(IDEX Online) - Police and customs officials blocked the export of almost $10m of diamonds from Namibia last week in an ongoing row over external valuations.The diamonds are produced by the state-owned Namib Desert Diamonds (Namdia). A five-year contract with external valuers came to an end last month. The stones are also valued, as a matter of course, by the Namibia Diamond Trading Company, which is co-owned by the Namibian government and De Beers.The Namibian newspaper claims diamonds have been under-priced "to enrich a clique of individuals in Namibia and Dubai". Last Wednesday police and customs officials refused to sign off a consignment of diamonds, claiming two valuation certificates were missing. The matter was resolved the following day.Namibia is the world's ninth biggest diamond producer. Total sales in the year to February 2020 were 253,000 carats, yielding an average $528 per carat, according to the company's annual report.