Mining stocks dropped sharply on Thursday as concerns about global growth eroded risk appetite amongst investors. The World Bank this week downgraded its outlook for the global economy, saying that developing countries are headed for a year of "disappointing growth", causing miners to decline on the back of concerns over fading demand."Although the bank still expects a rebound later this year, the news has been taken as a cue to sell FTSE mining stocks once again, pushing the sector to three-month lows," said David Madden, Market Analyst from IG.The World Bank now expects the global economy to expand by just 2.8% this year, lower than its previous forecast of 3.2% made in January due to poor weather in the US, the Ukraine crisis, a rebalancing in China, political strife in several middle-income economies, slow progress on structural reform and capacity constraints."Other factors arguing against a more buoyant acceleration include restructuring in China, a gradual move towards a more neutral policy stance in developing countries and, for commodity exporters, stable or even declining commodity prices," it said.Anglo American, BHP Billiton, Rio Tinto and Antofagasta were falling sharply in London this afternoon.Anglo was the hardest hit, trading down 3%, after its rating was cut from 'equal weight' to 'underweight' at Morgan Stanley.However, Lonmin was bucking the trend after the platinum miner and partners Amplats and Impala agreed an informal deal with a union in South Africa in an effort to tempt employees back to work after a 20-week strike.The Association of Mineworkers and Construction Union (AMCU) has agreed to take an offer relating to pay and employment conditions directly to employees. Lonmin shares were up nearly 8% in afternoon trade, after having fallen as much as 5% earlier on.Top performing sectors so far todayElectronic & Electrical Equipment 4,261.38 +2.07%Media 6,162.72 +0.88%Fixed Line Telecommunications 4,570.83 +0.86%Oil Equipment, Services & Distribution 24,424.95 +0.83%Industrial Engineering 10,965.44 +0.82%Bottom performing sectors so far todayMining 16,200.00 -2.05%Industrial Metals & Mining 1,189.78 -1.71%Food & Drug Retailers 3,785.90 -1.07%Technology Hardware & Equipment 1,090.52 -0.92%Mobile Telecommunications 4,487.02 -0.51%BC