For a long time, scholars have thought that the Aztecs had frequent contact with groups in what's now the American Southwest. But a new chemical analysis of ancient turquoise artifacts just put a giant hole in that theory. It now appears that the Aztecs and another Mesoamerican civilization known as the Mixtecs mined their own turquoise, rather than trading for it with northerners, reports Ars Technica. Both civilizations, which lived in what's now central Mexico to Central America, used turquoise extensively in their cultures, explains a post at Phys.org. But because archaeologists have never found turquoise mines in the region, scientists had long concluded that the mineral must have come from the US Southwest. In the study in Science Advances, however, a team at Dickinson College says its analysis shows that the turquoise instead comes from Mesoamerica.
"I saw the number pop up and I'm pretty sure I did a dance around the lab," geochemist Alyson Thibodeau tells the New York Times. "Not only do they have isotopic signatures that are absolutely consistent with the geology of Mesoamerica, but they are completely different from the isotopic signatures of the Southwestern turquoise deposits and artifacts that we have seen so far." The finding goes beyond where the groups got their gemstones—it calls into question the larger idea that the Aztecs and Mixtecs were regularly trading and otherwise in contact with cultures in the US Southwest before they were conquered in the 1500s. How to explain the lack of mines? Just because we haven't found them doesn't mean they didn't exist, says Thibodeau. (Another centuries-old Aztec mystery appears to have been solved earlier this year.)