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Andamooka opals?

hi everyone, especially those who are opal oriented,

today i was on autopilot. i had an opal that had nice play of
color and a light chocolate brown body color. i looked at it and
said to myself, ‘that looks nice, i’ve never seen one exactly
like this, i bet it is treated.’ without thinking i put it in
the cool sparex with the days work (i had mounted it in a ring)
and pulled it out and it didn’t look so nice anymore. i then
recalled ‘oolitic’ opals that are treated with sugar water and
then sulphric acid. i called my opal dealer and he said that it
was most likely ‘andamooka’ opal from my description. he also
described the same oolitic treatment. he said it was possible to
try to retreat the stone, but not usually. it came oout of the
pickle with some of the play of color, but an ugly, lighter
grayish brown. if i wet the stone, the play of color all but
disappears and the nice brown body color returns. not
acceptable.moral of the story: pay attention and don’t put
suspicious opals in the pickle.

my questions to all of you out there is this. does anyone know
of someone who does this type of treatment or would descibe the
process to me, or does anyone know where i may purchase a 7X5
(slightly larger) oval opal of the above description. mosaic, or
harlequin play of color, nice med high cab.

thanks for any help,

geo fox

George, Paul Downing in his book “Opal Cutting made Easy” talks
about the treatment of the matrix using sugar “batter” and
sulfuric acid. one of his comments is that the matrix opal shows
very little visible fire without treatment. So don’t throw the
stone away it may be possible to retreat it.

If you can’t run down a copy of the book let me know and I will
copy out the pages with instructions for you. Ed Ward

Geo Fox, you sweet fellow, you:

I know I’ve seen something about that damn sugar treatment for
opal, but I can’t remember where right now, and I’m up to my ears
in other stuff, so I can’t look; I hope someone else can help
before I find it, which will be when I move in a month and unpack
my books. Maybe in a book by Kurt Nassau you’ll find it.
Something about sulfuric acid and sugar. May be easier to buy a
new one. Now for the lecture: never, never, never put any opal
in pickle or even really hot water or grease. They are often
fragile. My ex-mother-in-law (and since the divorce, venal
person that I am, I’m glad) put the white Australian opal we cut
for her in hot dishwater and ended up with a brownish clear opal
with no play of color. Opals, I understand, can be a little
porous and take on the water or grease with bad effects. Never
put one in an ultrasonic or pickle or anything but water. Don’t
use hot water. Clean with a tooth brush and water, a little mild
soap if needed. Mount in a bezel from the back and cushion the
mounting with epoxy against the bezel applied before the stone
goes in as a cushion, not a glue. Use prongs from the back,
gently tightened — if they don’t go all the way down you can
use a little epoxy under them, they are on the back of the stone,
who will see? Opal is real expensive these days and doesn’t last
forever ( as someone eventually abuses it ), be gentle with it,
it is one of the glories of nature. HTH. Took you to the
woodshed, geo.

As to the Andamooka Opal, also known as Matrix Opal, also known
as Sugar Treat Opal the treatment for it is as follows. Take an
old ceramic lined crock pot, put in sugar [preferably fructose]
and water heat it up on low. Add as much sugar as will disolve
in the water, and then a little more [super saturated solution].
Put your opal in this solution [pre heated to avoid thermal
shock] and heat on low for 6 hours. Let cool to luke warm, do
not let it cool completely before removing opal or it may turn
to rock candy. Remove opal, rinse slightly, do not wash, wipe
off stone. Dispose of sugar solution, and clean crock, wipe out
dry. Next step must be done outside with all precautions taken
that you can, rubber gloves, goggles, ect. put stone back in
cock, add cold sulphuric acid to well cover stone [ acid must be
at least 90% pure, battery acid will not work] heat for 7 hours
on low, let cool COMPLETELY, remove stone. This last is
dangerous stuff. Hot Sulphuric of this strength will cause
SEVERE burns if it comes in contact with skin, also if God
forbid you do spill it on you wipe it off, BEFORE you wash, as
water will react with it by an increase in heat to upwards of
600 degrees before it dissipates the acid.

I’ve done this a several dozen times without harm to my person,
but it is not a walk in the park, and precautions must be taken,

If anyone wants to see what the finished product is like I have
a large selection of Andamooka Matrix opals on my site listed
below. Hope this helps, though I would hate to go
thru the entire process myself, for one stone.

Sincerely, Ron Schanfish - Noema Gems

hi jesse,

yes, customers can try and make one feel even guiltier than one
already is. one just has to stand up and be accounted for and
all should be well.

i knew better for sure, in this case, to put this particular
type opal in the pickle. but i must point out i’ve put literally
thousands of the white australian garden variety opals in the
ultrasonic and pickle intentionally, with no ill effects.
believe it or not, this is the only chemical mishap i’ve ever
had with an opal. this is anecdotal for sure, and your warnings
are certainly in the textbooks, but the prospect of toothbrush
cleaning that many jobs is a dreadful one.

normally, when i’m PAYING ATTENTION, i do not put unusual or
expensive opals in the ultrasonic or pickle.

can i come out of the woodshed now?

best regards,

geo fox

Sounds silly but I once recut and opal that had a brownish base
and good color and was left with no color. So sitting on my bench
was a Coke and so I got the bright idea it had both acidic and
lots of sugar and heated it and then let sit all night and low
and behold the color was back. But I will never sell this peice.

Does anybody out there know of a reference work, chart form
preferably, which lists all major stones and the recommended/not
recommended cleaning methods for them? Thanks in advance.

 llists all major stones and the recommended/not recommended
cleaning methods for them?

I seem to recall a table in the Rio Grande Gems and Findings
catalog, if you have that! Seemed pretty comprehensive,
although does not go into detail about the whys and wherefores.


Dave Sebaste
Sebaste Studio
Charlotte, NC (USA)

   Does anybody out there know of a reference work, chart form
preferably, which lists all major stones and the
recommended/not recommended cleaning methods for them? Thanks
in advance >>

GIA has a great one I had it laminated and hung it on my wall at
the shop.

Mark P.