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 Post subject: Colour Change Statement Note
PostPosted: Mon Jul 05, 2010 10:28 am 
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I know that some labs will note that a stone is a colour changer in their memo/cert but does AGTA do the same? For example, it is a colour shift sapphire (strong and dramatic blue to purple shift beyond the usual slight indoor to outdoor lighting shift). Will AGTA make a note saying it is a colour changer/shift?

Actually, I wonder if it should be considered a colour shift rather than a colour change despite the very clear shift because blue and purple are next to each other on the colour wheel. I have seen many vendors call it a colour change though.


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 Post subject: Re: Colour Change Statement Note
PostPosted: Mon Jul 05, 2010 11:05 am 
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hi

AGTA closed the gemological testing center since almost one year
ciao
alberto

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 Post subject: Re: Colour Change Statement Note
PostPosted: Mon Jul 05, 2010 11:17 am 
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Yes, I am aware of their closing but my question still stands because this is about a stone with an existing AGTA cert. It is advertised as a colour change sapphire yet the cert doesn't mention this anywhere. Therefore, I wonder if perhaps AGTA doesn't make that note or perhaps the shift isn't strong enough for AGTA to list it as a colour changer/shifter.


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 Post subject: Re: Colour Change Statement Note
PostPosted: Mon Jul 05, 2010 11:21 am 
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I think Bear Williams could answer this question for you.


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 Post subject: Re: Colour Change Statement Note
PostPosted: Mon Jul 05, 2010 12:17 pm 
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Hi Chrono,

Yes, normally the lab would have made notations/comments on the certs regarding color change, but not color shifts. Your observation about those colors being next to each other on the color wheel is quite true. And a color change does not mean it has be on the other side of the color wheel either. YET, quite often these sapphires will show a clear color shift where it appears to our eye to be making a color change, but some of the hues are shared in both colors. While the vendor can market the stone as a color shift, it should not be confused with C Chg.

Interestingly, more and more businesses and homes are eliminating incandescent lights. It will be interesting to see how it affects those phenomenon stones,, as one may need to carry about a pocket flashlight with them.

Typically, the function of a gem cert is to identify the stone. If the gem is genuine, beautiful or has special meaning and value to you, it need not be judged by what is not said on a piece of paper.

Best, Bear


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 Post subject: Re: Colour Change Statement Note
PostPosted: Tue Jul 06, 2010 7:14 pm 
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"Interestingly, more and more businesses and homes are eliminating incandescent lights. It will be interesting to see how it affects those phenomenon stones,, as one may need to carry about a pocket flashlight with them. "

Or simply buy my "Alexandrite and Color Shift Filter" and you will have no problems. It produces standard daylight and standard incancescent light. $25. I try to stay at least a step ahead of the crowd. :D


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 Post subject: Re: Colour Change Statement Note
PostPosted: Tue Jul 06, 2010 7:31 pm 
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For all those who have not read my praises of the Hanneman Color Change Filter:
It is the greatest; I use it very often and highly recommend it!


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 Post subject: Re: Colour Change Statement Note
PostPosted: Tue Jul 06, 2010 7:55 pm 
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Barbra Voltaire wrote:
For all those who have not read my praises of the Hanneman Color Change Filter:
It is the greatest; I use it very often and highly recommend it!


Barbra recommends a filter :shock: We lesser gemologists use them all the time, but when Barbra uses one, just buy it!

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 Post subject: Re: Colour Change Statement Note
PostPosted: Tue Jul 06, 2010 10:06 pm 
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Bill Hanneman wrote:
" Or simply buy my "Alexandrite and Color Shift Filter" and you will have no problems. It produces standard daylight and standard incancescent light. $25. I try to stay at least a step ahead of the crowd. :D


:? A view through a Chelsea filter can cause various emeralds to become color change stones, yet we know they are not classified as such. Filters should not of neccessity be the arbiter for the C-chg call. A pocket torch is still $1 and the eyeball & brain the judge.

.


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 Post subject: Re: Colour Change Statement Note
PostPosted: Tue Jul 06, 2010 10:11 pm 
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Have you tried using this specific filter Bear?
It's a good one.
I'm not a fan of any other filter, including the Chelsea.


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 Post subject: Re: Colour Change Statement Note
PostPosted: Tue Jul 06, 2010 10:41 pm 
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Barb. Upon your word, I will have a look at it.


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 Post subject: Re: Colour Change Statement Note
PostPosted: Wed Jul 07, 2010 7:56 am 
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Thank you. The vendor has advertised the stone as a colour change sapphire but as the stone is accompanied by an AGTA cert which doesn’t note this, I was merely curious. Would the stone have a premium as a colour changer sapphire (violetish blue to purple) or merely a violetish blue sapphire? Of course, one should buy for beauty and personal preference, but nobody likes to pay more than they should for what it is worth, thus understanding the value is of importance to me. Let’s say that this is a 3.5 ct unheated sapphire.


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 Post subject: Re: Colour Change Statement Note
PostPosted: Wed Jul 07, 2010 7:57 am 
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While on the same topic, has anyone heard of pink to purple colour change sapphires or blue to green colour change sapphires? How uncommon are these?


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 Post subject: Re: Colour Change Statement Note
PostPosted: Wed Jul 07, 2010 9:48 am 
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Pink to purple, no. Green to blue, yes. I have a sapphire of 3+ cts that in some light conditions is blueish green (tourmaline like) and in other steely blue. Mixed conditions it is a strange blue-green tint. How common I do not know, not very I think.
I also have one greenish khaki to purplish red CC sapphire. It is from Tunduru, Tanzania IIRC. One of these vanadium rich stones.

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 Post subject: Re: Colour Change Statement Note
PostPosted: Wed Jul 07, 2010 2:01 pm 
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Chrono wrote:
While on the same topic, has anyone heard of pink to purple colour change sapphires or blue to green colour change sapphires? How uncommon are these?


I purchased a pink to purple Tunduru sapphire a while ago. SO they do exist. How commonly i have no idea.

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