CIBJO releases Gemmological Special Report: considers process of separating measurable facts from opinion; See Gemological Articles below.
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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Sat Nov 26, 2011 5:51 pm 
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mikko wrote:
People want to use oil instead of modern chemistry because it's traditional and widely accepted.


Times are changing and people too

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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Sat Nov 26, 2011 9:31 pm 
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Yes, but from a consumer perspective, oil is "closer" to natural or is considered a minimal treatment.

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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Sun Nov 27, 2011 12:34 am 
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goldberg wrote:
thank you, Mikko

but their is no organic material in these non-hydrophane opals (no oil, wax, resin..... or other stuff), these opals are not impregnated, not coated

The method works on a molecular level, the increase of transparency of some opals is caused only by additional deposition of some silica in the pores (thus lowering the difference of the index of refraction particles/pores)

How should this be declared?



Could this "silica" in the pores be called a glass filling?


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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Sun Nov 27, 2011 5:03 am 
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Barbra Voltaire wrote:

Could this "silica" in the pores be called a glass filling?


As Barbra mentioned, adding silica to a silica based gemstone. With a method not described for us to understand or comment on respectively. Alternatively irrespective of the method, it would still be considered treating the gemstone, since it is no longer in its original state other then polishing or faceting said material.

"Glass Filled Opal" Seems like the best option of disclosure then thus far no? Unless you have more to share about the methods and materials with which you apply to these opals.


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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Wed Nov 30, 2011 6:06 pm 
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Barbra Voltaire wrote:
Could this "silica" in the pores be called a glass filling?


As you know, a glass is by definition an (x-ray-) amorphous material without a long-range periodic order.

In the case of the treatment I have no idea in which form the silica really exists. Is it crystalline or not?
(analysis is necessary)

The second question is when it should be called a "filling"?

Can it be in the range of per mill? Is it not a "filling" until it reaches some percent?
Where (regarding the volume fraction) a filling starts????

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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Wed Nov 30, 2011 6:41 pm 
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empress wrote:
Yes, but from a consumer perspective, oil is "closer" to natural or is considered a minimal treatment.



You should state that is STILL "closer", sooner or later it will be done with a long-time stable resin with the right index of refraction......... :D

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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Wed Nov 30, 2011 6:51 pm 
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Sounds a bit like how they created those "composite" emeralds that shook the markets confidence.

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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Wed Nov 30, 2011 6:53 pm 
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goldberg wrote:
Where (regarding the volume fraction) a filling starts????


Upon application.


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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Wed Nov 30, 2011 6:59 pm 
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allen wrote:
Sounds a bit like how they created those "composite" emeralds that shook the markets confidence.


You can imagine, what can be done will be done!

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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Wed Nov 30, 2011 7:01 pm 
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JB wrote:
goldberg wrote:
Where (regarding the volume fraction) a filling starts????


Upon application.


Is there a gemological definition of a "filling"?

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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Wed Nov 30, 2011 7:56 pm 
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Sure, glass filled rubies for one. But whether it's Gemology, Dentistry or baking, you're "filling" something in that wasn't there to start with. It's a treatment.

Name it what you want.


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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Thu Dec 01, 2011 3:28 am 
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goldberg wrote:
As you know, a glass is by definition an (x-ray-) amorphous material without a long-range periodic order.

In the case of the treatment I have no idea in which form the silica really exists. Is it crystalline or not?
(analysis is necessary)

The second question is when it should be called a "filling"?

Can it be in the range of per mill? Is it not a "filling" until it reaches some percent?
Where (regarding the volume fraction) a filling starts????


5.10. Coating
a layer of a substance spread over the surface, or part of the surface, of a stone for protection, colouration or decoration; a covering layer.

5.18. Filling
to occupy the whole or part of a cavity (5.8), fissure (5.19) or fracture (5.22); to pervade; to spread throughout; to occupy completely; make full.

5.27. Impregnation
to fill throughout; saturate.

5.31. Modified gemstones and organic substances
gemstones (5.23) or organic substances (5.35) changed in form or character by means of other than cutting and polishing, (4.1.3).

5.42. Stability
a measure of the ability of gemstones (5.23) and organic substances (5.35) to maintain their appearance.

5.46. Treated
the prefix ‘treated’ is added to the name of gemstones (5.23) or organic substances (5.35) whose appearance has been altered in a manner that requires specific information, sometimes also preceded or replaced by a description of the technique used. The declaration of such modifications is detailed in clause 4.7.


Take your pick, there are the definitions. "Silica Filled/Coated Treated Opal"

Any other definitions you need clarified, the blue book is quite freely available.


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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Thu Dec 01, 2011 7:32 pm 
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treatment of Ethiopian opals (found on youtube, of course not done by me and in my opinion (as an opalholic) the worst thing I have ever seen:

http://www.youtube.com/watch?v=JXcJwnHroC8

it is an Austrian opal-dealer: http://www.opal-auctions.at

Have fun!!!

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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Thu Dec 01, 2011 7:57 pm 
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empress wrote:
Yes, but from a consumer perspective, oil is "closer" to natural or is considered a minimal treatment.


There is an interesting page of Richard W. Hughes:

http://www.ruby-sapphire.com/catfights.htm

Roy

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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Thu Dec 01, 2011 8:21 pm 
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I have seen some shady practices on opals here in AU myself, seen in some of the lapidary clubs, sugar solutions, acid baths, cooking in oil.. all sorts.


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