Obsidian was used for hunting tools and weapons from the Paleolithic (old stone age) to the Yayoi period (c. 300 BCE–250 CE). There are about 100 known obsidian mining sites in Japan; however, obsidian of good enough quality to be used as tools were from 6 locations only: Shirataki in Hokkaido, Wada Pass in Nagano Prefecture, Kozushima Island in Tokyo, Mount Koshidake in Saga Prefecture, Himejima Island in Ōita Prefecture, and the Oki Islands in Shimane Prefecture. Since obsidian from different mines contains different trace components, it is possible to identify the location where it was mined using chemical analysis. It is clear that obsidian from the Oki Islands was distributed mainly in the Chūgoku region, and sometimes circulated around 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.