The true determinant for the evaluation of this precious stone will be the wearer's preference. The intensity of color and the clarity of the stone will contribute to the value of topaz as well, and should never be neglected.

Precious Topaz
The classical "precious topaz" is yellow or yellow to orange-brown in color. Sherry or Madeira would best describe the most desirable and most valuable color.

Blue Topaz
Over the last 10 years or so, jewelers' windows have become filled with Blue Topaz, which is very attractive and inexpensive. It has, to some extent, become a substitute for Ceylon Sapphire. Blue Topaz does occur naturally, but almost all commercially available material is produced from less attractive colors which are irradiated and heat treated to turn them blue. This treatment produces a stable color, and normally the stones are not radioactive when they are released on the market, although there have been cases where stones with an unsafe level of radiation have been sold.

There are distinct hues of Blue Topaz, which arise as a result of the different treatments. The most usual colors are known as "London Blue", "Swiss Blue" and "Sky Blue". These colors were listed in order from the deepest to the palest colors.

Cleavage
Perfect cleavage is one of the notable attributes of Topaz. Because of the nature of its crystal structure, Topaz has like one plane in which its bonds are relatively weak. If it receives a sharp blow in the wrong place or direction, it can fairly easily break cleanly in two. This is similar to the way in which large diamonds are cut, and should not be too great a concern in normal jewelry use, once the stone is mounted.

Sources
The world's largest supplier of topaz is Brazil. However, Pakistan and Russia are now emerging as the new sources for topaz supply. Topaz comes in a variety of shapes, colors and sizes making it ideal for a wide variety of applications.

Topaz is composed of Aluminium Fluosilicate, the fluorine (F) and the hydroxyl (OH) can partly replace each other.