Noble gas element with symbol Xe and atomic number 54 <http://periodic.lanl.gov/54.shtml>
This category is also used for Xe.
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The rare-earth elements: vital to modern technologies and lifestyles

Explains how and where rare-earth resources form and concentrate and how they are used and interact with the environment to affect human and ecosystem health. Discusses supply and demand trends and where undiscovered sources of rare-earths might be found.