Shares in AZ Electronic Materials plunged by almost a third after the chemicals company reported a decrease in first-quarter revenues and warned of a flat year overall.Group revenue fell 2.0% year-on-year to $19.9m for the three months to April 8th, following lower-than-expected sales in its IC Materials division. The company blamed weak performance and an unfavourable product mix in IC Materials, which includes products for use in integrated circuits and devices. Revenue in the division fell 7.0% year-on-year to $123.3m. Egyptian gold miner Centamin was also lower after Canaccord Genuity kept its 'sell' rating and 38p target price for the company despite the strong first-quarter production figures announced this morning, saying that legal issues still remain. Meanwhile, iron ore company Ferrexpo jumped after it reported a 10.1% rise in first quarter pellet production compared to the same period in 2012. Total production climbed to 2,485.7k tonnes in the first quarter, from 2,257.5k tonnes the same period the previous year, and 2,474.7k tonnes in the previous quarter. As on the top tier index, strong results from mining heavyweight Alcoa and slowing inflation in China were lifting resource stocks in London today, boosting Hochschild Mining, Kenmare and Heritage Oil. FTSE 250 - RisersFerrexpo (FXPO) 178.40p +15.02%Hochschild Mining (HOC) 282.10p +5.42%Man Group (EMG) 92.85p +5.39%Kenmare Resources (KMR) 29.70p +5.32%Heritage Oil (HOIL) 169.00p +4.97%Petropavlovsk (POG) 205.00p +4.91%Lonmin (LMI) 286.80p +4.75%Telecom Plus (TEP) 1,087.00p +4.52%Kazakhmys (KAZ) 385.90p +3.57%Go-Ahead Group (GOG) 1,493.00p +3.39%FTSE 250 - FallersAZ Electronic Materials SA (DI) (AZEM) 256.40p -30.51%Alent (ALNT) 333.70p -7.82%Spirent Communications (SPT) 129.80p -3.57%Michael Page International (MPI) 388.50p -3.53%Centamin (DI) (CEY) 44.25p -3.38%Diploma (DPLM) 530.00p -2.93%Anite (AIE) 111.40p -2.54%Synthomer (SYNT) 196.90p -2.52%Spectris (SXS) 2,238.00p -2.40%Betfair Group (BET) 685.50p -2.07%NR