The Road of Obsidian and Jade: The Jomon Trade Network That Crossed the Sea

As you dig at the site of a Jomon settlement, a fragment of black stone emerges from beneath your feet. Glossy as glass, and sharp as a razor when broken—it is obsidian. Yet strangely, nowhere around that settlement is there a mountain of obsidian. The nearest source is far away, deep in the mountains, or on an island across the sea. So how did this stone come all the way here? The obsidian and jade that come out of Jomon sites often pose such questions. And as you trace the answers, the Jomon settlements that looked like scattered dots slowly reveal themselves as having been linked, in fact, by long roads that crossed sea and mountain.

The Obsidian of Kozushima: Sharpness That Crossed the Sea

For the Jomon people, obsidian was no mere stone. This natural glass, born of volcanoes, splits into sharp edges, and as arrowheads, spear points, and small knives, it became a vital tool supporting the hunt and daily life. But the places where obsidian can be quarried are limited. That is precisely why finding this stone at a settlement far from its source becomes a clue that speaks of the movement of people and things.

Among them, what astonishes most is the obsidian quarried on Kozushima in the Izu Islands. Kozushima is an island floating tens of kilometers offshore from the tip of the Izu Peninsula, separated by sea, and it is thought that it did not become connected to the mainland by land even during the ice age when sea levels dropped. And yet, obsidian identifiable as Kozushima-sourced has been found at Honshu sites from the Late Paleolithic—that is, from an age even older than Jomon. This strongly suggests that people made voyages crossing the tidal currents by boats such as dugout canoes, traveling to the island and back. Even on a global scale, it is regarded as one of the early pieces of evidence for round-trip voyages across the sea.

Once the Jomon period began, Kozushima obsidian circulated even more widely. Especially in the Middle period, its circulation flourished, and at sites on the Izu Peninsula and in southern Kanto, many stone tools are said to have been made from this island’s stone. As scientific analysis to identify sources advanced, it became possible to trace, with considerable precision, ‘from which mountain or which island’ each piece of obsidian came. The black stone at one’s feet had linked a small island across the sea with this settlement—that fact is now being quietly reconstructed.

The Jade of Itoigawa: The Green Stone That Journeyed North to South

If obsidian was ‘stone for use,’ then jade was ‘stone for prayer and adornment.’ This hard stone, holding deep green and milky white, was polished and transformed into ornaments such as large beads and magatama, thought to reflect the special status and wishes of those who wore it.

The area around Itoigawa in Niigata Prefecture is known as a representative source of jade in Japan. From around five thousand years ago, a culture of working jade is said to have flourished centered on this land, counted among the world’s early instances of jade use. What is striking is its spread. Jade quarried and worked at Itoigawa did not stay near its source; it is said to have been carried as far north as Hokkaido and Aomori and as far south as Kyushu and Okinawa, with instances also noted of it reaching the Korean Peninsula across the sea. A green stone born at one riverbank had journeyed from one end of the archipelago to the other.

Symbolizing that spread is the Sannai-Maruyama site in Aomori. From the remains of this large Jomon settlement, jade from far-off Itoigawa in Niigata and obsidian from around Wada Pass in Nagano are both said to have been found. Each comes from a distant source in a different direction. In other words, a single settlement was connected by the exchange of goods with multiple remote places. Over distances that take many days to walk, jade and obsidian passed from hand to hand, or rode in boats, carried over long stretches of time.

Why Were the Stones Carried So Far?

Why did the Jomon people carry stones so far, at such great pains? For obsidian, part of the answer is clear. The material for fine tools with sharp edges was not obtainable everywhere, and for settlements far from a source, it was a resource of high value to acquire. Practical necessity is thought to have driven the circulation.

The journey of jade, on the other hand, holds something that practicality alone cannot fully explain. To take this hard, difficult-to-work stone, deliberately polish it into ornaments, carry it far afield, and wear it—there may have been at work a longing for beauty, the meaning of possessing something special, or a heart for prayer and communion. The exchange of goods was not merely about satisfying needs; it was also an act of binding together distant groups and forming relationships. When stones moved, human ties moved along with them.

In this way, the obsidian that crossed the sea and the jade that ran the length of the archipelago tell us that the Jomon world was connected far more broadly than one might think. The scattered settlements were not each an isolated little world; they were placed within a mesh of goods and ties. Yet upon this stable, cyclical world too, a great wave would eventually surge. From the continent across the sea, a single grain—rice, which would transform the lives and social forms of people from their very foundations—was about to arrive in the archipelago.