Obsidian (kokuyōseki in Japanese), a kind of black volcanic glass forged in the heat of eruptions, was a tremendously valuable commodity in the prehistoric Japanese archipelago, as it was in the Mediterranean and elsewhere where it occurs. Japan’s many volcanoes – over 110 of them still active – means that there are many sources of this important stone. Early exploiters often travelled far and wide, up steep mountain sides and across ocean straits, to find the best sources, searching for rocks that would give the best edges and the most aesthetically pleasing results. And those edges are the sharpest in the natural world, still used today in surgical procedures – as fine as a mere 30 angstroms (one angstrom being one hundred millionth of a centimetre) – dividing individual cells in half and causing minimal scarring. While there is no evidence that the ancient Japanese were using obsidian for any medical purposes (though their Neolithic counterparts elsewhere were not averse to opening up the heads of living patients / victims in procedures called trepanation – some particular unfortunates recovered sufficiently to go through this more than once), obsidian was worked into a range of stone tools for hunting and cutting. Caches of raw materials in some prehistoric Jōmon houses suggest that the commodity was valued, and perhaps brought its owners prestige.
In June 2025 as part of a research project investigating the human occupation of islands along the Sea of Japan coast, I found myself in a wondrous workshop belonging to Mr Koji Yawata on the larger of the two main Oki islands, today adminstratively part of Shimane prefecture, and included in the Daisen-Oki National Park, since 2013 a UNESCO-designated Global Geopark, one of nine such geoparks throughout Japan. Under the watchful gaze of a recuperating Japanese scops owl (Otus semitorques), with its distinctive ear tufts, awaiting release back into nature, and surrounded by a treasure trove of accumulated paraphernalia that would make Marie Kondo weep, we watched entranced as Mr Yawata produced sharp flakes using techniques that would have been familiar thousands of years ago. He subsequently amazed us with a miniature obsidian teapot and other trinkets.
Oki today is delightfully remote, requiring anything from 2.5 to 6 hours by ferry. But in antiquity it was tied into networks that saw obsidian being transported great distances. Through analysis of the chemical composition of obsidian it is possible to source obsidian very precisely, unlike its European counterpart flint. Yaroslav Kuzmin has recently published an excellent survey of the role of obsidian in prehistoric Japan and northeast Asia (Springer 2024). The Sainsbury Institute has a long-standing interest in obsidian through our engagement with the Hoshikuso obsidian mines in Nagawa-machi, part of the world’s first twinned archaeological site initiative with the Grimes Graves Neolithic flint mines in Thetford, Norfolk, which we brokered in 2016. We will be marking a decade of visits by the Young Obsidian Ambassadors from Nagawa and the Teenage History Club of the Ancient House Museum in Thetford – a wonderful museum celebrating its centenary this year. What would ancient Jōmon obsidian workers have made of their long-distant descendants’ globe-trotting? Given their own adventuring spirit, perhaps they would not be so surprised.
Acknowledgements: Many thanks to Mr Makoto Shirai of the Institute for Cultural Exploration for his kind arrangements and introductions for our visit to Oki. I travelled there with Susan Whitfield, Professor of Silk Road Studies at the Sainsbury Institute, and Pauline Coste, archaeologist and film maker. More details about Oki can be found at https://www.japan-insights.jp/pdf/essays/JIN_ExileandPoetry_01.pdf and https://www.japan-insights.jp/pdf/essays/JIN_FindingHomes_01.pdf
Simon Kaner, October 2025