Gold plunged 520 rupees, its biggest single-day fall this year, to an over three-month low of 26,540 rupees per ten grams at Delhi's bullion market, today, on subdued demand from jewellers and retailers. Silver fell 500 rupees, to 36,300 rupees per kilo, on reduced offtake by industrial users and coin makers. Silver coins plummeted 2,000 rupees, to 57,000 rupees for buying 100 pieces.Overseas, gold had dropped 2.5 per cent, to 1,169 dollars an ounce, yesterday.