VANCOUVER, British Columbia, Aug 21 (Reuters) - Ainsworth Lumber Co Ltd (Toronto:ANS.TO - news) said on Tuesday depressed prices for the building material oriented strand board drove down its net earnings in the second quarter. The company recorded a net profit of C$1.2 million, eight Canadian cents per share, on sales of C$89.8 million in the quarter ended June 30, down from net earnings of C$9.8 million, 67 Canadian cents per share, on sales of C$92.9 million.