A delay in its acquisition of a zinc asset in Zambia has sent shares in miner and metals processor Berkeley Mineral Resources sharply lower. Completion of the acquisition of the Kabwe tailings dump, where materials left over from previous mining operations are processed, is now expected to take place in early 2011. 'Discussions with the vendor, Sable Zinc Kabwe Limited, and Dorset Solutions Limited, which assisted the Company in securing the original option to secure the tailings dumps, are continuing and meetings to progress the transaction are due to take place in South Africa before Christmas,' said Berkeley.Goldplat is another miner under the cosh. The Africa-focused gold group has raised £5.5m from a placing of 55m shares at 10p a time.The funds will be used to develop assets in Burkina Faso and Ghana.Shares in Asia-focused teaching group AEC Education fell 19% Monday afternoon as it reported that trading at its UK business Malvern House has been hit by the uncertainty over the government's policy on student visas and immigration.As a result, the group intends to reorganise the Malvern House business model, expanding the brand outside the UK at a faster rate. AEC Education expects to record a pre-tax loss of £0.25m and revenues of around £17m for the year ending 31 December.Natural resources investment company Charles Street Capital is to acquire Westcork Copper Mining for £7m, to be funded by the issue of new ordinary shares 0.1p in the group. Westcork holds six prospecting permits totalling 18,500 hectares in the Allihies copper district in Ireland.