1. (Science: chemical) A mineral occurring in rhombic prisms, generally yellowish and pellucid, also colourless, and of greenesh, bluish, or brownish shades. It sometimes occurs massive and opaque. It is a fluosilicate of alumina, and is used as a gem.
The two tail feathers next to the central ones are much longer that the rest, curved, and crossed. The throat is metallic yellowish-green, with a tint like topaz in the center, the belly is bright crimson, the back bright red. Called also topaz hummer. False topaz.
Origin: OE. Topas, F. Topaze, L. Topazos, or topazion, a kind of precious stone, Gr. Topazos, topazion; possibly akin to Skr. Tap to glow (cf. Tepid). According to some, the name is from Topazos, a small island in the Red Sea, where the Romans obtained a stone which they called by this name, but which is the chrysolite of the moderns.