RAPAPORT... De Beers has revealed the newest member of its underwater mining fleet: a $420 million ship that is set to add 500,000 carats of high-value diamonds to its annual production from Debmarine Namibia.The custom-built vessel, called the Benguela Gem, will begin diamond-recovery operations this week, De Beers said Friday. Paid for by De Beers and the Namibian government — the miner’s 50:50 ...