Topaz is a very hard mineral and is well suited for all jewelry applications. It is readily available in a variety of colors of which blue and colorless are the most popular. Most natural topaz is virtually colorless. This material is then irradiated and heat treated to produce the desired blue color. The type and the intensity of radiation determines the final color of the gemstone. The more intense the radiation the deeper blue the gems become. The richest  shade of blue is termed London Blue. This darker color is much more expensive and therefore not as popular. The second richest shade is termed Swiss Blue. This is the most popular shade and can be found in virtually every jewelry store. Sky blue is the lightest color and sells for less than the others due to its pale color. Colorless topaz is frequently used as accent stones in jewelry settings.