When it comes to stone tools, archaeologists make a basic distinction between “chipped-stone” and “ground-stone” tools. Chipped-stone tools are generally those that need to be sharp, such as projectile points, knives, scrapers, and drills, and are typically made of hard stone that keeps an edge. Some ground-stone tools, such as axes, are also sharp, but for the most part ground-stone tools rely on other qualities of stone for purposes like hammering and grinding. In the Southwest, ground-stone tools are usually made of sandstone, basalt, or other types of stone that are plentiful in the area immediately around a site. These tools are heavy, and it generally wouldn’t have made any sense to import special types of stone to make them when, as is the case throughout the Southwest, there were plenty of rocks around. The types of stone used for ground-stone tools are also generally those used for masonry in areas where masonry construction was typical, including at Chaco, where sandstone was the usual material.
Chipped-stone tools are a different story. They are usually small and highly portable, and the best materials to make them are often scattered and not convenient for every habitation site. Thus, widespread trade in chipping stone has very early origins. Hunter-gatherers need very good stone for their projectile points, and also tend to be very mobile, so their chipped-stone tools tend to be very well-made and to be made of high-quality material from a wide variety of sources. Settled agriculturalists such as the Chacoans don’t rely so heavily on chipped-stone tools for their subsistence needs (ground-stone tools like metates are much more important), and they typically put much less effort into both procuring stone for chipped-stone tools and making the tools themselves.
When it comes to Chaco specifically, chipped-stone shows a much more muted form of the pattern of massive imports of other goods such as pottery, wood, turquoise, and even food. Cathy Cameron summarizes the patterns revealed by the chipped-stone assemblages from Chaco Project excavations in the 1970s in an article from 2001. The basic pattern is that most chipped stone was from local sources throughout the occupation of Chaco, although “local” really refers to a wider area here than the canyon itself. Good chipping stone is not plentiful in the canyon itself, but abundant sources of good chert and petrified wood occur a few miles to the north and would have been easily accessible to canyon residents in the course of their daily lives (i.e., special trips to gather stone would probably not have been necessary). These local sources always dominate assemblages from Chaco. Imported stone types do increase during the Chaco era from AD 1030 to 1130, especially at great houses such as Pueblo Alto. The most abundant import at this time is Narbona Pass chert, a distinctive pinkish type of stone that comes from a very restricted area in the Chuska Mountains to the west. The Chuskas are also the source of many other imports to Chaco, including huge amounts of pottery and wood, but the relative proportions of Narbona Pass chert in the overall chipped-stone assemblages are much more modest. It comprises 21.1% of the total Chaco Project sample for AD 1020 to 1120 and 18.9% of the sample for AD 1120 to 1220. This is much higher than any other type of imported stone ever reaches, and even higher than any single type of local stone for these periods (though much lower than the total proportion of local stone).
Other imported materials found in notable numbers include Brushy Basin chert from the Four Corners area, a type of yellow-brown spotted chert and a special type of petrified wood, both from the Zuni area, and obsidian. Brushy Basin chert (along with other materials from the same formation) and Zuni petrified wood reach relatively high proportions of the overall assemblage at the same time that Narbona Pass chert does, and Zuni chert does too but at a much lower level. The pattern of obsidian is different, and hard to understand. It’s the most common exotic type of stone before AD 920, rising to as high as 7.6% of the assemblage in the seventh century. Sourcing studies seem to show that most of the obsidian coming it at this point came from the area around Grants, New Mexico, near Mount Taylor, during this period. Once the Chaco system really gets going, though, the proportion of obsidian plummets to less than 1%. From 1120 on, however, it rises again, comprising 7.3% from 1120 to 1220 and 2% after 1220, still less than Narbona Pass chert but respectable. This obsidian seems to come mostly or entirely from sources in the Jemez Mountains to the east of Chaco.
So what were the Chacoans doing with this imported stone? Not much, as it turns out. One of the oddest things about the amount of Narbona Pass chert, particularly, is that it doesn’t appear to have been used for anything special. Like all other types of stone, both local and imported, it was used primarily for expedient, informal tools. The Chaco Project found 2,991 pieces of Narbona Pass chert, and only 18 of these were formal tools. This pattern is typical for most material types, though obsidian seems to have been more often used for formal tools, many of which were probably imported as finished tools rather than made in the canyon. Of the formal tools the Chaco Project did find, of all materials, about half were projectile points, and the rest were various types of knives, scrapers, and drills.
So what’s going on here? Hard to say. Cameron evaluates the chipped-stone data in the context of the models for the organization of production proposed by other participants in the conference from which this paper originated, and she decides that Colin Renfrew’s pilgrimage model fits best, with some adjustments. This conclusion is driven largely by the fact that so much of the Narbona Pass chert came from the Pueblo Alto trash mound and the idea that this indicates that it was deposited there as part of communal rituals. I find claims like this dubious, and I think it’s more likely that people in Chaco were just importing this type of stone either because it is so visually striking or because of their strong social connections to Chuskan communities (or both).
The thing I find most puzzling is the obsidian. Obsidian was hugely important in Mesoamerica, and in view of the appropriation and importation of many aspects of Mesoamerican culture by the Chacoans, most recently dramatized with evidence for chocolate consumption, it seems very odd that the rise of the Chacoan system would coincide with a steep decline in the amount of obsidian imported. This is particularly odd since the Grants area was very much a part of the Chaco world, and there were numerous outlying great houses and communities near Mt. Taylor. If the Chacoans had wanted obsidian, they could easily have gotten it. And yet, it seems they didn’t.
Or did they? Keep in mind that this data is based mostly on Chaco Project excavations, although Cameron does incorporate some insights from a study of formal chipped-stone tools done by Steve Lekson that incorporated other data as well. Lekson’s study noted that Pueblo Bonito in particular had an astonishing number of projectile points relative to most other sites, and I can’t help but wonder if part of the lack of obsidian at other sites was a result of more of it flowing to Bonito. The excavations at Bonito were done a long time ago without the careful techniques of the Chaco Project, so the data isn’t totally comparable, but I’m going to look at the artifact records from Bonito (conveniently made available at the Chaco Archive) to see how common obsidian was there.
Speaking of projectile points, another thing Cameron mentions is that many of them seem to have been imported to Chaco, some of them apparently embedded in meat. Others were particularly finely made and left in burials and caches, suggesting that they may have been specially made for votive purposes. That’s probably the case for many of the points Lekson identified as being particularly numerous at Bonito, but what I want to know is why arrowheads were such common grave goods and offerings there. Was there a particular association between Chaco and hunting? The great house residents do seem to have eaten a lot more meat than other people in the canyon and elsewhere.
On the other hand, arrows weren’t only used for hunting. Cameron notes that one projectile point found by Neil Judd at Pueblo Bonito was embedded in a human vertebra, and the Chaco Project also found a woman at the small site 29SJ1360 near Fajada Butte who had two points inside her. We often talk about how peaceful Chaco was and how little evidence there is for warfare during the Chacoan era, but I’m starting to wonder about that. It’s certainly true that Chaco itself and most other sites occupied during its florescence show less obvious evidence for violence than sites afterward do, but there are still some signs that things may not have been totally peaceful throughout the Southwest in Chacoan times. Arrowheads in vertebrae don’t get there on their own, after all. Who shot those arrows?
Cameron, C. (2001). Pink Chert, Projectile Points, and the Chacoan Regional System American Antiquity, 66 (1) DOI: 10.2307/2694319