CORUNDUM

corundom, corundum

(noun) very hard mineral used as an abrasive

Source: WordNet® 3.1

Etymology

Noun

corundum (countable and uncountable, plural corundums)

(mineral) An extremely hard mineral, a form of aluminum oxide with the chemical formula Al₂O₃, that occurs in the form of the gemstones sapphire and ruby; it is used as an abrasive.

Source: Wiktionary

Co*run"dum (k-rn"dm), n.; pl. Corundums (-d. [Also corindon.] Etym: [From Hind. kurand corundum stone.] (Min.)

Definition: 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.

Note: 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.

Source: Webster’s Unabridged Dictionary 1913 Edition