A worker (C) shovels cast-off tailings out of a channel sluicing crushed mineral ore containing rare earths to a disposal dam on the edge of the city of Baotou, in China's Inner Mongolia Autonomous Region October 31, 2010. The sludge has been rejected by large rare earth smelters nearby but workers sell it for around 300 Yuan ($45) per tonne to smaller operators eager for a slice of China's rare earth metals business - a market that China has a near monopoly on by producing 97 percent of the world's supply, and having around 87 percent of all known deposits. REUTERS/David Gray (CHINA - Tags: ENERGY ENVIRONMENT BUSINESS)