TORONTO, Sept 7 (Reuters) - Canada's main equity index opened higher on Friday, boosted by gold miners as bullion hit a six-month high and investors cheered the prospect of further monetary easing in both Europe and the United States. The Toronto Stock Exchange's S&P/TSX composite index was up 81.09 points, or 0.67 percent, at 12,220.82 shortly after the open, its highest level since early May.