Copper mining and smelting technology in the northern Lowveld, South Africa, ca. 1000 CE to ca. 1880 CE. (November 2016)

• Record Type: Journal Article
• Authors: Killick, David; Miller, Duncan; Thondhlana, Thomas Panganayi; Martinón-Torres, Marcos
• Is Part Of: Journal of archaeological science. Volume 75(2016:Nov.)
• Page Start: 10
• Page End: 26
• Publication Date: 2016-11
• Subjects: Technology -- Archaeometallurgy -- Copper -- Mining -- Smelting -- Slag -- South Africa; Archaeology -- Periodicals; Archéologie -- Périodiques; 930.1
• DOI: 10.1016/j.jas.2016.08.011
• Languages: English
• ISSNs: 0305-4403

Abstract

Abstract: We report chemical, petrographic and metallographic studies of copper ores and slags recovered during sporadic surface surveys and excavations over the past fifty years in the Phalaborwa and Murchison Range areas of the northern Lowveld of South Africa. The copper slags around Phalaborwa have unusual mineral assemblages, attributable to the unique geochemistry of the main ore body, the Phalaborwa Complex, where copper minerals were mined from a carbonatite composed of magnetite, calcite and apatite. Strongly reducing conditions had to be avoided to minimise contamination of the copper with iron and phosphorus. As the copper ores contain almost no silicates, silica/alumina flux was added to produce slag. The Precambrian zinc-copper ores of the Murchison Range were also smelted, but during smelting any zinc that was not volatilised was taken up by minerals in the slag, so brass was not produced. Highlights: The Phalaborwa copper deposit is geologically and geochemically unique. Smelting of these ores produced slags of unusual chemistry and mineral content. The ores contain almost no silica, so silica/alumina flux was added to produce slag. Smelting of zinc-copper ores in the Murchison Range produced zinc-free copper metal.