Mystic Topaz

Recently there was a discussion about coated gems in a gemmological internet forum.

Some gems, in particular topaz and quartz, are colour coated using various treatments like physical (PVD) or chemical vapour deposition (CVD).

With these treatments, layers of metal are deposited on the stones surface, commonly titanium or gold. The colours thus produced are pink and red, green and petrol blue/green. One type of PVD or CVD treated topaz shows iridescence in all colours of the rainbow and is marketed as "mystic topaz", "aurora topaz" or the like.

Experience shows that the coloured layer can very easily be removed. Even handling such stones with tweezers may suffice to produce scratches. Due to the thinness of the coating, usually only 1-4 micron, these stones cannot be re-polished.
mystic topas tpopaz
"Mystic topaz"

On the Website of an American producer of coated gems we found this remarkable statement:

The natural magnification properties of water make XY™ ideal for aquarium use

There´s nothing more to be said