Co*run"dum (k?-r?n"d?m), n.; pl. Corundums (-dmz). [Also corindon.] [From Hind. kurand corundum stone.] Min.
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.
⇒ The name corundum is sometimes restricted to the non-transparent or coarser kinds. Emery is a dark-colored granular variety, usually admixed with magnetic iron ore.
© Webster 1913.