Gold futures jumped the most in two weeks as the dollar headed for the longest slump since April, increasing demand for the metal as an alternative investment.

The Bloomberg Dollar Index, a gauge against 10 major trading partners, fell for the fifth straight session to a seven-week low. Total exports in July rebounded in China, the world’s second-biggest gold buyer, signaling a pickup in the economy.

“The continued weakness in the dollar is making gold look attractive,” Frank Lesh, a trader at FuturePath Trading in Chicago, said in a telephone interview. “Also, there is some buying in anticipation of a rise in retail Chinese demand as the economy improves.”

Gold futures for December delivery rose 1.9 percent to settle at $1,309.90 an ounce at 1:48 p.m. on the Comex in New York, the biggest gain for a most-active contract since July 22.

The metal has tumbled 22 percent this year, partly on concern that the Federal Reserve will trim monetary stimulus as the U.S. economy gains. American consumers last week were the most upbeat in more than five years, and applications for jobless benefits fell to the lowest since before the recession, data showed today.

India is the top gold consumer.

Silver futures for September delivery rose 3.5 percent to $20.193 an ounce, the biggest gain since July 22. The price has tumbled 33 percent this year.