Fresnillo declined 4 percent to 1,810 pence by the close, the steepest drop since June 22 and the second-biggest slide on the benchmark FTSE 100 Index of U.K. shares. Silver fell 1.7 percent to $29.655 an ounce, the lowest since Aug. 22.
UBS cut its recommendation on Fresnillo to neutral, saying the stock had outperformed the metal and peers. The company rose 21 percent last year, compared with a 9 percent gain in silver.
Fresnillo was also the second best-performing stock in the 21-member FTSE 350 Mining Index in 2012. The company, operating in Mexico, produced 30.4 million ounces of silver in the first nine months and plans annual output of 41 million ounces.
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