The Texas of prehistory indexed in the rock record presents a very different state from the one of modernity: a geological hotbed of activity and processes, the Lone Star State was undergoing dramatic changes over thousands of years that resulted in the familiar landscapes seen today, as well as some rare and valuable materials that are impossible to find elsewhere in the world. One such material comes from a select bed of rock in Texas called the Manning Formation - geographically situated close to the Trinity River of southeast Texas, this formation provided the Manning infused glass utilized by the indigenous Paleoindians who passed through the area and made it a residential site. [1] A scarce material at its source, Manning infused glass occurred in flakes and chunks that were better suited to the crafting of small items rather than large-scale artifacts. [2] Such small fragments meant that the material was highly portable, and though it has been found in other sites outside of Texas, Manning infused glass does not often stray far from its parent rock. [3]

One significant Texas site, Gault, has yielded a few artifacts featuring Manning infused glass: it is thought that the Gault site functioned as a major base camp for Paleoindians who moved through the area, a place for them to camp and craft stone tools and venture out from in order to find game and vegetation. [4] As such, the site saw repeated visitation over time by numerous groups, who took advantage of the boundless supplies of flint or chert stones found there from the site’s location on the eastern portion of the limestone Edwards Plateau. [5]

One group, the Clovis - a prehistoric group whose stone tools were discovered near Clovis, New Mexico in the 1930s - is thought to have been part of these residents. [6] Thought to be the initial group of indigenous people to enter the Americas from the Bering Land Bridge, the nomadic Clovis occupied North America during the last ice age, making weapons that were suited to bringing down large game like mammoths and mastodons. [7] In contrast, the findings at the Gault site suggest that the Clovis were instead hunter-gatherers, with tools for hunting game but also processing the hides and harvesting nearby grasses. [8] The Manning infused glass points that were found would have been too fragile to support hunting large game, as the Manning glass were volcanic in composition, and therefore somewhat brittle. [9]

The volcanic glass was the result of fusion: in the Cenozoic Era, roughly 65 million years ago, West Texas was a plain of active volcanoes that produced significant clouds of ash; the clouds of ash then would drift eastward to the Gulf Coastal Plains, settling in the sand- and silt-stones that laid there. [10] Below the sand- and silt-stone layers, beds of lignite in the lower Manning Formation, reaching temperatures estimated to be around 1100 degrees Celsius, would combust and fuse with overlying silt and silica tuff, creating the small deposits of Manning infused glass as it cooled over time. [11] This, combined with the Manning Formation’s confined land space, would mean that any population that utilized such materials would first have to know it was there; with its creation, it could only be found in small portions, thus explaining its rarity and value as a crafting material for indigenous Paleoindians. [12]


Hannah Bertling, “Manning Infused Glass,” East Texas History, accessed May 26, 2024,