(ShareCast News) - Mining giant Fresnillo reported a significant increase in gold and silver output in the first half of 2015.The group said silver production in the first six months of the year amounted to 23.8m ounces, a 10.6% increase year-on-year, as lower production from its Fresnillo mine in Mexico was offset by the Saucito II mine becoming operational earlier than expected.The FTSE 100 company reiterated full-year silver output guidance, which is expected to be between 45m to 47m ounces, although it has lifted its full year gold production guidance by 6.6% and it now forecast output to be between 0.71m and 0.73m ounces.The upwardly revised guidance for gold production comes on the back of a 37% year-on-year increase in gold production in the first half to 0.36m ounces."The increase in silver production was primarily driven by the ramp up of Saucito II and the increase in gold production by Herradura and its dynamic leaching plant being fully operational," said group chief executive Octavio AlvĂdrez.Fresnillo shares were down 1.61% to 641.50p at 0819 BST on Wednesday.