corundum

American  

[kuh-ruhn-duhm] / kəˈrʌn dəm /

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.

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corundum British  

/ 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)

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corundum Scientific  

/ 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 .

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Etymology

Origin of corundum

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

Example Sentences

Corundum is important to the jewelry trade as ruby and sapphire.

From Textbooks • Feb. 14, 2019

Corundum, ko-run′dum, n. a mineral consisting of mere alumina, yet of great specific gravity—about four times that of water—and second in hardness only to the diamond.

From Chambers's Twentieth Century Dictionary (part 1 of 4: A-D) by Various

For figures of other combinations see Calcite and Corundum.

From Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 7 "Crocoite" to "Cuba" by Various

Corundum is a mineral similar to emery, and corundum wheels are made and used in the same manner as emery wheels.

From Modern Machine-Shop Practice, Volumes I and II by Rose, Joshua

Corundum, the second species considered, was a little more complex, having two elements, aluminum and oxygen, in its make-up, but completely and definitely combined in a new compound that resembles neither aluminum nor oxygen.

From A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public by Wade, Frank Bertram

Related Words

• gem
• jewel
• rhinestone