Sierra de Las Navajas, Hidalgo, Mexicoi

Regional Level Types
Sierra de Las Navajas	Mountain
Hidalgo	State
Mexico	Country

It should be noted that most types of obsidian from Mesoamerican sources are black-grey-reddish colors; their different vitreous qualities were exploited for a wide variety of artifacts. However, their unique, highly vitreous quality and beautiful golden and green color varieties are notorious in America. Sierra de las Navajas ranks among Mesoamerica’s premier obsidian sources based on three lines of evidence: geochemical provenance studies (XRF/INAA) have traced obsidian artifacts from Teotihuacan, Tula, and even sites over 1200 km away. This long-distance transport and ubiquity in major urban centers testify to its central role in pre-Hispanic exchange networks. Field surveys and pit/mine mapping at Cerro de las Navajas permit a first-order estimate of total obsidian removed. When the map of the green obsidian source was drawn up between 1988 and 1992, during the Aztec period, lithic debris workshops were located on the surface of 187 open mines of vertical excavations, which had inclined and horizontal tunnels with an average depth of 18 m deep; the deepest reached 50 m deep. The extraction volume of the order of 5000 tons of nodules (equivalent to several hundred metric tons of worked artifacts) underscores the scale of production. Excavations and radiocarbon dates from mining workshops and discarded middens indicate continuous exploitation from at least the Late Preclassic (ca. 1200 BCE) through to the colonial period (16th century CE). In other words, obsidian was quarried here for roughly 2500 years, spanning Teotihuacan’s rise, Toltec hegemony, Aztec expansion, and even early Spanish colonial administration. Together, these distributional, volumetric, and chronological data confirm that SLN was not only geologically prolific but also socially and economically foundational for Mesoamerican societies.
At Cerro de las Navajas, four distinct eruptive events (EEs) have been identified with obsidian: EE1 produced a Plinian-type pyroclastic deposit composed of lapilli tuff, containing marekanite obsidian fragments. EE2 is evidenced by the remnants of a fluidal rhyolitic dome with green obsidian bands (<5 cm thick). EE3 involved an explosive pulse that generated a Block and Ash Flow Deposit (BAFD), containing green-gold obsidian blocks ranging from 6 to 100 cm in length. Finally, a fourth event (EE4) resulted in a Rheomorphic Ignimbrite unit with a glassy base (vitrophyre), characterized by highly fragmented black-grey obsidian blocks (<20 cm). This final event marks the end of volcanic activity at Cerro de las Navajas, sealing the previous deposits, and shows a distinct undefined magma vent.

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References