NEM), U.S. Steel ( X) and Nucor ( NUE). Mining companies are expected by analysts to post big gains, boosted by huge demand and record prices for gold and copper. Stronger economic growth and demand for metals in China, India and other emerging markets are driving the success of companies like Freeport-McMoRan, which is based in Phoenix. Still, steel firms are struggling as the rebounding economy has yet to filter through to new construction projects and car sales that boost demand for their products. Morningstar analyst Elizabeth Collins wrote in a year-end review that the fourth quarter should mark the bottom of earnings for U.S. steel producers in their current cycle. What follows are the fourth-quarter earnings expectations of five companies in the mining and metals sector, starting with Freeport-McMoRan: Freeport-McMoRan is seeing big revenue and earnings increases because of the skyrocketing prices of gold and copper. Freeport-McMoRan sold copper for an average price of $3.25 a pound in the fourth quarter, 110% more than in the year-earlier period, according to Argus Research analyst Bill Selesky. That's as demand from China, which buys about 40% of worldwide copper, outweighed the sluggish U.S. market for new homes. Standard & Poor's analysts project fourth-quarter earnings of $2.49 per share, bringing earnings for 2010 to $8.38, which agrees with its poll of 18 analysts. The company posted earnings of $5.86 per share in 2009. S&P analysts estimate 2011 earnings will grow to $9.24 per share, while an S&P poll of 18 analysts resulted in a mean earnings estimate of growth of 26% to $11.14. But on Jan. 14, S&P lowered its rating to "sell" from "hold," with the view that shares have had a sharp run-up and the stock is now overvalued. TheStreet Ratings gives the shares a "buy," noting that the company's revenue growth, including 24% in the third quarter, is carrying the improved results. Its analysts project earnings of $8.92 per share for 2010. On Feb. 2, the stock will begin trading on the NYSE on a split-adjusted basis, after a two-for-one split.