* TSX down 19.28 points, or 0.15 percent, at 12,781.95 * Weaker resource shares offset firmer financials * Cameco Corp down more than 3 percent after results By Claire Sibonney TORONTO, Feb 11 (Reuters) - Canada's main stock index fell on Monday, dragged down by weaker gold mining shares and Cameco Corp, after the world's biggest publicly traded uranium producer reported a sharply lower quarterly profit. Gold miners were among the heaviest laggards on the index as commodity prices fell. Gold extended earlier losses to one-month lows after recent technical support broke down. Goldcorp was the most influential decliner, down 1.1 percent to C$35.82, while Barrick Gold lost 0.8 percent to C$32.57. Cameco knocked off 3.1 percent to C$21.05 after the company announced it took a C$168 million ($168 million) write-down on an Australian exploration project, and said the current quarter would likely produce weaker earnings as well. "We used to own Cameco ... my problem with Cameco is that I think the future of nuclear energy has been very much cast in doubt by fracking and tight oil," said David Baskin, president of Baskin Financial in Toronto. "Because there's so much petroleum-based energy available now than people thought say five years ago, and because of what happened in Fukushima in Japan, I think that the whole future of nuclear energy is very much up in the air." At 10:14 a.m. (1514 GMT) the Toronto Stock Exchange's S&P/TSX composite index was down 19.28 points, or 0.15 percent, at 12,781.95. Seven of the 10 main sectors were in negative territory, including energy shares, down 0.4 percent. Stronger financial shares, up 0.2 percent, helped to stem the losses. Royal Bank of Canada, the country's largest lender, was the top gainer, rising 0.5 percent to C$63.22.