Find your diamond
Find your jewelry
shape
carat
color
clarity

Should we discourage or recommend FL stones?

TODiamonds

Shiny_Rock
Joined
Jul 27, 2019
Messages
182
G color- for every dollar you spend on an inert stone, you'd spend .58cents on an MB (MB- 42%)
J color- for every dollar you'd spend on an inert stone, you'd spend .82cents on an MB (MB -18%)
K Color- for every dollar you'd spend on an inert stone $1.09 on an MB......(MB +9%)\
This small sample shows a larger discount on higher colors, smaller discount on J, and actually a premium for K color SB
The data that I've seen on Flo discounts in the past differ significantly than what you've shown here.
 

Rockdiamond

Ideal_Rock
Trade
Joined
Jan 7, 2009
Messages
7,842
I’m unaware of published data on how fluorescence affect pricing- can you please share the data you’ve seen?
My post of the other day was not intended to be a broad based study- just the opposite. Since I didn’t intend to spend the amount or time necessary for a broad based study, I chose a limited sample to see what I’d find in that size/ quality, on that day.
Most days I do look at , and buy diamonds from cutters and other dealers. The small sample I found the other day jibes with what I see in general in the market.
 
  • Like
Reactions: AV_

Rockdiamond

Ideal_Rock
Trade
Joined
Jan 7, 2009
Messages
7,842
PS- if anyone has a specific category they would like to run this same test on, I'll be happy to oblige, if possible.
 
  • Like
Reactions: AV_

TODiamonds

Shiny_Rock
Joined
Jul 27, 2019
Messages
182
I’m unaware of published data on how fluorescence affect pricing- can you please share the data you’ve seen?
My post of the other day was not intended to be a broad based study- just the opposite. Since I didn’t intend to spend the amount or time necessary for a broad based study, I chose a limited sample to see what I’d find in that size/ quality, on that day.
Most days I do look at , and buy diamonds from cutters and other dealers. The small sample I found the other day jibes with what I see in general in the market.
No published data. Just anecdotally from diamond shopping over the years. I typically see 3-5% on lower grades and maybe low-mid teens discount higher end colors. I've never ever seen anything anywhere near 42% that's for sure!
 

Rockdiamond

Ideal_Rock
Trade
Joined
Jan 7, 2009
Messages
7,842
Hi @TODiamonds
A few things:
1) based on my experiences on the market, the differential has exacerbated over the past five years. So, if we looked years ago, the market was different.
2) As I've said, my post the other day referred to a limited sample showing limited results. I have seen discounts greater than 42% in certain, specific cases. A D/IF with VSB can be bought at about 1/2 the price of an inert stone ( if all else was equal).
If we do deeper dives into different specific articles, we will find variances for sure.

We look at massive amounts of goods here on a daily basis.....of course, everyone's anecdotal evidence is important- but you'd really need a lot of market exposure to get a sense.
 
  • Like
Reactions: AV_

AV_

Ideal_Rock
Joined
Aug 5, 2018
Messages
2,562
I’m unaware of published data on how fluorescence affect pricing
I have not seen any statistics either. Where can such data be? TBD


PS- if anyone has a specific category they would like to run this same test on, I'll be happy to oblige, if possible.
Any of three categories: D, step cut - VVS or VS or SI


A D/IF with VSB can be bought at about 1/2 the price of an inert stone (all else equal).
I am rather curious if SB discount is more or less the same, or weighs heavier on SI or IF, thinking of the more recent exercise about setting official denominations for color for sapphire - very different type of categories.
 
Last edited:

Texas Leaguer

Ideal_Rock
Trade
Joined
Jul 27, 2009
Messages
3,031
Hi Bryan,
Why did that thread go on for so many pages?
The reason is that there is NO consensus that Micheal's work is accurate- and I was not the only one stating this. When he was pressed, he simply changed the subject. This is NOT a scientific peer-reviewed study. Below was a post from the very first page. I'm by no means alone in the experience of certain fluorescent diamonds facing up whiter than the GIA grade, which is obtained through the pavilion.

I stated out the outset- you and I will never come to an agreement on this specific aspect, and that's perfectly ok.
One reason that "there is no consensus" is that some folks stubbornly hang on to old notions despite modern evidence that calls those beliefs into question. For page after page of debate!

And despite Garry's desire to 'rest his case' he only offered up an opinion based upon an assumption. And it is the same assumption that people arguing for a whitening benefit invariably make: because there are UV wavelengths in many indoor lighting environments, color masking blue fluorescence must therefore be stimulated.

But UV energy has to be INTENSE enough to cause this to happen. VV wavelengths have a smaller impact on stimulating fluorescence, but they too must be intense enough to have any effect. Indoor lighting simply does not provide enough intensity of either.

Here is an analogy that I think might help make this concept relatable. If you go sunbathing for an hour in direct sunlight without sunscreen, you may very well get a sunburn. But you can live your entire life indoors under fluorescent tube lighting and never get even a hint of a tan! Nobody feels the need to wear a hat or suncreen for protection indoors. Why? Because the intensity of the UV (and VV) is NEGLIGIBLE.
 
Last edited:

AV_

Ideal_Rock
Joined
Aug 5, 2018
Messages
2,562
This must be the place to ask:

How does GIA define the thresholds of Medium - Strong - Very Strong ? I assume there is a dull document where Google does not look.
 

Texas Leaguer

Ideal_Rock
Trade
Joined
Jul 27, 2009
Messages
3,031
The thresholds are officially defined by their fluorescent master stones. They also have a new UV box with a specially designed test strip that allows you to compare the stone in question to samples of faint, medium, strong and very strong.

GIA-UV-Lamp-and-Viewing-Cabinet-with-Test-Strip.jpg
 

Karl_K

Ideal_Rock
Trade
Joined
Aug 4, 2008
Messages
8,497
One reason that "there is no consensus" is that some folks stubbornly hang on to old notions despite modern evidence that calls those beliefs into question. For page after page of debate!
Way to much junk science out there on UV and diamonds.
Much of that junk science has been ingrained into the industry.
The very wavelength that the labs use is not the one that should be used judged by their own studies.
Even those studies are way to small to be considered high confidence and a double blind study with enough diamonds to be high confidence has not been done.
The current industry accepted teachings are in some ways stone age material.
The grading system was based on what was available for lighting to be used for it, not what was actually best. That is a historical fact.
An UV meter is not tuned to be used to speculate on diamond response, they are tuned to read and measure cancer causing UV wavelengths, not diamond specific ones.
That said im am somewhat skeptical if no sunlight is present that there will be enough 400nm to excite a diamond inside.
But I have no proof that it never happens either.
Since many window coatings will pass 400nm if sunlight is present there might be enough I speculate.
Then you enter the realm of other causes for florescence like the diamond I ran into and talked about in the other thread.
Inert in gia uv light, inert in many uv sources, very strong in one uv source and sunlight.
 
Last edited:

sledge

Ideal_Rock
Premium
Joined
Apr 23, 2018
Messages
3,790
What I can't seem to find much data on is how the UV lighting used in labs to judge colors plays into effect with fluor.

Do those bulbs produce enough intensity to activate fluor and potentially affect color grading? If so, is one of the potential dangers of buying a stone with fluor is that it could have been graded slightly different as a result of the fluor?

I know the labs consider 1+/- color grade acceptable. Also, I'd think it would be borderline stones that would get a slight bump.
 

Texas Leaguer

Ideal_Rock
Trade
Joined
Jul 27, 2009
Messages
3,031
What I can't seem to find much data on is how the UV lighting used in labs to judge colors plays into effect with fluor.

Do those bulbs produce enough intensity to activate fluor and potentially affect color grading? If so, is one of the potential dangers of buying a stone with fluor is that it could have been graded slightly different as a result of the fluor?

I know the labs consider 1+/- color grade acceptable. Also, I'd think it would be borderline stones that would get a slight bump.
@sledge This is a concern that is important to the full understanding of discounting of fluorescent diamonds, and is the topic of the long thread referenced above.

Here is a link to a summary of the Cowing article in the Pricescope knowlege base. I notice that the link within the article to the full Cowing study is broken, possibly a casualty of the last PS upgrade.


I will try to find another link to the full study and post it later.
 

Rockdiamond

Ideal_Rock
Trade
Joined
Jan 7, 2009
Messages
7,842
Hi Bryan,
I guess I’d have to ask you at this point- what’s your goal here?
This isn’t about “old notions”.(are you calling me a boomer??:) There’s simply no gemological consensus. The 22 pages of Cowing article completely debunked it.

You’re basing your statements on what you believe is credible science.
@Karl_K listed some extremely salient points about the measuring of UV
There’s the HRD study quoted below. Even if you’re not a fan of HRDs grading, I would not exclude their findings offhand.
And as you pointed out, it’s futile to try to prove a negative ( in this case , proving that stones can’t whiten outside direct sunlight)...especially when physical evidence shows otherwise.
This isn’t about trying to sell diamonds. It’s about education.
Maybe try to allow the possibility that what HRD, Garry, I and others are saying is based on what we have personally witnessed. There’s my experience at Harry Winston where such stones were prized and sold at a premium.
I know you’re telling the truth when you say you’ve never seen this whitening occur because I trust your word.
I’m asking the same of you.
I have witnessed whitening.

Garry H (Cut Nut) said:
"The results of HRD Antwerp’s study thus support findings from earlier studies conducted by other labs, adding additional objective assessments. It confirms that even very strong fluorescence has no detrimental effect on the appearance of diamonds in a laboratory setting, and when viewed through the pavilion in outdoor conditions, it results in a clear improvement in a diamond’s color. For the wearer or casual observer, fluorescence has a neutral or even positive impact on the appearance of a diamond, making it appear to be more colorless. Given these observations, HRD Antwerp concludes there are no grounds on which to justify the price penalties that currently apply to fluorescent diamonds."
 

Rockdiamond

Ideal_Rock
Trade
Joined
Jan 7, 2009
Messages
7,842
What I can't seem to find much data on is how the UV lighting used in labs to judge colors plays into effect with fluor.

Do those bulbs produce enough intensity to activate fluor and potentially affect color grading? If so, is one of the potential dangers of buying a stone with fluor is that it could have been graded slightly different as a result of the fluor?

I know the labs consider 1+/- color grade acceptable. Also, I'd think it would be borderline stones that would get a slight bump.
This is a very pertinent question!!
My experience is that the fluorescence absolutely affects the color grading. This is another crucial piece of the “whitening” puzzle.
In the case of yellow diamonds this inconsistency is so very easy to see.
In many cases, a Fancy Light Yellow with MB is dull. But in the minority of cases, where the fluorescence causes no issue, it can make the stone face up one grade darker.

The science on this is truly in its infancy.
 

sledge

Ideal_Rock
Premium
Joined
Apr 23, 2018
Messages
3,790
Some quick & dirty analysis on G colored stones.

First data set examines super ideal vendor with both a standard H&A stone with none/negligible fluor against a H&A stone with medium+ levels of fluor.

Second data set examines GIA 3x stones, that are NOT H&A, but using PS filters receives EX HCA scores, depths of 60-62 and tables 54-57. I haven't viewed each stone to determine if they are something I'd actually consider, but have to assume they are at least in the ballpark. Several of the stones are from JA, so proportion analysis is bunk on them anyhow.

Still, this gives us a decent representation of what BUYERS see. No where near a 42% discount. If G stones with medium+ fluor levels are really selling for 42% less in the wholesale market, it seems logical dealers would be buying them and pushing them harder as they can gain some fat profits.

Since XLS files not allowed, I have converted to PDF with hyperlinks to stones in case anyone wants to double check.

CaptureG.PNG
 

Attachments

TODiamonds

Shiny_Rock
Joined
Jul 27, 2019
Messages
182
Some quick & dirty analysis on G colored stones.

First data set examines super ideal vendor with both a standard H&A stone with none/negligible fluor against a H&A stone with medium+ levels of fluor.

Second data set examines GIA 3x stones, that are NOT H&A, but using PS filters receives EX HCA scores, depths of 60-62 and tables 54-57. I haven't viewed each stone to determine if they are something I'd actually consider, but have to assume they are at least in the ballpark. Several of the stones are from JA, so proportion analysis is bunk on them anyhow.

Still, this gives us a decent representation of what BUYERS see. No where near a 42% discount. If G stones with medium+ fluor levels are really selling for 42% less in the wholesale market, it seems logical dealers would be buying them and pushing them harder as they can gain some fat profits.

Since XLS files not allowed, I have converted to PDF with hyperlinks to stones in case anyone wants to double check.

CaptureG.PNG
Great analysis Sledge. These %'s are about where I would've expected.

The BGD discount is actually higher than I would have expected given how much effort he spends trying to market his blue line (genius marketing btw).
 

sledge

Ideal_Rock
Premium
Joined
Apr 23, 2018
Messages
3,790
@sledge This is a concern that is important to the full understanding of discounting of fluorescent diamonds, and is the topic of the long thread referenced above.

Here is a link to a summary of the Cowing article in the Pricescope knowlege base. I notice that the link within the article to the full Cowing study is broken, possibly a casualty of the last PS upgrade.


I will try to find another link to the full study and post it later.
Thank you for the link. I will do some reading and try to get a little smarter. ;)2

My initial off the cuff thoughts are that if a stone color is in risk of being accurate, then is it really a discount? For instance, if shopping for a G with medium+ fluor because of discount, etc then it may make sense to compare that price against H with none/negligible stones because of potential over grading issues.

Additionally from a vendor standpoint, I'd further assume (and we know what that does) that if you are trying to maintain strict control over the quality of your product in the market place then that is like tossing a grenade into your operations as it introduces too many what if's.

Lastly, add back in the potential negative factors and I can see how some just prefer to avoid the headache and bypass them altogether.
 

Rockdiamond

Ideal_Rock
Trade
Joined
Jan 7, 2009
Messages
7,842
Cool data @sledge - thank you!!
Just doing a quick check at retail- I checked on of the largest two virtual sites.
I found a G/VS2 in an"Ideal cut" for $7599. Then an SB, in the same cut categorization at $5578 ( -27%)

There are many reasons why we're getting different numbers.
First is methodology- I'm comparing discounts being offered at wholesale, which may not match numerically either from a mathematical or logistical standpoint. Sellers might easily use a different formula for deeply discounted MB/SB stones.
But IMO, the greater issue os the actual appearance of the diamonds.
The same Virtual site has a G/VS2 SB in a branded "Ideal Cut" for $7545- almost the same price as another inert stone mentioned above.

And more to the point, the subject of fluorescence effect on price deserves its own thread.
The Cowling article is about "Overgrading". In this aspect, I agree. Color grading of fluorescent diamonds is very tricky- and it's easy to find inconsistencies based on this aspect of grading.
But nothing I can read in it conclusively states whitening is not possible outside direct sunlight.
 
Last edited:

Rockdiamond

Ideal_Rock
Trade
Joined
Jan 7, 2009
Messages
7,842
I've made every effort to keep this discussion civil. It's interesting that a member actually stated I should be kicked off Pricescope for stating my views and experience.
And Bryan has termed my words as "opinion" versus his science. Or "old notions"
I politely reminded Bryan that maybe our different experiences are due to the fact that we look at different stones- and grew up in different diamond neighborhoods.
I can totally get why a brand would exclude fluorescent diamonds, I'm not criticizing that aspect at all.
The fact that his brand excludes fluorescence would seem to indicate he would not waste time assessing fluorescent diamonds.
.
 

sledge

Ideal_Rock
Premium
Joined
Apr 23, 2018
Messages
3,790
Great analysis Sledge. These %'s are about where I would've expected.

The BGD discount is actually higher than I would have expected given how much effort he spends trying to market his blue line (genius marketing btw).
Thanks, that's what my "gut" told me too but I was curious. The biggest problem is it's just a tiny data set and may not be representative of the whole market. However, it's probably pretty accurate for BGD.

That said, notice how the Blue line doesn't really discount much for VS2/VS1 clarity? Nor is there any significant and meaningful difference between strong & medium levels.

Also, I think the higher % difference between GIA and BGD stones has to do with 50% of the GIA none stones were VS1's. Those slightly higher prices push the average price higher, and in this case the medium+ stones are all VS2's (lower cost) so in effect you are getting a slight misread on the overall percentage.

Even if you neutralize those effects, you're probably still talking a 10-11% difference with GIA stones. On the data set we have it appears BGD is offering around 7.5% discount on average so that leaves a few percent extra they may be shaving off to cover the additional marketing expenses.


Cool data @sledge - thank you!!
Just doing a quick check at retail- I checked on of the largest two virtual sites.
I found a G/VS2 in an"Ideal cut" for $7599. Then an SB, in the same cut categorization at $5578 ( -27%)

There's many reasons why we're getting different numbers.
First is methodology- I'm comparing discounts being offered at wholesale, which may not numberically eq
You're welcome. Glad to help out. Wish I had data dumps and I could create a more meaningful analysis. Truly, the weakness is the size of the data set as I mentioned above.

Can you share the links to the two stones you analyzed? I don't think anyone is actually asking for opinions to purchase these stones, so I personally don't feel it's a violation of your trade agreement with PS, but then again I'm not the admin either. Just seems the spirit of the conversation would make it okay is all I'm saying.

I understand the 42% discount you mentioned earlier was at the wholesale level. What strikes me odd about that whole situation is that if a vendor can go buy a G with medium+ fluor for 42% discount and then only offer back 8-10% to the customer that leaves about 30%+ additional profit above normal profits. That's a fat hog!

But in reality I don't see that happening. Even if it were happening, what would keep vendor A from offering more of the discount back to the buyer to boost his sales? Then vendor B decides to oust vendor A, and so on and so forth. As the wheel goes round, each vendor essentially cuts the throat of the next vendor and before too long everyone is selling G's for 42% discounted prices at the retail level over stones with no flour.
 

TODiamonds

Shiny_Rock
Joined
Jul 27, 2019
Messages
182
We should focus more on medians and less on outliers like this 42% which obviously isn't representative of the norm.

Sure you could have had a 5 ct IF stone with strong flo that was hazy and traded down 42%... but cases like those aren't particularly relevant when we're trying to extrapolate statistically meaningful analysis that is representative of the broader market.
 

Rockdiamond

Ideal_Rock
Trade
Joined
Jan 7, 2009
Messages
7,842
Can you share the links to the two stones you analyzed?

Hi Sledge....I can't according to forum rules...but any member can go to the site ( one of the two main VD sites) and do a search for G/VS2 carat size stones. This site I used allows a filter for fluorescence ( hint hint..lol)

About the prices charged- in relation to wholesale: This is super interesting but not really possible to easily categorize.
@TODiamonds - good point about not focusing on outliers- although lets' not totally ignore them as well.
 

Texas Leaguer

Ideal_Rock
Trade
Joined
Jul 27, 2009
Messages
3,031
I've made every effort to keep this discussion civil. It's interesting that a member actually stated I should be kicked off Pricescope for stating my views and experience.
And Bryan has termed my words as "opinion" versus his science. Or "old notions"
I politely reminded Bryan that maybe our different experiences are due to the fact that we look at different stones- and grew up in different diamond neighborhoods.
I can totally get why a brand would exclude fluorescent diamonds, I'm not criticizing that aspect at all.
The fact that his brand excludes fluorescence would seem to indicate he would not waste time assessing fluorescent diamonds.
.
We process thousands of diamonds every year. A good portion have flourescence. We check fluoro on every diamond with the GIA device referenced above. The AGS 'negligible' category includes diamonds up to just below Medium. Our GIA diamonds (Premium Select category) allows up to medium fluorescence. In our virtual category we sell many strong blues sourced for customers looking specifically for this property, or taking advantage of associated discounts.

It has been important for me in my role to understand the property of fluorescence from both a visual and market perspective. The various studies I have availed myself to have helped in that effort.

In my earlier career I had many of the same preconceptions about fluorescence as most trade members. Some are mythical in nature and are passed down as part of diamond lore and romance, or because they are self-serving from a business standpoint. In other cases it is simply that many in the trade members have never taken an in-depth look at the issue.
 

Rockdiamond

Ideal_Rock
Trade
Joined
Jan 7, 2009
Messages
7,842
Some are mythical in nature and are passed down as part of diamond lore and romance, or because they are self-serving from a business standpoint. In other cases it is simply that many in the trade members have never taken an in-depth look at the issue.
Hi Bryan,
Which of these categories do I fall into?
 

Texas Leaguer

Ideal_Rock
Trade
Joined
Jul 27, 2009
Messages
3,031
Hi David,
I try my best not to judge, but since you asked... I think you are very confident in your eye for diamonds and I am sure you are sincere in your belief that you really do see the things in diamonds that you claim to see. But I think you resist anything that calls into question your long held beliefs, which is a very natural thing that all of us do on some level.

It is frustrating that you regularly misstate my positions in these discussions, and make a habit of cherry picking things that seem to support your opinions. And that a common theme of your commentary here on the forum is to dispute and deny information that does not conform to your opinions.

I don't think that approach is conducive to reaching a consensus on any topic. If the goal is to guide consumers (and other trade members) to a solid understanding it is important to be intellectually honest and avoid making erroneous or misleading comments.

Lastly, you should be aware that repetition of an opinion is not the same thing as fortifying an argument. And that simply being so relentless that others give up posting is not the same thing as winning a debate.
 

Texas Leaguer

Ideal_Rock
Trade
Joined
Jul 27, 2009
Messages
3,031
@sledge Attached is a pdf copy of the full Cowing study. Get a cup of coffee!

Whether one thinks that overgrading of blue fluorescent stones is a thing of the past, or may still be happening to some degree in the labs, the background information laid out in the article provides important insights and references on blue fluorescence and it's visual impacts.
 

Attachments

Rockdiamond

Ideal_Rock
Trade
Joined
Jan 7, 2009
Messages
7,842
Lastly, you should be aware that repetition of an opinion is not the same thing as fortifying an argument. And that simply being so relentless that others give up posting is not the same thing as winning a debate.
Bryan, this is so darn simple to solve. Your opinion is that there is conclusive science on this specific issue.
I do not share that opinion.
Nor do I feel what we have seen on Pricesope substantiates a claim that diamonds cannot possibly exhibit color change due to fluorescence outside of sunlight, or extremely close to a lamp.
I'm sure you feel differently about that too. My apologies if I have misstated your position in the past or now. If so please clarify.
You've never observed it, I have.
I like you- and have no desire to argue. This issue is never going to find consensus among gemologists, and other professionals. We can have different opinions and that's perfectly fine- and there's simply no need for this difference to be pejorative, one way or the other.
I know for a fact that this topic is interesting to a lot of readers. Let's agree to disagree so we can both enrich the discussion. It is my hope we can also agree to respect each other.
 

Texas Leaguer

Ideal_Rock
Trade
Joined
Jul 27, 2009
Messages
3,031
Fair enough David. Apology accepted.

I never demand that anyone agrees with me, so we can certainly agree to disagree.

I should not have to clarify this for you since we have had this discussion many times before, but here is my basic position on the topic at this point in time:
  • Blue fluorescence is capable of masking yellow color in response to UV and (to a lesser extent) VV of sufficient intensity.
  • I have seen color masking (whitening)
  • In the majority of indoor lighting environments whitening does not take place, because blue emissions are not sufficiently stimulated due to insufficient intensity of wavelengths capable of causing them.
  • The oft touted benefit of color grade improvement of fluorescent stones is WAY over-sold.
  • The concern about transparency deficits (milkiness) due specifically to fluorescence is similarly overblown for the fact that in most indoor lighting the milky effect is not produced because fluorescence is not stimulated.
  • Consumers need to evaluate strong fluorescent stones for any negative factors by viewing them in sunlight.
  • Lab overgrading of color of strong blue fluorescent diamonds is a potential concern and consumers should have diamonds reviewed by qualified professionals specifically for this issue.
  • Discounts of fluorescent diamonds can provide shoppers with potential savings due to irrational market perceptions.
  • Stuff that fluoresces is really cool. Especially diamonds.
My position is not in opposition to conclusions reached by the GIA in their studies and surveys.
 
Last edited:

AV_

Ideal_Rock
Joined
Aug 5, 2018
Messages
2,562
Just a sidenote:

GIA thresholds might be read in reverse - not of yield, but of how much UV intensity is required to get a given level of blue, that is to say when, how & where one gets to see anything. I recall that wavelengths make some difference, but do not have the time to dig up references & such. From the little I have seen, SB is not always enough to make a clear impression, VSB does.
 

AV_

Ideal_Rock
Joined
Aug 5, 2018
Messages
2,562
Then,

Yes, it is rather nice that so many diamonds some with a subtle blue tone that has obviously nothing to do with gray - unlike the other kind of faint blue. It would be highly fun to compare.
 
Be a part of the community It's free, join today!

Need Something Special?

Get a quote from multiple trusted and vetted jewelers.

Holloway Cut Advisor



Diamond Eye Candy

Click to view full-size image.
Top