Topaz is a birthstone for the month of November. It occurs in a wide range of natural and treated colors that include blue, pink, purple, yellow, brown, orange, and colorless. Topaz is a very durable stone with a Mohs hardness of 8. Diamond, ruby and sapphire are the only commonly used gemstones with a greater hardness.

The most popular color of topaz sold in jewelry today is blue. Natural blue topaz exists but it is very rare and very expensive. Fortunately for people born in November who like blue, colorless topaz can be treated with irradiation and heat to produce a variety of blue colors. Swiss blue and London blue are two of the most popular blue colors in treated topaz. Topaz is also coated to produce a range of iridescent colors and stones that appear to change color depending upon the angle at which they are viewed. These coated stones are called “mystic topaz”.