RTTNews - Bay Street stocks surrendered an early rally and finished lower on Tuesday for a third straight session. A drop in oil and copper prices contributed to the weakness.

The S&P/TSX Composite Index fell 87.38 points to 0.84% to finish at 10,307.40. The index had climbed above 10,500 in the early going before heading lower.

Mining stocks fell 2.6% as the price of copper turned lower on the Comex. Teck Cominco (TCK.B.TO) declined 5.8%, Inmet (IMN.TO) dropped 4.9%, HudBay (HBM.TO) slipped 2.8% and First Quantum (FM.TO) fell 2.8%.

Equinox Minerals (EQN.TO) rose 3.9% after the shares were upgraded to Sector Perform from Underperform by RBC Capital Markets.

Energy stocks fell 2.4% as crude oil gave back and early rally and finished slightly lower. Suncor dropped 3.4%, Encana (ECA.TO) fell 2.2%, Canadian Oil Sands (COS.UN.TO) and Canadian Natural Resources (CNQ.TO) both fell 1.8%.

Imperial Oil (IMO.TO) fell 2.6% after the shares were downgraded to Market Perform from Outperform at BMO Markets.

On the upside, gold stocks added 1.75% as Goldcorp (G.TO) added 2.25% after the stock was upgraded to Outperform from Market Perform.

In corporate news, Research in Motion (RIM.TO) finished flat following a choppy session. RIM, which will unveil its new BlackBerry Tour later this year, is expected to report quarterly earnings on Thursday.

In other corporate news, Magna International (MG.A.TO) rose 6.7% after the stock was upgraded to Overweight from Neutral by JPMorgan Chase.

Air Canada (AC.B.TO) surged 8.7% as the company has reportedly reached tentative deals with its pilots and flight attendants regarding the airliner's pension obligations.

Methanex (MX.TO) slipped 0.25% after the stock was downgraded to Neutral from Buy at UBS.

Biovail (BVF.TO) fell 2.1% despite seeing its target price raised to $15 from $13 at Credit Suisse. The stock's rating was reiterated at Neutral.

On the economic front, Stats Canada said the labor productivity of Canadian businesses rose 0.3% in the first quarter.

Traders looked ahead to a pair of economic reports from Canada at 8:30 a.m. ET tomorrow. The leading index is expected to fall 0.6% in May, compared to a 1.1% drop in April. Wholesale sales are forecast to have dropped 1% in April, compared to a 0.6% drop in March.

Across the border, consumer price index data is also expected at 8:30 a.m. ET. CPI is expected to come in down 0.9% in May, compared to an 0.7% decline in April. Core CPI is forecast to rise 0.3% for a second straight month.

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