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

The Gucci x Oura Ring is made out of “black synthetic corundum” detailed with a braided border and an 18-karat gold Gucci G. It weighs four grams, and the band measures 0.3 inches thick.

From The Verge

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

From Scientific American

These include substrates of strontium titanate, aluminium oxide and magnesium aluminate, which have perovskite, corundum and spinel crystal structures, respectively.

From Nature

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

From New York Times

Recent research suggests that traces of silicon, too, play a role in determining the color of corundum, but its exact role has not been determined.

From New York Times

Related Words

• gem
• jewel
• rhinestone