Obsidian (Volcanic Glass) and Ancient Trade Relations on Xwe’etay

For the ancestral peoples of the Pacific Coast, obsidian (volcanic glass) was a highly valued raw material because it could be used to make razor-sharp cutting tools. However, for many parts of the coast, where there are no ancient volcanos, good quality obsidian cannot be found locally. Thus, people had to rely on long-distance trade networks to access this valued item.

Luckily for archaeologists, it is possible to determine the origin of the obsidian from which the artifact was made. This is possible because the magma (molten material) associated with each volcanic eruption is composed of a distinct combination of minerals. Once scientists figure out the distinct combination of minerals associated with the eruptions from each volcano, they can match the makeup of the archaeological artifacts with the minerals from each source. By figuring out the source of the obsidian of several obsidian artifacts found throughout a region, we can begin to understand ancient trade and social relations.

As part of the Tla’amin-SFU Heritage and Archaeology project that took place from 2007-2013 (, we sent several obsidian artifacts to the lab that we recovered during our excavations. More recently, as part of the Xwe’etay/Lasqueti Archaeology Project, we submitted more artifacts from private collections from Xwe’etay to determine the source of the obsidian. Since we haven’t yet found small chips of obsidian on Xwe’etay, we assume that the artifacts were not modified in shape locally, but were transported to this region in their current form.

When we put it together, the obsidian sources tell us about broader regional trade and social relations, as well as the position of Xwe’etay in the physical and social center of the Salish Sea. At the regional level, there is a distinct pattern where obsidian in ancient settlements north of Powell River on the Sunshine Coast and in Desolation Sound primarily comes from Mount Silverthrone above Kingcome Inlet in Kwakwakwakw territory and Anahim Peak in Dakelh (Southern Carrier) territory in central BC. Obsidian from Nch’kay (Garibaldi) in Squamish territory –the only source of obsidian in the Salish Sea – is occasionally found in sites around Powell River but not further north. Of note is that both Nch’kay and Kingcome obsidian, while highly valued, would have been harder to work with since the glass has small inclusions (called “phenocrysts”) that make it more difficult to craft into tools. Because of this, both of these toolstones are not traded as far from their source as other types of obsidian.

Although Desolation Sound, the Sunshine Coast, and Xwe’etay are all within northern Coast Salish traditional territory, the array of obsidian sources represented on Xwe’etay suggests the island had a unique place in regional trade and social relations. The eight obsidian artifacts from the island that have been sourced come from Glass Buttes and Whitewater Ridge in Oregon (5), Nch’kay (2), and Timber Butte, Idaho (1). Artifacts include unmodified small cobbles and as well as finished tools (projectile points, hide scraper). Notably, none of the northern obsidian sources that are relatively common in archaeological sites in Desolation Sound and on the Sunshine Coast (Kingcome Inlet, Anahim Peak) have been recovered on Xwe’etay. This in turn suggests that at a broad regional level, the ancestral peoples of Lasqueti were more closely affiliated (at least for trading) with cultural groups to the south than to the north. These social relations allowed the people to access the higher quality obsidian from Oregon and Idaho.

What is so remarkable about the Xwe’etay obsidian collection is the diversity represented; this is especially notable given that there are so few artifacts in our sample (that is, with a larger sample, we expect to find more different sources). Adding to its uniqueness is that a small cobble found at the extreme south end of Xwe’etay is the only example in all of BC of obsidian from Timber Butte, Idaho.

The diversity of highly valued obsidian sources on Xwe’etay can only be explained by the island’s position in “the middle of everywhere” in the Salish Sea. That is, being physically central meant the ancestral peoples of Xwe’etay were able to access the best quality obsidian from a source as much 900 km away, as well as the more local Nch’kay obsidian. It also means the people of the island were ideally situated to be the locus of regional social relations in the Salish Sea and beyond. Thought of in this way, each obsidian artifact is as valuable today as it was in the past: it provides an opportunity to imagine and appreciate the breadth and complexity of the relations that supported Indigenous ways of life for generations.