March 15 (Reuters) - Canada’s main stock index opened higher on Monday, led by material stocks which tracked firmer bullion prices, as a clutch of upbeat economic data bolstered optimism over an economic rebound. * At 9:30 a.m. ET (13:30 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was up 59.29 points, or 0.31%, at 18,910.61.