Topaz is usually a clear or yellow colored crystal.   Some topaz turns pink when heated.  Topaz also turns blue when irradiated.  The blue is the type most often used in jewelry.  Yellow topaz in the birthstone for November.  Blue topaz is the birthstone for December.  In folklore, topaz is used for strength, wisdom and courage.  The ancient Romans believed it improved eyesight while the Egyptians thought it protected them from injury. As a blue stone, it is most attuned to the blue energy center near the base of the throat and will aid that center and the organs in that part of the body.