Gold prices retreated from a 21-month high by plunging Rs 600 to Rs 29,050 per ten grams at the bullion market on Saturday on weak cues from overseas markets amid fall in demand from jewellers at existing levels. The yellow metal snapped its biggest eleven-day rising streak this year. Silver too shed Rs 50 at Rs 7,800 per kg on reduced offtake by industrial units and coin makers. Traders said besides a weak global trend, fall in demand from jewellers and retailers at prevailing higher levels at domestic spot market.