The Haves and Have Nots of Obsidian

Posted April 28, 2024

Susan C. Ryan, Executive Vice President of the Research Institute

Obsidian is one of the few materials utilized by humans throughout history, prized for creating tools, ornaments, mirrors, containers, and much more. A type of volcanic glass, obsidian is produced by volcanism—the eruption of molten rock from the earth’s core. It’s created when magma, containing low gas and water properties, cools rapidly into a solid mass before large crystalline structures form. Although this glass-like rock is a comparatively rare material, its excellent flaking properties has attracted humans across the continents for thousands of years. Slightly harder than window glass, obsidian is typically jet-black in color but may display variations of red, brown, green, gray, gold, or yellow.

The oldest known obsidian artifacts were recovered from Melka Kunture, a Paleolithic site in the highlands of modern-day Ethiopia. Dating to approximately 1.7 million years ago, these obsidian tools are typical of the Oldowan tradition and made by hominins. Over time, modern humans (Homo sapiens sapiens) sought out obsidian sources hundreds of kilometers away from habitation sites, illustrating its increasing importance to nascent societies for the manufacturing of high-quality, razor-sharp cutting implements. While early artifacts were limited to tools such as scrapers and cleaves, by the Neolithic period (7,000-1,700 BCE) obsidian was used to produce a variety of artifacts including “luxury” items such as mirrors, bowls, vases, and beads.

In the United States, obsidian is used by surgeons as scalpel blades, though this practice has not been approved by the USDA. Having properties many times sharper than high-quality steel, the cutting edge of an obsidian blade is approximately three nanometers thick and, unlike metal blades, maintains a smooth, unpitted surface after repeated use. Research on post-surgical tissues indicate incisions made with obsidian blades reduce the rate of infections and scarring.

Obsidian is found in most western states and is particularly abundant in the Southwest. Mined by ancestral peoples, obsidian nodules and finished tools were widely distributed via social networks throughout present-day Arizona, Colorado, New Mexico, and Utah. Recreating these networks hinges on knowing the provenance of the material—where it originated—as well as its provenience—where it was found. Researchers developed methods for analyzing the composition of trace elements within a sample and compare these results with signatures of known sources on the landscape.

For more than three decades, Crow Canyon research colleague, Dr. Steven Shackley, has focused on geoarchaeological studies of lithic technologies in North America. As the director of an X-ray fluorescence spectroscopy (XRF) lab, Shackley and his team employ non-destructive techniques to determine elemental compositions of obsidian artifacts. Based on these analyses, researchers identified two of the most sought after sources within North America—the Mount Taylor and Jemez Mountains volcanic fields, located in present-day northern New Mexico. There are three primary sources of obsidian in the Jemez Mountains—El Rechuelos, Cerro Toledo, and Valles Rhyolite. The Mount Taylor volcanic field contains two primary sources—Grants Ridge and Horace Mesa—though they are often combined as “Mount Taylor” due to the similarity of major oxides found in both.

For over four decades, the Crow Canyon Archaeological Center has recovered obsidian tools and debitage (waste flakes created during tool production) from ancestral sites in the central Mesa Verde region. Recently, in 2016, our archaeologists and partners initiated the Northern Chaco Outliers Project, a multi-year research initiative focused on the Lakeview community, a 1 km² area comprised of one of the densest concentrations of great houses found north of the San Juan River. The Lakeview community contains four great houses—one at Wallace Ruin, one at Ida Jean Pueblo, and two at the Haynie site. There are at least two dozen smaller habitation sites ranging from the Basketmaker III period (A.D. 500–750) to the Pueblo III period (A.D. 1150–1300) within the community.

Analyzing the provenance of obsidian artifacts recovered from the Lakeview community has allowed us to reconstruct trade networks through time and across the landscape, lending insights into shifting social relationships. Using Shackley’s XRF technology, 11 pieces of obsidian were analyzed from the Ida Jean site. Remarkably, all were sourced to the Jemez Mountains (six from Valles Rhyolite, three from Cerro Toledo, and two from El Rechuelos). Twelve obsidian artifacts recovered from the Wallace site produced similar results—11 were sourced to the Jemez Mountains (seven Valles Rhyolite, three Cerro Toledo, and one El Rechuelos) and one sourced to Mount Taylor. Crow Canyon archaeologists, students, and citizen scientists recovered 71 obsidian artifacts from the Haynie site to date, one of the largest obsidian assemblages in the Mesa Verde region. Of these, 11 have been sourced. Nine produced signatures from the Jemez Mountains (four from Valles Rhyolite and five from El Rechuelos) and two have signatures from Mount Taylor (Grants Ridge).

Based on these results, we infer residents of all three villages within the Lakeview group established and maintained similar trade networks through time. However, there is a fascinating exception. Obsidian artifacts recovered from Green Stone Pueblo—a small, residential homestead located a stone’s throw (pun intended) from the Wallace great house—produced unexpected results. Of the six artifacts analyzed, three were sourced to the Jemez Mountains (two Valles Rhyolite and one El Rechuelos), one to Government Mountain (in present-day Arizona), and, surprisingly, one respectively from sources in Utah and Idaho. The diversity of obsidian from distant landscapes is unique among residents in the Lakeview group and the larger Mesa Verde region.

Residents of Green Stone Pueblo had access to more varied and distant social networks than others within the community. Moreover, it is plausible to infer residents of this household were afforded greater social standing within the community, lending insights into equality and inequality at local and regional scales. Examining equality/inequality through the lens of obsidian acquisition helps us better understand long-term social outcomes and provides transparency in how social organization was maintained and/or altered through time. It allows us to ask questions relevant to our lives today including: When did inequality first appear? Why does inequality continue and by what social mechanisms? Should we justify inequality? As we continue to seek answers to the questions above we do know one thing for certain—possessing detailed knowledge about our shared humanity leads to cultural understanding, empathy, and respect for others.