Fingerprinting Specular Hematite from Mines in Botswana, Southern Africa

Abstract

Specular hematite, or specularite (Fe 2 O 3 ), was a valued cosmetic in Southern Africa during the Late Stone Age (LSA) and Iron Age (IA), and there are ancient mines throughout the region. Early explorers reported that it was applied to the body and hair with animal fat and was traded extensively. We analyzed specularite samples from seven prehistoric mines in Botswana, including five in the Tsodilo Hills, and one each at Dikgatlampi and Sebilong to test the feasibility of geochemically fingerprinting sources. Most of the mines examined exploited specularite-rich schist or hydrothermal quartz veins. The heavy mineral fractions (density >2.9 g/cm 3 ) of 73 samples, separated by heavy liquid and consisting largely of specularite, were subjected to instrumental neutron activation analysis (INAA). Multivariate statistical analyses of the compositional data suggest that specularite can be fingerprinted to specific mines or groups of mines separated by tens to hundreds of kilometers. The method appears robust enough for determining the provenance of archaeological samples throughout the region and so could provide valuable information on past trade routes and patterns.