David Killick

Slag Identification at Southern African Archaeological Sites

nents of southern African Iron Age sites. Their correct identification is crucial to understanding technological processes performed at these sites. This paper presents criteria for distinguishing between iron smelting slags, iron forging slags, copper smelting slags, crucible slags resulting from melting activities, vitrified clay and various biomass materials. Slag identification should entail a combination of morphology, microscopic study, chemical analysis, and assessment of the archaeological context. It is a necessarily specialist activity and superficial classification without materials analysis can be misleading. Archaeologists need to be mindful of both the archaeological opportunities and the potential technical difficulties in the interpretation of slags.

The social geography of pottery in Botswana as reconstructed by optical petrography

Over the last 30 years Wilmsen and Denbow have recovered and studied pottery from 28 sites in Botswana dated between ca cal AD 200 and AD 1885. Some sherds in several of these assemblages appear, on stylistic evidence, to have been made in other sub-regions of Botswana than where they were found. These inferences are confirmed in this paper by use of an independent archaeometric technique, optical petrography. We are able to demonstrate the transport of pots from the Okavango Delta to Bosutswe in the eastern hardveld, some 400–600 km distant, as early as cal AD 900–1100, and of others over equal distances to the Tsodilo Hills probably before that time. We are also able to demonstrate several shorter itineraries at contemporary and later times in the Tsodilo-Delta-Chobe region as well as in the hardveld. Furthermore, we demonstrate that clays were transported from geological deposits to sites where pots were made from them. We consider some implications of these findings for a deeper appreciation of the movement of peoples and goods at several time periods of the past and present as well as further implications for understanding the participation of the region in the Indian Ocean trade during the 8th–10th centuries.

The strange case of the earliest silver extraction by European colonists in the New World

La Isabela, the first European town in the New World, was established in 1494 by the second expedition of Christopher Columbus but was abandoned by 1498. The main motive for settlement was to find and exploit deposits of precious metals. Archaeological evidence of silver extraction at La Isabela seemed to indicate that the expedition had located and tested deposits of silver-bearing lead ore in the Caribbean. Lead isotope analysis refutes this hypothesis but provides new evidence of the desperation of the inhabitants of La Isabela just before its abandonment.

Metal working in the Northern Lowveld, South Africa, A.D. 1000-1890

Abstract The Iron Age archaeology of the northern Lowveld of South Africa is notable for the abundance of mining, metal working, and salt production sites recorded in the region. We report the results of scientific studies of the metallurgical remains recovered from 1965 to 1978 by Nikolaas J. van der Merwe, David Killick, and colleagues in various campaigns of survey and excavation in the Phalaborwa region, a major center of precolonial metallurgy. Both iron and copper ores occur in a carbonatite complex at Phalaborwa and were smelted in low-shaft furnaces of two different designs. Two radiocarbon dates of ca. 1000 b.p. are available for the mines themselves, which have now been completely destroyed. All other radiocarbon dates for the archaeological sequence at Phalaborwa fall in two groups, the first from the 10th to 13th centuries A.D., the second from the 17th through the 20th centuries A.D. Both iron and copper were smelted in both periods; tin-bronze and brass appeared towards the end of the earlier period.

Archaeology and archaeometry: From casual dating to a meaningful relationship?

Most archaeology and anthropology departments are grouped as Humanities or as Social Sciences in university organizations. Where does that place the archaeometrists who approach the materials with the methods of physical and biological sciences? And where does it place the archaeologists themselves - especially when archaeometric studies have a large place in contract archaeology ?

Isotopic evidence for the provenance of turquoise in the southwestern United States

The archaeological record shows that turquoise was widely mined and highly valued by pre-Hispanic societies in the southwestern United States, and it has long been assumed that much of the turquoise noted in ancient Mesoamerica was traded from this region. However, little is understood about the acquisition and exchange of turquoise by Native American societies because the geological sources of most turquoise artifacts from archaeological sites in the southwestern U.S. and Mexico are not known. We evaluate the potential for Pb and Sr isotopic ratios to indicate the geological provenance of turquoise artifacts recovered from these regions. Pb and Sr isotopic measurements were made on 137 geological samples of turquoise from 19 mining districts across the southwestern United States and northern Mexico. These data reveal that isotopic signatures of turquoise deposits vary geographically according to regional and local differences in the geologic settings of turquoise mineralization. As an archaeological case study, we also report Pb and Sr isotopic data on 10 turquoise artifacts recovered from three late pre-Hispanic (ca. A.D. 1250–1400) ancestral Zuni sites located in the El Morro Valley of western New Mexico. These have isotopic signatures uniquely consistent with the turquoise deposits of the Cerrillos Hills, a location identified in Zuni traditional history as an ancient source of turquoise. These data thus establish Pb and Sr isotopic measurements as powerful tools for determining the sources of turquoise artifacts and provide a new framework for evaluating the role of turquoise in pre-Hispanic exchange networks across North America.

From Ores to Metals

The first steps in the production of a metal object are to extract the ore from the mine, process the ore for smelting, and then eventually smelt the ore into metal. As fundamental as these steps may be, they are also the least studied in ancient metallurgical research, as finished metal artifacts (i.e., the end result of the entire process) are usually more interesting to archaeologists than bits of ore or slag. However, the study of the earlier stages is often more enlightening on the social structures of metallurgical groups, on the choices made by ancient metal workers, and more generally about human engagement with ores and metals. In this chapter, the first steps of the metallurgical process are outlined and discussed, with an eye towards the sorts of anthropological and archaeological research questions that can be asked by both archaeologists and archaeometallurgists of ores, mines, furnaces, slag, etc.

Mineralogical study of precolonial (1650-1850 CE) tin smelting slags from Rooiberg, Limpopo Province, South Africa

Vitreous slag remains of prehistoric tin smelting activities (1650-1850 CE) excavated at Rooiberg, Limpopo Province, South Africa were analyzed by wavelength-dispersive X-ray fluorescence spectrometry (WD-XRF), energy-dispersive X-ray spectroscopy (EDX), and electron-microprobe analysis (EPMA). The slags were found to contain high concentrations of tin oxide suggesting a low level of metal recovery that resulted in substantial tin losses. In addition, skeletal cassiterite, and complex spinels, as well as tin prills ranging in size from a few to tens of micrometres were observed. The contribution discusses the role tin(II) and (IV) oxides are thought to play during formation of slag as well as the crystal chemistry of spinels precipitated during cooling.

A global perspective on the pyrotechnologies of Sub-Saharan Africa

ABSTRACT Although Sub-Saharan Africa has the oldest evidence for the deliberate production of fire, its recent record of pyrotechnology is more often presented as a list of absences than as a list of accomplishments. In this review I summarise the evidence, both before and after the initiation of long-distance trade with the Islamic world. The literature is decidedly unbalanced, with almost all attention so far having gone to African iron smelting, but the recent discovery of a unique type of glass production in Nigeria suggests that much more attention needs to be paid to other branches of pyrotechnology. I also suggest that we need to look outside the continent to understand why the record of preindustrial pyrotechnology in Sub-Saharan Africa is so different from that in other parts of the Old and New Worlds.

Invention and Innovation in African Iron-smelting Technologies

Sub-Saharan Africa is often characterized by Europeans as a region that saw no significant technological change from the adoptions of agriculture and ironworking until the European colonization of the entire continent after 1880. This article criticizes this view by exploring the distinction between invention and innovation, using African iron smelting as a case study. It argues that there is in fact much evidence for the invention of new technologies in recent African prehistory, but that very low population densities precluded innovations in mass production and transportation.