HOW Metals Were Worked Long before the Industrial Revolution
BYLINE: Shadreck Chirikure
Huge shafts sunk into the earth, the associated mining dumps and modern processing plants fitted with high-tech equipment are part of the modern iron and steel industry.
So important is the ferrous industry that it employs thousands and produces raw materials for other industries. This has positive spin-off effects for the local and global economies.
But this is in the present; what do we know about the history and technology of indigenous iron production? This invites us to revisit the history of indigenous iron production in South Africa with a view to highlighting the most salient features of the process. Such an endeavour falls within the ambit of archaeology and a sub-discipline known as archaeometallurgy.
The history of iron mining and smelting in South Africa did not start with colonialism. Nor did it begin with the process of industrialisation associated with it. Some 40 000 years ago, Late Stone Age folk mined iron oxide pigments on the Bomvu ridge in Swaziland. The smelting of those oxides to produce metal, however, did not immediately follow. Conventional archaeological wisdom says that metallurgy was introduced to southern Africa almost 1 800 years ago by Bantu agriculturalists.
During this time, iron was used for making items such hoes, axes and small tools. Copper was the only other metal to be worked at this early period. Archaeologists have recovered waste materials from early iron industries associated with first millennium AD sites such as Broederstroom in Limpopo province, Silver Leaves in Mpumalanga and Msuluzi in KwaZulu-Natal.
The period after 1000 AD was characterised by more metallurgical diversity with gold, tin and brass being added to the inventory of metals exploited by indigenous peoples.
It is believed that trade in metals, together with other factors, contributed to the development of complex societies and state systems at places such as Mapungubwe. This is confirmed in Arabic, Portuguese and other written sources of the second millennium AD. By the time colonialism began, there was increased metallurgical specialisation, with different communities known for working different metals.
Reports of missionaries and travellers talk of specialist iron and copper industries among the Lemba, Phalaborwa and the Tswana in the 19th century. Industrial methods of producing iron and steel have virtually ended and out-competed the laborious process of indigenous iron production.
David Livingstone once remarked in the late 18th century that the iron produced by southern African communities was of a superior quality to European imports at the time.
What do we know about the technology of indigenous iron production? Archaeologists use a variety of techniques from historical and scientific disciplines to generate information on how prehistoric technologies functioned. This approach has revealed the existence of major differences between modern iron and steel industries and indigenous ones. These range from the technology used and the scale of production, to the organisation of technology.
Indigenous iron production industries contrast remarkably with the blast furnace method of iron smelting exclusively used nowadays. As elsewhere in sub-Saharan Africa, pre-colonial iron smelting in South Africa was conducted through the direct or bloomery process.
In this process, iron ore was reduced to metallic iron by carbon monoxide in small charcoal-fuelled furnaces to produce a solid but spongy mass of metal bloom and a molten silicate called slag. Because the iron bloom contained occluded slag and charcoal remnants, it was refined and consolidated into usable iron through smithing.
Today, the smelting of iron ores in blast furnaces result in the production of liquid cast iron which contains a very high amount of carbon. The carbon is then removed through a process known as decarburisation to produce wrought iron. …