[Jewelry making - Article 00343] - Re: [Orchid] Colored Stones

[Webcarats]

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>     You could even use spectrophotometers to check clarity and
>     transparency through light transmission.  You could check to see
>     if the color of your chrysoprase ring has faded in sunlight, and by
>     how much. 

    Hi Blaine, I completely agree with your question, which has been
    mine for a long time. Spectros are commonly used in biological
    laboratories for testings, countings, ... why not in gemmology ? 

    Unfortunatly, ALL that I read about that topic claim it's hopeless
    ... Why? There are too much parameters, not only a plain color:
    quality of the cut and polish, thickness of the stone, brilliance
    (internal reflexion), reflexion (external reflexion), inclusions
    (just in the very middle of the table? not that easy: close to the
    girdle, or the same inclusions close to the culet and seen several
    times because of internal reflexions...), color zoning, and so on.
    The machine will easily compare a 1ct well cut, top quality stone and
    a 5 ct low end one. But its appreciation won't be the same as yours! 

    Spectros are very usefull if you have to test hundreds of biological
    analysi s a day, because they all come in the same tubes and the
    results of the tests are well known, with colorcharts given by the
    manufacturers. In gemmology, you won't have two identical stones: if
    you have, it's calibrated so you don't need the spectro, because you
    know what you have got . 

    I hope you won't agree with me, because this topic seems of some
    interest to  me, and I should like to read different opinions. 

Regards,
Yann
www.webcarats.com 

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