(Adds details throughout on market activity; updates prices)
* TSX falls 80.2 points, or 0.49 percent, at 16,204.01
* Five of the index's 10 main groups decline
* Energy falls 1 percent, materials down 1.4 percent
* Enbridge falls 2.4 percent, TransCanada declines 2.6 percent
TORONTO, Jan 25 (Reuters) - Canada's main stock index suffered its biggest drop since mid-December on Thursday as pipeline operators led declines for energy companies, while gold miners were pressured by a pullback in the price of the precious metal.
* The Toronto Stock Exchange's S&P/TSX composite index closed down 80.2 points, or 0.49 percent, at 16,204.01, its biggest drop since Dec. 14.
* Some of the biggest drags on the index were major oil pipeline operators. Enbridge Inc fell 2.4 percent to C$47.56 and TransCanada Corp declined 2.6 percent to C$57.72.
* The overall energy group fell 1 percent, while U.S. crude oil futures pulled back from an earlier three-year high to settle 0.2 percent lower at $65.51 a barrel.
* The materials group, which includes precious and base metals miners and fertilizer companies, lost 1.4 percent.
* Gold dropped more than 1 percent, retreating after an early rise as the U.S. dollar strengthened when President Donald Trump talked up a stronger greenback. * NovaGold Resources Inc tumbled 10.8 percent to C$4.80.
* The financials group, which accounts for more than one-third of the weight of the TSX, dipped 0.1 percent.
* Five of the index's 10 main groups ended lower.
* Marijuana stocks added to Wednesday's declines. Canopy Growth Corp fell 9.2 percent to C$31.68 and Aurora Cannabis Inc was down 6.2 percent at C$13.11.
* Canadians spent an estimated C$5.7 billion on cannabis in 2017, Statistics Canada said, with the country on track to legalize recreational use of the drug nationwide later this year. * Electronics manufacturing services company Celestica Inc fell 5.4 percent to C$12.87 after reporting fourth-quarter earnings after the bell on Wednesday that missed estimates.
* Shares of Bombardier Inc fell 2.2 percent to C$3.07. The planemaker is expected to lose a hotly contested U.S. trade dispute this week, a Canadian government source told Reuters on Thursday, likely inflaming tensions between the two countries during talks to modernize the North American Free Trade Agreement.
* U.S. officials on Thursday probed Canadian proposals for unblocking talks on NAFTA but there were few signs of progress, raising questions about whether any real movement is happening at the latest round of negotiations on the treaty. (Reporting by Fergal Smith; Editing by James Dalgleish)
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