In 1967 a hoard of eight X-shaped copper ingots was discovered in the village of Chombe, in central Malawi. These are all of the HXR ingot type, of which several hundred examples have been found in Zambia and Zimbabwe. They are thought to have been manufactured between the 14th and late 18th centuries CE. In 2024 we sampled five of the Chombe ingots to analyze for lead isotope analysis (LIA) and bulk ICP-MS chemical analysis at the University of Missouri Research Reactor (MURR). We conclude that all five ingots derive from the Kipushi ore body, located near Lubumbashi in the Democratic Republic of Congo (DRC). The straight-line distance between ore source and find spot is about 790 km, but we suggest that the ingots may have travelled a longer but easier route by canoe down the Kafue and Zambezi rivers, with only the last 220+ km overland to central Malawi (ca. 1200 km total). These ingots are much thinner, and therefore lighter, than typical HXR ingots, and are the only HXR ingots known so far to have been sand-cast. We infer that at some point along their journey the original ingots were recast, and discuss why this might have been done.

Published Sn isotope data along with 150 new analyses of cassiterite and four granite analyses constrain two major tin isotope fractionation steps associated with (1) separation of tin from the magma/orthomagmatic transitional environment and (2) hydrothermal activity. A distinct Sn isotope difference across deposit type, geological host rocks, and time of ore deposit formation demonstrates that the difference in the mean δ124Sn value represents the operation of a unified process. The lower Sn isotope values present in both residual igneous rocks and pegmatite suggest that heavier Sn isotopes were extracted from the system during orthomagmatic fluid separation, likely by F ligands with Sn. Rayleigh distillation models this first F ligand-induced fractionation. The subsequent development of the hydrothermal system is characterized by heavier Sn isotope composition proximal to the intrusion, which persists in spite of Sn isotope fractionating towards isotopically lighter Sn during hydrothermal evolution.

Optical and electron microscopy are relatively cheap and versatile techniques for investigating pyrotechnologies, and optical petrography is a proven technique for inferring the geological provenance of pottery. Both have been used for more than three decades in Southern Africa, but few archaeologists based in other parts of sub-Saharan Africa have made much use of them. We briefly review what applications of these techniques have revealed about the African past, identify the obstacles to their wider use, and make recommendations to resolve these.

Tin is a much rarer element (2.3 ppm in the earth’s crust) than copper (68 ppm), so in most regions, bronze can only be made with tin obtained from far away. In this paper, we investigate the sources of tin in 153 tin and bronze samples from southern Africa, dated between 1200 and 1800 CE, by integrating lead isotope, tin isotope, and trace element measurements. Our data show that tin from the prehistoric tin mines at Rooiberg (South Africa) was transported more than 900 km. We also present evidence of tin production from other sources, likely pegmatites, within the Bushveld Large Igneous Province of South Africa. Although many of the bronzes analyzed are from archaeological sites in present Zimbabwe, we have found no definite evidence so far for exploitation of tin sources within Zimbabwe.

Ingombe Ilede is located just north of the Zambezi River, and has often been seen as a trading station connected to Central Africa, the Zimbabwe Plateau and the Indian Ocean. Discussion of the richly appointed burials in its Central Cemetery has been hindered by uncertainty over their ages. In this article, we report four new radiocarbon dates from Ingombe Ilede and six new dates from sites in northern Zimbabwe that are relevant to a wider understanding of Ingombe Ilede and its connections. These ten dates are all on organic fiber cores within copper and bronze jewelry, for which we also report chemical compositions, lead isotope ratios, and (for bronzes) tin isotopic ratios. We show that the richer burials in the Central Cemetery were interred no earlier than the mid fifteenth century. By this time copper from the Central African Copperbelt, 500–700 km north of the Zambezi, had been transported into northern Zimbabwe for at least two centuries, as had tin from the Bushveld Large Igneous Province (BLIP) 900–1000 km south of the Zambezi. The rich burials at Ingombe Ilede represent a late phase of a longstanding trade in copper from the Copperbelt to the Zimbabwean plateau.

Research on Southern Africa between ca. 500 CE and ca. 1500 CE has been dominated by tracing the connection of the subcontinent to the maritime trade across the Indian Ocean. But until recently, the lack of effective tools to reconstruct precolonial movements of commodities made it appear as if Africa, despite its vast size, lacked internal long-distance exchange. We challenge this assumption by combining oral historical with archaeological and scientific data to identify long-distance internal African commodity exchange and associated variable networks of distribution. We identify long-distance exchange of commodities, such as iron hoes, copper ingots and ostrich eggshell beads that are fulfilled, as mediated by different cosmologies, quotidian and luxury desires in ancient southern and Central Africa. We conclude that precolonial Southern Africa was deeply interconnected through networks of production and exchange and that entanglements with the Indian Ocean provided optional commodities to complement the pre-existing and the locally available.

Methods for provenancing copper, lead, and silver using the isotopic composition of lead are well-established. Lead isotope analysis holds promise for the study of tin metal as well, as long as one accounts for the U-Th-Pb systematics of cassiterite (SnO2) 2 ) and cha & icirc;ne operatoire of tin production. Although Precambrian cassiterite may contain 10s of ppm Pb or more (predominantly radiogenic 206 Pb), Phanerozoic examples typically contain only a few parts per million Pb. However, all but one of the 133 raw tin ingots excavated from European Bronze Age shipwrecks contains more Pb than could have come from cassiterite alone, as do six of the twelve analyzed tin objects interpreted to have been derived from the ores of southern Africa. Accordingly, almost all tin objects must contain Pb from external cassiterite sources and interpretation of LIA must account for this contamination. The nature of the contaminant (sulfides, U-Th-bearing minerals, silicates) can be inferred from patterns in Pb concentration and LI values. The 3 major sources of Pb that can typically be identified in tin artifacts are original Pb from the tin ore, radiogenic Pb produced in- situ due to U decay, and external Pb added during the cassiterite smelting and ingot production. As cassiterite has high U/Pb but low Th/Pb, the 208 Pb/ 204 Pb may be representative of the initial Pb incorporated in the mineral. This is assuming either that no external Pb is added during the ore processing or that the added Pb is from coeval sulfides from the same Pb ore provenance. In such cases 208Pb/204 Pb can be used to estimate a Pb model age, which in turn can be used for provenance estimate of the ingots. If the addition of Pb is from U-Th-mineral contaminants to the ore concentrate, then this will also increase 208 Pb/ 204 Pb and point to erroneously young model Pb ages. In such cases, the problem would be evident in positively correlated values of 206 Pb/ 204 Pb and 208 Pb/ 204 Pb. If Pb concentrations are above a certain threshold (approximately 5 ppm). LIA typical common Pb isotope ratios will be clear indication that external, non-cassiterite Pb, is added to the tin artifact. This tin could be from impurities in the ore (e.g., inclusions in cassiterite, impurities in the ore concentrate, or added during ore smelting and/or metal processing. Overall, elevated Pb concentrations accompanied with non-radiogenic Pb isotopes typical for common Pb, is a clear indication that significant amount of external (contaminant) Pb is added to the tin artifact.

Rectangular, fishtail and croisette copper ingots have been found in many locations in Central and southern Africa where excavated samples date to between the fifth and eighteenth centuries cal. AD. For more than fifty years, scholars have debated whether these ingots were all made in the Central African Copperbelt, where there are many finds of matching moulds, or if moulds found in Zimbabwe show that copies were produced locally. Lead isotopic and chemical analyses have recently confirmed that the Copperbelt supplied copper ingots to both southern Congo-Kinshasa and the Zimbabwe Plateau between the ninth and eighteenth centuries, but that one HXR ingot can tentatively be sourced to the Magondi Belt copper deposits in northern Zimbabwe. We expand this discussion here by linking ingot chemistry and isotopic provenance with distribution patterns and ingot morphologies. The combined evidence suggests that groups making Luangwa Tradition pottery were responsible for transporting HIH and HXR ingots, and the technological styles for making them, far to the south of the Copperbelt. These croisette ingots link constellations of practice in the Copperbelt and Zimbabwe, possibly through the movement of specialised traders and metalworkers. We identify some of the individuals buried at Ingombe Ilede and Chumnungwa as possible examples of these specialists.

The southern third of Africa is unusually rich in copper ore deposits. These were exploited by precolonial populations to manufacture wound-wire bangles, other forms of jewelry, and large copper ingots that were used as stores of copper or as forms of prestige. Rectangular, fishtail, and croisette ingots dating between the 5th and 20th centuries CE have been found in many locations in the Democratic Republic of the Congo (DRC), Zambia, and Zimbabwe, with isolated finds in Malawi and Mozambique. Molds for casting these ingots have been found mostly in the Central African Copperbelt, but also around the Magondi Belt copper deposits in northern Zimbabwe. For years, scholars have debated whether these ingots were exclusively made in the Copperbelt or if the molds found in Zimbabwe indicate that local copies were produced from Magondi Belt copper ore (Garlake 1970; Bisson 1976). Before the recent application of lead isotopic and chemical methods to provenance copper in central and southern Africa, there was no way to discern between these hypotheses. Rademakers et al. (2019) and Stephens et al. (2020) showed that copper artifacts from southern DRC (mostly from Upemba) and from northwestern Botswana (Tsodilo Hills) match the lead isotope ratios of ores from the Copperbelt. Building upon these previous studies, we present here the first results from a copper provenance project across the southern third of Africa, from the Copperbelt to northern South Africa. We apply lead isotopic analysis (LIA) and chemical analyses to establish the provenance of 29 croisette ingots recovered in Zimbabwe, 2 fishtail and 1 rectangular ingot recovered from sites in Zambia, and an "X" shaped ingot smelted in an experiment in Zambia in the 1970's. Our chemistry and lead isotopic results indicate that 16 of these objects were smelted with copper from the Copperbelt, 16 objects source more specifically to the Kipushi deposit within this geological district, and only one HXR ingot sources to the Magondi Belt in Zimbabwe. Taken together, we clearly illustrate that croisette ingots were traveling significant distances to reach their eventual sites of deposition, and that there was also local production of these objects in Zimbabwe.

Recent literature is slowly stepping back from the idea that regions located away from centres of powerful social formations (such as chiefdoms, states and empires) lacked agency and initiative. We contribute to this conversation by engaging with the Rooiberg craft production landscape. We argue that Rooiberg was an 'open source' that was owned by no one, and provide some examples of 'open sources' elsewhere. Concerning the organisation of production, Rooiberg metalworking was more dispersed than concentrated. No centralised polity directly controlled the distribution of tin or other metals extracted from this resource -rich region. Consequently, different communities producing crafts at Rooiberg controlled their destiny and traded and exchanged with others through intricate capillary circulatory systems. The frequency of objects recovered from excavations indicates that these systems involved mostly internal commodities, with limited amounts of exotica from the Indian Ocean trade.

This article reconstructs the smelting and refining of copper at site 256A01 in the Pampa de Chaparrí, near Batán Grande, Department of Lambayeque, Peru. Two banks of furnaces were excavated, yielding calibrated radiocarbon dates between 1030 and 1180 AD (Middle Sicán through the Early Late Sicán period). This is the first published study from South America to have recorded evidence of copper smelting slags that were fully liquid in furnaces apparently powered by blowpipes. The copper prills produced at 256A01 contained up to 5.5% arsenic, but we have found no evidence for deliberate addition of an arsenic-bearing mineral to the furnace charge. Some of the primary copper was heavily contaminated with metallic iron, which was removed by selective reoxidation on shallow ceramic crucibles. Although there were residual sulfides in the ore, no evidence of co-smelting (reaction of copper oxides with copper sulfides) was noted.

Recent analytical developments in the field of mass spectrometry have made possible accurate measurements of “non-traditional” isotopic ratios of elements such as Fe, Cu, Ag, Sn, Sb and Hg. The stable isotopes of these elements do not have any radioactive parents, but their ratios undergo limited fractionation from various causes, most of them mass-dependent. These effects can lead to variation in isotopic ratios of natural materials (minerals, rocks, ores, etc.) and in archaeological artifacts derived from them. Research since 2010 has investigated whether variation in these isotopic ratios can be used to infer the geological provenance of archaeological materials, including bronze and glass. Here we review recent research on these isotopic systems in archaeology, their principal applications, as well as expected future developments in their use. We conclude that none of these isotopic systems are likely to be very useful for provenance, mostly because of limited ranges of isotopic ratios and/or extensive overlap between the isotopic ratios of most geological sources. Copper isotope ratios are however a reliable method for inferring the type of ore (supergene versus hypogene) smelted to produce copper, and recent studies indicate that silver isotope ratios can also be applied to this effect.

The first part of this paper is a brief critical history of the use of Pb isotopes for inferring the geological provenance of archaeological materials, with an emphasis on non-ferrous metals. The second part examines variation in the Pb isotopic ratios of oxide and sulphide ore minerals in selected regions of the world, and relates these to the geological histories of ore formation in each region. This exercise shows that in regions where most ore deposits are of similar geological age-as in the Andes, Europe and the circum-Mediterranean-provenance analysis with Pb isotopes is inherently difficult because geographically distant sources often exhibit similar isotopic ratios. Conversely, regions with many periods of ore formation-such as southern Africa-appear to be very promising regions for future studies of provenance with Pb isotopes. The wider implication of this exploratory survey is that archaeologists should carefully consider the range and clustering of geological Pb isotopic ratios in their regions of interest before investing large sums of money into Pb isotopic analysis of artefacts.

Copper was highly valued in sub-Saharan Africa for jewellery and as a store of wealth, but was rarely used for tools or weapons. The Central African Copperbelt is one of the world's largest copper deposits, and is known to have been mined since at least 400-600 cal CE, but has seen very little archaeological investigation. We measured lead isotope ratios and trace element concentrations in 20 copper objects, dating between ca. 650 cal CE and ca. 1200 cal CE, from two sites in the Tsodilo Hills in northwestern Botswana. The results show unequivocally that almost all derive from Copperbelt ore deposits in Katanga Province, Democratic Republic of the Congo, at least 1050 km from Tsodilo. Our results are very similar to those recently obtained for a suite of 45 copper ingots, dated between 9th and 18th centuries cal CE, most of which are from cemeteries in the Upemba Depression, about 200 km north of the Copperbelt (Rademakers et al., 2019).