TO'PAZ, n. [Gr.] A mineral, said to be so called from Topazos, a small isle in the Arabic gulf, where the Romans obtained a stone which they called by this name, but which is the chrysolite of the moderns. The topaz is of a yellowish color. It sometimes occurs in masses, but more generally crystallized in rectangular octahedrons. Topaz is valued as a gem or precious stone, and is used in jewelry. It consists of silex, fluoric acid and alumin, in the following proportions; alumin 57 parts, silex 34, and fluoric acid 7 or 8.
Of topaz there are three subspecies, common topaz, shorlite and physalite.