Mining the seafloor for rare-earth minerals

Known as manganese nodules, the rocks are plentiful in nickel, copper and cobalt, as well as manganese and other elements, but lie miles down in inky darkness.

Building giant machines to vacuum them up, despite much study and investment, has never proved to be economic.

Now, the frustrated visionaries are talking excitedly about the possibility of belated success, and perhaps even profits.

The nodules turn out to contain so-called rare-earth minerals — elements that have wide commercial and military application but have hit a production roadblock. China, which controls some 95 per cent of the world’s supply, had blocked shipments, sounding political alarms around the globe and a rush for alternatives. China ended its embargo late last month, but the hunt for other options continues.

So are seabed miners smiling at last?

In October, James R Hein, US Geological Survey, and five colleagues from Germany presented a paper on harvesting the nodules for their ‘rare and valuable metals’. They did so at the annual meeting of the Underwater Mining Institute, a professional group based at the University of Hawaii. The paper prompted visions of a fresh start.

Caution

Charles L Morgan, chairman of the institute, said he was considering whether to start analysing a collection he oversees of 5,000 nodule samples from around the globe so as to ascertain their rare-earth content. But he cautioned that the field of seabed mining has a history of ups and downs.

The elements known as rare earths number 17 in all and range from cerium and dysprosium to thulium and yttrium.

Their unique properties have resulted in their growing use in many technologies of modern life. Applications include magnets, lasers, fibre optics, computer disk drives, fluorescent lamps, rechargeable batteries, catalytic converters, computer memory chips, X-ray tubes, high-temperature superconductors and the liquid-crystal displays of televisions and computer monitors.

The US Geological Survey calls the rare elements “essential for hundreds of applications” and likely candidates in the near future for an ‘expanding array’ of high-tech products. Supply shortages that go on for a long time, the agency warns in a fact sheet, “would force significant changes in many technological aspects of American society.”

Secretary of State Hillary Rodham Clinton recently called China’s export embargo a ‘wake-up call’ for the world to find new resources.

Despite their name, most rare earths are not particularly rare. But their geochemical properties mean they seldom concentrate into economically exploitable ore pockets. During the last two decades, most production has shifted to China because of lower costs there and the country’s record of lax regulation of environmental hazards.

Scientists have known about rare earths in seabed rocks for decades, seeing them as a curiosity. In 1968, Alan M Ehrlich, a chemist at the Massachusetts Institute of Technology, wrote a PhD dissertation titled ‘Rare Earth Abundances in Manganese Nodules’.

In an interview, he expressed surprise at the interest of the seabed miners, saying the concentrations were too low to power a nodule renaissance.

The would-be miners agree. But they say rising global prices for the more common metals found in the seabed rocks are increasing the allure. Investors, they add, see the presence of the exotic elements as icing on the cake.

Hein said dwindling supplies of terrestrial copper — a key ingredient of industrialisation used in everything from wires and switches to pipes and roofs — have forced miners on land to go after increasingly low grades of ore and have raised interest in seabed resources.

The upshot is a new wave of global interest in vacuuming up the seabed nodules — rare earths and all. “It’s getting more active,” said Morgan.