[Jewelry making - Article 00408] - Re: [Orchid] Boulder opal

[Don Rogers]

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>      If so, what kinds of cuts do you prefer? 

    Derek, the nature of Boulder Opal is that the Opal decides the cut. 
    Most Boulder is in very thin seams that are not necessarily flat. 
    You end up with some interesting  shapes  and contours.  I
    especially like the "splits" which give you a matched pair of what
    ever shape they end up. 

>      How many are using the matrix type with color flashes, 

    The Ironstone Matrix was my first love in opals.  Depending on the
    opal, it can be an awesome piece or kind of 'Ho Hum'.  One thing to
    remember with the matrix is that the darker the matrix, the better
    the chance of a good finished stone.  This is because the lighter
    matrix is softer and more porous resulting in a very noticeable
    difference between the opal seam and the matrix when polished. 
    Getting a good polish on the matrix is a trick in its own.  You need
    to throw out all you knew about cutting and polishing opal. First,
    you need to plan on getting dirty.  It is nasty stuff to cut as the
    Ironstone leaves everything coated with a rusty colored coating.  So
    don't try to touch up one on your faceting machine that sets on the
    coffee table on your white carpet.  If you have ever seen a rusty
    radiator in a car boil over and leave that rusty brown stain all
    over, well that is what you end up with when cutting matrix opal. 
    Some times it is well worth the mess though. 

    My mentor in Australia who cuts matrix opal gave me the following
    "receipt" for cutting it and getting a good polish. 

    Rough cut it as any other stone. Start the sanding on 400 grit "DRY"
    Progress through 1200 grit still DRY Now go to an expandable drum
    with a resin belts and diamond paste starting at 6000 and going
    through 50,000. Little water in each step and limit the time in each
    step.  Let the diamond do its work to eliminate the under cutting. 
    You can end up with a very good polish and surface using this
    method.  Just plan on getting dirty and "Please wear a mask" . 

Don

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