Mining stocks were putting in an impressive performance as metals prices gained on a weaker dollar after the Fed announcement, with investors hopeful that an improved US economy will boost the demand for commodities. Aquarius Platinum, Ferrexpo, Talvivaara, Lonmin and Centamin were all firmly higher by the afternoon. Aquarius was in the top spot despite saying that it has temporarily suspended operations at its Kroondal platinum mine in South Africa to ensure the safety of its staff, as tensions rise in the region.Defence contractor Chemring jumped after pushing back the deadline for The Carlyle Group to make an offer, after not receiving word the US asset management group. Pubs group JD Wetherspoon was in demand after its new financial year has got off to a flying start, helped by a strong performance during the Olympic and Paralympic Games. FTSE 250 - RisersAquarius Platinum Ltd. (AQP) 48.73p +18.56%Petropavlovsk (POG) 440.90p +16.49%Essar Energy (ESSR) 132.50p +15.52%Ferrexpo (FXPO) 225.10p +14.85%Hochschild Mining (HOC) 499.00p +10.89%Fenner (FENR) 415.80p +8.99%Kenmare Resources (KMR) 43.48p +8.40%Centamin (DI) (CEY) 90.50p +8.38%Man Group (EMG) 88.60p +7.79%Talvivaara Mining Company (TALV) 168.70p +7.59%FTSE 250 - FallersDunelm Group (DNLM) 639.00p -3.03%Ruspetro (RPO) 112.00p -2.10%Dialight (DIA) 1,201.00p -1.15%RPS Group (RPS) 252.50p -0.90%UBM (UBM) 712.50p -0.70%Computacenter (CCC) 397.20p -0.48%BH Global Ltd. USD Shares (BHGU) 11.5 -0.43%William Hill (WMH) 314.00p -0.32%De La Rue (DLAR) 995.50p -0.25%Stobart Group Ltd. (STOB) 116.40p -0.17%NR