[kuh-ruhn-duh
m] 
| a common mineral, aluminum oxide, Al2O3, notable for its hardness: transparent varieties, as sapphire and ruby, are used as gems, other varieties as abrasives: often made synthetically. |
| co·run·dum (kə-rŭn'dəm) n. An extremely hard mineral, aluminum oxide, Al2O3, sometimes containing iron, magnesia, or silica, that occurs in gem varieties such as ruby and sapphire and in a common black, brown, or blue form used chiefly in abrasives. [Tamil kuruntam.] |
| corundum (kə-rŭn'dəm) Pronunciation Key
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: Al2O3. |