Topaz is a silicate mineral of aluminium and fluorine. Topaz crystallizes in the orthorhombic system. Its crystals are mostly prismatic terminated by pyramidal and other faces. It is the symbol of friendship.

Pure topaz is colorless and transparent but is usually tinted by impurities. Topaz can be wine colored, yellow, pale gray, reddish-orange, or blue brown. It can also be made by treatment into white, pale green, blue, gold, pink , reddish-yellow and from opaque to transparent or translucent.

Orange topaz or precious topaz, is the traditional birthstone of November. Imperial topaz is yellow, pink or pink-orange. Brazilian Imperial Topaz has a bright yellow to deep golden brown hue or even violet.

Many brown or pale topazes are treated to make them bright yellow, gold, pink or violet colored. Some imperial topaz stones fade due to proloned exposure to sunlight.

Blue topaz is the state gem stone of the US state of Texas. Naturally occurring blue topaz is quite rare. The colorless, gray, pale yellow or blue material is heat treated and irradiated to produce darker blue.