Definition of "lutetium" [lu•te•ti•um]

• A silvery-white rare-earth element that is exceptionally difficult to separate from the other rare-earth elements, used in nuclear technology. Atomic number 71; atomic weight 174.97; melting point 1,663°C; boiling point 3,395°C; specific gravity 9.840 (at 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.

• "China accounts for 95 percent of global production and about 60 percent of consumption of rare metals, including dysprosium, terbium, thulium, lutetium and yttrium, according to the U.S."
• "Depending upon which chemist you ask, rare earth elements consist of either: the so-called lanthanide series (elements having atomic numbers from 57 [corresponding to lanthanum] to 71 [corresponding to lutetium]) or the actinide (elements 89 to 103) and lanthanide series."
• "They had a little mom-and-pop trading post on one of the lutetium-producing islands. 1 was sixteen, away at boarding school on the mainland, when a pirate attack on the mine escalated into a firestorm that destroyed the entire settlement."