OFF THE COAST OF NAMIBIA — Deep beneath this frigid stretch of the Atlantic Ocean, some of the world’s most valuable diamonds are scattered like lost change.
The discovery of such gems has sparked a revolution in one of the world’s most storied industries, sending mining companies on a race for precious stones buried just under the seafloor.
For over a century, open-pit diamond mines have been some of the most valuable real estate on Earth, with small swaths of southern Africa producing billions of dollars of wealth. But those mines are gradually being exhausted. Experts predict that the output of existing onshore mines will decline by around 2 percent annually in coming years. By 2050, production might cease.
Now, some of the first “floating mines” could offer hope for the world’s most mythologized gemstone, and extend a lifeline to countries like Namibia whose economies depend on diamonds. Last year, mining companies extracted $600 million worth of diamonds off the Namibian coast, sucking them up in giant vacuum-like hoses.
“As [Namibia’s] land-based mines enter their twilight years, it’s very important for us and for Namibia that we have long-term mining prospects,” said Bruce Cleaver, the chief executive of De Beers, in an interview.
But as companies weigh the prospect of more offshore operations, environmentalists have raised concerns about the damage that could be inflicted on the seafloor.
From above, the mining vessels look like oil rigs, 300-foot-long ships with helicopter landing platforms, dredging equipment and industrial metal pilings. On a recent day, a family of seals swam off one of them, as the machines hummed and sediment was sucked on board through a 170-yard hose to be sorted. It might be the world’s most complex commercial mining endeavor.
Diamonds are formed when carbon is subjected to high temperatures and pressure deep underground. Some were hurled toward the surface millions of years ago in volcanic eruptions. In recent decades, geologists realized that because diamonds could be found in Namibia’s Orange River, there was a good chance they could also be detected at sea, swept there by the current. As it turned out, the underwater gems were among the world’s most valuable stones — with far greater clarity than diamonds mined on land.
De Beers, which historically dominated global diamond production, purchased mining rights to more than 3,000 square miles of the Namibian seafloor in 1991. So far, it has explored only 3 percent of that area.
The technology to extract the underwater diamonds took years to develop. Only recently has the firm been able to efficiently scavenge the sea for diamonds. Underwater gems only represent about 13 percent of the value of diamonds De Beers mines onshore each year, but more countries are pushing for exploration to begin along their coastlines.
At the unveiling last month of the SS Nujoma, a giant exploration vessel, former Namibian president Sam Nujoma smashed a bottle of champagne over the hull, surrounded by signs that read:
“The future of marine diamond mining is here, and it’s Namibian.”
Mining sites turned into ghost towns
In 1908, a railroad worker named Zacharias Lewala found a shiny stone in the desert of southwestern Namibia. South Africa’s diamond rush had been underway for a few decades, and now another boom began in the territory to its northwest, with miners finding some valleys strewn with the precious stones. Germany, which controlled present-day Namibia until World War I, extracted 7 million carats between 1908 and 1914.
A century later, many of those mining sites are now ghost towns. All that’s left of Kolmanskop, where Lewala found his diamond, is a cluster of abandoned wooden houses, their living rooms covered in sand. It is a portrait of the rapid boom-and-bust life cycle of diamond mining.
Mining companies have invested billions in technology that would lead to new finds. And there have been some big ones: In 1982 in Botswana, De Beers opened a mine called Jwaneng, which produces roughly 12 million carats per year, worth over $2 billion.
But known diamond deposits began to diminish in recent years, even as demand for the gems has remained strong. Last year, the world spent $80 billion on diamond jewelry, more than half of it in the United States, an all-time high. Demand in emerging economies such as China and India is also expected to increase.
Those trends — diminishing supply and rising demand — made Namibia’s offshore deposits all the more important. In the 1990s, De Beers sent its first commercial vessels into the Atlantic in search of diamonds. Now, more than 90 percent of Namibia's diamond-related revenue comes from offshore finds.
These days, the company uses drones to fly over vast stretches of the ocean, looking for areas that might be worth exploring. Then it sends vessels like the Mafuta to dredge the most promising areas. Most of the diamonds are close to the surface, De Beers said, so it does not go deeper than six feet beneath the seafloor.
The mining vessels combine technology from oil rigs, dredging ships and even canneries to do their work. A remote control, tractor-like crawler moves slowly along the surface of the seafloor, directing a hose that sucks up tons of sediment every hour.
The sediment is then passed through a series of machines that cull material first by size and then, using X-ray technology, by geological composition. Diamonds make their way down five floors of conveyor belts and machines into a metal container that looks like a soup can.
“The things we do for women,” quipped Mike Rogers, the chief engineer of the Mafuta, as the crawler descended from the vessel one day last month.
Ninety-eight people live aboard the Mafuta, which has the urgent, frenzied feeling of a naval ship. A few weeks ago, it was hammered with 30-foot swells as it tried to operate.
Diamond mining contributes roughly a tenth of Namibia’s gross domestic product, and its offshore contract with De Beers is a 50-50 partnership with the government. But while the soaring revenue has made some Namibians rich, this remains the world’s third most unequal country, according to the World Bank, with millions of people unaided by the diamond rush.
Debate over ecological damage
Although Namibia is considered the easiest place to extract offshore diamonds, mining executives are not ruling out exploring other stretches of ocean. Marine mining has also taken place off the coast of South Africa, though it has proven less lucrative.
“Never say never,” Cleaver said.
But environmental groups have raised concerns about the offshore mining operations, which spew the sediment back into the ocean after it is processed for diamonds. Companies also plan to begin mining offshore for gold in coming years, with one commercial operation scheduled to launch in 2018 off Papua New Guinea.
“My concern with this and all deep-sea mining is that we just don’t know much about the deep sea at all,” said Emily Jeffers, an attorney with the Center for Biological Diversity, a U.S. nonprofit organization. “The worry is that we are going to irreparably harm this environment and these species before we discover them.”
De Beers says its offshore operations do not cause significant ecological damage, as sediment is returned to the sea and eventually resettles. The company says it employs ecologists who monitor the environment where they have mined to make sure it is recovering.
Sitting on the bridge of the Mafuta one recent day, a middle-aged South African man named Leonard Bunce manned the joysticks that control the dredging equipment. In front of him, a series of screens showed a live stream of various stages in the mining process. Sometimes, he said, he sees fish and octopus sucked up by the hose, but they appear to survive as they are dumped back into the sea.
Mostly, what Bunce saw that day were the tons and tons of sediment churned into the vessel — any diamonds indistinguishable on his screen. The culling process is entirely mechanized, and the diamonds are only visible to workers when they are dropped into the can. When enough of the gems accumulate there, the can is sealed and flown to Windhoek, Namibia’s capital.
That is where, in an office on the 11th floor of a nondescript building, Peter Kayser inspects high-value diamonds that could be worth anywhere from tens of thousands to millions of dollars.
One day last month, his attention was on a diamond about the size of the tip of his thumb that had recently been vacuumed up from the ocean floor. He passed the gem through a machine that calculated its weight. It took a few moments before the number flashed on a screen: at least seven carats.
Kayser smiled.
“This could be a very expensive stone.”
By Kevin Sieff WashingtonPost