Diamond Mines of the World: Namibia
Namibia's Skeleton Coast
Article Copyright © 2009 AllAboutGemstones.com
The Republic of Namibia's "Skeleton Coast" is one of the most inhospitable and desolate environments on planet earth. The name "Namibia" means "land of open spaces," and along the country's northern coastline there are hundreds of miles of dry, deserted beaches and sand-dunes that are littered with shipwrecks that ran aground from treacherous crosscurrents and the pervasive nightly fog.
The Namib desert receives less than 15 mm of rainfall per year, and the coastal fog is the only life-giving moisture that this unique ecosystem receives. Only a handful of highly specialized plant and animal species can survive in such an extreme environment, and the only indigenous human inhabitants of this stark land are the Damara and Himba, who wear only simple goatskin clothing adorned with leather, metal and shell jewelry.
Marine mining in Namibia (Sat Image: NASA)
The fog-ladened winds are also responsible for creating Namibia's giant coastal sand dunes, which are some of the tallest in the world at close to 1,000 feet. The dunes of the 19,200-square-mile Namib-Naukluft National Park have a distinct orange color which is due to the oxidation of iron within the sand. Consequently, the deepness of a sand dune's color is an indication of its relative age.
Namibian Mining History
During the early 1900s, German prospectors were the first to attempt any diamond exploration south of Namib-Naukluf, near the town of Lüderitz on Elizabeth Bay (aka Elisabethbucht). After a Luderitz-Aus railway supervisor named August Stauch made the first diamond discovery in 1908, and before a diamond rush could overtake the area, Stauch laid down several mining claims. One such claim, 100 miles south of Lüderitz in Ida's Valley (near Bogenfels and Pomona) proved to be a major find . The German Government branded the area from the Orange River north to Walvis Bay as Sperrgebiet, or "forbidden territory."
The small mining town of 'Kolmanskop' (now a ghost town) was established to the east of Lüderitz, and at its zenith during the mid 1910s, the Sperrgebiet coast accounted for 20 percent of the worldwide diamond take. In 1920, after the first world war, Germany lost control of Namibia to the government of South Africa, and the company "Consolidated Diamond Mines of SWA Ltd." (predecessor to Namdeb) was formed.
In 1928, the discovery of Namibia's vast marine-terrace diamond reserves, just north of the mouth to the Orange River, slowed production in the north, and by 1956 the town of Kolmanskop was deserted, and replaced by Oranjemund as Namibia's diamond headquarters. With the recent discoveries of major secondary on-shore and off-shore deposits, Namibia may well have the largest diamond reserves of any country on earth, at an estimated 1.5 billion carats.
Alluvial Mining Along Namibia's Orange River
The Orange River forms a geographic dividing-line between the nations of South Africa and Namibia. For the last hundred million years, the Orange has been carrying eroded diamondiferous kimberlite material from its source on the Kaapvaal Craton, in central South Africa and Botswana.
Diamond-bearing material was deposited in river bank gravels and alluvium as it traveled westward towards the Atlantic Ocean. Other diamondiferous material was re-distributed by wind action, settling to form eluvial deposits in the desert sand. Material that completed the westward journey was deposited in beach terrace sediments, or redistributed by northerly ocean currents to off-shore marine deposits on the Skeleton Coast's sea floor.
Namib Desert (Namib-Naukluf) (Photo: Public Domain)
Orange River & Alexander Bay (Sat Image: NASA)
These secondary alluvial land and marine deposits are Namibia's only source for diamonds, but the Orange River has left an enormous amount of diamondiferous material in the vast drainage basin stretching 150 miles from Oranjemund to Elizabeth Bay. As the sea-level receded, diamond-bearing sediments were exposed, and eventually covered by blowing sand. Land-based secondary deposits must be excavated from this sedimentary layer that lies beneath a deep layer of surface sand.
Marine Mining on the Namibian Coast
As the diamond-bearing material exits the Orange River and is dumped into Alexander Bay, it is relocated by the churning effects of the prevailing ocean currents. The heavier diamonds tend to accumulate in low lying depressions, while lighter material is washed further to the north by the Benguela Current. This leads to concentrations of diamonds in topographical regions that tend to collect the moving material.
Namibia's Skeleton Coast (Photo: Public Domain)
Sand Dunes at Conception Bay (Sat Image: NASA)
Due to the amount of stress and weathering that the stones are subjected to during their long voyage westward, imperfect stones tent to fracture and disintegrate while stones that have less imperfections are able to complete the journey intact. For this reason, marine diamond deposits tend to have a higher concentration of gem-grade stones.
Although marine diamond mining using actual divers has been around since the 1950s, automated "vertical" and "horizontal" marine mining techniques were developed by DeBeers Marine Ltd. in the 1980s - specifically to mine the Namibian concessions.
Mairine Mining operations are conducted by off-shore mining vessels that vacuum material from the sea bed, scrape the sea floor with dredge pumps attached to "horizontal crawlers." With "vertical recovery," the mining vessels use boring drills to penetrate the sedimentary layer vertically. Onboard separators automatically sift and sort the diamonds from the dredged slurry, which is then dumped back into the ocean .
Companies involved in marine-mining operations in Namibia are SAKAWE Mining Corporation (aka Samicor), LL Mining Corporation (Lev Leviev Group), Trans Hex, De Beers Marine Namibia Ltd. of Windhoek, Namco (now part of Samicor), and Namdeb which is a 50/50 partnership between the Namibian Government and De Beers Centenary AG. Marine vessels include the MV Kovambo, Sakawe Surveyor, and Sucrose.
Bibliography on Namibia Diamonds
1. Trans Hex, The Trans Hex Group
2. Namdeb Mining Operations . www.namdeb.com
3. DFI, History of Mining on the Namibian Coast . www.diamondfields.com
4. Travel Africa, Namibia: The Legacy of the Desert Towns . www.travelafricamag.com
5. Namibian.com, Samicor starts diamond exports . www.namibian.com.na
6. Mining Technology, New Techniques in Mining Technology . SPG Media Group PLC
7. George E. Harlow, The Nature of Diamonds . Cambridge University Press
8. Namibia, Namibia Government Website . www.grnnet.gov.na
9. Namibia MME, Geological Survey of Namibia . www.mme.gov.na