A landowner in the Willamette Valley of western Oregon has made a unique find — a cache of obsidian blades that had been stashed away a thousand years ago or more by prehistoric traders.

Numbering at least 15 in all, the artifacts are double-sided stone blades known as bifaces, an essential part of every ancient hunter-gatherer’s toolkit.

[See a striking new find of bifaces in Texas: “ 16,000-Year-Old Tools Discovered in Texas, Among the Oldest Found in the West “]

But the Willamette bifaces are extremely rare examples of a kind of tools known as blanks.

The craftsmen who made these artifacts had roughly hewn them into their general shape, but they hadn’t yet knapped the stones into their final, sharp-edged form.

Such unfinished tools were valuable trade goods in the pre-contact West, archaeologists say, where tool-makers would travel to natural quarries, collect the best rock, and fashion them into blanks, before trading the blanks to others who could finish them into bifaces, or use them to make smaller flake tools.

The discovery of the obsidian cache has the potential to reveal crucial new insights into the economy of the Pacific Northwest, archaeologists say.

“Unmodified trade items of any kind typically do not survive in the archaeological record,” said Assistant State Archaeologist John Pouley, in a press statement.

“[This] archaeological site provides information on not only what prehistoric biface blanks brought into the Willamette Valley looked like, but also on the knappable properties of the stone, which may assist with developing hypotheses on their intended use.”

The find was made by a homeowner in an unspecified region of the valley in June 2015, when he was digging an irrigation ditch.

After finding one shaped piece of black glass, and then another, he contacted researchers from the Oregon State Historic Preservation Office to investigate.

Archaeologists found that the unfinished tools had been stashed in a cache — a collection that had been intentionally hidden to be picked up later.

Such an arrangement provides exceedingly rare clues into how such tools were moved, made, and traded, Pouley noted.

“Of approximately 35,000 recorded archaeological sites in Oregon, few — likely less than 25 — consist of biface caches,” he said.

“Of the known biface cache sites, it is believed to be the first recorded in the Willamette Valley.”

Dates for the artifacts haven’t yet been determined, but Pouley and his colleagues estimated that they’re at least 1,000 years old, and perhaps as old as 4,000.

The cache site is in the traditional range of the Santiam band of the Kalapuya, part of the Confederated Tribes of the Grand Ronde, who are contributing to the research, with insights into where the tools may have come from, and where they were going.

But by studying trace chemical elements in the obsidian, the researchers have already been able to track the black-glass blades to their source: the Obsidian Cliffs of the Cascade Mountains in central Oregon, some 200 kilometers away.

By what route they got to Willamette, and for what reason they were cached, remain to be understood, Pouley said. [See another site in Oregon that has experts wondering: “800-Year-Old Camp Found in Oregon Sand Dunes Poses Migration Mystery“]

When the landowner uncovered the cache, some of the artifacts appeared to have been disturbed, likely by natural processes, he noted.

But at least one of the bifaces appeared to have been found exactly as it had been left.

“We were pleased to find one biface in possibly its original position,” he said.

“Many times, things are moved beneath the ground, whether by later human impacts, burrowing animals, or repetitive freeze-thaw cycles.”

But finding artifacts as they had been left, known as in situ, gives researchers a more complete understanding of the context in which the objects were stored.

“A biface in situ assists with establishing context, which allows for comparison with other items recovered during the process of a controlled excavation,” he said.

“The information can help us address a number of research questions, such as possibly refining the estimated age of the site.”

After two and a half months of digging at the site, Pouley and his colleagues will continue to analyze the artifacts, with a view to publishing full details next year. [See a record-breaking stone tool found in Oregon: “Stone Tool Unearthed in Oregon ‘Hints’ at Oldest Human Occupation in Western U.S.“]

As for the bifaces themselves, they will remain property of the landowner, until or unless he decides to donate them to a scientific institution or the tribes.

Regardless of where they end up, Pouley said he was grateful that the owner shared his discovery with archaeologists.

“This site makes you wonder how many archaeological sites with the potential to shed light on the history of human occupation within Oregon have been found before, and never reported,” Pouley said.