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The killers rolled slowly down the narrow alley, three men on a single motorcycle. It was a little after 11am on July 31, 2013, the Sun beating down on the modest residential buildings lining a backstreet in the Indian farming village of Raipur Khadar. The smells of cooking spices, dust and sewage seasoned the air. The men stopped the bike in front of the orange door of a two-storey house. Two of them dismounted, eased open the unlocked door and slipped into the darkened bedroom on the other side. White handkerchiefs covered their lower faces. One of them carried a pistol.

Inside the bedroom Paleram Chauhan, a 52-year-old farmer, was napping after an early lunch. In the next room his wife and daughter-in-law were cleaning up while Paleram's son Ravindra played with his three-year-old nephew.

Gunshots suddenly thundered through the house. Preeti Chauhan, Paleram's daughter-in-law, rushed into the bedroom, Ravindra right behind her. Through the open door they saw the killers jump on their motorbike and roar away.

Paleram lay on his bed, blood bubbling out of his stomach, neck and head. "He tried to speak, but he couldn't," Preeti says, her voice breaking. Ravindra borrowed a neighbour's car and rushed his father to a hospital, but it was too late. Paleram was dead on arrival.

Despite the killers' masks, the family had no doubts about who was behind the shooting. For a decade Paleram had been trying to get local authorities to shut down a powerful gang of criminals headquartered in Raipur Khadar that had for years been robbing the village of a coveted resource, one of the most sought-after commodities of the 21st century: sand.

That's right. Paleram Chauhan was killed over sand. And he wasn't the first, or the last.

Civilisation is built on sand – literally. It's been a critical component of construction and progress since ancient times. In the 15th century an Italian artisan figured out how to turn it into the transparent glass that made it possible to make the microscopes, telescopes and other technologies that helped drive the Renaissance's scientific revolution. Sand is an essential ingredient in detergents, cosmetics, toothpaste, solar panels, windows, silicon chips and buildings; every concrete structure around the world is basically sand and gravel glued together with cement.

Apart from water and air, humble sand is the natural resource most consumed by human beings. People use more than 36 billion tonnes of sand and gravel every year. But not just any sand will do: desert sand, shaped by wind rather than water, is too round to bind together for construction.

In fact, only sand worn by water is suitable. And the worldwide construction boom of recent years -- all those megacities, from Lagos to Beijing -- is devouring unprecedented quantities. Extracting sand is a £45-billion industry. In Dubai, huge land-reclamation projects and breakneck skyscraper construction have exhausted all nearby sources, so insatiable construction companies now look elsewhere for their supply. Exporters in Australia are actually selling sand to Arabs.

As land quarries and riverbeds become tapped out, sand miners are turning to the seas, where ships vacuum huge amounts of the stuff from ocean floors. As you might expect, this all wreaks havoc on ecosystems. Sand mines in the US are blamed for beach erosion, water and air pollution and other ills from the California coast to Wisconsin's lakes. India's Supreme Court recently warned that riparian sand mining is undermining bridges and killing birds and fish all over the country. But regulations are scant and the will to enforce them is lacking.

Sand mining has erased two dozen Indonesian islands since 2005. The stuff of those former islands mostly ended up in Singapore, which needs titanic amounts to continue its programme of artificially adding territory. The city-state has created an extra 129km2 in the past 40 years and is adding more, making it by far the world's largest sand importer. The environmental damage has been so extreme that Indonesia, Malaysia and Vietnam have all restricted or banned exports of sand to Singapore.

As a result, the global black market is booming. Half the sand used for construction in Morocco is estimated to be mined illegally; whole stretches of beach there are disappearing. One of Israel's most notorious gangsters got his start stealing sand from public beaches. Dozens of Malaysian officials were charged in 2010 with accepting bribes and sexual favours in exchange for allowing illegally mined sand to be smuggled into Singapore.

On Indonesia's island of Bali, far inland from the tourist beaches, WIRED visits a sand mine. It looks like Shangri-La after a meteor strike. In the middle of a beautiful valley, surrounded by jungle and rice paddies, is a six-hectare pit of exposed sand and rock. On its floor, men wearing shorts and flip-flops wield sledgehammers and shovels to push sand and gravel into clattering, smoke-belching sorting machines. "Those who have permits to dig for sand have to pay for land restoration," says Nyoman Sadra, a former member of the regional legislature. "But 70 per cent of the sand miners have no permits." Even the companies with permits tend to spread bribes around so they can get away with digging wider or deeper pits.

But nowhere is the struggle for sand more violent than in India. Intense battles among and against sand mafias there have reportedly killed hundreds of people in recent years -- with the victims including police officers, government officials and ordinary people such as Paleram Chauhan.

The area around Raipur Khadar used to be mostly agricultural -- wheat and vegetables growing in the Yamuna River floodplain. But Delhi, less than an hour north, is encroaching fast. Driving down a new six-lane expressway, you pass construction site after construction site, new buildings sprouting skyward like the opening credits of Game of Thrones made real. Besides the countless generic shopping malls, apartment blocks and office towers, a 2,000-hectare "Sports City", including several stadiums and a Formula 1 racetrack, is under construction.

The building explosion got in gear about a decade ago -- and so did the sand mafias. "There was some illegal sand mining before," says Dushyant Nagar, head of a local farmers' rights organisation, "but not on a scale where land was getting stolen or people were getting killed."

The Chauhan family has lived in the area for centuries, Paleram's son Aakash says. He's slim, with wide brown eyes and receding black hair, wearing jeans, a grey sweatshirt and flip-flops. We're sitting on plastic chairs set on the bare concrete floor of the family's living room, a few metres from where his father was killed.

The family owns about four hectares acres of land and shares some 90 hectares with the whole village -- or used to. About ten years ago a group of local "musclemen", as Aakash calls them, led by Rajpal Chauhan (no relation -- it's a common surname) and his three sons, seized control of the land. They stripped away its topsoil and started digging up the sand deposited by centuries of the Yamuna's floods. To make matters worse, the dust kicked up by the operation stunted the growth of crops, according to a complaint Paleram and other locals filed.

As a member of the village panchayat, or governing council, Paleram took the lead in a campaign to get the sand mine shut down. It should have been pretty straightforward. Sand mining is not permitted in the Raipur Khadar area at all, because it's close to a bird sanctuary. And the government knew it was happening: in 2013 a federal fact-finding team found "rampant, unscientific and illegal mining" all over the district.

Nonetheless, Paleram and other villagers couldn't get it stopped. They petitioned police, government officials and courts for years, but nothing happened. Conventional wisdom says that many local authorities accept bribes from the miners to stay out of their business – or are involved in the business themselves. For those who don't take the carrot of a bribe, the mafias aren't shy about using a stick. "We do conduct raids on the illegal sand miners," says Navin Das, the official in charge of mining in the district. "But it's difficult because we get shot at." In the past three years, miners have killed at least three police officers and attacked many others, as well as officials, journalists and whistle-blowers.

According to court documents, Rajpal and his sons threatened Paleram and his family, as well as other villagers. Aakash has known one of the sons, Sonu, since they were kids. "He used to be a decent guy," Aakash says. "But when he got into the sand-mining business and started making fast money, he developed a criminal mentality and started to become very aggressive." In the spring of 2013, police arrested Sonu and impounded some of his outfit's trucks. He was soon out on bail.

One morning Paleram rode his bicycle out to his fields, right next to the sand mine, and bumped into Sonu. "He said, 'It's your fault I was in jail,'" according to Aakash. "He told my father to drop the issue." Instead Paleram complained to the police. A few days later, he was shot dead. Sonu, his brother Kuldeep and Rajpal were arrested, but all of them are out on bail. Aakash sees them around sometimes. "It's a small village," he says.

The broad, murky Thane Creek, just outside Mumbai, is swarming with small wooden boats on a recent winter morning. Hundreds of them are anchored together in a ragged line stretching almost a kilometre. The banks are lined with mangroves, towered over by apartment blocks. There's a tang of salt in the air from the nearby Arabian Sea, mixed with diesel from the boats' engines.

Each boat carries a crew of six to ten men. One or two of them dive to the creek bottom, fill a bucket with sand and return to the surface. Then two others, standing barefoot on planks jutting from the boat, haul up the bucket with ropes.

Pralhad Mhatre, 41, dives about 200 times a day. He's worked here for 16 years. It pays nearly twice what the pullers get -- about £10 a day. Mhatre wants his son and three daughters to go into another profession; he thinks the Thane will soon be mined out. "When I started, we only had to go down 20 feet," he says. "Now it's 40. We can only dive 50 feet. If it gets much lower, we'll be out of a job."

Rivers are excellent places to find sand. The stuff can be made by glaciers grinding up stones, by oceans degrading seashells, even by lava chilling and shattering upon contact with air. According to the Udden-Wentworth size scale, the most common geologic standard, sand is grains of any hard material between 0.0625mm and 2mm in diameter. But nearly 70 per cent of all sand is quartz. Time and the elements eat away at rock, grinding off grains. Rivers carry those grains, accumulating them in their beds, on their banks and where they meet the sea.

Quartz, a form of silicon dioxide, or silica, is one of the most common minerals on Earth. That's good, because it's really useful. Mixed with cement, water and gravel, it makes concrete. "Quartz is one of the hardest materials around, and the angularity of its grains makes them lock together well," says Michael Welland, a geologist and author of Sand: The Never-Ending Story. "And there's a hell of a lot of it."

In the wild, quartz comes mixed with other materials -- iron oxides, feldspar, whatever prevails in the local geology. For commercial products you have to filter that out or start with a high silica content. The sand of France's Fontainebleau region, for instance, is upwards of 98 per cent pure silica. Europe's finest glassmakers have relied on it for centuries. Corning operates the world's largest ophthalmic glass-making centre in Fontainebleau; for lenses, the sand needs to be refined to 99.7 per cent silica. Electronics-grade silicon is refined to at least 99.999999999 per cent purity. As Welland writes, that's one atom of not-silicon among a billion silicon atoms.

The day after my trip to Thane Creek, Sumaira Abdulali, India's foremost campaigner against illegal sand mining, takes me to see a different kind of mine. The 54-year-old is a gentle and well-heeled member of the Mumbai bourgeoisie. For years she has been travelling to remote areas in a chauffeur-driven sedan, taking photographs of the sand mafias at work. In the process she's had her car windows smashed, been threatened, pelted with rocks, pursued at high speeds and punched hard enough to break a tooth.

Abdulali got involved when sand miners started tearing up a beach near Mumbai where her family has vacationed for generations. In 2004 she filed the first citizen-initiated court action against sand mining in India. It made the newspapers, which brought a flood of calls from others who wanted to stop their own local sand mafias. Abdulali has since helped dozens file court cases while keeping up a stream of complaints to local officials. "We don't want to halt development," she says. "But we want to put in accountability."

Over in the rural town of Mahad, sand miners once smashed up her car. Sand mining is banned here because of its proximity to a protected coastal zone. But in the jungled hills just outside town, we come to a grey-green river on which boats, in plain view, are sucking up sand from the bottom with diesel-powered pumps. The banks are dotted with piles of sand, which men are loading on to trucks.

Back on a main road, we find ourselves behind a convoy of three sand trucks. They rumble, past a police van parked on the shoulder. A couple of policemen idle nearby. Another is inside taking a nap. This is too much for Abdulali. We pull up alongside. "Didn't you see those trucks carrying sand that just went past?" Abdulali asks an officer. "We filed some cases this morning," answers the cop. "We're on our lunch break now."

Later I ask a local government official about this. "The police are hand in glove with the miners," says the official, who asks me not to name him. "When I call the police to escort me on a raid, they tip off the miners that we are coming." In the rare cases that are brought to court, no one has been convicted. "They always get off on some technicality."

Back in Raipur Khadar, after talking to Paleram Chauhan's family, Aakash agrees to show WIRED and our interpreter, Kumar Sambhav, the land the mafia has taken over. We'd rented a car in Delhi that morning, and Aakash directs our driver to the site. It's hard to miss: across the road from the village centre is an expanse of torn-up land pocked with craters up to six metres wide. Men are smashing rocks with hammers and loading trucks. They stop to stare at our car as we drive past. Aakash points out a heavy-set guy in jeans and a collared shirt: Sonu.

We get out to snap pictures of a huge crater. After a few minutes Aakash spots four men, three of them carrying shovels, striding purposefully toward us. "Sonu is coming," he mutters.

We start making our way back to the car, but we're too slow. "Motherfucker!" Sonu, now just a few metres away, barks at Aakash. "What are you doing here?"

Aakash keeps silent. Sambhav mumbles that we're tourists as we climb into the car. "I'll give you sisterfuckers a tour," Sonu says. He yanks open our driver's door and orders him out. The driver obeys. Aakash stays put. "We're journalists," Sambhav says. "We're here to see how the mining is going." (This conversation was in Hindi; Sambhav translated for me afterwards.) "Mining?" Sonu says. "We are not mining. What did you see?" "We saw whatever we saw. And now we're leaving." "No, you're not," Sonu says.

The exchange continues for a couple of tense minutes, until one of Sonu's goons points out the presence of a foreigner -- me. This gives Sonu and his crew pause. Harming a westerner could mean trouble. We grab the chance to leave. Sonu, glaring, watches us go.

The case against Sonu and his relatives is grinding its way through India's courts. The outlook isn't great. "In our system you can buy anything -- witnesses, police, administrative officials," a legal professional explains. "And those guys have a lot of money from the mining business."

Aakash keeps in touch with investigators and has tried to get India's National Human Rights Commission to take an interest. His mother has wanted him to drop it since her other son, Ravindra -- the main witness in the case -- was found dead by some railroad tracks last year, run over by a train, apparently.

India is taking steps to get sand mining under control. The National Green Tribunal, a sort of court for environmental matters, hears citizen complaints about illegal sand mining. The government has enlisted India's space agency to provide satellite imagery to monitor river mining. Villagers have blocked roads to stop sand trucks, and almost every day some local or state official declares their determination to combat sand mining. The magistrate of Raipur Khadar's district confiscated sand trucks and made arrests this year. But India has hundreds, if not thousands, of illegal sand-mining operations.

And the world's population is growing. People want housing, offices, factories, malls and roads. "The fundamental problem is the massive use of cement-based construction," says Ritwick Dutta, an Indian environmental lawyer. "That's why the sand mafia has become so huge." Economic development requires concrete and glass. It requires sand.

Vince Beiser is an award-winning journalist based in Los Angeles

This article was originally published by WIRED UK