[Jewelry making - Article 00401] - Re: [Orchid] Gemstones Treatments

[docktor]

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>           Other than the few "matrix opals" from Andamooka, Australia
>     and Honduran "black" matrix opals that are treated with sulfuric
>     acid and sugar, opals that are sold as "solid" opals are untreated.
>     

    Hi Rick. I have a personal opal which is the first black opal I had
    ever seen. It hails from Andamooka, it has a black base color, and
    it is most definitely not treated with sugar or by the smoke method,
    either. Of course, nearly all "black" opal from Andamooka definitely
    IS treated; however, this one is not. I can't begin to tell you how
    many Andamooka mine owners have told me at trade shows that this
    piece can't possibly be naturally black. I understand skepticism
    about it, because of the nature of average Andamooka material, but
    bear with me and you'll see where I'm going with this. A sizeable
    chunk of Andamooka opal was unearthed some years ago weighing 43
    pounds. Yes, I said 43 pounds!!! This chunk of opal was appraised in
    1980 by Joseph Tenhagen, G.G., F.G.A. as "gem black opal from
    Andamooka Australia, valued at $45 per carat". The piece that is
    still left intact can be seen at the following URL:
    http://www.terrantreasures.com/images/andachunk3.jpg . The base of
    this piece is approximately eight inches across. The pieces I've cut
    from the main one can be seen at
    http://www.terrantreasures.com/images/and140de4X6.jpg
    http://www.terrantreasures.com/images/trimook.jpg and
    http://www.terrantreasures.com/images/Andamooka4X6LG.jpg Sure, it's
    marbled through with areas of brown, in some cases, and also the
    typical white precious opal of Andamooka fame, but not one bit of it
    has been treated in any way. Every slice from this unbelievable
    piece has proved to be shot through with the same base colors, not
    just limited to the surface, as typical of smoke and sugar treated
    material. I also have a few small slabs left of this material that I
    slabbed myself, with no evidence of the very shallow surface
    treatment that result from sugar and smoke treatments (and yes, I do
    have several examples of treated material as well). The larger chunk
    of this material still exists in South Florida. I don't write this
    post to "argue" or to "prove somebody wrong". Rather, I see over the
    years that very few even know of the existence of natural black
    Andamooka material...even the miners who work there every day! All I
    mean to do is to share new knowledge with those who wish to know.
    Thanks for hearing me out. 

James




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