* TSX down 12.26 points, or 0.09 pct, at 13,377.16
* Falls for 4th straight day, down 1.4 pct on week
* Finishes lower for third straight week (Adds comments, details)
By Solarina Ho
TORONTO, May 13 (Reuters) - Toronto's main stock index reversed early gains to finish slightly lower on Friday as volatile commodity prices weighed on the market.
Canadian Natural Resources (CNQ.TO) led the blue-chip decliners, giving back 1.48 percent to finish at C$39.41. Nexen NXY.TO slid 2.34 percent to C$21.70.
Gold miners were mixed, with Kinross Gold (K.TO) down 0.58 percent at C$13.81 and Goldcorp (G.TO) up 1.03 percent at C$46.28. Diversified miner Teck Resources TCKb.TO fell 2.03 percent to C$44.85.
The overall energy group slipped 0.35 percent, while the materials group, home to mining firms, was up a moderate 0.15 percent.
"We've just been basically going sideways for a while and until we actually break out of the recent range, it's probably more of the same," said Levente Mady, a market strategist at Union Securities.
"If anything, maybe a slightly negative bias due to all the upheaval we're seeing on the commodities front."
The Toronto Stock Exchange's S&P/TSX composite index .GSPTSE finished down a modest 12.26 points, or 0.09 percent, at 13,377.16 in its fourth straight day of declines.
The index was down 1.4 percent on the week, and marked its third straight week of declines.
Commodity prices had been steady early in the day and helped lift the market. But oil retreated and gold dropped about 1 percent as the U.S. dollar rose on safe-haven buying. [GOL/] [O/R]
Crude prices rose late in the session in short-covering, following European economic worries and news that Libyan leader Muammar Gaddafi may have been wounded.
Eight of the TSX's 10 main sectors ended lower. Bucking the negative trend, alongside materials, was the utilities group, which rose 0.25 percent.
Manulife Financial (MFC.TO) was one of the biggest drags on the index, ending down 1.26 percent at C$17.25. The overall financial group, which make up about 30 percent of the index, slipped 0.07 percent.
Major market in the United States and elsewhere also finished lower on economic concerns. [ID:nN13125357]
"There's clearly some massive positions being closed. Risk is being unwound," said Francis Campeau, broker at MF Global Canada, in Montreal
"We're finishing the week similar to how it started."
In corporate news, TMX Group (X.TO), which reported first quarter results that beat analyst expectations, advanced 1.83 percent to finish at C$41.75. [ID:nLDE74C1YE]
Tim Hortons THI.TO shares were up 1.05 percent at C$46.40. Chief Executive Donald Schroeder told Reuters on Friday Canada's biggest restaurant chain was eyeing more strategic alliances south of the border and said the U.S. could rank as its No.1 market someday. [ID:nN13121814]
($1=$0.97 Canadian) (Additional reporting by Ka Yan Ng; editing by Rob Wilson)