The ultra-pure, super-secret sand that makes your phone possible

The ultra-pure, super-secret sand that makes your phone possible

The processor that makes your laptop or cell phone work was fabricated using quartz from this obscure Appalachian backwater.


FRESH FROM CHURCH on a cool, overcast Sunday morning in Spruce Pine, North Carolina, Alex Glover slides onto the plastic bench of a McDonald’s booth. He rummages through his knapsack, then pulls out a plastic sandwich bag full of white powder. “I hope we don’t get arrested,” he says. “Someone might get the wrong idea.”

GLOVER IS A recently retired geologist who has spent decades hunting for valuable minerals in the hillsides and hollows of the Appalachian Mountains that surround this tiny town. He is a small, rounded man with little oval glasses, a neat white mustache, and matching hair clamped under a Jeep baseball cap. He speaks with a medium‑strength drawl that emphasizes the first syllable and stretches some vowels, such that we’re drinking CAWWfee as he explains why this remote area is so tremendously important to the rest of the world.

Spruce Pine is not a wealthy place. Its downtown consists of a somnambulant train station across the street from a couple of blocks of two‑story brick buildings, including a long‑closed movie theater and several empty storefronts.

The wooded mountains surrounding it, though, are rich in all kinds of desirable rocks, some valued for their industrial uses, some for their pure prettiness. But it’s the mineral in Glover’s bag—snowy white grains, soft as powdered sugar—that is by far the most important these days. It’s quartz, but not just any quartz. Spruce Pine, it turns out, is the source of the purest natural quartz—a species of pristine sand—ever found on Earth. This ultra‑elite deposit of silicon dioxide particles plays a key role in manufacturing the silicon used to make computer chips. In fact, there’s an excellent chance the chip that makes your laptop or cell phone work was made using sand from this obscure Appalachian backwater. “It’s a billion‑dollar industry here,” Glover says with a hooting laugh. “Can’t tell by driving through here. You’d never know it.”

n the 21st century, sand has become more important than ever, and in more ways than ever. This is the digital age, in which the jobs we work at, the entertainment we divert ourselves with, and the ways we communicate with one another are increasingly defined by the internet and the computers, tablets, and cell phones that connect us to it. None of this would be possible were it not for sand.

Most of the world’s sand grains are composed of quartz, which is a form of silicon dioxide, also known as silica. High‑purity silicon dioxide particles are the essential raw materials from which we make computer chips, fiber‑optic cables, and other high‑tech hardware—the physical components on which the virtual world runs. The quantity of quartz used for these products is minuscule compared to the mountains of it used for concrete or land reclamation. But its impact is immeasurable.

Spruce Pine’s mineralogical wealth is a result of the area’s unique geologic history. About 380 million years ago the area was located south of the equator. Plate tectonics pushed the African continent toward eastern America, forcing the heavier oceanic crust—the geologic layer beneath the ocean’s water—underneath the lighter North American continent. The friction of that colossal grind generated heat topping 2,000 degrees Fahrenheit, melting the rock that lay between 9 and 15 miles below the surface. The pressure on that molten rock forced huge amounts of it into cracks and fissures of the surrounding host rock, where it formed deposits of what are known as pegmatites.

It took some 100 million years for the deeply buried molten rock to cool down and crystallize. Thanks to the depth at which it was buried and to the lack of water where all this was happening, the pegmatites formed almost without impurities. Generally speaking, the pegmatites are about 65 percent feldspar, 25 percent quartz, 8 percent mica, and the rest traces of other minerals. Meanwhile, over the course of some 300 million years, the plate under the Appalachian Mountains shifted upward. Weather eroded the exposed rock, until the hard formations of pegmatites were left near the surface.

Native Americans mined the shiny, glittering mica and used it for grave decorations and as currency. American settlers began trickling into the mountains in the 1800s, scratching out a living as farmers. A few prospectors tried their hands at the mica business, but were stymied by the steep mountain geography. “There were no rivers, no roads, no trains. They had to haul the stuff out on horseback,” says David Biddix, a scruffy‑haired amateur historian who has written three books about Mitchell County, where Spruce Pine sits.

The region’s prospects started to improve in 1903 when the South and Western Railroad company, in the course of building a line from Kentucky to South Carolina, carved a track up into the mountains, a serpentine marvel that loops back and forth for 20 miles to ascend just 1,000 feet. Once this artery to the outside world was finally opened, mining started to pick up. Locals and wildcatters dug hundreds of shafts and open pits in the mountains of what became known as the Spruce Pine Mining District, a swath of land 25 miles by 10 miles that sprawls over three counties.

Mica used to be prized for wood‑ and coal‑burning stove windows and for electrical insulation in vacuum tube electronics. It’s now used mostly as a specialty additive in cosmetics and things like caulks, sealants, and drywall joint compound. During World War II, demand for mica and feldspar, which are found in tremendous abundance in the area’s pegmatites, boomed. Prosperity came to Spruce Pine. The town quadrupled in size in the 1940s. At its peak, Spruce Pine boasted three movie theaters, two pool halls, a bowling alley, and plenty of restaurants. Three passenger trains came through every day.

Toward the end of the decade, the Tennessee Valley Authority sent a team of scientists to Spruce Pine tasked with further developing the area’s mineral resources. They focused on the money‑makers, mica and feldspar. The problem was separating those minerals from the other ones. A typical chunk of Spruce Pine pegmatite looks like a piece of strange but enticing hard candy: mostly milky white or pink feldspar, inset with shiny mica, studded with clear or smoky quartz, and flecked here and there with bits of deep red garnet and other‑colored minerals.

For years, locals would simply dig up the pegmatites and crush them with hand tools or crude machines, separating out the feldspar and mica by hand. The quartz that was left over was considered junk, at best fit to be used as construction sand, more likely thrown out with the other tailings.

Working with researchers at North Carolina State University’s Minerals Research Laboratory in nearby Asheville, the TVA scientists developed a much faster and more efficient method to separate out minerals, called froth flotation. “It revolutionized the industry,” Glover says. “It made it evolve from a mom‑and‑pop individual industry to a mega‑multinational corporation industry.”

Froth flotation involves running the rock through mechanical crushers until it’s broken down into a heap of mixed‑mineral granules. You dump that mix in a tank, add water to turn it into a milky slurry, and stir well. Next, add reagents—chemicals that bind to the mica grains and make them hydrophobic, meaning they don’t want to touch water. Now pipe a column of air bubbles through the slurry. Terrified of the water surrounding them, the mica grains will frantically grab hold of the air bubbles and be carried up to the top of the tank, forming a froth on the water’s surface. A paddle wheel skims off the froth and shunts it into another tank, where the water is drained out. Voilà: mica.

The remaining feldspar, quartz, and iron are drained from the bottom of the tank and funneled through a series of troughs into the next tank, where a similar process is performed to float out the iron. Repeat, more or less, to remove the feldspar.

IT WAS THE feldspar, which is used in glassmaking, that first attracted engineers from the Corning Glass Company to the area. At the time, the leftover quartz grains were still seen as just unwanted by‑products. But the Corning engineers, always on the lookout for quality material to put to work in the glass factories, noticed the purity of the quartz and started buying it as well, hauling it north by rail to Corning’s facility in Ithaca, New York, where it was turned into everything from windows to bottles.

One of Spruce Pine quartz’s greatest achievements in the glass world came in the 1930s, when Corning won a contract to manufacture the mirror for what was to be the world’s biggest telescope, ordered by the Palomar Observatory in Southern California. Making the 200‑inch, 20‑ton mirror involved melting mountains of quartz in a giant furnace heated to 2,700 degrees Fahrenheit, writes David O. Woodbury in The Glass Giant of Palomar.

Once the furnace was hot enough, “three crews of men, working day and night around the clock, began ramming in the sand and chemicals through a door at one end. So slowly did the ingredients melt that only four tons a day could be added. Little by little the fiery pool spread over the bottom of the furnace and rose gradually to an incandescent lake 50 feet long and 15 wide.” The telescope was installed in the observatory in 1947. Its unprecedented power led to important discoveries about the composition of stars and the size of the universe itself. It is still in use today.

ignificant as that telescope was, Spruce Pine quartz was soon to take on a far more important role as the digital age began to dawn.

In the mid‑1950s, thousands of miles from North Carolina, a group of engineers in California began working on an invention that would become the foundation of the computer industry. William Shockley, a pathbreaking engineer at Bell Labs who had helped invent the transistor, had left to set up his own company in Mountain View, California, a sleepy town about an hour south of San Francisco, near where he had grown up. Stanford University was nearby, and General Electric and IBM had facilities in the area, as well as a new company called Hewlett‑Packard. But the area known at the time as the Santa Clara Valley was still mostly filled with apricot, pear, and plum orchards. It would soon become much better known by a new nickname: Silicon Valley.

At the time, the transistor market was heating up fast. Texas Instruments, Motorola, and other companies were all competing to come up with smaller, more efficient transistors to use in, among other products, computers. The first American computer, dubbed ENIAC, was developed by the army during World War II; it was 100 feet long and 10 feet high, and it ran on 18,000 vacuum tubes.

Transistors, which are tiny electronic switches that control the flow of electricity, offered a way to replace those tubes and make these new machines even more powerful while shrinking their tumid footprint. Semiconductors—a small class of elements, including germanium and silicon, which conduct electricity at certain temperatures while blocking it at others—looked like promising materials for making those transistors.

At Shockley’s startup, a flock of young PhDs began each morning by firing up kilns to thousands of degrees and melting down germanium and silicon. Tom Wolfe once described the scene in Esquire magazine: “They wore white lab coats, goggles, and work gloves. When they opened the kiln doors weird streaks of orange and white light went across their faces . . . they lowered a small mechanical column into the goo so that crystals formed on the bottom of the column, and they pulled the crystal out and tried to get a grip on it with tweezers, and put it under microscopes and cut it with diamond cutters, among other things, into minute slices, wafers, chips; there were no names in electronics for these tiny forms.”

Shockley became convinced that silicon was the more promising material and shifted his focus accordingly. “Since he already had the first and most famous semiconductor research and manufacturing company, everyone who had been working with germanium stopped and switched to silicon,” writes Joel Shurkin in his biography of Shockley, Broken Genius. “Indeed, without his decision, we would speak of Germanium Valley.”

Shockley was a genius, but by all accounts he was also a lousy boss. Within a couple of years, several of his most talented engineers had jumped ship to start their own company, which they dubbed Fairchild Semiconductor. One of them was Robert Noyce, a laid‑back but brilliant engineer, only in his mid‑20s but already famous for his expertise with transistors.

The breakthrough came in 1959, when Noyce and his colleagues figured out a way to cram several transistors onto a single fingernail‑sized sliver of high‑purity silicon. At almost the same time, Texas Instruments developed a similar gadget made from germanium. Noyce’s, though, was more efficient, and it soon dominated the market. NASA selected Fairchild’s microchip for use in the space program, and sales soon shot from almost nothing to $130 million a year. In 1968, Noyce left to found his own company. He called it Intel, and it soon dominated the nascent industry of programmable computer chips.

Intel’s first commercial chip, released in 1971, contained 2,250 transistors. Today’s computer chips are often packed with transistors numbering in the billions. Those tiny electronic squares and rectangles are the brains that run our computers, the Internet, and the entire digital world. Google, Amazon, Apple, Microsoft, the computer systems that underpin the work of everything from the Pentagon to your local bank—all of this and much more is based on sand, remade as silicon chips.

Making those chips is a fiendishly complicated process. They require essentially pure silicon. The slightest impurity can throw their tiny systems out of whack.

Finding silicon is easy. It’s one of the most abundant elements on Earth. It shows up practically everywhere bound together with oxygen to form SiO2, aka quartz. The problem is that it never occurs naturally in pure, elemental form. Separating out the silicon takes considerable doing.

Step one is to take high‑purity silica sand, the kind used for glass. (Lump quartz is also sometimes used.) That quartz is then blasted in a powerful electric furnace, creating a chemical reaction that separates out much of the oxygen. That leaves you with what is called silicon metal, which is about 99 percent pure silicon. But that’s not nearly good enough for high‑tech uses. Silicon for solar panels has to be 99.999999 percent pure—six 9s after the decimal. Computer chips are even more demanding. Their silicon needs to be 99.99999999999 percent pure—eleven 9s. “We are talking of one lonely atom of something that is not silicon among billions of silicon companions,” writes geologist Michael Welland in Sand: The Never-Ending Story.

Getting there requires treating the silicon metal with a series of complex chemical processes. The first round of these converts the silicon metal into two compounds. One is silicon tetrachloride, which is the primary ingredient used to make the glass cores of optical fibers. The other is trichlorosilane, which is treated further to become polysilicon, an extremely pure form of silicon that will go on to become the key ingredient in solar cells and computer chips.

Each of these steps might be carried out by more than one company, and the price of the material rises sharply at each step. That first‑step, 99 percent pure silicon metal goes for about $1 a pound; polysilicon can cost 10 times as much.

The next step is to melt down the polysilicon. But you can’t just throw this exquisitely refined material in a cook pot. If the molten silicon comes into contact with even the tiniest amount of the wrong substance, it causes a ruinous chemical reaction. You need crucibles made from the one substance that has both the strength to withstand the heat required to melt polysilicon, and a molecular composition that won’t infect it. That substance is pure quartz.

THIS IS WHERE Spruce Pine quartz comes in. It’s the world’s primary source of the raw material needed to make the fused‑quartz crucibles in which computer‑chip‑grade polysilicon is melted. A fire in 2008 at one of the main quartz facilities in Spruce Pine for a time all but shut off the supply of high‑purity quartz to the world market, sending shivers through the industry.

Today one company dominates production of Spruce Pine quartz. Unimin, an outfit founded in 1970, has gradually bought up Spruce Pine area mines and bought out competitors, until today the company’s North Carolina quartz operations supply most of the world’s high‑ and ultra‑high‑purity quartz. (Unimin itself is now a division of a Belgian mining conglomerate, Sibelco.)

In recent years, another company, the imaginatively titled Quartz Corp, has managed to grab a small share of the Spruce Pine market. There are a very few other places around the world producing high‑purity quartz, and many other places where companies are looking hard for more. But Unimin controls the bulk of the trade.

The quartz for the crucibles, like the silicon they will produce, needs to be almost absolutely pure, purged as thoroughly as possible of other elements. Spruce Pine quartz is highly pure to begin with, and purer still after being put through several rounds of froth flotation. But some of the grains may still have what Glover calls interstitial crystalline contamination—molecules of other minerals attached to the quartz molecules.

That’s frustratingly common. “I’ve evaluated thousands of quartz samples from all over the world,” says John Schlanz, chief minerals processing engineer at the Minerals Research Laboratory in Asheville, about an hour from Spruce Pine. “Near all of them have contaminate locked in the quartz grains that you can’t get out.”

Some Spruce Pine quartz is flawed in this way. Those grains are used for high‑end beach sand and golf course bunkers—most famously the salt‑white traps of Augusta National Golf Club, site of the iconic Masters Tournament. A golf course in the oil‑drunk United Arab Emirates imported 4,000 tons of this sand in 2008 to make sure its sand traps were world‑class, too.

The very best Spruce Pine quartz, however, has an open crystalline structure, which means that hydrofluoric acid can be injected right into the crystal molecules to dissolve any lingering traces of feldspar or iron, taking the purity up another notch. Technicians take it one step further by reacting the quartz with chlorine or hydrochloric acid at high temperatures, then putting it through one or two more trade‑secret steps of physical and chemical processing.

The result is what Unimin markets as Iota quartz, the industry standard of purity. The basic Iota quartz is 99.998 percent pure SiO2. It is used to make things like halogen lamps and photovoltaic cells, but it’s not good enough to make those crucibles in which polysilicon is melted. For that you need Iota 6, or the tip‑top of the line, Iota 8, which clocks in at 99.9992 percent purity—meaning for every one billion molecules of SiO , there are only 80 molecules of impurities. Iota 8 sells for up to $10,000 a ton. Regular construction sand, at the other end of the sand scale, can be had for a few dollars per ton.

At his house, Glover shows me some Iota under a microscope. Seen through the instrument’s lens (itself made from a much less pure quartz sand), the jagged little shards are as clear as glass and bright as diamonds.

Unimin sells this ultra‑high‑purity quartz sand to companies like General Electric, which melts it, spins it, and fuses it into what looks like a salad bowl made of milky glass: the crucible. “It’s safe to say the vast majority of those crucibles are made from Spruce Pine quartz,” Schlanz says.

The polysilicon is placed in those quartz crucibles, melted down, and set spinning. Then a silicon seed crystal about the size of a pencil is lowered into it, spinning in the opposite direction. The seed crystal is slowly withdrawn, pulling behind it what is now a single giant silicon crystal. These dark, shiny crystals, weighing about 220 pounds, are called ingots.

The ingots are sliced into thin wafers. Some are sold to solar cell manufacturers. Ingots of the highest purity are polished to mirror smoothness and sold to a chipmaker like Intel. It’s a thriving multi-billion dollar industry in 2012.

The chipmaker imprints patterns of transistors on the wafer using a process called photolithography. Copper is implanted to link those billions of transistors to form integrated circuits. Even a minute particle of dust can ruin the chip’s intricate circuitry, so all of this happens in what’s called a clean room, where purifiers keep the air thousands of times cleaner than a hospital operating room. Technicians dress in an all‑covering white uniform affectionately known as a bunny suit. To ensure the wafers don’t get contaminated during manufacture, many of the tools used to move and manipulate them are, like the crucibles, made from high‑purity quartz.

The wafers are then cut into tiny, unbelievably thin quadrangular chips—computer chips, the brains inside your mobile phone or laptop. The whole process requires hundreds of precise, carefully controlled steps. The chip that results is easily one of the most complicated man‑made objects on Earth, yet made with the most common stuff on Earth: humble sand.

The total amount of high‑purity quartz produced worldwide each year is estimated at 30,000 tons—less than the amount of construction sand produced in the United States every hour. (And even construction sand is in high demand; there’s a thriving black market in the stuff.) Only Unimin knows exactly how much Spruce Pine quartz is produced, because it doesn’t publish any production figures. It is an organization famously big on secrecy. “Spruce Pine used to be mom‑and‑ pop operations,” Schlanz says. “When I first worked up there, you could just walk into any of the operations. You could just go across the street and borrow a piece of equipment.”

NOWADAYS UNIMIN WON’T even allow staff of the Minerals Research Laboratory inside the mines or processing facilities. Contractors brought in to do repair work have to sign confidentiality agreements. Whenever possible, vice‑president Richard Zielke recently declared in court papers, the company splits up the work among different contractors so that no individual can learn too much.

Unimin buys equipment and parts from multiple vendors for the same reason. Glover has heard of contractors being blindfolded inside the processing plants until they arrive at the specific area where their jobs are and of an employee who was fired on the spot for bringing someone in without authorization. He says the company doesn’t even allow its employees to socialize with those of their competitors.

It was hard to check out Glover’s stories, because Unimin wouldn’t talk to me. Unlike most big corporations, its website lists no contact for a press spokesperson or public relations representative. Several emails to their general inquiries address went unanswered. When I called the company’s headquarters in Connecticut, the woman who answered the phone seemed mystified by the concept of a journalist wanting to ask questions.

She put me on hold for a few minutes, then came back to tell me the company has no PR department, but that if I faxed (faxed!) her my questions, someone might get back to me. Eventually I got in touch with a Unimin executive who asked me to send her my questions by email. I did so. The response: “Unfortunately, we are not in a position to provide answers at this point in time.”

So I tried the direct approach. Like all the quartz mining and processing facilities in the area, Unimin’s Schoolhouse Quartz Plant, set in a valley amid low, thickly treed hills, is surrounded by a barbed‑wire‑topped fence. Security isn’t exactly at the level of Fort Knox, but the message is clear.

One Saturday morning I go to take a look at the plant with David Biddix. We park across the street from the gate. A sign warns that the area is under video surveillance, and that neither guns nor tobacco are allowed inside. As soon as I hop out to snap a few photos, a matronly woman in a security guard uniform popped out of the gatehouse. “Watcha doin’?” she asks conversationally. I give her my friendliest smile and tell her I am a journalist writing a book about sand, including about the importance of the quartz sand in this very facility. She takes that all in skeptically, and asks me to call Unimin’s local office the following Monday to get permission.

“Sure, I’ll do that,” I say. “I just want to take a look, as long as I’m here.” “Well, please don’t take pictures,” she says. There isn’t much to see—some piles of white sand, a bunch of metal tanks, a redbrick building near the gate—so I agree. She lumbers back inside. I put away my camera and pull out my notebook. That brings her right back out.

“You don’t look like a terrorist”—she laughs apologetically— “but these days you never know. I’m asking you to leave before I get grumpy.”

“I understand,” I say. “I just want to take a few notes. And anyway, this is a public road. I have the right to be here.”

That really displeased her. “I’m doing my job,” she snaps. “I’m doing mine,” I reply.

“All right, I’m taking notes, too,” she declares. “And if anything happens . . .” Leaving the consequences unspecified, she strides over to my rental car and officiously writes down its license plate number, then asks for the name of “my companion” in the passenger seat. I don’t want to get Biddix in any trouble, so I politely decline, hop in, and drive off.

IF YOU REALLY want a sense of how zealously Unimin guards its trade secrets, ask Tom Gallo. He used to work for the company, and then for years had his life ruined by it.

Gallo is a small, lean man in his 50s, originally from New Jersey. He relocated to North Carolina when he was hired by Unimin in 1997. His first day on the job, he was handed a confidentiality agreement; he was surprised at how restrictive it was and didn’t think it was fair. But there he was, way out in Spruce Pine, with all his possessions in a moving truck, his life in New Jersey already left behind. So he signed it.

Gallo worked for Unimin in Spruce Pine for 12 years. When he left, he signed a noncompete agreement that forbade him from working for any of the company’s competitors in the high‑purity quartz business for five years. He and his wife moved to Asheville and started up an artisanal pizza business, which they dubbed Gallolea—his last name plus that of a friend who had encouraged him.

It was a rough go. The pizza business was never a big money‑maker, and it was soon hit with a lawsuit over its name from the E. & J. Gallo Winery. Gallo spent thousands of dollars fighting the suit—it’s his name, after all—but eventually decided the prudent course would be to give up and change the company’s name. The five‑year noncompete term had run out by then, so when a small startup quartz company, I‑Minerals, called to offer Gallo a consulting gig, he gladly accepted. I‑Minerals put out a press release bragging about the hire and touting Gallo’s expertise.

That turned to be a big mistake. Unimin promptly filed a lawsuit against Gallo and I‑Minerals, accusing them of trying to steal Unimin’s secrets. “There was no call, no cease‑and‑desist order, no investigation,” Gallo says. “They filed a 150‑page brief against me on the basis of a press release.”

Over the next several years, Gallo spent tens of thousands of dollars fighting the suit. “That’s how billion‑dollar corporations terrify people,” he says. “I had to take money out of my 401(k) to defend myself against this totally baseless lawsuit. We were afraid we would lose our house. It was terrifying. You can’t imagine how many sleepless nights my wife and I have had.” His pizza business collapsed. “When Unimin filed suit, we had just gotten over the Gallo thing. It was the sledgehammer that broke the camel’s back. We’d worked on it for five years. It was more than we could handle emotionally, psychologically, and financially.”

Unimin eventually lost the case, appealed it to federal court, and finally dropped it. I‑Minerals and Gallo separately countersued Unimin, calling its suit an abuse of the judicial process aimed at harassing a potential competitor. Unimin eventually agreed to pay an undisclosed sum to have the suits withdrawn. Under the terms of the settlement, Gallo can’t disclose the details, but says bitterly, “When you get sued by a big corporation, you lose no matter what.”

For all the wealth that comes out of the ground in the Spruce Pine area, not much of it stays there. Today the mines are all owned by foreign corporations. They’re highly automated, so they don’t need many workers. “Now there’s maybe 25 or 30 people on a shift, instead of 300,” Biddix says. The area’s other jobs are vanishing. “We had seven furniture factories here when I was a kid,” he says. “We had knitting mills making blue jeans and nylons. They’re all gone.”

Median household income in Mitchell County, where Spruce Pine sits, is just over $37,000, far below the national average of $51,579. Twenty percent of the county’s 15,000 people, almost all of whom are white, live below the poverty line. Fewer than one in seven adults has a college degree.

People find ways to get by. Glover has a side business growing Christmas trees on his property. Biddix makes his living running the website of a nearby community college.

One of the few new sources of jobs are several huge data processing centers that have opened up in the area. Attracted by the cheap land, Google, Apple, Microsoft, and other tech companies have all opened up server farms within an hour’s drive of Spruce Pine.

In a sense, Spruce Pine’s quartz has come full circle. “When you talk to Siri, you’re talking to a building here at the Apple center,” Biddix says.

I pull out my iPhone and ask Siri if she knows where her silicon brains came from.

“Who, me?” she replies the first time. I try again.

“I’ve never really thought about it,” she says.

From THE WORLD IN A GRAIN by Vince Beiser.

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