A worker assesses the quality of a diamond before certification at the World Diamond Centre in Antwerp February 5, 2009. It wouldn't be fitting to mount a barrage of "sale" and "special offer" signs in the windows of jewellers crowded into Antwerp's diamond square mile. But traders, cutters and retailers say business is terrible. Just a handful of diamonds can be worth a fortune, so the diamond industry -- centred since the 16th century on the Belgian port city of Antwerp -- has for years depended on debt. Now plunging demand, falling prices and lender reticence have left it looking uncomfortably overdrawn. To match feature FINANCIAL-DIAMONDS/ REUTERS/Yves Herman (BELGIUM)