corundum

noun

co·run·dum | \ kə-ˈrən-dəm

Definition of corundum

: a very hard mineral that consists of aluminum oxide occurring in massive and crystalline forms, that can be synthesized, and that is used for gemstones (such as ruby and sapphire) and as an abrasive

Examples of corundum in a Sentence

Recent Examples on the Web

With a Mohs hardness score just a point shy of diamond’s, corundum becomes a red ruby through the timely addition of chromium atoms. — Natalie Angier, New York Times, "Precious Gems Bear Messages From Earth’s Molten Heart," 11 Dec. 2017 After all, sapphires and rubies are built of the same basic mineral, corundum, a crystallized collaboration of aluminum and oxygen that would be transparent and colorless if not for some artful chemical doping. — Natalie Angier, New York Times, "Precious Gems Bear Messages From Earth’s Molten Heart," 11 Dec. 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'corundum.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.