document: Flexing its muscles as a cartel , De Beers Consolidated Mines Ltd. is raising its diamond prices an average 10 % next month . The South African concern , which controls 80 % of the world diamond market through its London-based Central Selling Organization , sells a vast array of diamonds , varying in quality and size , dealers say . So the increase could be as much as 20 % on top-grade diamonds . The rise follows an average price increase of 14.5 % last year . `` The diamond price increase was expected , '' said Jacques Zucker , of Lachowsky Zucker , diamond dealers in Antwerp , Belgium . By changing the mix of diamonds that it sells to dealers several months ago , De Beers signaled to the market that it intended to raise quotes , he said . `` Few listened to us two years ago when we advised clients to buy diamonds at depressed values , '' Mr. Zucker said . `` Now they must accept higher prices . '' `` The price rise provides the necessary psychological lift to the market , '' said Peter Miller , a mining analyst at Shearson Lehman Securities in London . It will help the diamond producers `` consolidate their gains . '' Prices of one-carat D-flawless diamonds have risen to about $ 14,800 a carat from $ 12,000 at the beginning of the year , dealers said . In 1985 , at the low point of a deep slump , a top quality stone was $ 8,500 a carat , down from an average of $ 55,000 in 1980 . A carat equals 200 milligrams . De Beers decided to raise prices because rough diamonds were already trading at a premium over its own quotes on the open market , said Andrew Lamont , a company spokesman . Demand is especially buoyant in the Far East . In the first seven months of 1987 , Japanese imports of polished diamonds surged 60 % from the similar period last year to $ 777 million , he added . After the U.S. , Japan is the second biggest diamond jewelry market , followed by West Germany . Only one out of 17 Japanese couples bought engagement rings less than two decades ago ; now more than two-thirds buy . `` The sharp appreciation of the yen reduced the cost of diamonds for Japanese buyers , '' Mr. Lamont says . Stronger currencies and lower interest rates in West Germany and other European countries also boosted diamond sales , he says . Diamonds are priced in U.S. dollars . Demand for polished diamonds in the U.S. , Hong Kong , Thailand , Singapore , Korea , and the Philippines also raised exports of the leading diamond cutting and dealing centers , primarily Antwerp , Tel Aviv , Bombay and New York . To meet growing orders from diamond dealers and cutters who supply the retail trade , De Beers sales of rough diamonds jumped to $ 1.56 billion in the first half of this year from $ 1.2 billion in the similar period in 1986 . Sales of $ 2.56 billion last year were the highest since the 1980 boom when De Beers turnover reached $ 2.72 billion . Analysts are predicting sales of $ 3 billion in 1987 . Yet some dealers worry because world diamond production surged to 89.6 million carats last year from 47 million carats in 1982 . Only about 10 % to 20 % of the diamonds are gems , but De Beers must continue to find new markets , they say . De Beers surprised skeptics and revived trade from the slump in the first half of the decade by withholding stocks and pursuing an intensive marketing campaign . An advertising and promotion budget which rose to $ 110 million this year from $ 43 million in 1980 helped raise world-wide sales of diamond jewelry to a record 49 million pieces valued at $ 24.6 billion last year . In 1979 , about 42 million pieces valued at $ 16 billion were sold , De Beers says . In more than half a century of its existence , the Central Selling Organization , which includes as members black African state producers , has outlasted other commodity cartels by never cutting diamond prices . The cartel controls most of the world 's rough diamond market via a `` pipeline '' that stretches from mines in Africa to Australia to diamond dealers and cutters .
extractive_keyphrases: diamond prices south african concern world diamond market diamond price increase diamond dealers diamond jewelry market world diamond production diamond sales
abstractive_keyphrases: de beers consolidated mines ltd. london-based central selling organization