corundume

例句：

1. 1. The gemstone is a rare and valuable mineral.
   这块宝石是稀有且有价值的矿物。
2. 2. The jeweler carefully selected the most brilliant corundum for her engagement ring.
   珠宝商精心挑选了最璀璨的红宝石为她订婚戒指。
3. 3.The ancient civilizations of the world relied on corundum for their cutting tools.
   古代世界的各个文明依赖红宝石作为他们的切割工具。