REQUEST TO CONDUCT SR ISOTOPE ANALYSIS ON FIFTEEN OSTRICH EGG SHELL BEAD FRAGMENTS

1 OSTRICH EGGSHELL BEADS STRONTIUM ISOTOPE ANALYSIS
1.1 Introduction
PGS Heritage (Pty) Ltd (PGS) was appointed by the Nkomati Anthracite Mine to manage the Phase 2 archaeological mitigation work required for the mitigation of several identified archaeological sites and to investigate features that may be graves. The planned expansion of mining activities in the area known as “Block L” will affect these archaeological sites and features.

PGS obtained an excavation permit from the SAHRA (Case no: 18339) to undertake archaeological mitigation, test excavations, and ground penetrating radar scans to extensively excavate the archaeological sites and features and to collect representative samples of the archaeological material for analysis to determine the temporal localisation, cultural affiliation, and possible social structure and layout of the settlements. The mitigation work must also identify unmarked burials and ensure, as far as possible, that no unmarked burials are left in the area after the completion of the mitigation work.

The purpose of the analysis is to investigate the strontium (Sr) values of the Nkomati sites’ ostrich eggshell beads using Thermal Ionization Mass Spectrometry (TIMS). The analysis requires a small sample size of approximately 5mg of powder from the ostrich eggshell bead interiors to possibly identify and establish regional trade networks with the results of the analysis.
1.2 Background
More than a thousand ostrich eggshell beads or bead fragments have been recovered thus far during the excavations. Ostrich eggshell beads are made from small fragments of eggshell, which are referred to as preforms or blanks. No preforms were recovered during the excavations, which suggests that no bead manufacturing took place on these sites. The beads were most probably traded for from somewhere else. The ostrich eggshell contains/absorbs strontium in the same way that bone contains/absorbs it.

Strontium is a chemical element and has the symbol Sr and atomic number 38. The human and animal bodies absorb strontium through the food consumed as if it were its lighter congener calcium. Because the elements are chemically very similar, stable strontium isotopes do not pose a significant health threat. Strontium is so similar to calcium, and it is incorporated into the bone. All four stable isotopes are incorporated in roughly the same proportions they are found in nature. However, the actual distribution of the isotopes tends to vary greatly from one geographical location to another. Thus, analysing the bone of an individual can help determine the region it came from (Price et al 1985). Strontium isotopic ratios are widely used as tracers in geological processes and as indicators of provenance in an archaeological context (Schweissing & Grupe 2003).
1.3 Methodology
The analysis of the ostrich eggshell beads will be conducted after permission from SAHRA is obtained. The bead interiors of 15 OES fragments will be drilled out using a sterilized dental microdrill, and the powder will be extracted through a cold digestion process using concentrated HNO3 (Nitric acid) and H2O2 (Hydrogen peroxide). The samples will then be loaded onto filaments and analysed using a Triton Plus Thermo Scientific Mass Spectrometer. This will be facilitated at the University of Cape Town, in the Department of Geosciences, by Professor Petrus Le Roux, in the Laser Ablation MC-ICP-MS Laboratory
 
2 BIBLIOGRAPHY
PRICE, T. D; SCHOENINGER, M. J.& ARMELAGOS, G. J. (1985). "Bone chemistry and past behaviour: an overview". Journal of Human Evolution. 14 (5): 419–47.

SCHWEISSING, M. M. & GRUPE, G. (2003). "Stable strontium isotopes in human teeth and bone: a key to migration events of the late Roman period in Bavaria". Journal of Archaeological Science. 30 (11): 1373–83.