And before someone gets cute with me, this ain’t hyperbole. I’m not being fancy and describing a sexy gemstone. This was not a diamond. It was not an emerald. It is definitely not something that sounds expensive when you say it at a cocktail party. Try it. Say “flint chert” out loud. Sounds like a tween apparel item you’d only find at a Claire’s, doesn’t it? And now partygoers are afraid you are having a stroke. Congratulations.

No, this was a rock. A sedimentary rock, specifically, made of the same chemical compound as sand and window glass, found in a cow pasture in Licking County, Ohio, roughly forty miles east of Columbus. Now I, having described said rock, am flying in the face of Ohio’s General Assembly who, in 1965, looked at this rock and said, "Yes. This is our gemstone. This is the one." They put it in the Revised Code, Section 5.07 and said "Flint is the official gemstone of the state." Because, it turns out, it was traded as such, and is objectively worth more than any other gemstone an indigenous Eastern North American could come across.

For roughly twelve thousand years, from the moment the first Paleo-Indian hunter walked into what is now Ohio at the end of the last ice age through the collapse of one of the most sophisticated ceremonial networks in pre-Columbian North America around 400 CE, this rock was the most valuable thing on the North American continent east of the Mississippi. I’m not shitting you. That’s not an exaggeration. It was mined from hundreds of hand-dug pits along a six-square-mile ridgetop (Stout and Schoenlaub 1945, 79). It was shaped into tools so precise they could split a hair down the middle. It was carried by hand, on foot, without wheels, without horses, without roads, to archaeological sites in Louisiana, Florida, New York, Kansas, and everywhere in between, distances of five hundred to a thousand miles, because it was that good and people wanted it that badly (Knepper 2003, 3). And it powered a trade network that moved prestige goods across half of North America with a regularity and sophistication that most of us cannot achieve without Amazon Prime.

The Part Where We Explain How to Hit Your Rocks Correctly

I’d suggest low and slow with the heat, personally, but it depends on the high you’re loo-ooooooh, the chert. Riiiiight.

Chert is a sedimentary rock composed almost entirely of silica (silicon dioxide, SiO₂), the same compound that makes quartz, glass, opal, and the beach sand currently stuck between your toes (Stout and Schoenlaub 1945, 13). The difference between chert and all of those other things is its structure. Quartz forms big, visible, Instagrammable crystals. Glass is amorphous, with no crystal structure at all. Chert splits the difference: it is cryptocrystalline, meaning it is composed entirely of crystals, but the crystals are so microscopically small that you cannot see them without magnification (Stout and Schoenlaub 1945, 13). Each one is measured in micrometers. The word "cryptocrystalline" translates literally to "hidden crystals," which sounds like the title of a 2007 Enya album but is actually just a description of grain size.

This hidden crystal structure is the entire reason chert matters. When you strike a piece of chert with sufficient force at the correct angle, it breaks in smooth, curving, predictable patterns called conchoidal fractures (from the Latin concha, "shell," because the fracture surfaces look like the inside of a clamshell). Importantly, the fractures are predictable. A skilled knapper (someone who shapes stone by controlled fracturing; you can still do this for fun in competition, btw!) can tell before striking exactly where and how the stone will break. This means they can shape it into anything: a knife edge sharper than surgical steel, a scraper thin enough to shave hide, a projectile point that will punch through a mastodon's ribcage, a drill bit that will bore clean through bone (Stout and Schoenlaub 1945, 7). Chert is, for practical purposes, a programmable stone material. You tell it what shape to be by hitting it correctly, and it becomes that shape, whereas most stone will chip or crack.

Flint, by the way, is chert. There is no mineralogical distinction between the two. It’s the same shit you burn your friend’s house down in Minecraft by striking steel. Geologists traditionally use "flint" for chert that forms as nodules within chalk or limestone, but the material is chemically and structurally identical (Stout and Schoenlaub 1945, 13). This is the geological equivalent of the "is it a grilled cheese or a melt" argument, and it matters exactly as much, which is to say it matters deeply to a small number of people and not at all to everyone else. This is unlike the “is a hotdog a sandwich?” question, which determines, among other things, your marriage prospects, future career, and how roasted you’ll be in the comments for calling a burrito a sandwich.

So how does a rock made of hidden crystals form in the first place? Through a process called diagenesis, which is geology's way of saying "other stuff slowly turned into this stuff over millions of years." Specifically, silica-bearing fluids percolated through existing layers of limestone (which is calcium carbonate, made from the accumulated shells and skeletons of marine organisms, aka it’s a stone made of fucking prehistoric skeletons). Over millions of years, the silica replaced the calcium carbonate molecule by molecule, atom by atom, converting a rock made of dead sea creatures into a rock made of glass (Stout and Schoenlaub 1945, 12). The silica itself often originated from a different set of dead sea creatures, like the dissolved skeletons of sponges, radiolarians, and other siliceous organisms whose tiny glass support structures broke down after death and went into solution. In the case of Ohio's Vanport formation, this replacement happened in limestone roughly 320 million years old, from the Pennsylvanian period (Ohio Department of Natural Resources; Stout and Schoenlaub 1945, 71).

You are, in a very real sense, looking at a rock made from the ghosts of two separate ecosystems layered on top of each other. The ocean died twice to make this rock.

Nature is metal as fuck.

Now, most chert is not pretty. Most chert is gray, or brown, or a dishwater gray-brown that geologists describe with words like "undistinguished" and the rest of us describe by walking past it. It is the beige Toyota Camry of the mineral world: functional, ubiquitous, and invisible.

Flint Ridge chert is not most chert. Flint Ridge chert is what happens when you let some cholos get their hands on a Camry.

The Vanport flint at Flint Ridge, OH, occurs in colors that have no business existing in a sedimentary rock formed at the bottom of a Carboniferous sea, let alone a random patch of Ohio farmland. Translucent blues, deep reds, vivid yellows, greens, lavenders, pinks, and whites, all banded together in swirling, layered patterns that look less like geology and more like someone marbled a wedding cake with food coloring and then turned it to stone (Stout and Schoenlaub 1945, 11). The color variation comes from trace mineral impurities trapped during silicification. Iron oxides produce the reds and yellows, organic carbon produces the blacks and grays, and various trace elements contribute the blues, greens, and lavenders that make this material immediately identifiable in any archaeological assemblage anywhere on the continent. Heat treatment, which Hopewell knappers practiced deliberately, intensifies the colors further, deepening reds and bringing out blues and lavenders that were invisible in the raw stone. They figured out that if you buried the rock in sand and slowly heated it, the colors got better and the fracture mechanics improved.

They were heat-treating stone to improve its engineering properties and its aesthetics simultaneously. This is three hundred years before the Roman Empire, by the way, on a ridgetop in Ohio. Don’t say they didn’t know what the fuck they were doing with stone. Just because they weren’t building with it doesn’t mean they weren’t fucking geniuses with it.

The deposit sits along a low escarpment in gently rolling farm country, straddling the Licking-Muskingum county line. The flint-bearing stratum runs in a discontinuous band roughly six square miles in extent, varying in thickness from one foot to twelve feet, with an average of around four (Stout and Schoenlaub 1945, 79). In many places, the chert outcrops at or near the surface, which meant that prehistoric peoples could mine it without the deep-shaft technology that characterized Neolithic flint mines in Europe. Instead, they dug pits. Hundreds of them. The pits range from twelve to eighty feet in diameter; a few are as deep as twenty feet, though most sit between three and six (Ohio History Connection, "Ohio's First Industry"). Gerard Fowke, surveying the ridge for the Smithsonian in the 1890s, estimated that roughly nine-tenths of the flint carried from the quarry pits was rejected as inadequate (Ericson and Purdy 1984, 5). The waste flakes alone (the debitage left behind during twelve thousand years of tool production) form a layer across the ridge floor that is an industrial landfill predating industry by about eleven and a half millennia.

The Hopewell did not invent the quarry. People had been coming to Flint Ridge since the Paleo-Indian period, at least 13,000 years ago (Kern and Wilson 2014, 14). But the Hopewell industrialized it.

The Part Where Ohio’s Pretty Rock Organizes Half a Continent Around a Ridgetop

But Flint Ridge chert traveled. Not because rocks travel on their own (they do not; they are rocks), but because people picked it up, worked it into tools and tradeable blanks, and carried it extraordinary distances on foot. By the Middle Woodland period, roughly 200 BCE to 400 CE, when the Hopewell ceremonial complex was operating at full capacity, Flint Ridge material had been identified at archaeological sites from the Great Lakes to the Gulf Coast, from the Atlantic Seaboard to Kansas (Knepper 2003, 3; Kern and Wilson 2014, 36). It has been recovered in Louisiana, in Florida, and in New York. The material is so visually distinctive, those polychrome bands of blue and red and cream, that archaeologists can identify it on sight, and geochemical sourcing studies using neutron activation analysis and X-ray fluorescence have confirmed what the naked eye already suggested: this rock comes from one place on Earth, and that place is a ridgetop in Licking County, Ohio (Prufer and McKenzie 1967, 115, 136).

Now, how did the rock travel? The Hopewell Interaction Sphere.

Personally, I hate this term. A lot of other archaeologists and historians hate it, too, because it was not a trade network as we envision often. The Interaction Sphere was not an empire. It was not a state. It had no capital, no written laws, no coinage, no standing army, and no centralized government. It was a network: a web of exchange relationships, shared ritual practices, shared artistic traditions, and shared mortuary customs that linked communities across eastern North America for roughly six hundred years with a consistency that implies a level of social organization far more sophisticated than "people traded stuff sometimes" (Seeman 1979, 1-5). The Ohio Hopewell sat at the center of this Sphere, organized around the Hopewell Ceremonial Earthworks. You can still visit them today (as I’ve described in a post previously about the unhinged process to reclaim the land). The Scioto Valley, in southern Ohio, functioned as the hub (Kern and Wilson 2014, 39).

The goods that moved through this network constitute a geological atlas of eastern North America's most desirable raw materials. There’s native copper from the upper Great Lakes, pounded (not smelted) into sheets, earspools, breastplates, and artificial noses. There’s mica from the western Carolinas, cut into human and animal effigies so delicate they can be held up to the light. There’s obsidian from the Yellowstone Plateau in Wyoming, which is roughly 1,500 miles from the Ohio Valley, carried overland to be fashioned into ceremonial blades so thin they are translucent. There’s silver from near Cobalt, Ontario. There’s marine shells, shark teeth, and alligator teeth from the Gulf Coast and Florida. Grizzly bear canines from the Rocky Mountains. Chalcedony from North Dakota. Galena from Missouri and Illinois (Kern and Wilson 2014, 39; Milner 2020, 78-80). The list goes on and on.

And then there’s Flint Ridge chert, the rainbow rock, as Ohio's contribution to this transcontinental exchange system, quarried on an industrial scale, worked into standardized forms, and distributed across half a continent.

Two of the hundreds of burials at the Hopewell type site (the site the entire tradition is named after) contained a young adult male and an adult woman accompanied by foot-long copper rods, copper bracelets, fifty copper earspools, a necklace of grizzly bear canines inlaid with pearls, several large copper plates, scores of copper-covered buttons, artificial copper noses, and hundreds of freshwater pearl beads (Kern and Wilson 2014, 36). Alongside all of this are found Flint Ridge bladlets.

Bladelet’s are batshit insane the more you learn about them. A bladelet is a small, thin, parallel-sided flake of stone, typically two to five centimeters long and less than a centimeter wide, struck from a specially prepared cylindrical core using either direct percussion or pressure flaking. The production requires a level of skill that borders on absurd: the knapper prepares a core with a flat striking platform and a series of guide ridges running down its length, then removes bladelets one after another by striking or pressing at the platform edge. Each bladelet peels off the core in a long, thin strip, like peeling a carrot if the carrot were made of stone and required several thousand hours of apprenticeship to peel correctly.

The Hopewell made bladelets constantly. They made them from Flint Ridge chert, from Wyandotte chert (southern Indiana), and from Knife River flint (North Dakota; because apparently no distance was too far for a nice rock). In one study of 128 bladelets from Hopewell sites, roughly 25 percent were Flint Ridge material. At Ohio sites specifically, the proportion was higher: 48 percent Flint Ridge, 46 percent Wyandotte, 2 percent Knife River flint (Ohio History Connection, "Bladelets, Flint Ridge Flint, and the Hopewell Interaction Sphere"). Core-and-bladelet technology is considered a quintessential marker of the Hopewell Interaction Sphere, one of the practices that links otherwise disparate communities across eastern North America into a recognizable shared cultural tradition.

But what were the bladelets for? We don’t fucking know. 

Cutting things. Scraping things. Possibly ritual activities. Possibly functions we have no way of recovering because the organic materials they were used on decomposed thousands of years ago. A variety of purposes have been proposed, and the argument has been going on for decades with no resolution in sight (Ohio History Connection). My personal favorite is Dr. Brad Lepper’s, (yep, that Lepper! Guinness Book of World Records Lepper!) who has envisioned them as the equivalency of a gift shop tourist trap: it was the way to tell you’d been at the Hopewell sites. All we know is that the bladelets were made, were traded, and were deposited in graves and ceremonial contexts.

And the Hopewell did not merely trade Flint Ridge chert. They cached it in mounds with their most honored dead. They made bifaces (tools worked on both faces) from the most colorful material they could find, shaped them into standardized forms too uniform and too finely made for daily use, and deposited them in mortuary contexts alongside copper, mica, obsidian, and pearls (Milner 2020, 78-80). This was rock special enough to bury as an offering.

The Hopewell came to Flint Ridge with a specialized labor force, quarried the material on an industrial scale, reduced it to bifaces, cores, and bladelets, packed them up, and carried them fifteen miles west to the Newark Earthworks, where they were exchanged or given as gifts to visiting pilgrims from across the network (Prufer and McKenzie 1967, 23; Ohio History Connection, "Ohio's First Industry"). The proximity of Flint Ridge to the Newark Earthworks, the largest Hopewell ceremonial complex in existence, sprawling over four square miles, is not coincidental. The earthworks include a great circle, a square whose perimeter matches the circle's, and a fifty-acre octagon whose openings align with the 18.6-year cycle of maximum and minimum moonrises and moonsets (Kern and Wilson 2014, 37-39). This is a giant world ceremonial clock embedded in earth as instruments of geometry and astronomy, built one basketful of earth at a time, taking an estimated 200,000 person-hours per mound (Kern and Wilson 2014, 36), by people whose most ubiquitous trade good was a rainbow-colored rock from a ridgetop down the road. Oh, and Newark was one of thousands of mound sites spanning from Chillicothe, OH, to Newark, OH. It was the pilgrimage destination of North America.

The Hopewell Ceremonial Earthworks are among the most significant pre-Columbian constructions anywhere on the planet (Kern and Wilson 2014, 37), and they ran on Flint Ridge chert the way Silicon Valley runs on venture capital. It was the prestige commodity that attracted people, funded ceremonies, and kept the whole system turning.

The Part Where It's the End of the Rainbow

Around 400 CE, the Hopewell ceremonial system collapsed (Kern and Wilson 2014, 40). The earthwork complexes were abandoned. the exchange networks contracted, and the flow of exotic materials slowed to a trickle and then stopped.

Paleoclimatologists identified a prolonged cooling period beginning around 1,600 years ago. Tree ring data show that the Hopewell core area suffered an extended drought: seventy percent of the years from 396 to 460 CE were drier than normal, with extreme drought years in 398, 420, and 436 (Kern and Wilson 2014, 40). Population pressure from the Hopewell florescence itself may have overtaxed available food resources in a period of declining productivity (Abrams and Freter 2005, 40-44). DNA analysis has shown that the populations living in southern Ohio after the Hopewell collapse were not closely related to the Hopewell themselves. The closest known genetic match to Ohio Hopewell DNA comes from a burial mound in central Illinois dating to roughly seven hundred years later (Kern and Wilson 2014, 40). 

The Hopewell did not simply decline in place. They left. And where they went, and why, is among the most significant unanswered questions in North American archaeology today.

The quarries at Flint Ridge continued to be used during the Late Woodland period and beyond, but never again at the scale the Hopewell had achieved (Kern and Wilson 2014, 41). Late Woodland peoples still valued the material, still traveled to the ridge to obtain it, and still made tools and weapons from it. But the continental distribution network was gone. The rock that had traveled a thousand miles now traveled only a hundred. The prestige economy it had anchored evaporated.

Flint Ridge is still there. The Ohio History Connection maintains it as Flint Ridge Ancient Quarries and Nature Preserve. You can walk the trail between the old quarry pits, which look like shallow depressions in the forest floor, unremarkable unless someone tells you that each one represents a mining operation sustained across centuries. The museum displays pieces of the chert in all its polychrome glory, not like something you'd find in the dirt next to a cornfield.

Archaeologist Barbara Luedtke, studying the ridge for her contribution to Prehistoric Quarries and Lithic Production, calculated the total demand for lithic material in stone-tool-using cultures and concluded that flint procurement was, for most communities, "a rather casual, mundane, and low-labor-intensive activity" (Ericson and Purdy 1984, 65). Most people needed a few kilograms of workable stone per household per year, and could procure it walking along a river creek bed like that one in only a few hours of labor for the entire year. The fact that the Hopewell organized specialized labor forces to quarry Flint Ridge on an industrial scale, standardized their products, and distributed them across a continent tells you that whatever was happening at Flint Ridge transcended utility. You do not carry a rainbow-colored rock a thousand miles because you need a knife. You carry it because it means something. Because the network that produced it means something. Because the relationships it maintains, the ceremonies it enables, the dead it accompanies, all of those things mean something far larger than the object itself.

So you know what? Fuck diamonds. Fuck emeralds. Ohio’s got chert for days, baby.

Works Cited (for those who to hit some silicon dioxide at the end of a long work day)

Abrams, Elliot Marc, and AnnCorinne Freter. The Emergence of the Moundbuilders: The Archaeology of Tribal Societies in Southeastern Ohio. Athens: Ohio University Press, 2005.

Ericson, Jonathon E., and Barbara A. Purdy, eds. Prehistoric Quarries and Lithic Production. Cambridge: Cambridge University Press, 1984. Chapter cited: Luedtke, Barbara E., "Lithic Material Demand and Quarry Production," 65-80.

Holmes, William Henry. Handbook of Aboriginal American Antiquities, Part I: Introductory, the Lithic Industries. Bureau of American Ethnology Bulletin 60. Washington, D.C.: Smithsonian Institution, 1919.

Kern, Kevin F., and Gregory S. Wilson. Ohio: A History of the Buckeye State. 2nd ed. Malden, MA: Wiley, 2014.

Knepper, George W. Ohio and Its People. Bicentennial ed. Kent, OH: Kent State University Press, 2003.

Milner, George R. The Moundbuilders: Ancient Societies of Eastern North America. 2nd ed. London: Thames & Hudson, 2020.

Ohio Department of Natural Resources. "Flint." Discover and Learn: Rock, Minerals, Fossils. https://ohiodnr.gov/discover-and-learn/rock-minerals-fossils/minerals/flint.

Ohio History Connection. "Bladelets, Flint Ridge Flint, and the Hopewell Interaction Sphere." Archaeology Blog, December 7, 2014. https://www.ohiohistory.org/bladelets-flint-ridge-flint-and-the-hopewell-interaction-sphere/.

Ohio History Connection. "Ohio's First Industry: The Archaeology of Flint Ridge." Archaeology Blog. https://www.ohiohistory.org/ohios-first-industry-the-archaeology-of-flint-ridge/.

Prufer, Olaf H., and Douglas H. McKenzie, eds. Studies in Ohio Archaeology. Cleveland: Press of Western Reserve University, 1967.

Seeman, Mark F. The Hopewell Interaction Sphere: The Evidence for Interregional Trade and Structural Complexity. Indiana Historical Society Prehistory Research Series 5, no. 2. Indianapolis: Indiana Historical Society, 1979.

Stout, Wilber, and Robert A. Schoenlaub. The Occurrence of Flint in Ohio. Geological Survey of Ohio Bulletin 46. Columbus: State of Ohio, 1945.

Picture Credit: Vanport Flint, James St. John