[Jewelry making - Article 00365] - Re: [Orchid] Disputing all opal cracks theory

[Derek]

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    The reason I say that opal can crack when it's old and being
    repolished is that I've had it happen completely without
    explanation, even under sufficient water to keep it flushing. 

    Upon father reflection I realized a couple of things. First that
    since opal that needs repolishing is more than likely a ring or
    bracelet stone that's been abraded through wear. It has by
    definition had a bit of a tough time of life or it wouldn't be
    scratched to begin with. That's the exact reason it needs
    repolishing. Had it not received rough wear, it wouldn't need
    repolishing. The other part of that is that when it needs
    repolishing, obviously it's because it's cloudy and you can't see
    through that cloudiness. It seems very possible that there are
    problems underneath that cloudiness that a person polishing wouldn't
    know about because you can't see through it until it's somewhat
    better polished or unless you wet it. Of course then the water gets
    into and fills the crack temporarily  which is why you can see
    through the clouds. Then when it dries again, the crack might
    reappear but you can't see though it again. Even a tiny crack could
    cause a big problem. As all of us who have cut opal know, once a
    crack begins somewhere, it will sooner rather than later extend
    across the stone unless that part of the stone where the crack is is
    removed. Actually one question has always kind of struck me and is a
    little difficult to explain. Why is it when a small crack is removed
    from a stone the rest of the stone tends to stay stable but when the
    crack is left it seems to inevitably want to extend? The part of the
    stone that remains uncracked, or uncrazed if you will, should not
    seem to be affected by a crack that's not reached there whether you
    remove the crack of leave it. It's possible that a weakness or
    instability actually remains whether you've removed the crack or
    not. 

    Incidentally, I believe it was Charles who made a distinction
    between cracking and crazing. To me that's a distinction without a
    difference. I know it is semantically the same, dictionary-wise. At
    least according to the Oxford English dictionary. I wonder what the
    difference in stone speak would be. 

Derek

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