| Summary: | The excavation of a smelting furnace in Area 14/15 produced about 4000 fragments, or approximately 12.5kg, of mostly platy slag, and a further 900 grams of technical ceramic, most likely tuyère fragments. The metallurgical activity represented by this debris dates to the seventh or eighth century AD (see Chapter 8). In order to reconstruct the smelting process involved, a detailed archaeometallurgical study was undertaken. According to the results obtained, a rich sulphidic copper ore, probably chalcopyrite, was smelted for pure copper. The possible extraction of either lead, silver, or arsenical copper is discussed, and can be safely excluded. Smelting was done under relatively oxidising conditions, producing matte initially and finally metallic copper. Sandstone fragments were added as flux, possibly in a multi-step process with intermediate roasting of matte, either outside or within the furnace. The total amount of copper produced in the one furnace specifically studied was estimated to about 5kg.
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