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: Thu Dec 01, 2011 9:31 pm 
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Quote:
There is an interesting page of Richard W. Hughes


I had intended to look for this, or other references, for you and got side-tracked.

My reference was about "consumer" preferences for untreated stones and oil being perceived as a "traditional" treatment and therefore more acceptable.

I do have a question, though, you seem to be "up" on all this stuff so why are you asking if there are thresholds for calling something an enhancement or filling? It's sort of like " it depends on what the meaning of the word 'is' is..."

:lol:

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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Fri Dec 02, 2011 5:15 pm 
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I do have a question, though, you seem to be "up" on all this stuff so why are you asking if there are thresholds for calling something an enhancement or filling?


I've just asked out of curiosity, maybe this is precisely defined and I simply should know it.
It had nothing to do with filling, enhancement, treatment....

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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Fri Dec 02, 2011 9:25 pm 
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Esjayp provided a reference that seems to be clear that it's about "if" rather than "how much."

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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Thu Feb 16, 2012 5:02 am 
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Update:

Before christmas some treated opals were sent to a gemological laboratory for testing.

Results:

Values for density and index of refraction are in the range of untreated opals.

By IR-spectroscopy the treatment could be identified, because some unusual absorption bands typical for organic molecules could be found in the spectra.

Furthermore, under short UV a bluish-white fluorescence was visible.

It is planned to publish detailed results about treated opals from Ethiopia in Spring.

Pinfire - Gems & Colloids

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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Tue Mar 20, 2012 10:33 am 
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I think what people are saying is that if ANY material has be introduced into the opal (or any other gem for that manner) no matter how little it is and it changes the appearance and or durability then the gem should be stated to be treated and the method (Filling, diffusion, etc.) should be disclosed.

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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Tue Mar 20, 2012 12:03 pm 
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goldberg wrote:
Quote:
I do have a question, though, you seem to be "up" on all this stuff so why are you asking if there are thresholds for calling something an enhancement or filling?


I've just asked out of curiosity, maybe this is precisely defined and I simply should know it.
It had nothing to do with filling, enhancement, treatment....

There may be differences between legal and ethical requirements for gem treatment disclosure. As far as I know, the U.S. Federal Trade Commission is the only government entity that sets forth specific disclosure terms. But in operating my own business I disclose any known or suspected treatment per the AGTA's treatment Source Directory.

The FTC regulations on gem treatment disclosure are as follows, but it seems to me they allow quite a bit of "wiggle room" for unethical sellers:

§ 23.22 Disclosure of treatments to gemstones.

It is unfair or deceptive to fail to disclose that a gemstone has been treated if:

(a) the treatment is not permanent. The seller should disclose that the gemstone has been treated and that the treatment is or may not be permanent;

(b) the treatment creates special care requirements for the gemstone. The seller should disclose that the gemstone has been treated and has special care requirements. It is also recommended that the seller disclose the special care requirements to the purchaser;

(c) the treatment has a significant effect on the stone's value. The seller should disclose that the gemstone has been treated.

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 Post subject: Re: Water-repellent non-hydrophane opal (Welo/Ethiopia)
PostPosted: Wed Sep 26, 2012 10:08 am 
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Three treated water-repellent opals were analyzed by the "German Gemmological Association" and the results are part of an article written by Dr. Milisenda & Dr. Henn (2012):

Einige Besonderheiten der Opale aus Äthiopien
Some pecularities of opals from Ethiopia

Zeitschrift der Deutschen Gemmologischen Gesellschaft 61/1-2, pp. 43-54

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