corundum

[ kuh-ruhn-duhm ]

noun

1. a common mineral, aluminum oxide, Al 2 O 3 , notable for its hardness: transparent varieties, as sapphire and ruby, are used as gems, other varieties as abrasives: often made synthetically.

corundum

/ kəˈrʌndəm /

noun

1. 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: Al 2 O 3 . Crystal structure: hexagonal (rhombohedral)

corundum

/ kə-rŭn′dəm /

1. An extremely hard mineral occurring in many colors, either as shapeless grains or as rhombohedral crystals. It also occurs in gem varieties such as ruby and sapphire and in a dark-colored variety that is used for polishing and scraping. Corundum is found in igneous and carbonate rocks. Chemical formula: Al 2 O 3 .

Word History and Origins

Origin of corundum¹

1720–30; < Tamil kuruntam; akin to Sanskrit kuruvinda ruby

Word History and Origins

Origin of corundum¹

C18: from Tamil kuruntam; related to Sanskrit kuruvinda ruby

Example Sentences

If the quartz can’t scratch the specimen, it might be beryl or corundum, which are harder than quartz.

From Scientific American

A. Both rubies and sapphires are mostly the same clear mineral: aluminum oxide, in a crystalline form called corundum.

From New York Times

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.

From New York Times

I was not sure if it was a diamond or corundum, a sparkling stone that has little value.

From BBC

The Bronco mane and eyeball were created from orange sapphires while the head features pave-set diamonds and custom-cut corundum blue stone.

From Washington Times

Related Words

• gem
• jewel
• rhinestone