LOS ANGELES (AP) â¿¿ Shares of several metals companies were mixed Tuesday amid falling prices for aluminum, copper and nickel. The tepid U.S. economy has helped to dampen manufacturers' demand for some metals, and prices have softened as a result. In addition, the U.S. dollar has been strengthening in light of mounting debt crises in Europe, which can lead holders of higher-valued foreign currency, like the euro, to pull back from buying up metals futures. The price of aluminum slipped 2.6 percent to $2,578 a ton in afternoon trading on Tuesday, dragging down shares of the world's biggest aluminum producers. Alcoa Inc. sank nearly 3 percent to $16.46. Aluminum Corp. of China's shares slid 38 cents to $21.33. Noranda Aluminum Holding Corp. bucked the trend, adding 65 cents, or 4.6 percent, to $14.72. Copper producers also saw their shares take a hit as copper prices fell 1.7 percent to $8,710 a ton. Shares in Freeport-McMoRan Copper & Gold Inc. slipped 65 cents to $46.70; Southern Copper Corp. fell 55 cents to $33.56; and, Encore Wire Corp. shed 66 cents, or 2.7 percent, to $23.66. The price of Nickel fell 2.6 percent to $24,100 a ton. But shares in BHP Billiton Ltd. added 49 cents, to $93.61.