[Jewelry making - Article 00671] - Re: [Orchid] Heat treatment of Topaz

[Steve Green]

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    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

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