corundum

1. 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. Source: opted

2. n. very hard mineral used as an abrasive Source: wordnet

3. 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

4. The earth alumina, as found native in a crystalline state,including sapphire, which is the fine blue variety; the orientalruby, or red sapphire; the oriental amethyst, or purple sapphire; andadamantine spar, the hair-brown variety. It is the hardest substancefound native, next to the diamond. Source: adambom

5. n:100 n very hard mineral used as an abrasive Source: ecdict

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