Blue pigment made from azurite was moving across the ancient American Southwest roughly 1,400 years ago, and a new study led by Kari Schleher of the University of New Mexico suggests some of it traveled a considerable distance from its source. By matching the chemical fingerprints of recovered pigment to known mineral deposits, the researchers were able to point to specific mines that supplied Ancestral Pueblo communities.
The team focused on azurite, a blue copper mineral that was prized as a pigment. They tested twelve specimens recovered from the Four Corners region, the area where Utah, Colorado, Arizona and New Mexico meet. To establish a baseline, they also analyzed two reference samples, one from a mine in New Mexico and one from a mine in Utah. The comparison relied on isotopes of lead, strontium and copper, which carry signatures tied to the geology where a mineral formed.
Most of the specimens matched the Lisbon Valley source in Utah. Two others traced back to the Zuni Mountains in New Mexico. Taken together, the results indicate that pigment moved from New Mexico into central Utah in the centuries before the modern era, rather than being sourced only from nearby deposits.
The work is not finished. The researchers plan to analyze more samples from the New Mexico Mining Museum and to consult local oral histories about how the mines were used. They also have not yet mapped the boundaries of the traditional territories involved, a step they see as necessary for understanding how these resources were shared and controlled.