Topaz is a fluorine-containing silicate, which is commonly encountered as both a faceted gemstone and uncut crystal specimen. Although traditionally associated with yellowish and/or brownish hues, modern-day irradiation and subsequent heating of previously colorless material today produces the light “sky” blue, bright “Swiss” blue and dark-toned, grayish “London” blue varieties in huge quantities. At the opposite end of the rarity and price spectrum, reddish, pinkish and/or orangish “Imperial” topaz is by far the most valuable variety - especially when cut in such a way so as to display an intense pleochroic coloration at the stone’s outer extremities.

It is important to note that the term “topaz” was historically used for a wide variety of yellow gem materials prior to the introduction of the modern gemological definition, with the name itself derived from that of a well-known ancient peridot source locality, namely the Red Sea island of Topazios.