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Recently archaeological materials analysis has focused on the development and application of new techniques, such as handheld x-ray fluorescence (XRF) analysers, for the geochemical provenance of artefacts (e.g. Goren et al. 2011). While these studies are important for the continued growth of the discipline and stimulate valuable discussion about quantitative, semi-quantitative, quasi-quantitative and qualitative data sets (e.g. Shackley 2010), they ignore the underlying uncertainties inherent in the data itself. Measuring the elemental composition of ceramic artefacts with the highest degree of accuracy and precision, to the lowest detection limits possible, using either quantitative or semi-quantitative instruments is only valuable for establishing artefact provenance if that chemical profile actually provides information about provenance. The premise of ceramic provenance using geochemical analyses is that raw material signatures are chemically distinct and that those chemical signatures can be detected in ceramic fabrics. Sediments are generally not directly suitable for potting and must first be processed and refined, changing their mineralogical and chemical signature (Rice 1987: 118-119). What is measured then, in chemical provenance studies, is the chemical profile of a ceramic fabric, which may or may not be related chemically to the raw sediment from which it is composed (e.g. Hein et al. 2004). The degree to which ceramic fabrics reflect their raw materials provenance is a level of uncertainty which is often overlooked when communicating results of these studies. An additional level of uncertainty exists related to the chemical homogeneity of the ceramic raw materials themselves. Geochemical variability in the natural world is limited: a finite number of elements bond in predictable ways to crystallise a finite number of minerals, and those minerals combine to form a predicable and finite number of rock types. Like crystallisation, weathering of rocks follows an established trajectory so that the chemical and mineralogical heterogeneity of detrital sediments is limited further still. Sediments from different geographic locations or provenance can have the same chemical signature (e.g. Klein and Langmuir 1989). This geochemical homogeneity is another level of uncertainty which is often ignored in ceramic provenance studies. These layers of uncertainty and failure to effectively communicate them in geochemical provenance studies impact the larger archaeological narrative through the misidentification of ceramic provenance upon which social, economic and political theories and relative chronologies are based. This paper evaluates uncertainty in chemical provenance studies of archeological ceramics related to human behaviour and natural geological homogeneity and proposes new vocabulary for communicating this uncertainty within the wider archaeological community. Goren, Y., Mommsen, H., Klinger, J., 2011. Journal of Archaeological Science 38, 684-696. Hein, A., Day, P.M., Quinn, P.S., Kilikoglou, V., 2004. Archaeometry 46, 357-384. Klein, E.M., Langmuir, C.H., 1989. Journal of Geophysical Research 94, 4241-4252. Rice, P.M., 1987. Pottery Analysis, University of Chicago Press, Chicago. Shackley, M.S., 2010. The SAA Archaeological Record November, 17-20.