Gold prices plunged 235 rupees, to a six-month low of Rs. 30,390 per ten grams at Delhi's bullion market on Saturday, on brisk selling by stockists, amid a weak global trend.Silver fell Rs. 570, to Rs. 56,530 per kilo. Silver coins dropped Rs. 2,000, to Rs.78,000 for buying 100 pieces.In Mumbai, also, gold slipped Rs. 200 , to close below the psychological Rs. 30,000 level, at a fresh six-month low of Rs. 29,890 per ten grams. Overseas, gold had dropped below 1,600 dollars an ounce on Friday, after the US central bank chairman said the US economy is recovering.Reports said that some of the world's largest gold investors had offloaded their holdings in exchange-traded products backed by gold, last quarter, further hit sentiment.