corundum
noun /kəˈrʌndəm/
/kəˈrʌndəm/
[uncountable]- an extremely hard form of alumina found in rubies and sapphires. Corundum is used as an abrasive.
刚玉：在红宝石和蓝宝石中发现的一种极其坚硬的氧化铝形式。刚玉用作研磨剂。 词源early 18th cent.: from Tamil kuruntam and Telugu kuruvindam.