Awwal 17, 1432 H/April 21, 2011, SPA -- Gold prices rallied to record highs on Thursday for a fifth straight session and silver soared, as the dollar index tumbled for a third day, prompting investors to buy bullion as a currency hedge, according to Reuters. Gold, which jumped above $1,500 an ounce for the first time on Wednesday, once again rose in tandem with riskier assets such as equities on inflation fears. "The driving factor is currency uncertainty. The dollar index is down again, so the inflation factor is creeping into the market," said Bill O'Neill, partner of commodity firm LOGIC Advisers. A weaker dollar means Americans will have to pay more for imports, which can feed inflation. Spot gold rose 0.5 percent to $1,505.34 an ounce by 12:21 p.m. (1621 GMT), after hitting a record $1,508.75 an ounce. U.S. gold futures for June delivery rose $7 an ounce to $1,505.90. Silver gained 1.6 percent to $45.93 an ounce. U.S. silver futures trade was active, with volume approaching 150,000 lots, set to be one of the busiest sessions in 2011. The gold/silver ratio -- which shows how much silver an ounce of gold can buy -- is set to fall for a ninth consecutive session to below 33, a 28-year low. "Silver continues to attract huge speculative interest. Even though silver is outperforming gold, the genesis of this rally is still related to the flight-to-safety factors supporting gold," O'Neill said.