*TSX down 0.55 percent at 13,258.57, down 1.5 pct on week
*Late-day drop in materials more than offsets energy rally
*Health-care group jumps more than 1 pct on Nordion gains
*Canada's earnings season starts in earnest next week (Updates to close)
By Ka Yan Ng
TORONTO, Jan 21 (Reuters) - Toronto's main stock index finished lower for a third straight day on Friday, accelerating its decline toward the close due to a late-day selloff in the materials group.
The Toronto Stock Exchange's S&P/TSX composite index .GSPTSE, which was largely flat for much of the afternoon, finished down 72.75 points, or 0.55 percent, at 13,258.57.
Seven of the index's 10 main groups ended lower, pressured by a sharp 1.7 percent drop in materials, a lot of the fall taking place in the final minutes of the session.
"(It was) a tug-of-war between energy stocks and material stocks today," said Kate Warne, Canadian market strategist at Edward Jones in St. Louis, Missouri.
The weakness in materials was broad with both base- and precious-metals miners falling. The price of bullion notched its third week of losses, while copper stabilized after falling to a one-month low.
Diversified miner Teck Resources TCKb.TO shed 2.67 percent to C$58.66, while Barrick Gold (ABX.TO) lost 1.03 percent to C$46.33.
The overall decline was cushioned by a rally in the oil and gas sector, which rose 1.08 percent.
Strength in the price of natural gas drove energy issues higher, rather than U.S. crude oil, which was softer on rising supply. Warne noted that cold weather and higher heating demand were helping to push up gas prices.
Advancers included Suncor Energy (SU.TO), up 1.04 percent at C$38.06, and Talisman Energy TLM.TO, up 2.24 percent at C$22.34.
The index advanced at the beginning of the session, spurred by rising U.S. stock markets and a higher than expected profit from General Electric (GE.N) and higher net revenues from Google Inc. (GOOG.O) [.N]
More U.S. earnings reports next week will likely be one of the main cues for the TSX, which finished this week down 1.5 percent. Canada's fourth-quarter earnings season also begins, with resource sector profits the main focus.
Youssef Zohny, associate portfolio manager at Van Arbor Asset Management in Vancouver, said attention next week will also shift towards a U.S. Federal Reserve meeting and U.S. President Barack Obama's State of the Union address.
Solid retail sales figures for November in Canada added to the positive sentiment early on Friday. Canadian retail sales showed surprising resilience in the month and posted their biggest gain in eight months, beating analysts' expectations. [ID:nN21236351]
The index's health-care sector was notably firmer on Friday, one of two sectors that registered gains greater than 1 percent.
The rise was largely fueled by a jump in shares of Nordion Inc NDN.TO NDZ.N, which reported stronger than expected results. Nordion advanced as much as 14 percent during the day, but pared the gain to 9.4 percent at C$11.06 at the close. [ID:nN21256837]
($1=$0.99 Canadian) (Reporting by Ka Yan Ng; editing by Peter Galloway)