Topaz actually has an exceptionally wide colour range that, besides brown, includes various tones and saturations of blue, green, yellow, orange, red, pink, and purple.  

Colourless topaz is plentiful, and is often treated to give it a blue colour. Topaz is also pleochroic, meaning that the gem can show different colours in different crystal directions.

Most authorities agree that the name topaz comes from Topazios, the old Greek name for a small island in the Red Sea, now called Zabargad. (The island never produced topaz, but it was once a source of peridot, which was confused with topaz before the development of modern mineralogy.)  Some scholars trace the origin back to Sanskrit (an ancient language of India) and the word topas or tapaz, meaning “fire.”
 
The ancient Greeks believed that topaz gave them strength.  In Europe during the Renaissance (the period from the 1300s to the 1600s) people thought that topaz could break magic spells and dispel anger.  For centuries, many people in India have believed that topaz worn above the heart assures long life, beauty, and intelligence.
 
The name for imperial topaz originated in nineteenth-century Russia.  At the time, the Ural Mountains were topaz’s leading source, and the pink gemstone mined there was named to honour the Russian czar.  Ownership of the gem was restricted to the royal family.

 

Quality Factors

Colour

The most valued topaz colours are orangey red to red. Blue gems are widely available.

Clarity

Topaz used in jewellery is typically eye clean with no visible inclusions.

Cut

Topaz crystals are usually columnar, and cut as oval or pear shapes to improve yield.

Carat Weight

Topaz can often form as large crystals. These can yield sizeable cut gems.