Two yrs ago I bought some red topaz at the Tucson gem show. The dealer said red topaz is really white topaz that has been treated (I think diffusion was the word he used). The color is only on the surface of the stone (unlike blue topaz) and if you chip the stone, you will see the original white topaz. Some of my red topaz is reddish/pink, some is pink. I tell my customers that it is treated stone and they don't care because they're buying it for the color.
Don’t do that.There is a genuine natural color Red Topaz that occurs
in Ouro Preto,Minas Gerias,Brazil.It is termed ‘Imperial Topaz". It is
highly prized and quite valuable.I have never heard of diffused to the
color Red,but I guess it is possible,diffusion refers to a coating
that they manage to penetrate UNDER the surface of the stone even a
fraction of a milimeter.As I understand it,commercial diffusion
treating process won’t rub off,or wear off,you can chip,sand or grind
though it. Your Reds and pinks may be natural colored material from
Ouro Preto.They also could be pale natural color straw Topaz from Ouro
Preto that has been given an irradiation process.This would be a
totally through coloring,but if done on low dosage irradiation may not
be stable to ultraviolet light.If done on a high dosage should be
stable,and undetectable.Now you will ask me next how to tell the
differance,there is no test,lay them out on the window sill for a few
days,or know your dealer.This is very important,as in Brazil the only
irradiation facility available to them is a Colbolt 60 in Sao Paulo.So
most often,the lower dosage treatment is performed on pale Imperial
Topaz.The lower dosage is also considerably less expensive,and time
consuming. Imperial Topaz is just now making rebirth.I know as I am
involved and will be in Ouro Preto next week.There are a couple
factors that need to be overcome for this fine wonderful gemstone,and
sold mostly natural color untreated,to come out in the market.It must
be understood,that White Topaz,which is available worldwide in
bulk,and inexpensively,and has been doctored every which way you
can,is an entirely seperate variety of the species Topaz.“Smoky Topaz”
is a trade name for Morion,or Smoky Quartz,the natural Browns that are
found in Guerro,Mexico,Ukariane,USA,Utah,and reported to be now found
in Vietnam,are not Imperial Topaz.In fact,they are basicly white Topaz
that has been colored by irradiation in nature.The word "Topaz’ is
often tacked on the Orange and reddish Orange Citrine Quartz that is
found in Rio Grande do Sul,Para,and Bahia Brazil.This is all
incorrect. Imperial Topaz is a natural colored gemstone that occurs in
Straw,Orange,Red,Pink and Purple primarily occuring in Ouro
Preto,Minas Gerias,Brazil.Here is a series of photos of this gemstone
http://www.liccini.com/Preview/ImTop/TopCover.html Mark Liccini