Fluorescent Diamonds - some thoughts after my experience

[FB.]

It's no surprise that I've recently been analysing strongly fluorescent diamonds in some detail.

The general beliefs seem to be:

In the colourless grades (D-F), more than faint fluorescence is bad.
In the slightly tinted grades (I-J and possibly slightly lower colours), some fluorescence is beneficial because the colour is complementary to blue and makes the diamond appear whiter.

I plan to put a torpedo into the latter idea, with my own observations and some reasoning.

In strong light, almost all well-cut diamonds reflect so much light that they "face-up" colourless, due to the very strong light return. Even I-J can look colourless.
Even casual glances at the side-views of I/J stones don't show much (if any) colour in strong light.
Therefore, I don't see that fluorescence adds anything to the colour grade in bright light.

In low light, I seem to notice diamond body colour much more easily - even face-up. I can usually tell a H from a D when mounted and possibly distinguish G from D.
This is where the lower colours would most need the "complementary" blue colour of the fluorescence to offset the yellow body colour. But diamonds don't fluoresce in most low-light situations.
Therefore, although fluorescence would improve the colour grade in low light, the lack of light means no fluorescence and no ability to improve the colour.

As I see it; only in mediocre-cut-grades, of slightly-tinted-colour diamonds, in bright light, would fluorescence manage to make an improvement to the perceived colour.

I'm not saying that fluorescence is bad. I'm just saying that I can't see how it is as beneficial to low colour stones as the price premiums suggest - except at the point of sale, where a jeweller can pass-off an uncertificated fluorescent J as perhaps an H.

Regards
FB

 

[strmrdr]

Go outside on a cloudy day, you know one of those days where it is neither dark nor bright.
Look at a stone with fluorescence and you will understand.
Stand within a few feet of a window that is letting in dispersed sunlight and you will understand.
Take a UV meter and walk through your house and you will understand.
:}

 

[strmrdr]

That said I do have trouble with anyone saying a well cut J or strong blue fluorescence makes a stone like an H...

It is still a J because the body color is J!
Body color is just somewhat related to the actual diamond color you see face up it is not a direct relationship but the price is based on body color.

 

[FB.]

strmrdr (Karl)

I'm not sure of the point you're trying to make in your first posting - and how that relates to fluorescence being able to improve the colour of a well-cut diamond.
Can you clarify.

 

[strmrdr]

Date: 8/14/2009 4:26:55 PM
Author: FB.
strmrdr (Karl)


I'm not sure of the point you're trying to make in your first posting - and how that relates to fluorescence being able to improve the colour of a well-cut diamond.

Can you clarify.

You have been doing your homework,,, my first post was adding to your homework by mentioning lighting you didn't mention.

 

[FB.]

Ah!
Thanks.

 

[I Love Carats]

What is the issue with D-F colors with strong blue Fluorescence? I found an F SI2 Ideal with Strong Blue that is clearly much more inexpensive than other diamonds of the same stats and less Fluor.

 

[FB.]

I'm not sure why D-F with strong fluorescence is always labelled as bad. Maybe one of PS's experts can give a good reason.

I've seen several "theories" mentioned. Draw your own conclusions.

1.
The fluorescence can improve the colour grade in the laboratory, due to some UV being given off by the grading lamps. You might buy a stone graded "E" colour that's really "F" colour when viewed in light that contains no UV.

2.
Fluorescence can be caused by substitution of carbon atoms within the diamond structure. Therefore, the diamond is less "pure".

3.
There are not enough strongly fluorescent diamonds available, so people are diverted away from what would be difficult to supply in large quantities, if fluorescence became fashionable again.

4.
Some diamonds at the stong/very strong end of the fluorescence spectrum are reported to go cloudy/oily/milky/hazy.

I've seen some diamonds that contain individual inclusions that fluoresce - including one with a fluorescent cloud under the middle of the table (but only the cloud inclusion was fluorescent and not the whole diamond). Perhaps if fluorescence is caused by clouds in diamonds, then that is the cause of murkiness. Perhaps less clouds mean less haziness?

Here's a pic of a GIA-cert, 1.1ct, D, VS1 pear with very strong fluorescence. It only has a few inclusions - a small feather under a prong, a small feather in the pavilion, and a small crystal/cloud merging together under one of the star facets. The stone is 100% eye clean. It doesn't go hazy - so you can still see into the stone - but it does take on a strange appearance when fluorescing and when viewed up close.

 

[WinkHPD]

Some people consider fluorescent diamonds bad because they don''t know the history.

When I entered the business we paid a premium on all colors that exhibited strong blue so long as they were not overblues. Depending on how extraordinary the diamond looked in fluorescent light, the premium could be as high as 15%.

During the investment craze in the late 70''s people who had been shoe clerks the week before were now selling "investment" diamonds. Since they did not know or understand fluorescence they could not explain it, not could their bosses be bothered to train them.

Also large stores such as Zales were now buying bazillions of diamonds at a time and could not check all of them to see if any of the fluorescent diamonds were overblues. They then made it a requirement to their vendors that the stones not have fluorescence. Thus it came to pass that fluorescence was deemed as bad by those who did not know, and since so few of the trade really knew or even understood the issue it became to be accepted as gospel.

Thankfully, with the advent of intelligent conversations on sites such as this, it is becomming slowly understood that fluorescence is not a desease, but a factor. Like Cindy Crawford''s beauty mark, some like it, some don''t, but each is now allowed to choose what they like.

Thus sayeth Wink as he goeth out the door to have dinner with his lovely wife!

Wink