The Quest for Obsidian: How Jōmon People Accessed Obsidian | Jomon Period | Japan

Obsidian is natural glass that results from the cooling of volcanic lava. As the splitting of obsidian produces very sharp edges, these sharp edges were used as a material for making tools by globally distributed Palaeolithic peoples for tens of thousands of years. The skills needed to produce useful tools from this raw material would have been as valuable as the resource itself.

Although Japan is dotted with numerous volcanoes, there are only a limited number of sites where the Jōmon people mined this valuable resource, and one of the closest sites is nearby in Nagano Prefecture, perhaps just a few day’s walk from the Umenoki site (about 49 kilometers). It is almost certain that obsidian was a valuable trading good, and it might be interesting to imagine what the local people at this site could have offered in exchange for something that was as indispensable to their lives as semiconductors are to our lives in the twenty-first century.

Metalworking techniques had not yet developed in the Japanese archipelago when the Jōmon people thrived here between circa 14000 and 800 BCE. They made all their tools from the stones, animal bones, antlers, and wood they could find. Virtually all tools made from organic substances decompose and are lost to time, but stone tools are almost always unearthed wherever ancient archaeological sites are excavated. The stone tools used by Jōmon peoples vary by period and region, but the main tools include polished stone axes for felling trees, obsidian arrowheads for hunting, tapered stone tools for digging the ground, and flat stones accompanied by grinding stones for processing hard fruits and nuts. By examining the chemical composition ratios of these stone tools, we can infer the subsistence activities of Jōmon peoples.

Stone tools were made of suitable stones according to their functions. For stone axes, hard, heavy stones with comparatively greater density are suitable, for example, green tuff or serpentine. For tools such as arrowheads, which require sharp edges, obsidian and chert are suitable. The Jōmon people were particularly keen of obsidian. Obsidian is a hard, dark, glasslike volcanic rock formed by the rapid solidification of lava without crystallization. It is easy to work and produces sharp edges when hit precisely. Furthermore, the black to almost transparent color of obsidian is also a reason for its appeal.

Although there are over 100 source-sites for obsidian across the Japanese archipelago, there are only a limited number of high-quality obsidian centers that can be mined using Jōmon-era techniques. In the Chubu region (the center of the main island of Honshu), the obsidian source areas of the Kirigamine Plateau in Nagano Prefecture are “Hoshigatou” and “Hoshikuso-tōge”. In these obsidian fields, there are many holes where obsidian was clearly mined by the Jōmon people. Interestingly, people in the more recent past referred to the pieces of obsidian that glittered on the ground as stars.

Mined obsidian was distributed from person to person and from village to village through reciprocal networks of exchange. In one case, obsidian was carried from the Kirigamine Plateau in Nagano Prefecture to a site on the southern tip of Hokkaido, 650 km to the north. The exchange and distribution of obsidian allowed for the movement of people and information over a wide area. This can be seen in Jōmon pottery. The middle Jōmon pottery (circa 3520–2470 BCE) excavated at the foot of Mt. Yatsugatake in the Chubu region (the central part of Japan west of Tokyo) and the middle Jōmon pottery found in the western part of the Kanto Plain (Tokyo and surrounding area) are very similar.