1. (Science: chemical) native alumina or aluminium sesquioxide, Al2O3; corundum; especially, the blue transparent variety of corundum, highly prized as a gem. of rubies, sapphires, and of pearles white. (Chaucer)
Sapphire occurs in hexagonal crystals and also in granular and massive forms. The name sapphire is usually restricted to the blue crystals, while the bright red crystals are called oriental rubies (see under Ruby), the amethystine variety Oriental amethyst (see under Amethyst), and the dull massive varieties corundum (a name which is also used as a general term to include all varieties). See Corundum.
Origin: OE. Saphir, F. Saphir, L. Sapphirus, Gr, of Oriental origin; cf. Heb. Sappir.