| CAPE TOWN, June 18
CAPE TOWN, June 18 Huge mud-sifting machinery
and other technological advances pioneered by De Beers over the
past decade have enabled it to profitably exploit the world's
largest marine diamond deposits in deep waters off Namibia.
A bright green crawling machine that weighs 286 tonnes and
stretches over three storeys tall recovers diamonds by sucking
up sand and silt 100 metres and deeper underwater.
It is controlled remotely by a mining vessel called the
"Mafuta", and both are undergoing major refurbishment in Cape
Offshore diamond mining started in 1961 in less than 35
meters of ocean, but it has been only in the past decade that
technology has allowed operations in deeper water.
"Ten years ago a crawler would be mining at about 200 to 250
square meters an hour. Today we believe that our crawler would
mine at about 1,000 square meters an hour," said Domingos
Valbom, general manager of De Beers Marine.
"Mafuta" is the flagship vessel of Debmarine Namibia, a
50/50 joint venture between the Namibian government and De
De Beers Marine provides technical support and five
exploration vessels for the venture's Atlantic 1 concession,
which is just offshore of Oranjemund near the South African
The crawler uses a nozzle to slurp up tonnes of sediment an
hour from ancient submerged beaches as it scours the ocean floor
for diamonds carried from the Orange River to the Atlantic
millions of years ago.
The prizes are big. Marine diamonds on average are of higher
quality than land-based stones, because any gems with flaws are
broken up by the battering they receive from the wind and waves.
"It is the best way to extract marine diamonds, but the
geology in which we operate has to lend itself and the crawler
has to have a surface to operate," Valbom said of the
"horizontal mining" process.
When the sea bed becomes too rocky and uneven for the giant
vacuum, the firm can switch to "vertical mining" by four other
ships, which each use a large-diameter drill to bring
diamond-bearing gravel to the surface.
Each Debmarine Namibia ship, a self-contained floating
mining operation, processes the debris, and helicopters then
take the 'concentrate' in jam-sized jars to land, where the
diamonds are sorted by hand.
Debmarine Namibia, which bought "Mafuta" for N$650
million($60 million) last year, said at the time that the ship
was expected to produce 350,000 carats a year, or about 30
percent of Debmarine production.
"The crawlers have made a step-change in our mining and to
our productivity and the financial performance of marine
mining," Valbom said.
He also said the company aimed to improve the efficiency of
the crawler, which could be used to suck up other minerals such
($1 = 10.8400 Namibian Dollars)
(editing by Jane Baird)