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

Pliny says, corundum was used in the form of a splinter fixed in an iron style.

From Project Gutenberg

The stones have been rubbed into shape apparently by corundum.

From Project Gutenberg

This is true whether it has reference to a grindstone, emery, corundum wheel, or a plain oil stone.

From Project Gutenberg

Corundum and pure emery are ores that are very rich in aluminum, containing about fifty-four per cent.

From Project Gutenberg

Corundum is the hardest substance known, next to the diamond.

From Project Gutenberg

Related Words

• gem
• jewel
• rhinestone