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Heat treatment of Topaz


#1

To All members,

I have radiated white topaz, it turned brown. Than I heated it at 200
C (for one hour) ,it became white. But I want it to become blue.
Anyone can guide me why topaz became white after heating instead of
blue. Is there another process of heating after radiation?

In Chanthaburi(Thailand), there are heat treaters,they are expert in
heating process.If anyone can give me contact info. of heat treaters
in Thailand.

Thank you in advance.
Dharmendra
e-mail: sagarart@vsnl.com


#2

Mr. Bhansali, First of all I would buy the book “Gemstone
Enhancements” by Kurt Nassau. In the book he describes the
mechanics of the irradiation and heat cycle used on many different
You can forget about the specifics. How much radiation,
how much heat, in what sequence of steps and durations are all
secrets of the industry. Yes, they know how to keep their mouths
shut and make money. Even in the USA the cycle is not disclosed.
You can have material treated, but they will not tell you how they
accomplished the treatment. Gerry Galarneau
www.galarneausgems.com


#3

Dharmendra, There are many types of topaz in the world with different
trace elements contained within. These trace elements act to
stabilize and affect the color of treated topaz. All these types of
topaz are not equally suitable to become the irradiated blue topaz.

There are also different sources and intensities of irradiation
available - not all equal. You have the very common Cobalt 60 used
in sterilization plants and hospitals, expensive Linear Accelerators
and government controlled Nuclear Reactors.

I think all topaz will turn brown with irradiation. Much of this
material is not stable and has what is known as
Brown-Fading-Color-Center. It will revert to a colorless state in
sunlight.

Only some topaz will turn blue or blue-brown. In this material the
brown can be driven off with heat leaving only the stable blue
color-center.

Then there are different types of treatments that this material can
be subjected to… i.e. Linear Accelerator, or Nuclear Reactor.
These different treatments result in different colors of blue in
this topaz.

Most likely you have Brown-Fading-Color-Center Topaz which was
subjected to Cobalt 60 treatment.

For more info. refer to Kurt Nassau’s book - Gemstone Enhancement -
Butterworths

Regards,
Steve Green