(ShareCast News) - De Beers said it had sold $520m of rough cut diamonds in the sixth auction of the year compared with $564m in the previous sale.De Beers, owned by Anglo American, said the numbers were "encouraging".Chief executive Bruce Cleaver said: "This is an encouraging sales performance for this point in the year, supported by positive sentiment from our customers. We maintain a cautious outlook for the remainder of 2016."De Beers is 85% owned by Anglo with the Botswana government holding the rest. It produces about one third of the world's rough cut diamonds.