Obsidian was used as hunting tools and weapons from the Paleolithic period to Yayoi period. There are about 100 known obsidian mining sites in Japan, however, stones of good quality and used as tools were from 6 locations only, with Oki included (Shirataki in Hokkaido, Wada Pass in Nagano Prefecture, Kozushima Island in Tokyo, Mount Koshidake in Saga Prefecture, Himejima Island in Ōita Prefecture and Oki in Shimane Prefecture). Since obsidian from different mines contain different trace components, it is possible to identify the location where it was mined using chemical analysis. It is clear that obsidian from Oki were distributed mainly in Chugoku region, and sometimes circulated in the Seto Inland Sea and as far as Niigata Prefecture.
From such findings, we can see that obsidian of good quality was an indispensable tool for those in the past. In addition, the distribution of remains where obsidian was found shows the route of exchange between people and culture back in those days.