TORONTO, July 10 (Reuters) - Toronto's main stock index opened lower on Friday as falling prices for oil, gold and other precious metals rattled the resource-heavy index.

The S&P/TSX composite index .GSPTSE was down 88.51 points, or 0.91 percent, at 9,685.41 at the open. Eight of the TSX's 10 sectors were lower, led by a 2 percent drop in the weighty energy group and a 1.6 percent fall in the mining-laden materials sector.

The TSX index entered Friday's session down 4.9 percent on the week. Last week it fell 1 percent. (Reporting by Frank Pingue; editing by Peter Galloway)