Topaz makes an excellent gem. A good hardness and pleasing colors, combined with a relative abundance and availability make it one the most popular gemstones. The most important colors of Topaz are the golden orange-yellow type, called Imperial Topaz, and the dark pinkish-red and orange-red colors. The value grows with a deepness of color in orange and reddish tones. The most commonly used colors of Topaz in jewelry are the blue varieties. It was not until this past century that blue Topaz became popular on the gem market since virtually all blue gem Topaz is irradiated and heat treated.