection of the beads was studied non-destructively by classifying them according to morphological attributes, supplemented by Raman analyses and XRF measurements. It became evident that a morphological classification of beads recovered from sites that include imports into Africa after the seventeenth century AD could be problematic due to apparent morphological similarities between earlier and later beads. This paper demonstrates the use and archaeological application of Raman and XRF measurements to separate earlier imported beads from later counterparts by identifying glass nanostructure, as well as pigments and opacifiers, which were not used in bead series pre-dating the seventeenth century AD. Results obtained from Raman and XRF measurements indicate that although some beads retrieved from Magoro Hill pre-date the seventeenth century and belong to the Indo-Pacific (K2, East Coast, Khami) and Zimbabwe series, the largest number of beads is from a later European origin. This ties in with the settlement history of the site, which suggests that it primarily served as a rendezvous for episodic rainmaking rituals before it became the stronghold and capital of a Venda chiefdom, headed by the Magoro dynasty, in the second half of the eighteenth century AD. The comparative analysis of the long bead sequence sheds new light on changing patterns in the availability, range, consumption and origin of glass trade beads imported into the northern interior of South Africa over a period of about 1000 years.
Highlights
A considerable demand for ivory, rhinoceros horn and gold drew foreign traders towards trading centres along the eastern and southern coasts of Africa since earliest times
This implies that the economic use of cadmium pigments was limited to a small window of time, which facilitated the accurate dating of the beads and eliminated a pre-1920 date for the associated archaeological deposit and structure on Magoro Hill
In this paper we demonstrate the use and archaeological application of Raman and X-ray fluorescence (XRF) measurements to separate earlier imported beads from later counterparts by identifying glass nanostructure, as well as pigments and opacifiers, which were not used in bead series pre-dating the sixteenth century AD
Summary
A considerable demand for ivory, rhinoceros horn and gold drew foreign traders towards trading centres along the eastern and southern coasts of Africa since earliest times. The Raman spectra of the other beads place them in the soda-lime group, confirmed by XRF measurements (Al too low, Ca too high, absence of uranium and the presence of small amounts of antimony (Sb) and arsenic (As) probably added as opacifiers) and they can be assigned to the European period. Zimbabwe series beads (size: 2–3.5 mm), with a similar glass structure as the Mapungubwe Oblates, include translucent blue–green, blue, yellow, transparent dark green and opaque black cylinders and oblates [2] They are made of plant ash glass (soda-lime group) and contain no uranium and have higher levels of CaO (6.9%) and MgO (4.3%) than the Indo-Pacific series [23]. This heterogeneous composition indicates that the bead was made of a variety of recycled glasses and corroborates the existence of beads made of reused glass in the Khami period, as shown in reference 6
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