Sand covers so much of the earth’s surface that shipping it across borders—even uncontested ones—seems extreme. But sand isn’t just sand, it turns out. In the industrial world, it’s “aggregate,” a category that includes gravel, crushed stone, and various recycled materials. Natural aggregate is the world’s second most heavily exploited natural resource, after water, and for many uses the right kind is scarce or inaccessible. In 2014, the United Nations Environment Programme published a report titled “Sand, Rarer Than One Thinks,” which concluded that the mining of sand and gravel “greatly exceeds natural renewal rates” and that “the amount being mined is increasing exponentially, mainly as a result of rapid economic growth in Asia.”
Pascal Peduzzi, a Swiss scientist and the director of one of the U.N.’s environmental groups, told the BBC last May that China’s swift development had consumed more sand in the previous four years than the United States used in the past century. In India, commercially useful sand is now so scarce that markets for it are dominated by “sand mafias”—criminal enterprises that sell material taken illegally from rivers and other sources, sometimes killing to safeguard their deposits. In the United States, the fastest-growing uses include the fortification of shorelines eroded by rising sea levels and more and more powerful ocean storms—efforts that, like many attempts to address environmental challenges, create environmental challenges of their own.
Geologists define sand not by composition but by size, as grains between 0.0625 and two millimetres across. Just below sand on the size scale is silt; just above it is gravel. Most sand consists chiefly of quartz, the commonest form of silica, but there are other kinds. Sand on ocean beaches usually includes a high proportion of shell pieces and, increasingly, bits of decomposing plastic trash; Hawaii’s famous black sand is weathered fragments of volcanic glass; the sand in the dunes at White Sands National Monument, in New Mexico, is mainly gypsum. Sand is almost always formed through the gradual disintegration of bigger rocks, by the action of ice, water, wind, and time, but, as the geologist Michael Welland writes, in his book “Sand: The Never-Ending Story,” many of those bigger rocks were themselves formed from accumulations of the eroded bits of other rocks, and “perhaps half of all sand grains have been through six cycles in the mill, liberated, buried, exposed, and liberated again.”
Sand is also classified by shape, in configurations that range from oblong and sharply angular to nearly spherical and smooth. Desert sand is almost always highly rounded, because strong winds knock the grains together so forcefully that protrusions and sharp edges break off. River sand is more angular. William H. Langer, a research geologist who retired from the U.S. Geological Survey a few years ago and now works as a private consultant, told me, “In a stream, there’s a tiny film of water around each grain, so when the grains bang together there’s enough energy to break them apart but not enough to let them rub against each other.” The shape of sand deposited by glaciers and ice sheets depends partly on how far the sand was moved and what it was moved over. Most of the sand in the Hutcheson quarry is “sub-angular”: the grains have fractured faces, but the sharp edges have been partly abraded away. Sand that’s very slightly more smooth-edged is “sub-rounded.”
Aggregate is the main constituent of concrete (eighty per cent) and asphalt (ninety-four per cent), and it’s also the primary base material that concrete and asphalt are placed on during the building of roads, buildings, parking lots, runways, and many other structures. A report published in 2004 by the American Geological Institute said that a typical American house requires more than a hundred tons of sand, gravel, and crushed stone for the foundation, basement, garage, and driveway, and more than two hundred tons if you include its share of the street that runs in front of it. A mile-long section of a single lane of an American interstate highway requires thirty-eight thousand tons. The most dramatic global increase in aggregate consumption is occurring in parts of the world where people who build roads are trying to keep pace with people who buy cars. Chinese officials have said that by 2030 they hope to have completed a hundred and sixty-five thousand miles of roads—a national network nearly three and a half times as long as the American interstate system.
One engineer I spoke to told me that transporting sand and stone for ordinary construction becomes uneconomical after about sixty miles, and that builders usually make do with whatever is available within that radius, even if it means settling for materials that aren’t ideal. In some places, though, there are no usable alternatives. Florida lies on top of a vast limestone formation, but most of the stone is too soft to be used in construction. “The whole Gulf Coast is starved for aggregate,” William Langer, the research geologist, told me. “So they import limestone from Mexico, from a quarry in the Yucatán, and haul it by freighter across the Caribbean.” Even that stone is wrong for some uses. “You can build most of a road with limestone from Mexico,” he continued, “but it doesn’t have much skid resistance. So to get that they have to use granitic rock, which they ship down the East Coast from quarries in Nova Scotia or haul by train from places like inland Georgia.” When Denver International Airport was being built, in the nineteen-nineties, local quarries were unable to supply crushed stone as rapidly as it was needed, so vast quantities were brought from a quarry in Wyoming whose principal product was stone ballast for railroad tracks. The crushed stone was delivered by a freight train that ran in a continuous loop between the quarry and the work site.
Deposits of sand, gravel, and stone can be found all over the United States, but many of them are untouchable, because they’re covered by houses, shopping malls, or protected land. Regulatory approval for new quarries is more and more difficult to obtain: people don’t want to live near big, noisy holes, even if their lives are effectively fabricated from the products of those holes. The scarcity of alternatives makes existing quarries increasingly valuable. The Connecticut quarry I visited is one of a number owned by Stanley’s company, and like many in the United States it’s in operation today only because it predates current mining regulations.
Ten years ago, I spent a week in Dubai, which at the time was one of the fastest-growing cities in the world. Construction cranes and imported laborers were everywhere. The work went on all night, and the city’s extraordinary traffic congestion was continually being made worse by road-widening projects intended to relieve it. Exhaust from cars and trucks, in combination with wind-borne dust from the Arabian Desert and humid air from the Persian Gulf, formed a thick, phlegm-colored haze that made breathing unpleasant—an effect exacerbated by the ferocious heat. (Dubai gets so hot during the summer that many swimming pools are cooled, rather than heated.)
One day, I played golf with an Australian who worked for a major real-estate developer. The course, like Dubai itself, had been built on empty desert, and I commented that creating fairways and greens in such a forbidding environment must be difficult. “No,” the Australian said. “Deserts are easy, because you can shape the sand into anything you like.” The difficult parts, paradoxically, are the areas that are supposed to be sand: deserts make lousy sand traps. The wind-blown grains are so rounded that golf balls sink into them, so the sand in the bunkers on Dubai’s many golf courses is imported. Jumeirah Golf Estates—on the outskirts of the city, next to the desert—has two courses, Fire and Earth, both designed by Greg Norman. The sand in the bunkers on the Earth course is white (the most prized color for golf sand) and was bought from a producer in North Carolina. The sand on the Fire course is reddish brown—more like the desert across the road. Norman’s company bought it from Hutcheson, which mined it at its quarry in Ontario, sifted it to make it firmer than volleyball sand, kiln-dried it, dyed it, and loaded it onto a ship.
Unfortunately for Dubai’s builders and real-estate developers, desert sand is also unsuitable for construction and, indeed, for almost any human use. The grains don’t have enough fractured faces for concrete and asphalt, and they’re too small and round for water-filtration systems. The high-compression concrete used in Dubai’s Burj Khalifa, the world’s tallest structure, was made with sand imported from Australia. William Langer told me that other desert countries face similar shortages. “Mauritania is trying to catch up with the world,” he said. “They’ve got sand all over the place, but it isn’t good even for highway construction.” Stone is so scarce in Bangladesh that contractors commonly resort to making concrete with crushed brick.
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