Though it can be found in almost every color, the most prized hue of topaz is referred to as imperial topaz. A rare type topaz ranging from yellow to reddish orange in color, this shade of topaz derives its name from its association with the Russian Czars of the 1800s. It is this celebrated color of topaz that is considered the birthstone for November. In antiquity, all yellow gems were referred to as topaz. Modern definitions of gems are more discriminating and allow us to identify topaz in a wide spectrum of colors. In fact, topaz in its purest state is colorless. In antiquity, the gem was sometimes mistakenly identified as a diamond. Colored varieties include the classic spectrum from yellow through sherry orange as well as blue, pale green, pink, and red. Some of these colors are unstable and can fade over time.