The De Beers diamond recovery vessel PEACE IN AFRICA (former Dock Express 20)
When most people think about diamond mining, they picture shafts extending down into the earth for a mile or more, open pit mines and miners wearing hard hats and carrying picks. How many people picture aquatic diamond mining? It sounds exotic, doesn’t it? Offshore diamond mining conjures up images of miners wearing diving helmets, wielding shovels deep under water. It doesn’t work quite that way, though.Offshore diamond mining has actually been going on for a number of years. Obviously, De Beers is one of the leaders, but other companies like Namco, Nambed, Diamond Fields International and Afri-Can are also exploring the seafloor off the coast of Namibia. Contrary to the picture conjured above; the mining is actually carried out with huge vacuum pumps, tubes and ROVs.
There are two (edit: well, actually three) forms of offshore diamond mining, horizontal mining and vertical mining. The most common form is horizontal mining. In this form, an ROV crawls across the seabed, equipped with sensors, suction tubes and equipment to sort out stones that are of the wrong size. In essence, the ROV sucks up any gravel on the seabed and sends it up a waiting ship above. Once on board, real workers get busy sorting through the slurry of gravel and sand, separating the diamonds from the gravel and dirt. The refuse goes back over the side, while the diamonds are stored away.
Vertical mining operates differently. A large drill head (6 to 7 meters across) is used to drill into the diamond bearing rock of the ocean floor. The resulting debris is then sucked up to the ship, where it is sorted and graded. With both methods, cargo ships visit on a periodic basis to offload the diamonds and bring new supplies and workers to the mining operation.
There is a third method that has been successfully deployed for marine diamond mining and that is the airlift system. This is a method by which a vacuum is created using compressed air in order to suction the sediment to an onboard separation plant.
How effective is offshore diamond mining? According to some sources, the deposits off the coast of Namibia alone hold over 1.5 billion carats of diamonds. De Beers is actually constructing another ship and ROV for use off the coast of South Africa to mine the diamond deposits suspected to be located in the region. Given the vast wealth of diamonds harvested from the earth in South Africa, this could be an incredibly profitable venture for the troubled diamond giant.
Will offshore diamond mining ever take the place of land-based operations? The experts say it is unlikely, but as the diamond reserves found in traditional locations are mined out, expect the sea to play an ever-increasing role in diamond mining. In addition to diamonds, there are companies that are exploring extinct black smokers (volcanic vents on the deep sea floor) in a search for gold, copper and other precious metals.
With the ever-increasing cost of metals on the world’s hungry markets, new avenues of exploration are continually sought, and the sea floor is an excellent place to look for these resources. As far as diamonds are concerned, the sources being mined at the moment are only alluvial deposits, though other mining methods are being developed to help reach underwater kimberlite pipes and other deposits.