The Toronto Stock Exchange's S&P/TSX fell 18.21 points, or 0.11 percent, to 16,484.21.
Leading the index were OceanaGold Corp , up 10.4 percent, First Majestic Silver Corp , up 8.7 percent, and Pan American Silver Corp , higher by 6.7 percent.
Lagging shares were Precision Drilling Corp , down 4.9 percent, TFI International Inc, down 4.3 percent, and Nexgen Energy Ltd, lower by 4.0 percent.
On the TSX 110 issues rose and 127 fell as a 0.9-to-1 ratio favored decliners. There were 20 new highs and 4 new lows, with total volume of 165.5 million shares.
The most heavily traded shares by volume were Encana Corp , Enbridge Inc and Barrick Gold Corp.
The TSX's energy group fell 1.82 points, or 1.3 percent, while the financials sector slipped 0.81 points, or 0.3 percent.
West Texas Intermediate crude futures fell 1.84 percent, or $1.06, to $56.56 a barrel. Brent crude fell 1.17 percent, or $0.75, to $63.6.
The TSX is up 15.1 percent for the year.