I had a customer come into my showroom yesterday and asking why Blue Topaz,
especially London Blue Topaz was so expensive.
In general, blue gemstones with good hardness and brilliance tend to be rare and fairly expensive.
Blue Topaz can be found in lighter and darker tones usually known in the trade as Sky Blue Topaz, Swiss Blue topaz and London Blue Topaz.
As in the case of other blue gemstones (such as sapphire), the more saturated blues tend to have a higher value - i.e. such as London Blue Topaz.
|Blue Topaz loose gemstones|
Natural Blue Topaz is very rare.
Virtually all the blue topaz in the market is produced by treating white topaz with radiation.
|London Blue Topaz faceted briolettes set in 14kt gold|
London Blue Topaz is produced by exposure to radiation in a nuclear reactor. When topaz is exposed to fast neutrons, the radiation changes the color centers, producing the deep blue color. Subsequent heat treatment is often used to lighten the inky color.
Note: Material treated in this way is likely to be radioactive and may require several months of storage before the radioactivity decays to safe levels. There are very strict rules in place to protect not only consumers but also the cutters and gem dealers who handle these gems on a daily basis.
Most of the Blue Topaz in the market is safe.