Technical ceramics for salt production in Western Sahara

Abstract

This paper presents evidence of ceramic technology in western Tiris (Western Sahara), dated by thermoluminescence to the third millennium cal. BP. Western Tiris is an arid region mostly covered by desert where recent archaeological fieldwork has nevertheless revealed a significant network of settlements from the Neolithic period inhabited by nomadic people. Domestic pottery and lithic materials are common in the archaeological register of these sites, but three sherds found in the Lejuad XVII rockshelter present features typical of technical ceramics. Laboratory analyses reveal that abundant mineral and organic temper was added to the natural clay which, in addition to the presence of thicker walls than those usually found in domestic pottery, is interpreted as an attempt to increase resistance to thermal shocks. However, the fragments present only mild signals of exposure to high temperatures, up to a maximum of 900 °C. Discussion of these contradictory data leads to the conclusion that the sherds may have been part of a briquetage mould to extract salt by evaporation, a pyrotechnical industry previously unknown in Western Sahara. Its appearance in an arid environment far from production centres is explained as result of sporadic economic activity rather than cross-cultural mobility and trading, which seems to have been intense in the area from Neolithic times. In addition, this paper introduces the use of micro-computed tomography (µ-CT) as a technique for measuring large porosity derived from burned organic materials.