Microwear analysis of a 10000-year-old rhyolite blade assemblage from Sujala, northernmost Finland

In this paper, the authors investigate tool use among hunter gatherers of the eastern Post-Swiderian tradition through a microwear analysis of a partly weathered rhyolite blade assemblage from the Early Mesolithic site Sujala in Finnish Lapland. To test the possibilities for a microwear analysis, a stratified sample including both weathered and unweathered artefacts was selected. Most of the artefacts came from the production of blades at the site. The blades had been turned into different types of formal tools such as scrapers, burins and arrowheads; however, most of the sample consisted of different types of blade fragments. The analysis showed that several pieces in the sample were well preserved and had observable traces of microscopic wear. This made it possible to separate the artefacts, mainly parts of broken blades, into different tool types used to process different raw materials. This first glimpse into a group of cognitive tool categories can in the next stage serve as a basis for a second-generation experiment to test the suggested use, contact materials and kinetics, extending the sampling to other parts of the assemblage. It is also concluded that the combination of the universal use of the two-stage process of low-power and high-power light microscopy in the analysis can give surprisingly good information on ancient tool use, also on igneous rocks such as rhyolite. However, the large variation of rocks within the lava category as well as between different subtypes of this general category is identified as a key problem for the use wear community in the future. Difficulties in finding suitable raw materials for reference collections are crucial and obstruct communication between scientists. In any case, a systematic integration of mineralogical analyses and adjusted use wear protocols must be developed based on tribological research .