Rising for the third straight day, gold added 60 rupees, to 28,180 rupees per ten grams at Delhi's bullion market, on Thursday, on sustained buying, in line with a firm global trend. But silver declined 750 rupees, to 52,450 rupees per kilo. Silver coins plunged 3,000 rupees, to 57,000 rupees for buying 100 pieces.In Singapore, gold rose 0.8 per cent, to 1,624 dollars an ounce. Silver gained 1.4 per cent, to 29.58 dollars an ounce.