Use-Wear Analysis of Obsidian and Other Volcanic Rocks: An Experimental Approach to Working Plant Resources

Abstract

This experimental study aims to contribute to functional analysis research on tools which specifically served to work wood and non-woody plants. They were made of obsidian and other volcanic rocks (basalt, trachyte, and phonolite) characterised by an amorphous matrix and phenocrysts of different number and size. In spite of prior functional analysis research resorting to these raw materials, there remain gaps in our understanding of specific activities. The work thus focused on working different types of wood from the Canary Island as well as on harvesting cereals. It is likewise centred on craftwork, especially regarding certain rarely studied contact materials such as palm leaves and rushes. The results reveal use-wear differences stemming from working woody and non-woody plants with both obsidian and other volcanic rocks. A special attention was given to the identification and description of the different features depending on the raw materials and the characteristics of their knapped surfaces. Identifying the combination of attributes has been essential to attain more accurate diagnostics. There are limits to each of the types of raw materials. The surfaces of obsidian are easier to observe and allow more specific identifications. In turn, the heterogeneous surfaces of volcanic rocks with phenocrysts that require more to time to develop diagnostic traces render use-wear amongst these types of rocks more difficult to observe. It is possible to distinguish longitudinal and transversal actions between woody and non-woody plants on every rock. Actions related to basketry, such us splitting and scraping, are more complicated to identify. The state of the worked plant (dry or fresh) and the time of use are key factors to consider in each case.