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Boulder opal

I’m just curious. Are there many people here using boulder opal?
If so, what kinds of cuts do you prefer? How many are using the
matrix type with color flashes, what about larger seams accented by
matrix? What kinds of sizes are you using? Etc.

I just picked up some old boulder rough and I am wanting to cut to
meet the market need.

Derek Levin

 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” .


We sell boulder opal almost exclusively. We sell all types, however
we don’t use much inexpensive material. Generally we look for pieces
that have all opal on the top, usually strong blue/greens and
purples. We would probably buy more red material but these days a lot
of it is out of our price range (which isn’t small). This does not
mean that we are interested in purchasing any however. We have one
source that we use exclusively for boulder material.

Daniel R. Spirer, GG
Spirer Somes Jewelers
1794 Massachusetts Ave
Cambridge, MA 02140

I personally use only a few select pieces to make jewelry but that
being said, I look for stones that reach out and grab your
attention. I like the so called “natural doublets” that come from
following a seam and I like stones that the opal slashing through
them either makes a picture or is striking. I then design a piece
around the stone. Two good examples come to mind. I have one stone
thats matrix itself is unremarkable, just simple gray stone. The
opal though is fantastic and cuts through the dark gray stone in a V
that makes it look like a dark mountain surrounded by a sunset. The
stone is about 50 x 70. Another stone I have is in a dark wood
colored matrix with swirls in the matrix that make it look like well
polished mohogany. Through this stone is laced thin purple fire that
is so bright it looks like a lightening bolt. This too had its own
setting designed for it. These are the kind of stones that I look

Alicia Miller

Hi, I love to set nicer larger pieces of boulder opal. The shape
doesn’t matter as I build each piece to the stone. I also do well
with better quality ring sized gems.

Let me know what you have.