Western Desert tjiwa- and tjungari- type grindstones, and their archaeological significance

In the southern part of the Western Desert, the regional geology constrains the form of grinding slabs and their reduction. Grinding slabs in this area, locally called tjiwa, are rudimentary implements, which are not shaped prior to use, nor extensively reworked or resharpened during use, nor are they heavily worn. Yet even such basic grindstones can effectively process seeds, which are a seasonal food staple in this area, though tjiwa are much less efficient than millstones for processing large volumes of grain. The question arises as to whether tjiwa can be used as an archaeological marker for seed-grinding. The answer to this is no. Tjiwa are general purpose grinders, used for a variety of materials, and even when used for seed exhibit few diagnostic traits of such use. I propose that any identification as seed-grinders will rely on associated evidence (residues, assemblage composition, use-wear and type of associated topstones). Tjiwa should be distinguished from more elaborate grindstones, such as millstones. In this paper I formally describe tjiwa and tjungari (their associated topstones) to complement similar studies of millstones.