Another Fancy Yellow Diamond with Blue Fluorescence Question

[simplysplendid]

Hi,

I've read some of the older threads here which mentioned that medium blue fluorescence on a fancy yellow diamond is not desirable as it makes the yellow appears lighter.

I have several fancy yellows which has no fluorescence and I recently purchased one that has. I noticed that the colour wasn't any lighter than those without fluorescence in the store and it seems to have a greenish tinge. It has the green tinge under the jeweler's halogen lighting and even under daylight. Despite reading about the negative effect of medium blue fluorescence, I purchased it as I was quite intrigued by it.

FCD experts, could it be possible that the medium blue fluorescence makes the fancy yellow diamond appear slightly greenish? It was graded by GIA as 'Fancy Yellow". Thank you!

 

[y2kitty]

Re: Another Fancy Yellow Diamond with Blue Fluorescence Ques

Yellow + blue = green. I have a picture that illustrates this. Let me find it.

ETA: This is a fancy light yellow with medium blue fluorescence and I think it looks a little green. So do some of the side stones.

 

[simplysplendid]

Re: Another Fancy Yellow Diamond with Blue Fluorescence Ques

Hi Herekittykitty, thank you..

I read somewhere the blue fluorescence on fancy yellow does not make it look green, I might have been mistaken.

 

[Tom Gelb]

Re: Another Fancy Yellow Diamond with Blue Fluorescence Ques

Hello,

It is pretty common for a yellow diamond to display blue fluorescence. The Summer 2008 Gems and Gemology article about yellow diamonds reports that of the almost 25,000 diamond in their study about 25% showed fluorescence, and 92% of these were blue. Thus it is not uncommon at all. I am not an expert in desirability, only in grading and evaluation, so whether it is more or less desirable is not really in my purview.

It has been my experience that many of the more greenish, but still graded as yellow, diamonds do indeed have some blue fluorescence. This is not the only way diamonds can appear more greenish, but it does happen. Not all of these diamonds appear greenish, and not all greenish diamonds have blue fluorescence. I have not heard of an instance where the greenish cast devalues a diamond, but a fancy colored diamond is worth what you can sell it for, so it may depend on the individual buyer.

I would be happy to answer any more of your questions. Since I usually do not post in this forum I would mention that my background is pretty extensive in colored diamonds. I worked at the GIA for almost 15 years, and focussed on colored diamonds for all but two of those. When I left GIA in 2008 I was the manager of the colored diamond department in GIA's New York office.

Good luck,

 

[simplysplendid]

Re: Another Fancy Yellow Diamond with Blue Fluorescence Ques

Thanks herekittykitty for the picture, that's a very pretty ring!

Thanks Tom, for the information. It's great to get an input from an expert.I went to revisit some of the threads that I have read and there were views that that blue fluorescence would make the diamonds look whiter, so it is less desirable. It is good to know that blue fluorescence can also have the effect of making a fancy yellow look greenish. Mine's like that. Not only it does not look whiter but somehow the colour looks quite rich and it is really an interesting stone. When I first saw my diamond before I saw the certificate, I already noted a greenish tinge.

 

[kenny]

Re: Another Fancy Yellow Diamond with Blue Fluorescence Ques

Hello,

It is pretty common for a yellow diamond to display blue fluorescence. The Summer 2008 Gems and Gemology article about yellow diamonds reports that of the almost 25,000 diamond in their study about 25% showed fluorescence, and 92% of these were blue. Thus it is not uncommon at all. I am not an expert in desirability, only in grading and evaluation, so whether it is more or less desirable is not really in my purview.

It has been my experience that many of the more greenish, but still graded as yellow, diamonds do indeed have some blue fluorescence. This is not the only way diamonds can appear more greenish, but it does happen. Not all of these diamonds appear greenish, and not all greenish diamonds have blue fluorescence. I have not heard of an instance where the greenish cast devalues a diamond, but a fancy colored diamond is worth what you can sell it for, so it may depend on the individual buyer.

I would be happy to answer any more of your questions. Since I usually do not post in this forum I would mention that my background is pretty extensive in colored diamonds. I worked at the GIA for almost 15 years, and focussed on colored diamonds for all but two of those. When I left GIA in 2008 I was the manager of the colored diamond department in GIA's New York office.

Good luck,

Hi Tom.
I believe there was much discussion if not controversy on the UV content of the light that GIA uses for grading the color of white diamonds precisely because of fluorescence.

Do you know if the light GIA uses to grade the color of FCDs is free of UV?

 

[kenny]

Re: Another Fancy Yellow Diamond with Blue Fluorescence Ques

Tom, I forgot to state the reason I'm asking about this ...
UV in GIA's FCD color-grading light may add thousands of dollars or much more to the value of FCDs.
Here's why:

Blue is one of the most expensive diamond colors.
A blue FCD that is a hue grade or two more-saturated is worth MUCH more than a weaker blue.
If blue fluorescence makes a yellow FCD look green the value goes way up.

The most common color of fluorescence is blue.
I think you can see where I'm going with this.

If I was selling FCDs I would want GIA to have as much UV in their light as possible.
If I was buying FCDs I would want no UV so I don't overpay.

 

[LD]

Re: Another Fancy Yellow Diamond with Blue Fluorescence Ques

I think if you look back at the threads you'll find that those who joined in said that it's impossible to predict how fluor will affect a FCD. There are so many variables that it's impossible to predict if it makes a difference. In some cases it will make a diamond appear more whiter, in others it makes no difference at all. With a white diamond you can be confident that it will hopefully make a diamond look whiter and perhaps have a blue tinge in sunlight (assuming the fluor is blue). However with FCDs it's dangerous to even guess as it's purely that, a guess!

I gave an example in one of the threads of a yellow diamond I had with blue fluor. The fluor made the diamond look quite white in some lights and the yellow much less obvious. Clearly, as I wanted a yellow diamond, I didn't like this.

Having said that I have a number of FCD and that is the first and only time that I've not liked how the diamond looked because of fluor. In all other cases, I love it.

 

[Tom Gelb]

Re: Another Fancy Yellow Diamond with Blue Fluorescence Ques

Tom, I forgot to state the reason I'm asking about this ...
UV in GIA's FCD color-grading light may add thousands of dollars or much more to the value of FCDs.
Here's why:

Blue is one of the most expensive diamond colors.
A blue FCD that is a hue grade or two more-saturated is worth MUCH more than a weaker blue.
If blue fluorescence makes a yellow FCD look green the value goes way up.

The most common color of fluorescence is blue.
I think you can see where I'm going with this.

If I was selling FCDs I would want GIA to have as much UV in their light as possible.
If I was buying FCDs I would want no UV so I don't overpay.

Hi Kenny,

Sorry for the delayed response. The GIA uses the same type of lighting and bulb for colored diamond color grading as it does for white stones. An important difference is the distance from the light that the diamond is viewed. In colored diamonds it is either 18 or 24 inches (I will check), whereas in white stones it is closer. Thus the effect of UV would be less. I would state the GIA's argument (which I believe also) that a daylight equivalent bulb, with approximately the same spectrum of light as diffused sunlight, makes the most sense for grading color. There are very few UV free light sources outside of a laboratory setting, so while one could get a UV free grading, they argue (and again I agree) that this would not reflect the color that most consumers would ever see. But I would rather not get into a long discussion here, especially since I am likely in the minority in the forum.

Please remember that I am not an expert in pricing, but given my experience it is quite rare for blue fluorescence to move a yellow diamond into the greenish yellow hue (certainly less than 1%, maybe less than 0.1%). Also it is my understanding the yellow and greenish yellow diamonds are approximately the same value (but again I am not a pricing expert).

Also, the vast, vast majority of blue diamonds are inert to long wave UV. I do not remember ever seeing a type IIB blue diamond react to UV that was a natural diamond (I have seen some synthetics do this). Thus the UV content of the lighting when grading these diamonds is irrelevant. There are other type of blue diamonds. The type Ia :"argyle" blues (almost always graded as Violet) usually have a yellow reaction to long wave fluorescence. I am unsure what, if any, this reaction has to the resultant color of these diamonds. I do not ever remember an instance where the GIA graded a diamond as even faint blue due to it's fluorescent reaction.

I hope this helps answer some of the questions.

Good luck,

 

[kenny]

Re: Another Fancy Yellow Diamond with Blue Fluorescence Ques

Thanks much for the clarification!

 

[TristanC]

Re: Another Fancy Yellow Diamond with Blue Fluorescence Ques

I chanced upon this thread prowling for information on FCDs and I found it extremely interesting.

Funny thing is, I just did up my new place this year, and one decision we made was to use warm coloured LEDs almost exclusively.

This means there will be zero UV light at home each night so long as I don't turn on some flourescent tubes in ceiling coves (these are just for mood lighting). I guess as long as the TV

LEDs are actually picking up quite a lot, so if this trend continues, it might actually be that there will come a time in the next decade when GIA might reconsider this test again.

Now if only I had a FCD collection with a flourescent heart shaped gem to look at in various lighting conditions...