Corundum

[kә'rʌndәm]

解释:

(n.) The earth alumina, as found native in a crystalline state, including sapphire, which is the fine blue variety; the oriental ruby, or red sapphire; the oriental amethyst, or purple sapphire; and adamantine spar, the hair-brown variety. It is the hardest substance found native, next to the diamond.

卡洛斯录入

解释:

n. a mineral consisting of mere alumina yet of great specific gravity—about four times that of water—and second in hardness only to the diamond.

校对:潘西