Final answer:
Topaz varies in color from colorless to various hues, with imperial topaz being prized for its golden to reddish-orange color. Unlike ruby and emerald, topaz coloration often results from treatments. Disclosures about such treatments are essential but are not always provided.
Step-by-step explanation:
The differences between topaz gem varieties such as topaz and imperial topaz stem mainly from their color and quality. Topaz can be found in a wide range of colors, including colorless, which is the purest form of topaz, and various shades of blue, green, yellow, orange, red, pink, and purple. Imperial topaz is a highly prized variety of topaz that exhibits an intense golden to reddish-orange color. The distinct color variation in topaz is often due to natural trace elements found within the crystal structure or through treatments such as irradiation.
In comparison to other gemstones like ruby and emerald, which get their colors due to the presence of small amounts of Cr+ impurities, topaz does not rely on these impurities for its color. Instead, natural topaz is often treated to enhance its color; treatments should be disclosed, but this is not always the case, leading to asymmetric information in the gem market. Therefore, understanding the nature of the topaz and whether it has been treated, is crucial for gemstone buyers