Precolonial Metallurgy and Mining across Africa
Abstract and Keywords
Since their inception, precolonial mining and metallurgy gradually became essential social, technological, and even politico-economic pillars of African communities of varying time periods. However, the onset of metallurgy and mining and the associated technology and sociocultural beliefs varied from region to region in a way that defies generalization. Owing to their cultural and geographical location, Egypt, the Sudan, North Africa, and the Horn of Africa share some very broad similarities in their metallurgical histories. This in some cases sharply differs from that of many regions such as West, central, East and southern Africa. Interestingly, these regions too are characterized by technological similarity and diversity. When considered together, the multiple trajectories taken by metallurgy and mining in Africa’s different regions are essential for achieving a comparative understanding of the continent’s rich technological history. Achieving this, however, requires an interdisciplinary approach from documentation through data analysis to eventual interpretation. This contribution combines insights from various disciplines to present an overview of precolonial metallurgy and mining in Africa’s many regions.
From Ancient Egypt to South Africa: Origins of Mining and Metallurgy in Precolonial Africa
To a considerable extent, today’s technologically “addicted” world is heavily reliant on mining and metallurgy. This industry is deeply embedded in multiple facets of society such as the technological, economic, and sociopolitical. Alone, this multiscalar contribution makes modern mining and metallurgy the lifeblood of essential sectors such as transportation (e.g., automobiles), communications (e.g., cell phones), and buildings (e.g., residential, industrial). With millions employed in mining and metallurgy across Africa, the economic and to some extent political fortunes of many countries that are mineral dependent (e.g., Zambia on copper, Botswana on diamonds) is to a certain extent hinged on these industries. Not surprisingly, labor federations such as the Congress of South African Trade Unions (COSATU) play an important sociopolitical role in countries such as South Africa. Significant as this contribution to society is, perhaps the most important question is, spatially and temporally, what do we know about precolonial mining and metallurgy across Africa? This is essential because it is possible that this technology might have varying consequences from region to region, and time to time. When considered diachronically, regional similarities and differences paint an intellectually nourishing picture of how this technology evolved in space and time. In this article, an attempt was made to avoid “fragmenting” the African continent into Egypt and North Africa, on the one hand, and sub Saharan Africa, on the other. Rather, effort was invested in establishing connections and cultural relations among various areas to forge a rich comparative understanding of the mining and metallurgical past in Africa’s many regions.
Current evidence indicates that Egypt was Africa’s first recipient of metallurgy around 5000 bce in what is known as the Copper Age (5000–3000 bce); this was followed by the Bronze Age (3000–1500 bce) and the Iron Age (c. 800 onward).1 Interestingly, while the picture in Egypt resembled that of the adjoining regions of the Middle East until the Late Bronze Age, the former was far more conservative when it came to iron, only embracing it after the invasion of the Assyrians.2 The picture in Nubia broadly mimics that in Egypt.3 However, other parts of Africa sharply differ. In North Africa, metallurgy was introduced by Phoenicians around 800 bce.4 However, West, central, and East Africa present a picture that contrasts with that of Egypt and North Africa.5 Here, the limited data available suggest that metallurgy might have begun with copper and iron around or before 800 bce. Although there are problems associated with dating the beginning of metallurgy in these regions of Africa, it is clear that metallurgy was well established by the end of the last millennia bce.6 Southern Africa is, however, the only exception—metallurgy only appeared in the early 1st millennium ce, when ancestral Bantu peoples migrated southward from northwest Africa.7 Unlike in Egypt and Nubia, where initially gold and later bronze were known from very early times, in West, southern, and possibly East Africa, the two were only worked after the strengthening of contact between West and North Africa through the trans-Saharan trade and between southeast Africa and the Indian Ocean Rim region. So in a way, the developmental picture of metallurgy in these areas of Africa appears in some sense to be the reverse of that in Egypt, Nubia, and North Africa.
What is surprising, however, is that despite the existence of several differing cultural contexts and techniques, the technology of mining and metallurgy did not vary significantly across Africa.8 Alluvial and underground mining (open and underground mining sensu Summers) were all practiced across the continent.9 Similarly, the techniques of smelting were more or less the same but often varied from area to area in variables such as furnace types and methods of air provision. The range of metals worked in Egypt, Nubia, the Horn of Africa, and North Africa was broader than that in other areas of the continent. While the inventory of metals worked in Egypt and adjacent regions include copper, gold, silver, lead, iron, mercury, and tin, only iron, copper, gold, tin, and lead were worked in other areas of Africa. Metal fabrication techniques were also mostly similar for ferrous and nonferrous metals and alloys.10 While iron could only be hammered, nonferrous metals such as copper and gold were cast using the sophisticated technique of lost wax casting. However, there were differences across regions; for example, soldering using lead was very common in Egypt, but was probably unknown in West or East Africa. Across Africa, mining and metallurgy were embedded in different sociocultural contexts to the extent that a great variability can be seen through time.11 While mining and metallurgy were closely regulated and monopolized in Egypt, in other areas of Africa, it was less so. However, mining and metallurgy appear to be associated with religious and spiritual beliefs, regardless of region. Despite these differences, there is more in common across the continent than is often believed to be the case.
Sources and Techniques of Studying Mining and Metallurgy across Africa
The process of producing usable metal involved a series of stages that include raw-material acquisition, smelting or melting, fabrication, and distribution and use. Along this chaîne opératoire, different stages left remnants that include disused mine shafts, collapsed furnaces, slag, broken tuyeres, and even finished objects. As illustrated below, these remains, which can be interrogated from interdisciplinary perspectives—archaeological, historical, and anthropological—are the staple of studies of metallurgy and mining in precolonial Africa.12
Because of its unique ability to study cultural behaviors relating to deep time periods, archaeology, the study of the past using material and nonmaterial remains, is strategically placed to study Africa’s precolonial mining and metallurgical past.13 Archaeology is however conditioned by the nature of the surviving evidence and therefore by what is potentially recoverable using any selection of techniques. Across the chaîne opératoire of mining and metallurgy, some of the most frequent categories of evidence relate to processes such as mining, clay extraction, charcoal preparation, smelting, smithing, and use of metal objects. Because different generations added their own activities onto the landscape, resulting in an accretion of layers, archaeological excavations are essential for exposing diachronically successive metallurgical and associated cultural processes. Archaeologists study the context of different mining and metallurgical remains in the field to reconstruct the technology and embedded sociocultural contexts.14 Not surprisingly, field-based archaeometallurgy is now one of the most important branches of modern archaeology.15
When brought into the laboratory, the remains from mining and metallurgy become a staple of laboratory based archaeometallurgy.16 Laboratory archaeometallurgy thrives on the application of techniques from earth and engineering sciences to gain technical and cultural information from slags, ores, and even collapsed furnaces. The main principle behind laboratory archaeometallurgy is that as high-temperature–process products, remains from past metallurgical practices such as slags, heated technical ceramics, and metal objects contain within their microstructures and composition partial histories of the processes they have undergone.17 Various categories of information such as the efficiency of reduction, temperatures reached in the furnaces, and fuel-to-ore ratios can be estimated through reading microstructures of slag samples using light microscopy and Scanning Electron Microscopy.18 For example, Chirikure and Rehren studied the microstructures of slags from the Early Iron Age site of Swart village and the Late Iron Age site of Baranda in northern Zimbabwe and concluded on the basis of quantities of wustite or free iron oxide in the studied samples that Early Iron Age furnaces were more reducing when compared to Late Iron Age furnaces.19 Besides microstructural information, the chemical composition of various categories of metallurgical remains also host essential information on the likely source of ores, and when plotted on ternary diagrams may make it possible to estimate, within limitations, temperatures achieved in the furnaces.20 Not surprisingly, compositional techniques such as Wavelength Dispersive X-ray Fluorescence (WD-XRF) are an integral component of laboratory archaeometallurgy.21 Other techniques such as ICP-MS make it possible to provenance the source of raw materials such as ores and finished objects, thereby throwing light on distribution and consumption mechanisms at local, regional, and even international levels.22
In sum, when combined, the information from laboratory and field archaeometallurgy illuminates not just technical processes set in precolonial mining and metallurgical remains but also the cultural factors embedded in various technological contexts.
History and Ethnography
History is often defined as the study of the past using oral and written texts. However, that different parts of Africa adopted written literacy at different points in time, when combined with the time-depth limitation of oral sources, makes it clear that the utility of history as a source of metallurgical and mining information varies from time to time and place to place. Regions such as Egypt and Nubia have Africa’s longest tradition of written literacy: there exist in these areas written scripts on papyrus scrolls as well as inscriptions on tombs, buildings, and other places.23 Often, tomb depictions of metalworking episodes were accompanied by textual descriptions of the metalworking processes.24 In the Horn of Africa, Ethiopia also has a long-established tradition of literacy, but not much research on early mining and metallurgy has been done to date.25 In West Africa, written records appear with the intensification of trans-Saharan exchanges from the late 1st millennium ce onward.26 From the time of the Empire of Ghana and certainly by the time of Mali and Songhai, a tradition of written literacy was well established in West Africa by local scholars who wrote in languages such as Hausa, Wolof, and many others.27 However, most of the early written works were biased in favor of religion. In east Africa, there also exist some written texts that vary in detail from those based on hearsay to those based on firsthand accounts.28 However, most written records appear with increased contact between Europe and Africa via the Atlantic. For example, upon their settlement in what are now Angola (late 15th century) and northern Zimbabwe (early 16th century), the Portuguese left various documents relating to the Kongo and Mutapa states. Like the Islamic records on West Africa, some of the Portuguese reports are limited in that they do not contain much useful information on metallurgy and mining, thereby demonstrating the necessity of a combined-source approach.
Unlike written records that only cover sections of Africa, oral traditions—defined as verbal testimonies transmitted by word of mouth from one generation to another—are found in most African communities. In Africa, Schmidt used oral traditions to study the chaîne opératoire of iron production in Tanzania going back to the early 1st millennium ce.29 MacKenzie collected many oral traditions among the Njanja of central Zimbabwe and illuminated the quality of the ore, technology of the process, organization of labor, and distribution of iron and its sociopolitical consequences.30 What is clear from these and other studies that utilized oral traditions is that because they are wrapped in local knowledge, they provide nuanced information on the entire chaîne opératoire often missing from written records. However, oral traditions often do not go very far back in time and, among other limitations, can be easily distorted.31 However, when combined with other sources, their information value cannot be disputed.
Historical linguistics is important for studying Africa’s metallurgical and mining past. Historical linguists of the Bantu such as Ehret have argued that the word “iron” is closely related among Bantu languages, suggesting a linguistic relationship and history of contact between communities making up this very large population.32 Data from historical linguistics can be useful for estimating the time when languages changed, thereby potentially assigning a time period to any implied interaction or human mobility.
At various points of the African past, there existed contact between literate and nonliterate communities, which created numerous ethnographic records. Contact, however, accelerated from the 15th century onward, when European communities settled along the Atlantic Coast of Africa. Even if mining and metallurgy may not have been their major preoccupation, various observers recorded different aspects of mining and metalworking across the continent. For example, the Czech medical doctor Holub described metalworking by a Mambari smith in Zambia. He described the forge, illustrated the tools used, and provided a very rich description of the entire process.33 In central Africa, De Hemptine described in detail a major copper-mining expedition led by a woman in modern-day Lubumbashi, Democratic Republic of Congo.34 The renowned missionary David Livingstone observed that iron produced by communities on the Zambezi was of much better quality than that produced in contemporary Europe at the time. Throughout the 20th century, various scholars recorded and reenacted processes of African mining and metallurgy. Huysecom and Augustoni recorded in documentary form the chaîne opératoire of iron smelting in natural draught furnaces among the Dogon of Mali from mining through smelting to the fabrication of finished products.35 Along the way, they showed associated taboos and symbolism. All this information is useful for studying precolonial metallurgy and mining in Africa.
On its own, no single source is sufficient to tell the story of Africa’s metallurgical and mining past. As such, a combined-source and combined-technique approach is the best way forward. The techniques and sources used to study metallurgy and mining vary by the strength of the available evidence and the region under study.
Mining for Metallurgy across Africa
As a cultural behavior, mining has on the African continent extends to around 120,000 years ago, when communities living on the southern Cape Coast in South Africa processed iron-rich oxides to make pigments.36 However, mining performed with the intention of gaining usable metal from ores through the application of heat in an atmosphere-controlled environment is relatively recent.37 In Africa’s multiple regions, such mining was adopted variously depending on when an area developed or adopted metallurgy. Mining produced a fundamental raw material—ore, which was essential for metal production. However, the abundance of ores in nature and the nature of mineralization gestated the evolution of numerous techniques of mining.38
Techniques of Mining
Since the inception of metallurgy, the availability of ores in concentrations sufficient for human exploitation above or below ground determined the techniques used to extract those ores. Initially, outcropping ores were surface collected, but when these were exhausted, miners followed the mineralization underground. Once underground, the branching out of mineralization horizontally or obliquely created shafts and adits.
Alluvial deposits form after cycles of erosion wash ores from sources and deposit them in economically exploitable quantities along drainage channels such as rivers.39 Based on the evidence from the Eastern Desert in Egypt, alluvial mining is one of the earliest techniques used to extract gold. Within varying temporal and cultural contexts, alluvial mining involved the scooping of mineral-rich sand into a receptacle such as a bowl. After shaking the sand, the earthy material floated on top while the heavy mineral settled at the bottom. Alluvial techniques were used to mine the gold from the Nubian Desert. The gold fields of Bambuk in West Africa, which supplied gold to the legendary empires of Ghana (700–1230 ce), Mali (1230–1600 ce) and Songhai (1375–1575 ce) were similarly mined using alluvial techniques. With the settlement of Europeans on the Atlantic Coast, various descriptions of gold mining in the Gold Coast (modern-day Ghana) became abundant. Toward the late 17th century, Olfert Dapper records the technique of scooping sand from the rivers by divers who had weights strapped on their backs.40 Once on the surface, auriferous sand was panned using conventional techniques. In West Central Africa, the Mafa of northern Cameroon are known to have panned magnetite sands for use as ore.41
Shifting to East Africa, Kikuyu women panned magnetite sands, which were smelted to produce iron in the late 19th century.42 In southern Africa, gold was mined using alluvial techniques on the Zimbabwe plateau and adjacent lowlands. From the early 16th century onward, Portuguese reports make it explicit that men and women panned gold from the auriferous sands in rivers such as Mazowe and Mukaradzi.43 The same reports also noted the practice of underwater sand dredging similar to that reported by Dapper in Ghana. From the 16th century onward, it appears that the tin miners of Rooiberg in northern South Africa panned river sand for cassiterite (tin ore).44 Early mining geologists who visited the area reported what they called tin feed, consisting of alluvial ores at smelting sites in the Blaauwbank Donga.45
In the literature on precolonial mining, underground mining is often split into open mining and underground mining.46 However, on closer reflection, the difference between these techniques is not sufficient to create discrete categories. However, given the genetic relationship between the two, the discussion initially considers what is conventionally referred to as open mining before shifting to the conventional underground mining. When outcropping ore was exhausted, miners dug into the ground, following the mineralization. Like the distribution of alluvial mining, the technique of open mining was widely practiced across Africa, from antiquity to more recent times. Perhaps one of the earliest known techniques of open mining in Africa was practiced in the Eastern Desert of Egypt, where various miners followed gold mineralization into the ground. In this region, there is evidence that miners dug into the ground, to extract ore for processing above ground. The gold-rich rock was ground, washed, and panned to extract gold, which was then melted and transported to the Pharaohs.47
In West Africa, copper may have been mined using open-mining techniques at Akjoujt in modern-day Mauritania and at Agadez in the modern-day Niger sometime in the first millennium bce.48 With time, in the 1st millennium ce, gold and iron were also mined using the same techniques, where relatively deep holes were sunk into the ground to extract ore. In the legendary copper-producing area of Lubumbashi and adjacent regions of the copper belt in Zambia, carbonate copper ores such as malachite were also mined using techniques of underground mining.49
Depending on the geological formation, miners often had to sink vertical and inclined shafts to connect to the ore veins and followed them in different directions. This often created a series of shafts and galleries underground.50 Following ore mineralization horizontally or obliquely underground created challenges with maintaining the structural integrity of the mine. At Harmony block in modern-day Mpumalanga (South Africa), Evers and van Den Burg exposed dramatic evidence of timbers that were inserted to act as props to prevent collapse by copper miners, around the 15th century.51 Besides collapse, underground mining was faced with ventilation challenges, which forced them to sink narrow holes that connected to galleries below the ground. At Phalaborwa, Van der Merwe documented very narrow but 45-metre-deep ventilation shafts that connected to galleries on Lolwe Hill.52 From ancient Egypt in the north to Lolwe in South Africa, miners of various time periods often fired difficult host rock underground and poured water for easy workability. This technique of fire setting has a very wide spatial and temporal distribution in Africa. These few examples illustrate that precolonial Africa deployed similar techniques of mining across regions and periods.
Metal Smelting across Africa
With the exception of gold, which exists in native form, ores of metals such as copper, iron, and tin were reductively smelted to gain usable metal.53 The gold dust or nuggets were melted in crucibles to consolidate them into ingots, which were then worked for a variety of purposes.
Because copper ores exist as carbonates and among other forms of oxides, they required smelting to extract metal from the gangue in the ore.54 This was achieved through the application of heat in an atmosphere-controlled vessel (furnace or crucible). The raw materials for precolonial copper smelting are clays for making furnaces and tuyeres (blow pipes for supplying air to furnace), air (supplied by bellows or through the mouth), charcoal (for heat generation), and ore. When all the raw materials were gathered, the process of smelting began, and after a few hours and temperatures exceeding 1000 degrees Celsius, the incomplete combustion of carbon (charcoal) created carbon monoxide, which reduced the ore to usable metal and slag-waste products.55 Early smelting practices in Egypt did not generate free-flowing slags such that metal droplets were trapped. Upon termination of the smelt, the slags were crushed to mechanically remove prills that were molten in crucibles.56 With improvements in furnace-air provision through the use of bellows, free-flowing slags were formed. However, because of density differentials, the slag floated on top while the metal formed at the bottom of the furnace. In Egypt, Nubia, and North Africa, smelters could smelt sulfide-rich copper ores by initially heating the ores in an oxidizing environment to drive off the sulfur—a process known as roasting. This produced a mass known as copper matte, which was smelted in the furnaces. On the basis of current evidence, sulfide-ore smelting seems to be uncommon in other regions in Africa. However, Bisson suggests that some groups in the modern Democratic Republic of Congo may have roasted copper ores in the late 19th century.57
The evidence of precolonial copper-extractive metallurgy consists of remnant furnaces, remains of ore, and broken tuyeres. Based on the surviving evidence, bowl furnaces were the first to be used at places such as Wadi Dara in Egypt.58 By about 3000 bce, Egyptian copper smelters used their mouths to blow into reeds that were tipped with clay nozzles. By the Late Bronze Age, shaft furnaces and bellows were widely in use. There exist numerous tomb paintings that illustrate the use of crucible furnaces, bowl furnaces, and in some cases shaft furnaces. Shaft furnaces had the advantage that they could produce high volumes of metal. From blowing air into the furnace using the mouths, pot, bag, and drum bellows were added to the metalworking toolkits. Improvements in bellows were associated with the need to increase the provision of air into the furnaces for increased metal yield.
Archaeometallurgical studies of copper-smelting residues from Agadez, Niger (c. 800 bce), suggests that some of the earliest furnaces used were shaft types that were possibly connected to bellows. The technology of coper smelting was similar to that used in Egypt and elsewhere in the Old World.59 However, in West and central Africa, smelters used both bowl and shaft furnaces that were bellow driven. One of the best-known cases of copper smelting is that of central Africa. Here, Bisson studied the archaeology of copper smelting in the modern-day Democratic Republic of Congo and adjacent regions of Zambia.60 The evidence from Kansanshi suggests that early in the 1st millennium ce, smelters may have experimented with reducing copper in crucibles that resembled domestic pots. With time, shaft furnaces were utilized such that by 1200 ce, it appears that smelters at the same site experimented with reducing copper in natural draught furnaces (which suck in air through inlets at the bottom of the furnace using the chimney effect). However, it appears that the experiment was not repeated, for there is no known ethnographic example of copper smelting in natural draught furnaces, whose disadvantage is that because they are highly reducing, they could also reduce iron oxides, into metal thereby creating iron and copper alloys of no utilitarian value.61 Ethnographically, however, copper was smelted using slag-tapping techniques by the Luba of the Democratic Republic of Congo. Luba furnaces, a shaft type of furnace, were designed such that they drained molten metal directly from the furnace into ash-lined ingot molds outside the furnace.62 Miller et al. and Thondhlana et al.’s research at Phalaborwa analyzed copper-smelting slags and reconstructed the technology of smelting.63 Phalaborwa slags were dominated by magnetite crystals and remnant minerals such as apatite, which are common accessory minerals in the Phalaborwa ore body. The metal from Phalaborwa furnaces was melted in pottery crucibles and cast into distinctive ingot types known as lerale (pl. marale).
Compared to other metals, more is known about iron smelting across Africa. Across much of the continent, iron was smelted in bowl and shaft furnaces, but it appears that in regions such as Egypt, Meroe, and related places, iron was primarily smelted only in shaft furnaces. One interesting observation is that in West, central, East and southern Africa, there existed very tall shaft furnaces that were powered by natural draught. These furnaces were highly reducing and could produce significant quantities of iron per smelt.64 In precolonial Africa, the technology for reducing iron involved the solid-state reduction of iron-rich ores such as hematite and magnetite in charcoal-fueled furnaces to create a bloom of iron and slag-waste products. The raw materials for iron smelting were fuel (charcoal), air (from bellows or natural draught), and clay (for making furnaces and tuyeres). The process was self-fluxing such that the fuel-ash and melting-furnace wall performed the role of a flux.65. When all the raw materials were gathered, the process of reduction was initiated, resulting in the production of a bloom that was subsequently cleaned and consolidated in the forge, ready for fabrication into a wide array of utilitarian and expressive objects.
In West Africa, the earliest furnaces appear to be low shaft types that were non–slag tapping. Remains of these are known from Niger, Nigeria, and parts of Senegal. Interestingly, bowl furnaces were also used alongside the low-shaft furnaces in many parts of Africa from the deep time to the present.66 Bowl furnaces and low-shaft furnaces are also known as forced-draft furnaces because they were bellow driven. In the Cameroon–Nigeria border area, there existed unique down-draft furnaces that could produce cast iron, soft iron, and low carbon steels.67 In addition to forced-draft furnaces, there existed the very tall natural-draught types whose ethnographic and archaeological distribution extends from Ivory Coast in the West to the area around Great Zimbabwe and the Tswapong Hills in the south.68 Archaeologically, natural-draft furnaces were used from the mid-1st millennium ce in the Dogon region of Mali in West Africa.69 In regions such as Bassar in Togo, natural-draught furnaces were used to sustain large-scale iron-production industries with significant consequences for the environment.70 Current evidence appears to suggest that the earliest iron-smelting furnaces in Egypt were shaft furnaces that were bellow driven. Remains of these were found at places such as Naucratis.71 One of the best-known precolonial iron-production centers in precolonial Africa is Meroe, the capital of the Kingdom of Kush.72 Here, large-scale iron smelting was practiced in slag-tapping shaft furnaces powered by pot bellows. Slag tapping appears to have been widely practiced across Africa from West to East and north to south and was associated with all known furnace types.
Studies of residues of slag, furnace walls, broken tuyeres, and remnant ore in the laboratory provide unique technological information such as the nature of the ores used, the efficiency of reduction, and the technological choices invested by smelters to increase the yield of metal.73 For example, Iles and Martinon-Torres studied remains from pastoralist iron production in Kenya and concluded that smelters exploited ilmenite-rich sands.74 Killick analyzed remains of iron production from the Senegal River area and showed that some of the furnaces were highly reducing.75 Chirikure’s analysis of slags produced by the Njanja of central Zimbabwe revealed that the furnaces were highly reducing so that very little free iron oxide was left in the slags.76 Apart from maintaining high fuel-to-ore and high fuel-to-air ratios, the Njanja used tuyeres and furnace walls that melted and partly contributed to fluxing, a technological solution that may have increased metal yields.
Tin is another important metal smelted in precolonial Africa. Unlike iron, which is hugely abundant on the earth’s crust, the geological distribution of economically exploitable tin is restricted, making it a semi-scarce metal. While not much is known about the smelting of tin across Egypt, the tin ore cassiterite was smelted in the Jos Plateau of Nigeria during the Iron Age. Compositional and trace-element analyses of the renowned Igbo Ukwu bronzes indicated that they were made of tin produced in the Jos Plateau area of Nigeria.77 However, to date the most detailed study of tin smelting in precolonial Africa was performed by a team led by David Killick at Rooiberg in South Africa.78 At Rooiberg, cassiterite was smelted in bowl and shaft furnaces at places such as Smelterskop. The smelting produced very glassy slags, some of which contained molten feldspars and iron oxides interspersed with a few tin droplets. Rooiberg tin was cast into ingots, some of which were found across southern Africa at places such as Great Zimbabwe.
Metal Smithing and Fabrication across Africa
The metals and alloys that were worked in precolonial Africa can be grouped into ferrous and nonferrous types. Because of each category’s physical properties and limitations of technology, there were broad similarities and also sharp differences in the manner in which metals and alloys were fabricated across the continent.79 Copper, gold, silver, bronze, and tin and brass are some of the most popular nonferrous metals and alloys used in Africa. Silver, lead, and the gold-silver alloy electrum were widely used in Egypt, Nubia, Ethiopia, and North Africa. Although adopted at different times, copper, tin, bronze, and brass appear to have a universal presence across the continent. However, silver was not worked in regions such as southern Africa.80 The techniques for manipulating nonferrous metals and alloys exploited their malleability and ductility. The most common technique of fabricating these metals and alloys was hammering. At the forge, pieces of metals or alloys were fired to red-hot temperatures and were repeatedly hammered to shape, as was necessary. The resulting object was polished using pebbles to achieve a shiny surface. Among many examples scattered across the continent, in ancient Egypt and Nubia, gold, copper, bronze, and electrum sheets were produced in this way, along with small objects.81 In southern Africa, the famous Mapungubwe golden rhino was produced through cycles of hammering to produce thin gold leaf that was attached to a wooden core.
Throughout precolonial Africa, nonferrous metals and alloys were cast to produce spectacular objects.82 The Katanga copper crosses (X-shaped copper ingots) widely produced in the modern-day Democratic Republic of Congo but with a wider circulation in southern Africa were produced when molten copper was poured into molds that were either portable or fixed onto the ground.83 Perhaps the most spectacular form of casting achieved in precolonial Africa is that of lost-wax casting, which reached spectacular levels in West Africa, ancient Egypt and Nubia, and Ethiopia, among others. Lost-wax casting involved making a model of a desired object in wax and dipping it in clay, before subsequently hardening it through firing. The wax inside the clay mold melted and was drained away. Molten metal was then poured to create spectacular shapes and objects. The well-known Igbo Ukwu objects from Nigeria were produced using this technique, which continued to be used and reached spectacular levels of workmanship in the later Benin bronzes and brasses. In West Africa, the Akan gold workers in Ghana impressively marshalled the technique of lost-wax casting to produce impressive gold objects used for ceremonial purposes.84
Because iron was produced as solid metal, this limited the working options available to precolonial ferrous metallurgists. The “universal” technique for fabricating iron objects involved successive cycles of hot and cold working pieces of metal on an anvil. Billets of iron were placed in a fire in the forge and were heated to red-hot temperatures.85 Back-and-forth cycles of hammering ended with the production of an object that was then polished as needed. Although the range of tools varied from region to region, some of the common tools included axes, hoes, spears, and arrows. Musical instruments such as gongs, whose distribution stretches from the Ivory Coast in West Africa to as far south as northern Zambia, were also made of iron. In Africa south of the Zambezi, iron gongs are only known from Great Zimbabwe. In other contexts, iron was used to make decorative items such as beads, bangles, and necklaces.
Wire drawing is another technique that was used to work both ferrous and nonferrous metals and alloys. The technique of wire drawing involved pulling pieces of metal through a gauge with holes of different diameters until the desired diameter was reached. This produced very thin wires that in southern Africa were coiled to produce bracelets, bangles, and earrings. According to Cline, wire drawing appears to be concentrated mostly in southern, East, and North Africa.86 More research is required, but the wires that appear on Igbo Ukwu bronzes may have been drawn or hammered.
Anthropology of Mining and Metallurgy
Precolonial metallurgy and mining across Africa constituted a socially embedded technology. As such, the full chaîne opératoire of metallurgy and mining was imbued with religious, sociocultural, and symbolic attributes, all of which were inseparable from the associated technology. At a general level, metallurgy and mining were immersed in sociocultural beliefs and assumed to be under the control of supernatural powers. For example, the belief in supernatural powers motivated ancient Egyptians to construct a temple precinct adjacent to the copper mines in the Arabah Desert.87 Ancient Egyptians were not alone in this belief, and the Dogon of Mali made it explicit that by digging into the ground, miners crossed the boundary into the spirit world.88 A number of taboos were observed by miners during the process of ore extraction. For example, women undergoing their monthly periods were allowed to neither enter the mines nor touch the ore. In cases where suitable ore proved difficult to find, miners often sacrificed chickens or goats and used medicines to neutralize the power of malevolent forces.
The issue of gender participation in mining is very crucial. Although there were rituals and taboos that were observed, women are known to have been successful miners who extracted gold in Ghana, and iron in Kenya and Zimbabwe and copper in the DRC.89 One of the most fascinating reports is that of a woman who was leading a team of male copper miners in the Katanga region of the Democratic Republic of Congo. Thus mining was an activity that utilized the labor of men, women, and children.
Across many parts of Africa, the smelting of iron was viewed as a very powerful act of heat-mediated transformation that symbolized human reproduction and copulation. As such, the furnace was symbolically viewed as a woman, who after smelting produced a child-iron. Often, some furnaces, particularly those used by the Shona of Zimbabwe, were decorated with female anatomical features such as breasts and genitalia. Some parts of the furnaces were also gendered; tuyeres, which symbolized the penis, were known as nyengo in Shona. The sexually explicit nature of this symbolism comes from the observation that sexual intercourse is known as kunyengana in Shona. Similarly, Childs observed that the name of tuyeres among the Toro of Uganda is the same as that of the penis.90 Often, taboos mandated that smelters were supposed to practice sexual abstinence from their wives to avoid unsuccessful smelts. It was traditionally assumed that because of these rituals and taboos, smelting was always practiced in seclusion. However, it is now well known even in contexts where such taboos were observed and furnaces were decorated with explicit sexual symbols that smelting could be performed inside settlements or in areas contiguous to settlements.91
Because it was socially embedded, smelting often reflected the general ideas that pervaded society. For example, it was believed that witchcraft could negatively influence the outcome of smelts. As such, smelters often buried medicines underneath the furnaces. Rowlands and Warnier excavated iron-smelting furnaces in Cameroon and observed the presence of holes dug at the base of furnaces whose function was to act as receptacles for medicine.92 Those features were also recorded among the Phalaborwa of South Africa, the Barongo of Tanzania, and the Phoka of Malawi.
Although metallurgy and mining played an important role in the political economy of African communities of various time periods, the status of miners, smelters, and smiths varied from context to context. In ancient Egypt, metallurgy and mining were under strict royal control and monopoly. At the temples, metalworkers weighed metal before and after use, carefully recording weights. According to Scheel, the weighing balance used by ancient Egyptians was decorated by the goddess of truth known as Ma’at.93 In other regions such as southern Zambezia, mining and metallurgy were not under any bureaucratic control, as was the case in many areas. Metalworkers in this region had an elevated social standing. This contrasted with other regions such as Egypt, where metalworkers occupied a lowly position. In Mali, smelters were part of a caste that could only intermarry with potters, a practice that had similarities with some Ethiopian communities.
Discussion of the Literature
Africa is a culturally diverse continent with a variegated history. However, the tendency in the past was to present metallurgy and mining history of the different regions in isolation. In their book Ancient Egypt in Africa, O’Connor and Reid lamented at the absence of serious collaboration between researchers working in Egypt and Nubia and those working on the rest of the African continent, which makes it seem as if the later were not part of Africa.94 The major advantage of discussing Africa as a single continent is that it becomes possible to elicit trends and patterns, diachronically and synchronically. However, in any discussion, it is important to bear in mind that chronological differences among various areas should not always be used to suggest directionality in the dispersal of knowledge and techniques from one area to another without the backing of hard evidence.95
For there to be usable metals and alloys, ores had to be mined and smelted. Despite the differences in the timing of the adoption of metallurgy across the continent, the techniques of mining are very similar temporally and spatially, and were constrained by more or less the same factors, such as a lack of means to pump water out of the mines.96 While alluvial techniques had a presence throughout the continent, some communities in Ghana and Zimbabwe made innovations that saw them diving into rivers to scoop sand that was panned to produce gold.97 Underground techniques were also practiced in every region, but most precolonial mines hardly exceeded 50 meters in depth because of problems with flooding. Also, maintaining the structural integrity of the mines at deep depths was a problem that often precipitated collapse, resulting in the deaths of miners.98 The challenges presented by precolonial mining stimulated innovations in the provision of air to below-ground chambers and the use of timbering to create props for preventing mine collapse. Fire setting was also commonly practiced from Egypt, through West Africa to South Africa. What is interesting, however, is that the infrastructure for processing ore was the same: ancient Egyptians (around 2000 bce) used grinding stones for milling the ore just like the Rooiberg tin miners who came 3,500 years afterward did (1500 ce).99 The only major difference is in the organization of mining. Ancient Egyptians often built temples and semi-permanent settlements around mines in regions such as the Eastern Desert. In other parts of Africa, the scale of production dictated that miners could access the required ore in one day with no need for permanent settlement. However, it is possible that seasonal settlements were built by miners in and around Rooiberg.100
Across Africa, the technology of copper and iron smelting remained remarkably the same and involved the reduction of ores in charcoal-fueled furnaces of various sizes and types. However, there are many regional differences in areas such as furnace design. In Nubia and other areas, furnaces were built of bricks, while in Mali, they were made of blocks of slag plastered with clay. The tall natural draught furnaces are not known from Egypt and adjacent areas, while drum bellows are only known in Egypt and Nubia, but not in other areas. Furthermore, a clear evolution of furnace types can be seen in those used in Egypt (from bowl furnaces to shaft furnaces) and the methods of air provision (from blowing using mouths versus bellows). In other parts of Africa, the situation is less clear, as different furnace types were all mixed up. An attempt by Kense to model the evolution of iron-smelting furnaces across Africa south of Egypt and Nubia showed that different groups of people used different types of furnaces: it was common for one group to use shaft furnaces while a neighbor used bowl furnaces or tall natural-draught furnaces (see also Cline).101 The different furnace types were associated with significant innovations—for example, the Mafa of northern Cameroon could produce cast iron in their bloomery furnaces. Just as there were similarities and differences in the area of mining and smelting, so too in the area of metal fabrication. The repertoire of techniques and metals and alloys available to ancient Egyptians and Nubians was very wide when compared to other parts of Africa. However, techniques such as hammering and lost-wax casting were all the same. However, ancient Egyptians worked silver and practiced soldering and gliding, which have not yet been documented in other regions.
Perhaps one of the greatest contributions of metallurgy and mining to precolonial African societies was in the realm of political economy. The production and use of metal was shaped by many variables that include demography, scale of production, and level of sociopolitical organization. Across the time and geography of Africa, metal-production contexts differed from those of the nomadic pastoralists in regions such as Kenya to centralized production under very strict bureaucratic control in Egypt and among the Zulu under Shaka. In areas where mining and smelting were concentrated in specific areas, often large-scale evidence accumulated on the landscape. For example, De Barros showed that Bassar iron smelting in Togo produced very large mounds of slag, attesting to large-scale iron production.102 The capital of the kingdom of Kush, Meroe, also yielded large slag mounds, and the same can be said about iron production among the Babungo of Cameroon. However, it is interesting to observe the variation in the organization of production. At Rooiberg, early mining geologists observed that significant tons of ore were mined, and yet archaeologists have only recovered ephemeral scatters of smelting evidence around the mine. Furthermore, Shaka’s army consumed at least 50,000 spears, but no large slag mounds are known. The same applies to west central Africa, where Sukur produced 60,000 iron hoes annually, but there are no massive slag concentrations. Specialized production need not only be measured by the concentration of remains in one place—dispersed production systems also resulted in a large output that equate to specialization. Yet specialization must be understood relative to demography since some production systems are considered large scale when servicing small populations.
Often, the nature of the level of political organization determined whether metal production and mining were under the control of a centralized political economy. In ancient Egypt, mining and metal production were under very strict bureaucratic control to the extent that rigorous methods of stock control were enforced. Often, the Egyptian army controlled the mining areas. In other contexts, such as the Mutapa state, production at the mines was decentralized, and the same applies to metal working centers that were not under royal control. However, even in southern Africa there was a great deal of variation, for during the reign of Shaka, the king controlled all iron production and distributed brass, spears, and other weapons to sustain a patronage system in which those who were loyal to the king and distinguished themselves in battle were rewarded with brass objects. Trade in metal and metal objects often fitted an existing system of exchange in any given situation, beginning local and extending outward. While in some contexts there was centralized control of trade, in others trade was decentralized to the extent that there is no uniformity across Africa. The valuation of metals and alloys also differed from region to region. For example, while silver used to be more valuable than gold in Egypt, only for the situation to be reversed, in southern and central Africa, copper was more valuable than gold—another indicator that the story of mining and metallurgy in Africa defies generalizations.
One of the most important points to consider relates to the ecological impact of mining and metallurgy in precolonial Africa. Mining currently has a significant negative environmental impact due to large mine dumps and increased chemical pollution. However, in the past, mining did not leave large spoils heaps and in West, central, and southern Africa, mercury was not used in metallurgical operations, meaning that because of the scale, negative impact in terms of big dumps was minimal. However, metallurgy required large amounts of charcoal for smelting and smithing, so the direct impact of metallurgy on the environment was through charcoal consumption. Indirectly, metallurgy made food production a lot easier, which in turn resulted in increases in population and the associated impact on the environment. Taken together, charcoal production and agriculture will have left an impact on the environment, but more studies are required to quantify the direct and indirect impact of metallurgy.
One underexplored area of study relates to the contribution of metallurgy to urbanism in pre-colonial Africa. However, a look at some of the most iconic mining and metallurgical landscapes in pore-colonial Africa suggests that often urban centers developed away from mines and smelters. In ancient Egypt, no permanent urban centers developed in the Eastern Desert where ores of gold and copper were mined, which also appears to be the pattern across the continent, as the legendary goldfields of Bambuk that covered portions of modern-day Senegal, Mali, and Mauritania did not attract any urban settlement. Rather, the gold from the mines of Bambuk was transported to the capitals of states such as Ghana, Mali, and Songhai. The same applies to Rooiberg, where no urban center developed around the tin mines at Rooiberg. This may stem from the scale of precolonial mining and metallurgy and the prevailing economic system, which contrasts with the modern system in which the scale of economic activities promoted large-scale human aggregation around cities such as Johannesburg.
In summary, precolonial metallurgy and mining across the African continent have a variegated history. It is clear that different parts of the continent adopted metallurgy and mining at different points in time. Egypt, Nubia, and adjacent regions adopted metallurgy earlier than in other areas such as West Africa. More importantly, the inventory of metals worked in different regions also differed. Regardless of this, the techniques of mining appear the same just as the methods of extractive metallurgy. Within variation, different types of furnaces were used across space and time with different consequences per region. It cannot be denied that a significant amount of interaction occurred among various areas, resulting in an interchange of technologies, knowledge, values, and specific innovations.
Because it is an interdisciplinary endeavor, the study of precolonial mining and metallurgy relies on primary sources that are located within different archives and countries. As far as historical records and transcriptions of oral interviews are concerned, these can be obtained from the national archives of different African countries. Furthermore, photographs from the late 19th and early 20th centuries are also found in these archives. For example, the National Archives of Mali in Bamako and the Ahmed Baba Institute in the same country host essential archives for the study of precolonial mining and metallurgy.
In terms of archaeology and archaeological objects, African countries have museums and antiquities bodies that are empowered by law to identify, protect, and conserve remnants from the past. Objects from archaeological excavations are mostly found in these museums and antiquities bodies. However, objects from some of the first archaeological excavations may be scattered across various institutions in the world. For example, excavations from archaeological sites in the Upemba Depression of the Democratic Republic of Congo are in the Royal Museum for Central Africa in Belgium. The British Museum has various collections from Egypt to Zimbabwe. Access to archaeological sites is generally granted after successful permit applications by researchers as required by the laws in individual countries.
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Thondhlana, Thomas Panganayi, Marcos Martinón-Torres, and Shadreck Chirikure. “The Archaeometallurgical Reconstruction of Early Second-Millennium AD Metal Production Activities at Shankare Hill, Northern Lowveld, South Africa.” Azania: Archaeological Research in Africa 51.3 (2016): 327–361.Find this resource:
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(2.) Bernd Scheel, Egyptian Metalworking and Tools (Oxford: Shire Publications, 1989).
(3.) David Killick, “From Ores to Metals,” in B. W. Roberts and C. Thornton (Eds.), Archaeometallurgy in Global Perspective (New York: Springer, 2014), 11–45.
(4.) Stanley B. Alpern, “Did They or Didn’t They Invent It? Iron in sub-Saharan Africa,” History in Africa 32 (2005): 41–94.
(5.) Augustin F. C. Holl, “Early West African Metallurgies: New Data and Old Orthodoxy,” Journal of World Prehistory 22.4 (2009): 415–438.
(6.) For a summary, see Shadreck Chirikure, Metals in Past Societies: A Global Perspective on Indigenous African Metallurgy (New York: Springer, 2015).
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(14.) David Killick and Thomas Fenn, “Archaeometallurgy: The Study of Preindustrial Mining and Metallurgy,” Annual Review of Anthropology 41 (2012): 559–575.
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(16.) Rehren and Pernicka, “Coins, Artefacts and Isotopes.”
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(18.) Duncan Miller and David Killick, “Slag Identification at Southern African Archaeological Sites,” Journal of African Archaeology 2.1 (2004): 23–47.
(19.) Shadreck Chirikure and Thilo Rehren, “Iron Smelting in Pre-colonial Zimbabwe: Evidence for Diachronic Change from Swart Village and Baranda, Northern Zimbabwe,” Journal of African Archaeology 4.1 (2006): 37–54.
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(37.) Chirikure, Metals in Past Societies.
(38.) Summers, Ancient Mining in Rhodesia and Adjacent Areas.
(39.) Summers, Ancient Mining in Rhodesia and Adjacent Areas.
(40.) Timothy F. Garrard, Gold of Africa: Jewellery and Ornaments from Ghana, Côte d’Ivoire, Mali and Senegal in the Collection of the Barbier-Mueller Museum (Geneva, Switzerland: Prestel, 1989).
(41.) Nicholas David, Robert Heimann, David Killick, and Michael Wayman, “Between Bloomery and Blast Furnace: Mafa Iron-Smelting Technology in North Cameroon,” African Archaeological Review 7.1 (1989): 183–208.
(42.) Walter Buchanan Cline, Mining and Metallurgy in Negro Africa (George Banta, 1937).
(43.) Innocent Pikirayi, “The Archaeological Identity of the Mutapa State: Towards an Historical Archaeology of Northern Zimbabwe,” (Uppsala: Societa Archaeologica Uppsaliensis, 1995).
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(45.) Robert B. Heimann, Shadreck Chirikure, and David Killick, “Mineralogical Study of Precolonial (1650–1850 CE) Tin Smelting Slags from Rooiberg, Limpopo Province, South Africa,” European Journal of Mineralogy 22.5 (2010): 751–761.
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(47.) Dietrich Klemm, Rosemarie Klemm, and Andreas Murr, “Gold of the Pharaohs: 6000 Years of Gold Mining in Egypt and Nubia,” Journal of African Earth Sciences 33.3 (2001): 643–659.
(48.) Augustin F. C. Holl, “Metal and Precolonial African Society,” in Joseph O. Vogel (Ed.), Ancient African Metallurgy (Walnut Creek, CA: AltaMira, 2000), 1–83.
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(53.) Paul T. Craddock, Early Metal Mining and Production (Washington, DC: Smithsonian University Press, 1995).
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(70.) Philip De Barros, “A Comparison of Early and Later Iron Age Societies in the Bassar Region of Togo,” in J. Humphris and T. Rehren (Eds.), The World of Iron (London: Archetype Publications, 2013), 10–21.
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(72.) Thilo Rehren, “Meroe, Iron and Africa,” Der Antike Sudan 12 (2001): 102–109.
(73.) Thilo Rehren, Michael F. Charlton, Shadreck Chirikure, J. Humphris, A. Ige, and H. A. Veldhuijzen, “Decisions Set in Slag: The Human Factor in African Iron Smelting,” in S. La Niece, D. Hook, and P. Craddock (Eds.), Metals and Mines: Studies in Archaeometallurgy (London: Archetype Publications, 2007), 211–218.
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(75.) David J. Killick, “Iron Smelting Technology in the Middle Senegal Valley, ca. 500 BCE–1500 CE,” in R. J. McIntosh, S. K. McIntosh and H. Bocoum (Eds.), Seeking the Origins of Takrur: Archaeological Excavations and Reconnaissance along the Middle Senegal River Valley (New Haven, CT: Yale University Press, 2016).
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(77.) Paul T. Craddock, Janet Ambers, Duncan R. Hook, Ronald M. Farquhar, Vincent E. Chikwendu, Alphonse C. Umeji, and Thurstan Shaw, “Metal Sources and the Bronzes from Igbo-Ukwu, Nigeria,” Journal of Field Archaeology 24.4 (1997): 405–429.
(78.) Shadreck Chirikure, Robert B. Heimann, and David Killick, “The Technology of Tin Smelting in the Rooiberg Valley, Limpopo Province, South Africa, ca. 1650–1850 CE,” Journal of Archaeological Science 37.7 (2010): 1656–1669.
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