Griffin Mining said record levels of zinc, lead and silver production in China drove revenues up in the first half.Revenues reached $39.7m, up from $33.9m the year before.Griffin hailed a record six-month production of 386,313 tonnes of minerals at its Caijiaying Mine in China.This came despite production being impacted by the Chinese Spring Festival holidays in January and February, as well as restricted delivery of explosives during the Chinese National Party Congress, it said.However, profits were hit by foreign exchange losses of $684,000 due to a stronger US Dollar against both the Renminbi and Sterling, as well as $1.39m interest owed on Chinese bank loans.Pre-tax profits came in at $15m, down from $17.9m the year before.Basic earnings per share dropped to 4.3c, from 4.79c in the first half of 2011.Chairman Mladen Ninkov said that assuming commodity prices stayed at or above current levels, the company expected to see a significant improvement in the full year results.