Monday, May 03, 2004

Rare-earth Element, Sources and extraction

Though numerous minerals rich in rare earths are found in the Earth's crust, many are extremely rare, and many more are found only in small pockets in more massive rocks. Although such minerals are of considerable research interest they are not used commercially. Monazite, a mixed phosphate of calcium, thorium, cerium, and various lanthanides, occurs in extensive deposits

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