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A silvery metallic element, not a rare earth but occurring in nearly all rare-earth minerals, used in various metallurgical applications, notably to increase the strength of magnesium and aluminum alloys. Atomic number 39; atomic weight 88.906; melting point 1,522°C; boiling point 3,338°C; specific gravity 4.45 (25°C); valence 3. See Table at element.
(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.