* TSX down 0.08 percent at 11,463.40
* Tech sector leads as RIM jumps 10.3 pct
* Potash, base miners weigh (Adds official close, comments)
By Cameron French
TORONTO, Dec 18 (Reuters) - Toronto's main stock index ended slightly lower in a volatile session on Friday as a drop in energy and materials shares offset a huge jump in heavyweight tech stock Research In Motion RIM.TO.
RIM jumped 10.3 percent to C$73.96 after reporting a better than expected quarterly profit and outlook late on Thursday.
The stock pushed the TSX information technology sector up by 2.3 percent. Altogether, five of the 10 TSX index subgroups ended the session higher.
"RIM's really been the standout performer," said Elvis Picardo, strategist at Global Securities in Vancouver.
Materials stocks weakened 0.78 percent, hit by an early slide in copper prices and company-specific news. Gold miners, however, put in a strong performance.
Weighing on the sector was fertilizer producer Potash Corp (POT.TO), which dropped 6 percent to C$112.00 after an analyst downgrade, and base-metals miner HudBay Minerals (HBM.TO), which sank 8.8 percent to C$12.83 after it revealed disappointing drill results at a deposit in Manitoba.
All told, the S&P/TSX composite index .GSPTSE retreated 9.66 points, or 0.08 percent, to 11,463.40.
The index initially appeared to close higher, but then adjusted lower as final trades were calculated.
Analysts said the concurrent expiry of stock options and futures and stock index options and futures -- a quarterly occasion known as quadruple witching -- contributed to the market's volatility as big investors adjusted or exercised derivative positions late in the session.
($1=$1.07 Canadian) (Reporting by Cameron French; editing by Peter Galloway)