Overgrading of blue fluorescent diamonds

[kmoro]

In today’s wander through various diamond articles, I found this one.

I had no idea that diamonds were graded in a UV environment ...this article has an example where a strong blue fluorescent marquise was graded four and half grades higher than when viewed with a UV filter (no UV light). Four and a half!

So many times we hear stories of diamonds where colour does not seem to have been graded correctly. I wonder how often UV light during grading is to blame?

Anyway, I thought this article was interesting ... it’s a three year old PS article stemming from a 2010 article ... I assume there have been no changes to the lighting used when grading diamonds since this article was written. I really love the pictures of the diamonds side-by-side, where they were all graded “I” colour and then have glaring face-up differences in tint.

ETA .... the link, lol ...https://www.pricescope.com/articles/blue-fluorescent-diamonds-color-grading-issues

 

[the_mother_thing]

I really love the pictures of the diamonds side-by-side, where they were all graded “I” colour and then have glaring face-up differences in tint.

Diamonds are color-graded face down, are they not?

I know I’ve looked at several diamonds where the face-up color had me puzzled when comparing them to like-graded ‘colors’, but knowing they’re graded face-down, it kind of makes sense/isn’t surprising the face-up color can vary to some degree. I do wish there was more consistency in the appearance of color face-up.

 

[Karl_K]

The discussion from that time:
https://www.pricescope.com/communit...f-blue-fluorescent-diamonds-revisited.219341/

 

[Karl_K]

There is another super long thread on the subject that is more recent but I dont have time to hunt it down right now.

 

[the_mother_thing]

There is another super long thread on the subject that is more recent but I dont have time to hunt it down right now.

Thinking about this one?

https://www.pricescope.com/community/threads/fluorescence-ags-question.245367/

 

[Karl_K]

Thinking about this one?

https://www.pricescope.com/community/threads/fluorescence-ags-question.245367/

That's a good one but I was thinking there was another 20+ page thread from a few months ago but maybe I am remembering wrong.

 

[OoohShiny]

That's a good one but I was thinking there was another 20+ page thread from a few months ago but maybe I am remembering wrong.

I think I know the one you mean - is it the one where Garry is disagreeing with another Trade person on the correct wavelengths to use to maximally excite (and therefore accurately assess) fluor?

 

[kmoro]

Diamonds are color-graded face down, are they not?

I know I’ve looked at several diamonds where the face-up color had me puzzled when comparing them to like-graded ‘colors’, but knowing they’re graded face-down, it kind of makes sense/isn’t surprising the face-up color can vary to some degree. I do wish there was more consistency in the appearance of color face-up.

Yes - graded face down - and in the face down photo where they are in UV grading light, they all look the same.

 

[Rockdiamond]

It wasn't just Garry- this article was debunked thoroughly.
In general- color grading is by no means an exact science- and without a doubt fluorescence complicates it.
As does cut.
Some K colors look really tinted and others don't. Some D colors look whiter than others.
No matter what lighting is agreed upon, these variations will still exist.
We recently re-submitted a stone with a 2010 report- grading it as an L color. This time GIA called it K, Faint Brown. Same diamond. I chalk this up to the fact GIA has gotten so much busier- and as I said- it's not an exact science.

https://www.pricescope.com/articles/blue-fluorescent-diamonds-color-grading-issues