Copper smelting from Xinjiang, NW China. Part 1: Kangcun village, Kuche county, c18th century AD
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Abstract
selection of glassy copper slags from Xinjiang, NW China were analysed by optical microscopy and SEM-EDXA. The results indicate that a very rich copper ore was smelted, probably pure copper sulphide with a gangue rich in feldspar and quartz. The slag is dominated by silica, lime and alumina, which together contribute 90–95wt%. The redox conditions are discussed, including the formation of metallic iron and iron phosphide within the copper metal, and the melting temperatures are estimated to be at least 1300°C, based on the bulk composition of the glass. The combination of redox conditions and high temperature indicates that the smelting would have taken place in a blast furnace, probably bellows-blown. A single radiocarbon date from charcoal trapped in the slag places the operation in the 18th century AD, well after the widespread adoption of blast furnaces in China. Despite the apparent large scale of the operation there are no historical records or local memories of such an operation.
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