Mining stocks were making moderate gains on Tuesday morning, attempting to recover after the heavy sell-off the day before, but the FTSE 100 still opened in the red, on track for its third straight day of losses.Markets were on the cautious side this morning as investors awoke to the news of fatal explosions at the Boston marathon last night which left three dead and hundreds injured. It is still unknown who is responsible for bombs at the finishing line, though the White House has said that the incident would be handled as an "act of terror".Disappointing first-quarter growth figures from China caused gold prices to plummet on Monday to a two-year low. Commodity prices tumbled across the board, with silver, copper and crude oil all taking a hit. Reports that Cyprus is selling part of its bullion holdings to raise money and speculation that the Federal Reserve could scale back quantitative easing were also a factor.The 9.1% one-day slump for the price of gold was the steepest fall in 30 years. Gold prices had recovered by as much as 2.0% this morning."At some point gold could well be subjected to participants looking to own gold at cheaper levels than over the last few months. But, critically, calling the bottom on any such process is hazardous at best," said David White, a Financial Trader at Spreadex.FTSE 100: Miners rebound after heavy sell-offMetal producers were doing their best to recover this morning as traders see yesterday's heavy falls as potential buying opportunities. Fresnillo, ENRC, Randgold, Xstrata and Glencore were among the best performers early on.Rio Tinto was also higher after reporting record first-quarter iron-ore production, driven by an improvement in capacity of the Pilbara mine in Western Australia.Polymetal however was bucking the trend despite saying that the flotation concentrator at its Mayskoye mine has been started up, producing its first dry gold concentrate.AB Foods, the food ingredients and retail firm, was falling this morning after Credit Suisse downgraded the stock to 'neutral'. Utilities firm SSE was also being weighed down by a ratings cut from Investec to 'hold'.FTSE 250: Michael Page drops as profits declineRecruitment group Michael Page slumped early on after saying that it expects another challenging quarter ahead after "tough economic conditions and weak market confidence" weighed on its performance at the start of the year. Gross profit fell 6.7% in the first quarter.Oil and gas group Salamander Energy gained after starting drilling on the Bedug-1 exploration well in the Bontang production sharing contract, in which it has a 100% operated interest.FTSE 100 - RisersEurasian Natural Resources Corp. (ENRC) 248.60p +4.41%Fresnillo (FRES) 1,127.00p +4.35%Randgold Resources Ltd. (RRS) 4,716.00p +3.76%Xstrata (XTA) 985.70p +2.01%Vedanta Resources (VED) 1,127.00p +1.90%Glencore International (GLEN) 327.10p +1.87%Rio Tinto (RIO) 3,025.50p +1.77%BHP Billiton (BLT) 1,854.00p +1.62%Antofagasta (ANTO) 948.00p +1.17%Anglo American (AAL) 1,584.00p +0.57%FTSE 100 - FallersARM Holdings (ARM) 874.00p -2.51%Prudential (PRU) 1,040.00p -2.07%Associated British Foods (ABF) 1,827.00p -1.98%GKN (GKN) 251.20p -1.84%Bunzl (BNZL) 1,261.00p -1.79%Burberry Group (BRBY) 1,262.00p -1.71%Babcock International Group (BAB) 1,043.00p -1.60%Marks & Spencer Group (MKS) 391.20p -1.58%easyJet (EZJ) 1,120.00p -1.58%International Consolidated Airlines Group SA (CDI) (IAG) 246.80p -1.44%FTSE 250 - RisersCentamin (DI) (CEY) 39.41p +4.18%Lonmin (LMI) 266.10p +3.70%Kazakhmys (KAZ) 351.10p +3.02%African Barrick Gold (ABG) 178.50p +2.94%Hochschild Mining (HOC) 247.90p +2.91%New World Resources A Shares (NWR) 197.00p +2.60%Kenmare Resources (KMR) 28.99p +2.01%Bumi (BUMI) 253.80p +1.72%Afren (AFR) 128.30p +1.66%Ophir Energy (OPHR) 406.70p +1.52%FTSE 250 - FallersMichael Page International (MPI) 371.70p -6.44%Ashtead Group (AHT) 598.00p -2.76%Barratt Developments (BDEV) 281.00p -2.63%Taylor Wimpey (TW.) 89.20p -2.41%Home Retail Group (HOME) 151.60p -2.19%Cable & Wireless Communications (CWC) 41.56p -2.17%Redrow (RDW) 200.20p -2.01%Thomas Cook Group (TCG) 114.70p -1.97%Bellway (BWY) 1,295.00p -1.89%Persimmon (PSN) 1,111.00p -1.86%BC