Mining stocks were under the weather on Wednesday afternoon, bearing the brunt of reduced risk appetite on markets.Concerns about the global economy were behind the risk-off tone on markets today, after the World Bank and German government both downgraded growth forecasts for 2013.Meanwhile, iron ore prices took a hit today following its recent surge which has seen prices climb 68% since September. After strong gains in the run up to Christmas, owing to strong demand from the heavyweight consumer China, concerns over the demand outlook are starting to hit prices.According to Reuters, an iron-ore trader in Shanghai said: "Most of the mills have stopped buying iron-ore for the time being and sales of steel products are also very slow." Ore with 62% iron content fell 4.9% to $145.40 a dry metric ton, its worst one-day fall in 13 months.Gold and platinum prices were also on the decline today.Anglo American was extending losses from yesterday after the restructuring of its platinum operations prompted backlash from South African politicians and unions. Shares continued to fall after a number of workers protested against plans to close several mines. The employees refused to enter a number of mines and are now engaged in an "illegal work stoppage", according to Anglo American Platinum (Amplats).UBS kept its 'neutral' rating on the stock today, saying that Anglo's "value, EPS momentum/growth, heightened South Africa risk and Minas Rio challenges make the risk/reward less compelling than for other diversified UK miners". Sector peers Xstrata and Glencore were also registering losses today.Top performing sectors so far todayForestry & Paper 7,647.66 +1.79%Food Producers & Processors 6,553.62 +1.39%General Industrials 3,571.11 +0.87%Health Care Equipment & Services 3,963.58 +0.64%Oil Equipment, Services & Distribution 25,126.53 +0.59%Bottom performing sectors so far todayAutomobiles & Parts 5,597.33 -1.97%Mobile Telecommunications 3,738.60 -1.91%Mining 19,671.89 -1.52%General Retailers 1,986.75 -1.00%Insurance (non-life) 1,654.50 -0.85%BC