CORUNDUM

Co‐run″dum (kō̍‐rŭn″dŭm), n.; pl. Corundums (–dŭmz). [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.