Evaluating the Knapping Quality of the Japanese Early Upper Paleolithic Raw Materials: Mechanical Characterization of Obsidian, Andesite, and Shale in the Kanto Plain and Adjacent Areas

This study investigates the mechanical characteristics of lithic raw materials used during the Paleolithic in the Japanese Archipelago, focusing on Wada‐toge obsidian, Happusan andesite, and shale from the Akaya Formation. Although these sources have been well documented, few studies have examined their mechanical behavior. To evaluate the knapping quality (or fracture predictability), we measured several mechanical indicators on geological samples. Comparisons with Paleolithic assemblages suggest that the distinct mechanical signatures may have constrained prehistoric knapping strategies and influenced lithic artifact morphology. These findings highlight the mechanical property measurement for understanding prehistoric resource procurement and technological behavior in the Japanese Archipelago.