A
gemstone extremely varied in color. Natural topaz is usually yellow or tan (the latter being called "
champagne topaz") or colorless. The pale yellow and colorless gems (known as "white topaz") can be turned several other colors by intense
heat and/or
irradiation; blue and pink are the most popular of the colors created by
gem enhancement. These colors do occur in nature occasionally but the naturally colored ones are extremely
expensive.
In the gem world, the word "topaz" without any color named usually means the yellow-pink-tan "Imperial topaz" (also called "sherry topaz" or "golden topaz") -- these are all less brown than the champagne topaz. This is a naturally found color and the most expensive of all topaz -- citrine has occasionally been called "Madeira topaz" to try and capitalize on the higher price of topaz.
A new thing being done with white topaz is to apply a very thin synthetic film to the part of the stone which will be inside the setting. Depending on the properties of the film, the stone can be made to reflect different colors and do other unusual displays.