(Updates prices, adds sector details) March 30 (Reuters) - Canada’s main stock index fell on Tuesday, dragged down by shares in mining and energy companies as bullion and crude oil prices weakened. * At 9:39 a.m. ET (1339 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was down 80.35 points, or 0.43%, at 18,638.87. * The materials sector, which includes precious and base metals miners and fertilizer companies, lost 2.1% as gold futures hit a three-week low of $1,683.9 an ounce. * The energy sector dropped 0.3% as oil prices fell after the Suez Canal reopened to traffic, while focus turned to OPEC+ possibly agreeing to output cuts this week. * Miners B2Gold Corp and Pretium Resources Inc fell 5.6% and 4.9%, respectively, and were the biggest decliners on the TSX. * The financials sector gained 0.2%. The industrials sector fell 0.1%. * On the TSX, 70 issues were higher, while 152 issues declined for a 2.17-to-1 ratio to the downside, with 16.76 million shares traded. * The largest percentage gainers on the TSX were Exchange Income Corp, which jumped 2.9%, and pot producer Aphria Inc, which rose 1.8%. * The most heavily traded shares by volume were Bank of Nova Scotia, Power Corporation of Canada, and TC Energy Corp.. * The TSX posted three new 52-week highs and no new lows. * Across all Canadian issues there were 22 new 52-week highs and four new lows, with a total volume of 31.53 million shares. (Reporting by Amal S in Bengaluru; Editing by Ramakrishnan M.)