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Andamooka opal


#1

I am wondering about the on Andamooka opal. I am
slightly familiar with the material, and did not think that all of
it was treated. Can anyone verify this one way or the
other?


#2

Dear David

Methinks you might have been a little misinformed. Andamooka is the
name of an opal mining town in South Australia, the area around
which produces some very fine opal indeed with much “play of
colour”. This opal is sometimes found in a matrix of pale creamy
colour which when treated may show up some lovely colours lurking
there.

The treatment method consists of soaking in a sugar solution and
then a sulphuric acid solution (or maybe vise versa, can’t quite
remember) which stains the stone black. This process does not affect
any precious opal in the matrix at all as it is not porous like the
matrix. Personally, I don’t think it looks like precious black opal
at all. The only name I’ve ever heard it given is just plain old
"treated matrix".

Since my Pa spent a couple of winters for digging opals at Andamooka
and Ma had fun treating a lot of matrix, I can spot a treated matrix
a mile off.

Renate, Adelaide, South Australia


#3

Renate, thank you for the It basically expands on what I
know. It’s sugar solution first, acid second, turning the sugar into
carbon. I have seen enough of it to USUALLY recognize it easily, but
some of it looks very much like the finest black opal, and at a price
ratio of one to a hundred, I think it is great stuff.

My wife has a pendant which I made for her with a 40 carat piece
several years ago, and it never fails to elicit positive comment when
she wears it. David Barzilay, Lord of the Rings


#4

In addition to the sugar and acid treatment, you should know that most
Andamooka matrix also needs to be treated with opticon, as it is
fairly porous and will not take a good polish otherwise. –

Lee Einer


#5

When opticon is used as a treatment does it permeate the surface.
Is there a method to force the opticon into the stone? Can someone
who has used opticon satisfactorily describe the process? Thanks KPK


#6

Thanks to David for the photos of treated opal matrix. The obvious
difference suddenly came to me - it has everything to do with the
transluscency of the material. Precious opal of whatever type is
always transluscent whereas the matrix is quite opaque and the “play
of colour” is merely on the surface. You can look “into” precious
opal. Hope that makes sense.

Lee Einer - I have a couple of boxes full of lovely treated opal
matrix with vitreous lustre that has never been treated with
opticon. I admit to knowing nothing about opticon in fact. Is this
something like an epoxy resin and how is it generally used?

Regards, Renate


#7
When opticon is used as a treatment does it permeate the surface.
Is there a method to force the opticon into the stone?  Can
someone who has used opticon satisfactorily describe the process?
Thanks KPK

All, Opticon is only one of many liquids that will readily absorb
into other materials. From window repair to turquoise stabilization
these liquids are used. Process for application of these liquids
vary, but in general they require that the object to impregnate be
clean and dry prior to being subjected to the liquid. In the case
of glass a vacuum is not used. In rock stabilization the best
treatment is to immerse the rock in the liquid with a vacuum pull
from the bottom of the container. That will pull the liquid into
the rock. In order for an item to accept the liquid the item must
be porous. A solid item wil not accept liquids because there is no
entry available for the liquid. Some of the liquids like Opticon
require a second treatment in a chemical that hardens the first
chemical, others can be hardened with ultaviolet light. Be advised
the stabilization of rocks by impregnating them with liquids that
can be hardened has progressed very far past the Opticon stage.
Many new chemicals are being used on emeralds, rubies, turquoise and
almost any rock that can be enhanced by stabilization.

Gerry Galarneau


#8

Hi, All-

I also have purchased Andamooka matrix, and what I have purchased is
porous enough that it needs surface treatment in order to take an
acceptable polish. I have spoken with dealers in this rough who have
confirmed that this material normally requires such treatment in
addition to the sugaring and acid bath.

If you all have worked Andamooka matrix which does not require
Opticon (basically a two part epoxy) treatment, well, I’m happy for
you. But I don’t believe that is the norm for this type of rough. –
Lee Einer

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