Obsidian is a volcanic glass that was highly valued for its effectiveness as a stone tool during the Stone Age. Obsidian is found in Dōgo Island and was used to make tools such as arrowheads in ancient times.
The geological composition of obsidian differs from place to place. This means it is possible to analyse obsidian artifacts and determine their place of origin. Also, despite there being over 70 different places around Japan where obsidian is found, only a small handful of these sites contain obsidian that could be used to make stone tools. Including Oki, there are six different locations where obsidian was mined in ancient times. Oki is the only location in the whole of the Chugoku Region of Honshu Island that has obsidian.
From as long as 30,000 years ago, Oki obsidian was mined and transported widely around the Chugoku Region as well as Niigata and Shikoku. Because the quality of Oki obsidian was so high, we can imagine that it was an indispensable tool in the lives of ancient people.
Moreover, looking at sites containing Oki obsidian artifacts, we can also determine prosperous areas in ancient times. These areas often appear throughout history, and can be considered as routes of cultural exchange and trade.