Topaz is found in many colors and shades, and blue topaz was originally the most rare. However, today a permanent treatment, diffusion — which is heating with a coating of an element such as beryllium — turns colorless topaz a light blue. The treatment is permanent. Deeper blues, known as “London blue” and “Swiss blue,” are caused by irradiation and heating, and the treatment is considered permanent. Blue topaz is a hardy stone, and the many shades look gorgeous in a variety of jewelry styles, from earrings and pendants to bracelets and rings. Blue topaz has historically been associated with love and affection — pretty perfect reasons to give it as an anniversary gift.