Significant Fluorescence Difference between AGS and GIA Report...what gives?

[OECfan]

Hi everyone,

I am considering a diamond that happens to have both an AGS and GIA report (included as attachments in post). It's a Hearts on Fire Dream cut diamond.
The diamond, which is currently available at a local jeweller, is a trade-up from a client. The client didn't provide the original documentation so the jeweller sent it to GIA for certification and inscription back in 2019. I got in touch with Hearts On Fire and was able to find the AGS report from 2014.
I know branded cuts are marked up, but my jeweller is giving me an excellent trade-in price for my current stone, so this stone would cost me the equivalent of ~$4,500 US.

In reviewing the two lab reports, I've noticed:
- AGS has one of the measurements the diagonal measurements, making the stone seem rectangular while GIA shows the measurement of the sides
- GIA report is missing a few pinpoints shown on the AGS report and has given the diamond a VS2 while AGS graded it an SI1
- AGS says there is negligible fluorescence while GIA says there is strong blue

I'm not too concerned about the difference in measurements and I'd imagine the clarity difference isn't uncommon since GIA didn't report the pinpoints, but in terms of the fluorescence... what gives? Can something happen to a diamond to make it have fluorescence all of a sudden?

I'm also sad that AGS doesn't have a cut grade on this report and so I don't know if this is a true AGS000 diamond. I thought all HOF diamonds are supposed to be 000 but I don't know for sure. Any insight would be appreciated.

 

[lovedogs]

Those measurements are VERY different between GIA and AGS, so that would concern me. Are you sure the report is for the correct stone? Also, what is your current stone?

 

[OECfan]

Those measurements are VERY different between GIA and AGS, so that would concern me. Are you sure the report is for the correct stone? Also, what is your current stone?

AGS measurements is one edge (5.58mm) + diagonal (6.65 mm). All of the % are based on the diagonal edge. I did some research here and there were past discussions about other HOF dream and Brian Gavin cushions reporting the diagonal as one of the measurements vs. the two edges.
GIA measurements is the two edges.

So for example, AGS depth = 4.06/6.65 = 61.1% but GIA depth = 4.07/5.58 = 72.9%
They're the exact same stone. I have seen this stone in person and it's square. Both of them have the HOF inscription, I just deleted it from the PDF.

My current stone is a 0.70 ct G VS2 princess cut.

 

[lovedogs]

AGS measurements is one edge (5.58mm) + diagonal (6.65 mm). All of the % are based on the diagonal edge. I did some research here and there were past discussions about other HOF dream and Brian Gavin cushions reporting the diagonal as one of the measurements vs. the two edges.
GIA measurements is the two edges.

So for example, AGS depth = 4.06/6.65 = 61.1% but GIA depth = 4.07/5.58 = 72.9%
They're the exact same stone. I have seen this stone in person and it's square. Both of them have the HOF inscription, I just deleted it from the PDF.

My current stone is a 0.70 ct G VS2 princess cut.

ok perfect--I just wanted to make sure. But that all makes sense.

I am also confused by such a big difference in fluor between AGS and GIA.

 

[OECfan]

I just went down a rabbit hole in this thread....and answered my own question: Fluorescence-AGS question | PriceScope

Seems like it could be the range that AGS calls negligible, and the UV wavelength used...

I'll reserve judgement for when I get to see this under sunlight tomorrow. If it has no negative effect on the performance, fluorescence or not won't matter to me!

 

[OECfan]

Came back from the jeweller. She explained to me some similar things to what was in the thread above and she believes AGS and GIA are both right.

The intensity of the fluorescence is minimal, which is what AGS pointed out by saying “negligible”.

She thinks GIA’s “strong blue” is referring to the deep blue colour and not necessarily the intensity. Because while I did see fluorescence when compared to another diamond with no fluorescence, the diamond didn’t necessarily glow - it just changed to a deep blue colour under UV while remaining clear and sparkly.

She showed me an example of diamonds with “strong” fluorescence (including some of the melee on my halo) and the stones glowed really bright with strong fluorescence.

 

[diamondseeker2006]

I think the round HOF diamonds would possibly be graded for cut by AGS, but I doubt the Dream shape stones are.

It is odd that AGS and GIA grade fluorescence so differently!

 

[OECfan]

I think the round HOF diamonds would possibly be graded for cut by AGS, but I doubt the Dream shape stones are.

It is odd that AGS and GIA grade fluorescence so differently!

You’re right, I thought I saw other Dream cut diamonds get an “ideal” grade but I think I may have been looking at the round HOF reports! Based on the light performance I saw from today though it sure seemed pretty darn close to ideal

 

[sledge]

Came back from the jeweller. She explained to me some similar things to what was in the thread above and she believes AGS and GIA are both right.

The intensity of the fluorescence is minimal, which is what AGS pointed out by saying “negligible”.

She thinks GIA’s “strong blue” is referring to the deep blue colour and not necessarily the intensity. Because while I did see fluorescence when compared to another diamond with no fluorescence, the diamond didn’t necessarily glow - it just changed to a deep blue colour under UV while remaining clear and sparkly.

She showed me an example of diamonds with “strong” fluorescence (including some of the melee on my halo) and the stones glowed really bright with strong fluorescence.

To be clear, GIA doesn’t report color of fluor it reports intensity. Refer to myth #5.

If the dark blue looks as below, GIA would recognize as none or faint, possibly medium depending how dark it really is.

For clarity AGS rating of negligible encompasses none, very faint & faint.

Fact Checking Diamond Fluorescence: 11 Myths Dispelled

Diamond fluorescence is a glow some diamonds emit under UV light. Need to worry? Let’s clear up some common myths so you can enjoy your diamond.

4cs.gia.edu

Home

American Gem Society is comprised of the top jewelers in the U.S. and Canada and offers the best gemstone and diamond information. Find top jewelers today.

www.americangemsociety.org

If she is suggesting GIA misgraded, the simplest answer would be to have the stone re-graded. Not exactly a bad idea anyhow considering it is pre-loved and you have 2 outdated certs with conflicting info on fluor & clarity. At their expense of course

Keep in mind, being 1 grade apart could mean the stone is borderline and within standard tolerance for grading.

Some food for thought, if you’ve made up your mind to buy I would do a little research and see which scenario gets you the biggest discount. Either an SI1 with negligible or a VS2 with SBF. My guess is she wants to debunk the SBF so she doesn’t have to discount the stone for it because market says SBF is less valuable than none, faint or negligible.

Again if the stone is sparkle bomb and the SBF isn’t an issue (cloudy, hazy and/or turns blue in the sunlight) then this may be a great opportunity to leverage negotiations in your favor!

 

[John Pollard]

A possible explanation for the fluorescence strength discrepancy is a difference in approach.

GIA places the diamond table-down and compares the strength of fluorescence to reference stones, as with with D-Z color grading.

AGS determines the strength and color of fluorescence in the face-up position.
https://www.pricescope.com/education/diamond-color/diamond-flourescence#AGS

Fluorescence can be directional, meaning its appearance viewed from the side can be different than what's observed face-up. This seems to agree with OECfan's observations here.

...Because while I did see fluorescence when compared to another diamond with no fluorescence, the diamond didn’t necessarily glow - it just changed to a deep blue colour under UV while remaining clear and sparkly.

She showed me an example of diamonds with “strong” fluorescence (including some of the melee on my halo) and the stones glowed really bright with strong fluorescence...

Of course I wasn't in the room where it happened, but I believe the difference in approach is worth mentioning.

 

[OECfan]

Very informative, thank you @sledge and @John Pollard ! I’m honoured to have experts like you come visit and respond to my thread!

My jeweller wasn’t trying to say it was misgraded at all. Sledge, to my eyes the diamond looked like the “faint” shown in that GIA photo you included. It didn’t really glow that much.

In light of what John mentioned in his post in terms of different approach between AGS and GIA, it makes even more sense. My stone could have had a stronger fluorescence from the side, but I was only concerned about the face up view because I’m having it set into my existing halo.

I already bought the diamond, as it was too good of an offer to pass up and I couldn’t think of another reason I don’t want this particular stone. The stone was heavily discounted already as a preloved, and the discounted price itself wasn’t amazing but with the ridiculous trade-in they’re giving me... it was a good price.

It was a stunning diamond and my primary concern was that this would be one of the 2% negatively affected by fluorescence. But that wasn’t the case at all, so it’s already being sent to the bench for setting! In terms of cut quality and light performance it’s a significant improvement from my existing stone.