Topaz, and especially blue topaz, has grown in popularity over the years. The "pure" topaz color is yellow, and it was often confused with chrysolite, the yellow variety of peridot. Blue topaz is available in many shades, from icy blue to sky blue to deep blue. The blue color is often enhanced through heat treatment and irradiation.
Topaz was believed to have incredible medicinal powers in The Middle Ages, even against the plague. For a healthy individual, it brought about a pleasant disposition and patience, and was a symbol of fidelity and love.
Blue topaz is the traditional birthstone for December. It has a Mohs hardness rating of 8, making it a very durable stone.