* Market swings erratically, reflects investor jitters
* Materials sector down 6 pct, oil group off 2.1 pct
TORONTO, Oct 16 (Reuters) - The Toronto Stock Exchange’s S&P/TSX composite index .GSPTSE swung 300 points lower in erratic dealings on Thursday morning as jittery investors weighed the risk of recession as commodity prices weakened.
Softening commodity prices put yet another chill on the heavily-weighted energy and materials sectors at the open, pushing the index down more than 100 points minutes after the opening bell.
But the index quickly reversed course and raced 100 points higher, only to see all 10 main sectors turn negative by midmorning.
A 5.96 percent drop in the materials sectors, which includes miners and fertilizer issues, led the declines. The gold-mining subindex sagged nearly 7 percent, with Barrick Gold (ABX.TO) off 8.6 percent at C$30.33.
Shortly after 10:30 a.m. (1430 GMT), the S&P/TSX composite index .GSPTSE was down 300.00 points, or 3.2 percent, to 9,023.85. ($1=$1.19 Canadian) (Reporting by Ka Yan Ng; Editing by Peter Galloway)