[Jewelry making - Article 00950] - Re: [Orchid] Opal care

[Rick Martin]

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>      If you're serious about opal, store it dry. That way you will know
>     if a parcel is cracky and not waste your time cutting it. I wait at
>     least 6 mo. to a year before cutting especially if the parcel is
>     newly mined. (old stock is best when you can get it)

    Now there's some advice I can pretty much agree with!  Reading
    Orchid over the past few years I've been amazed by the many accounts
    I've read about unstable opal.  I speak from many years of
    opal-cutting and have experienced very few "cracky" opals in all that
    time.  There are two reasons for that. I buy only Australian opals
    (unless I want an expensive thrill).  And I know my opal dealers and
    expect them to pre-screen any unstable material or replace any that
    goes bad.  There are bad Australian opals, too, but the word gets
    around to reliable dealers quickly.  They don't want cracky opal any
    more than I do. 

    I'm from Idaho and have mined opal in both Idaho and Nevada.  Here's
    the sad truth: most opal from that region is far too hydrated and is
    almost guaranteed to crack.  It makes incredibly beautiful specimens
    but is not commercially useful opal.  There are a few stable stones
    and there are people who claim to be able to stabilize the rough; it
    may be true but I'll let others take the risks.  Anyone who expects
    to successfully sell this opal in jewelry is looking for trouble in
    my opinion (with the exception of properly made triplets from
    Spencer, Idaho material). 

    The only other precious opal I've found to be mostly stable is from
    Piaui State in Brazil.  In the 1970s when rough was briefly
    available, there were two types: alluvial and mined.  Brazilian
    alluvial crystal opal may be the most stable I've ever cut.  It is
    harder than opal from other sources, with over 60% of the pieces
    tested by late opal dealer Bill Maison able to scratch quartz!  It
    also occurred in large gem-quality pieces (up to 4 oz. with a few
    pieces to 10 oz.) and featured unusual and dazzling columnar fire
    patterns.  Unfortunately the mined opal was stressed by heavy
    machinery rumbling over it and would often crack within a year of
    being cut.  I don't know the present status of that location but see
    very little material on the market. 

    I'm wary of Mexican precious opal.  It's gorgeous but very prone to
    cracking, especially the so-called Canterra matrix type.  I've heard
    the same thing about Indonesian opal and the "thunderegg" opal from
    Ethiopia. In general they are all volcanic opals and very few
    volcanic opals are stable in my experience. 

    Storing opals in water is like eating chicken soup for a cold: it
    can't hurt but it probably doesn't help either.  Opal is either
    stable or it isn't. Unstable opal will eventually craze.  I consider
    oiling opal a shady practice, mostly to hide cracks from buyers. It
    actually hurts good opal which needs to "breathe" to keep itself
    hydrated from humidity in the air. That's why you should never store
    opal in a safe deposit box.  The same low humidity that preserves the
    paper in wills and stock certificates will dehydrate even stable
    opals and crack them. 

    If you are lucky enough to own a fine opal protect it from hard
    knocks, too much heat and sudden temperature changes.  Then just
    enjoy it. 

Rick Martin
MARTIN DESIGNS

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