Alcoa Inc , the largest U.S. aluminum producer, said third-quarter profit jumped from a year ago, but earnings and revenue slipped from the second quarter as economic growth slowed from the first half of this year.

Net earnings were $172 million, or 15 cents per share, compared with $61 million, or 6 cents per share, a year earlier, the Pittsburgh-based company said on Tuesday.

Income from continuing operations was also 15 cents per share, but down from 28 cents per share in the second quarter.

Revenue rose 21 percent to $6.4 billion from a year earlier, but was 3 percent lower than the second quarter of this year as metals prices slumped sharply.

Aluminum prices fell almost 20 percent in the third quarter on global economic concerns and Alcoa's share price fell 41 percent during the same period.

(Reporting by Steve James; editing by Andre Grenon)