AIM-listed gold miner Aureus Mining said that both the capital and operating costs at its New Liberty Project in Liberia have reduced as a result of the metallurgical optimisation test work programme.The company said that the test work has shown "encouraging results" with improved leach kinetics indicating that the potential gold recovery of 93% (modelled in a previous 'Technical Report' in October) is now achievable at a reduced carbon in leach (CIL) residence time of 24 hours, down from 48 hours preciously. Aureus also said that there would also be significantly lower reagent consumption."These metallurgical results, which indicate significantly lower operating costs due to factors which include a shorter CIL residence time and lower consumption of reagents, further demonstrate the strong economics of New Liberty," said Chief Executive Officer David Reading. "This is the first set of results for what is an on-going optimisation programme, the full results of which will be available towards the end of the first quarter of this year. We are confident the results of this programme will further enhance the returns for all stakeholders on what will be Liberia's first commercial gold mine."New Liberty has an estimated proven and probable reserve of 910,000 ounces of gold grading 3.3g per tonne.Aureus, which has a market capitalisation of nearly £60m, also has gold exploration permits in Cameroon.