common corundum

例句：

1. 1. The gemstone is the hardest of all gems and is used in jewelry.
   这种宝石是所有宝石中最硬的，用于制作珠宝。
2. 2. The mineral is commonly found in river sediments.
   这种矿物通常存在于河流沉积物中。
3. 3.Common corundum is often used as an abrasive material.
   普通刚玉通常用作磨料材料。