Mining stocks were in demand on Wednesday with precious metals group Hochschild Mining the standout performer after saying that it remains on track to hit its full-year production target of 20m silver equivalent ounces following an in-line second quarter. The company also said that its 'cashflow optimisation programme' has been extended to deliver further material cost savings, the impact of which will begin to be seen in the second half.Sector peers EVRAZ and Polymetal were also higher in afternoon trade.Investors welcomed Balfour Beatty's announcement that its water networks contract with Yorkshire Water has been extended by a further five years, worth around £70m to the infrastructure group.Meanwhile, travel group Thomas Cook was given a boost by UBS which upgraded the stock from 'neutral' to 'buy' and lifted its target price from 145p to 180p.Heading the other way was UK multi-utility supplier Telecom Plus which went ex-dividend today, meaning that investors won't be able to get their hands on the firm's latest payout. The company also released a first-quarter statement which said that organic growth was comfortably ahead of levels seen last year.WH Smith and WS Atkins also went ex-dividend today.FTSE 250 - RisersHochschild Mining (HOC) 149.40p +9.77%Salamander Energy (SMDR) 134.70p +5.65%Dialight (DIA) 1,080.00p +4.85%Keller Group (KLR) 1,144.00p +4.28%Supergroup (SGP) 988.00p +4.00%Evraz (EVR) 100.00p +3.25%Polymetal International (POLY) 570.00p +3.17%Balfour Beatty (BBY) 230.50p +3.04%Thomas Cook Group (TCG) 146.70p +2.88%Spectris (SXS) 2,078.00p +2.77%FTSE 250 - FallersTelecom Plus (TEP) 1,311.00p -5.68%esure Group (ESUR) 312.40p -4.76%Xaar (XAR) 850.00p -2.30%Bank of Georgia Holdings (BGEO) 1,775.00p -2.20%Imagination Technologies Group (IMG) 284.40p -2.03%Ted Baker (TED) 1,830.00p -1.88%RPS Group (RPS) 214.00p -1.83%Atkins (WS) (ATK) 1,054.00p -1.77%BH Global Ltd. USD Shares (BHGU) 11.65 -1.77%Diploma (DPLM) 590.00p -1.58%BC