[Jewelry making - Article 00204] - Re: [Orchid] Fragile gemstones

[Douglas Turet]

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>     I have also noticed an acute fragility with watermelon tourmaline
>     of late. The question here is....are treatments also being used on
>     this tourmaline or is it just my aging fat fumbling fingers? One
>     comment was made to me by an associate that watermelon tourmaline
>     is never treated as it is already of light color.


    Hi Don, After benefitting from so many of your postings, over the
    last year or so, it feels great to be able to return the favor... 

    The truth of the matter is that most "true" Watermelon Tourmalines
    -- i.e. pinks, with green rinds (as opposed to Bicolor Tourm's,
    which display two or more colors in striae, perpendicular to the
    crystal axis) -- are not treated, except through gentle heating,
    which tends to reduce the brown overtones inherent in some of them.
    The more garrishly colored pieces you'll occasionally see, nowadays,
    with their intense blue rinds and violet-red Rubellite cores are,
    indeed, often the result of a bit of irradiation, but this shouldn't
    detract from their overall durability, unless they've been
    overheated, in the process. 

    The single biggest source for confusion and frustration with these
    gems, as a whole, seems to stem from jewelers' lack of understanding
    of some of the chemistry/mineralogy involved in the whole pink range
    of Tourmalines, in general, and those with multiple colors, in
    particular. The real culprit behind these, lurking unbeknownst to
    most, is the element lithium, which imparts its pink color to not
    only these beauties, but several others in the gem & mineral
    kingdoms. Lithium is both a blessing and a curse, like its sister,
    chromium. In both cases, these elements' presence in a given
    crystal's molecular lattices, in relatively small percentages,
    causes both beautiful coloring and crystallographic instability; as
    with the chromium in fine Emeralds or Rubies, the more lithium you
    add, the better the color AND the more included and tempermental the
    finished gem. 

    From a lapidary's perspective, faceting multicolored Tourmalines
    requires taking steps usually reserved for far less hardy materials,
    like Apatite or Rhodochrosite. In order to guard against a bicolored
    rough's tendency to split along its color lines, the lapidary must
    "rough out" the stone with a much finer lap than he'd otherwise use,
    and must also take precautions to use only warm water as a coolant,
    lest any thermal shock occur and split or shatter the stone.
    Similarly, when polishing, care must be taken to assure that the
    polishing lap remains smooth and true, without irregularities that
    could, again, split the stone. 

    Alas, when a great many setters receive these stones -- regardless
    of whether the pieces in question are true, rinded "Watermelons" or
    bicolors -- they see them as just another splotch of color, and
    treat them without any regard to their inherently delicate nature.
    As a result, I'm often asked to repair the unrepairables: stones
    that've neatly split into a green half and a pink half, or a few
    green "rind" chips and a pink core. (Yes, there _are_ some
    cyanoacrylates that are suitable for such repairs, but do you want
    to be the one to tell your customer how her stone came to feature
    that glue line? I sure don't!) In summary, the best advice I can
    offer you, Don, is to handle every mutlicolored stone you see as if
    it were a 1.0mm thick Opal cabochon (very delicately), and/or expect
    problems to arise otherwise, each time the beautiful pink thing in
    from of you isn't a Sapphire, Spinel or Rhodolite. 

Hope I've helped,
Doug
Douglas Turet, GJ
Lapidary Artist, Designer & Goldsmith
Turet Design
P.O. Box 162
Arlington, MA 02476
Tel. (617) 325-5328
eFax (928) 222-0815
anotherbrightidea AT hotmail.com

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