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noun Corundum n. (pl. corundums) (Also corindon) (Min.) The mineral alumina (Al2O3), as found native in a crystalline state. Transparent varieties are used as gemstones, 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.
Collaborative International Dictionary of English 0.48
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