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| Al2O3 | Corundum \Co*run"dum\ (k[-o]*r[u^]n"d[u^]m), n.; pl. {Corundums} (k[-o]*r[u^]n"d[u^]mz). [Also corindon.] [From Hind. kurand corundum stone.] (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. [1913 Webster +PJC] 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. [1913 Webster] |
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