[Jewelry making - Article 00139] - Re: [Orchid] Agatized dinosaur bones

[John Donivan]

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>     Chalcedony nomenclature is colloquial and not scientific. 

    Yeah, I had in mind to write something like what Todd wrote today.
    It's been interesting to see the contrast of those who learned
    geology from books or from experience. The thing about rocks, as
    opposed to minerals, is that nature wasn't kind enough to supply us
    with neatly categorized specimens. Translucent cryptocrystalline
    quartz is agate if, when and because we (as a society) say it is,
    otherwise it's not. Kevin essentially said this long ago, and he was
    correct. Quartz is quartz, yes. It can be truthfully said that
    amethyst is not really quartz, because of the iron and aluminum that
    colors it - that would be a chemist's take, but geology isn't that
    anal about it - it is a variety of quartz. There are no lines, that
    THIS is agate, and THIS is not (Of course, something that's just not,
    like chysocolla, for instance, just is not). I was out with a
    geologist once and somebody picked up a rock and said, "So, what's
    this?" He said it was a rock. That the Earth gives us an endless
    variety of them, and not everything is or can be categorized.
    Sometimes a rock is just a rock, though it could be analyzed in a lab
    to pin it down. Geology is science, to be sure, but it's also an
    inexact science due to the nature of the planet. I've been reading
    this thread since it just kept bouncing back - all this
    pseudo-science about what agate is. Agate is agate if, when and
    because we (as a society) say it is. It's not a scientific term, it's
    descriptive. 

http://www.donivanandmaggiora.com
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