Mining stocks were among the worst performers on Tuesday afternoon as investors booked profits after a strong showing the previous session.Metal producers' shares had surged on Monday following news that China has lowered its reserve requirement ratio by the most since 2008 in an effort to spur bank lending and support economic growth.Heavyweights Rio Tinto, Anglo American, BHP Billiton and Glencore were all in the red, joined by smaller peers Lonmin and Evraz.Rio Tinto was leading the decline, down 2.5% after missing analysts' forecasts with first-quarter production results due to wet weather during the period. The group mined 75m tonnes of iron ore compared with the 83m-tonne estimate.Also weighing on Rio's share price was a ratings downgrade at Barclays Capital, which cut the stock from 'overweight' to 'equal weight', cautioning that the company may struggle to continue combating the ongoing iron ore price free-fall.Even with iron ore prices at multi-year lows, Rio is looking to ramp up output to offset weak prices and put pressure on smaller rivals, according to IG analyst David Madden."The slump in metal prices has turned commodity companies against each other, and with Glencore on the prowl Rio Tinto will have to up its game or go onto the acquisition trail in order to avoid another takeover approach," Madden said.BarCap also lowered Anglo from 'equal weight' to 'underweight' as it slashed forecasts for commodity prices across the board.Gold prices were holding below $1,200 an ounce on Tuesday after dropping the previous session as the dollar gained on increased speculation about policy-tightening in the States.Gold miners such as Fresnillo, Polymetal, Petropavlovsk and Acacia Mining were all trading lower, though Randgold was little changed.Top performing sectors so far todayTechnology Hardware & Equipment 1,387.50 +2.97%Media 7,677.47 +2.30%Travel & Leisure 8,940.19 +1.48%Aerospace and Defence 5,208.92 +1.47%Financial Services 9,948.12 +1.45%Bottom performing sectors so far todayFood Producers & Processors 7,660.86 -2.40%Industrial Metals & Mining 1,857.47 -2.08%Mining 13,941.39 -1.46%Oil Equipment, Services & Distribution 19,007.86 -1.29%Oil & Gas Producers 7,669.08 -0.60%