[Jewelry making - Article 00306] - Re: [Orchid] Gem ID for "Peruvian Opal"

[Terry Ogden]

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Bonnie

    Your question is difficult to answer for several reasons. 

    1. Opal, chalcedony and quartz are all the same thing chemically,
    they only vary in how they are produced. 

    2. Not all Opal is, like the precious opal, there are clear (Mexican
    Fire Opal) and colored varieties which may or may not have the color
    flashes we expect. There is also material called common opal (potch)
    which abounds, and currently from the advertising, I believe 4 from
    Peru, Pink, Blue, Green, White which are available as rough. 

    3. Cutting the stone would probably be the only way you could tell if
    it had been dyed assuming that the process had not been performed
    after shaping. 

    As I don't have your stone, I can not tell. Chalcedony and Opal are
    both porous and both would be susceptible to coloring. Most
    chalcedony and Potch Opal are stable, but there are exceptions. 

    Sorry I could not provide a better answer, but maybe one of the GIA
    folks would care to chime in. I rely on obtaining rough from sources
    with the matrix still attached, quality dealers who could ill afford
    the scandal, or to personal collecting. (My favorite since I was
    about 4 years old) 

    Sorry I could not provide you a better answer, but it seemed the
    genealogy of opal and chalcedony might be in order on this question. 

Terry
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