MELBOURNE--Rio Tinto PLC (RIO) said Wednesday the fall in coal prices means it will close its Blair Athol coal mine in central Queensland this year after almost 30 years of production, rather than seek to extend the life of the operation by mining poorer quality coal and harder-to-reach seams for a few more years. The Anglo-Australian mining giant said it had planned since 2005 to close the mine at the end of the year, but had sought to extend the operation as prices rose in recent times. "Unfortunately, the recent significant drop in thermal coal prices, and other factors such as rising costs and the foreign exchange rate mean this is no longer a feasible option," said Dawid Pretorius, general manager of operations in the Clermont region of the eastern Australian state. Mr. Pretorius said the final day of production at Blair Athol will depend on the progress of mining operations over coming months, but is expected before December. There are currently about 170 employees and contractors working at the operation. Write to Robb M. Stewart at robb.stewart@wsj.com Subscribe to WSJ: http://online.wsj.com?mod=djnwires