[H-TT15] Non-destructive techniques applied to stone cultural heritage

[HTT15-P02] Magnetic susceptibility of obsidian from Shirataki, Hokkaido, Japan, to identify the source of obsidian tools

*Kyohei Sano¹ (1.Graduate School of Regional Resource Management, University of Hyogo)

Keywords:magnetic susceptibility, obsidian, nondestructive analysis, rock texture

Magnetic susceptibility is often used to identify the source of tools and tombstones that are made from igneous rocks, such as obsidian and granite. This study reports on how the relationship between magnetic susceptibility and sample thickness of obsidian contributes to identifying the source of obsidian tools. Obsidian samples from Shirataki, Hokkaido, Japan, were analyzed, focusing on those from the lava flows of Tokachi-Ishizawa (TI), Akaishiyama (AK), and Horoka-Yubetsu (HY). The sample thickness ranges from 2.74 to 20.84 mm and the magnetic susceptibility ranges from 6.1 × 10^–5 to 4.2 × 10^–4 SI for the TI lava, from 2.52 to 13.78 mm and 3.3 × 10^–5 to 2.1 × 10^–4 SI for the AK lava, and from 2.05 to 23.28 mm and from 1.9 × 10^–4 to 7.3 × 10^–4 SI for the HY lava, depending on the thickness of the sample wafer. The results revealed that obsidian from the HY lava demonstrated the highest value of magnetic susceptibility among the analyzed samples; thus, obsidian from the HY lava could be identified by this characteristic. Concurrently, heterogeneity in the magnetic susceptibility within a single lava flow was observed in the AK lava. These results could contribute to the identification of the source of obsidian tools and development of nondestructive techniques for measurement of magnetic susceptibility.