Sourcing without sources: Measuring ceramic variability with pXRF

Sourcing studies usually focus on interpreting movement from source to place of deposition. These studies typically use materials like obsidian that lend themselves to chemical characterization. Less attention has been paid to sourcing materials that are also abundant in the archaeological record such as ceramics. Most studies of ceramics are destructive which limits their application. Portable x-ray fluorescence (pXRF) is a non-destructive alternative that can be used to determine the geochemical composition of a material. The ability to characterise ceramic materials non-destructively and rapidly permits the analysis of large numbers of vessels and sherds, but the nature of ceramics does not allow sourcing data to be interpreted in the same way as for other materials. An approach proposed looks for groups based on relative differences among objects in order to identify materials that fall outside of the most common geochemical composition within an assemblage. A total of 1626 ceramic artefacts from four assemblages from middle Holocene contexts in Egypt are assessed to determine inter and intra assemblage geochemical variability. The results are used to interpret mobility and settlement patterns indicating more variability than previously thought.