corundum
/kəˈrʌndəm
/noun [mass noun]
Extremely hard crystallized alumina, used as an abrasive. Ruby and sapphire are varieties of corundum.Although blue corundum, zircon, and tourmaline occur in Colorado, they are not known to produce gems....
- Red gem-quality corundum is known as ruby; all other colors of gem corundum are referred to as sapphire, with a prefix denoting the color of the stone.
- Several Colorado gem minerals (lazurite and the state's minor occurrences of corundum and cordierite) form in metamorphic rocks.
Origin
Early 18th century: from Tamil kuruntam and Telugu kuruvindam.