corundum
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Related to corundum: Artificial Corundum
co·run·dum
(kə-rŭn′dəm)n.
An extremely hard mineral, aluminum oxide, Al2O3, sometimes containing iron, magnesia, or silica, that occurs in gem varieties such as ruby and sapphire and in a common black, brown, or blue form used chiefly in abrasives.
[Tamil kuruntam.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
corundum
(kəˈrʌndəm)n
(Minerals) a white, grey, blue, green, red, yellow, or brown mineral, found in metamorphosed shales and limestones, in veins, and in some igneous rocks. It is used as an abrasive and as gemstone; the red variety is ruby, the blue is sapphire. Composition: aluminium oxide. Formula: Al2O3. Crystal structure: hexagonal (rhombohedral)
[C18: from Tamil kuruntam; related to Sanskrit kuruvinda ruby]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
co•run•dum
(kəˈrʌn dəm)n.
a mineral, aluminum oxide, Al2O3, noted for its hardness: transparent varieties, as sapphire and ruby, are used as gems, other varieties as abrasives: often made synthetically.
[1720–30; < Tamil kuruntam; akin to Skt kuruvinda ruby]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
co·run·dum
(kə-rŭn′dəm) An extremely hard mineral composed mainly of aluminum oxide. It occurs in gem varieties such as ruby and sapphire and in a dark-colored variety that is used for polishing and scraping. Corundum is the mineral used to represent a hardness of 9 on the Mohs scale.
The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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| Noun | 1. | corundum - very hard mineral used as an abrasive mineral - solid homogeneous inorganic substances occurring in nature having a definite chemical composition emery - a hard grey-black mineral consisting of corundum and either hematite or magnetite; used as an abrasive (especially as a coating on paper) alumina, aluminium oxide, aluminum oxide - any of various forms of aluminum oxide occurring naturally as corundum ruby - a transparent deep red variety of corundum; used as a gemstone and in lasers sapphire - a precious transparent stone of rich blue corundum valued as a gemstone |
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