Rare earth is any of the seventeen metallic chemical elements found in atomic numbers 21, 39 and 57 through 71, typically found dispersed in deposits of chemicals with similar chemical properties.(noun)
An example of rare earth is cerium, a chemical oxidizing agent, that provides the yellow color in glass and acts as a catalyst for self-cleaning ovens.
See rare earth in Webster's New World College Dictionary
See rare earth in American Heritage Dictionary 4
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