Fluorescence / UV-permeability of HRD cases.

[dkaut]

Dear all,

I was offered an HRD certified diamond.

The stone scores TIC 1.1 on HCA and looks stunning but has a strong fluorescence which bothers me. My jeweller allowed me to inspect the stone in bright midday sunlight but as it showed hardly any sign of fluorescence, I wonder whether HRD''s see-through casing is actually permeable to UV light or whether the casing prevents the UV light from reaching the stone. I am willing to purchase the stone unless the strong fluorescence has a negative impact.

Thus, I have two questions:

1. Is the HRD casing permeable to UV light?

2. If it is not, would an HRD certificate indicate if a stone, in particular due to its strong fluorescence, had a milky/hazy appearance when looked at in bright sunlight?

As the stone is with the jeweller for inspection purposes only and needs to be returned to the Antwerp-based trader as soon as possible, I would very much appreciate a quick response.

Thank you

David

 

[Paul-Antwerp]

Hi David,

I do not think that the sealing of HRD prohibits you from seeing possible negative effects of strong fluorescence. It is often said here that the commented hazy look of some strong fluorescent stones is actually a very rare instance.

I do however have a problem with sealed certificates. It is a habit in some parts of the world, like the Middle East, but it is not commonly used elsewhere.

Especially if the stone is either LC or SI2 in clarity, I would be very suspicious.

Live long,

 

[dkaut]

Date: 7/21/2008 6:00:06 AM
Author: Paul-Antwerp
Hi David,

I do not think that the sealing of HRD prohibits you from seeing possible negative effects of strong fluorescence. It is often said here that the commented hazy look of some strong fluorescent stones is actually a very rare instance.

I do however have a problem with sealed certificates. It is a habit in some parts of the world, like the Middle East, but it is not commonly used elsewhere.

Especially if the stone is either LC or SI2 in clarity, I would be very suspicious.

Live long,

Hi Paul,

Thank you very much indeed for that comment!

The diamond is a VS2 clarity, the HRD certificate was issued just recently and I absolutely trust my jeweller who has been my family''s jeweller for more than three decades (and the jeweller trusts his diamond dealer). As HRD (their stones afaik always come in sealed see-through boxes) is quite common and renowned here in Europe, the fact that I am not buying an AGS or GIA stone does not bother me. My only concern was about the casing of the diamond shielding the UV light, thus hiding the possible negative effects of the flourescence.

Your comment makes me feel much better.

Thanks again
David

 

[dkaut]

Uh...I just realize that you are from Antwerp. And I tell you about "here in Europe"...sorry about that, Paul.

Kind regards
David

 

[Indira-London]

Hello David
Just to clarify that HRD do not seal all their diamonds as standard - its IGI who seals for free so that many more IGI diamonds are sealed. HRD diamonds are only sealed on request - it could be that your jeweller''s diamond trader provides sealed diamonds for ease of logistics i.e. that way he and your jeweller know that the diamond he lends your jeweller diamonds cannot be switched or mixed up accidentally.

What does puzzle me is that given that you are so keen on that diamond and would have bought it if you could have seen it loose in sunshine last Saturday then why your jeweller did not open the seal for you as that way he would most likely have made a sale?

When I get sealed diamonds, I would open a seal for clients who are serious about purchasing that particular diamond.

 

[dkaut]

Date: 7/21/2008 10:04:53 AM
Author: Indira-London
Hello David
Just to clarify that HRD do not seal all their diamonds as standard - its IGI who seals for free so that many more IGI diamonds are sealed. HRD diamonds are only sealed on request - it could be that your jeweller''s diamond trader provides sealed diamonds for ease of logistics i.e. that way he and your jeweller know that the diamond he lends your jeweller diamonds cannot be switched or mixed up accidentally.

What does puzzle me is that given that you are so keen on that diamond and would have bought it if you could have seen it loose in sunshine last Saturday then why your jeweller did not open the seal for you as that way he would most likely have made a sale?

When I get sealed diamonds, I would open a seal for clients who are serious about purchasing that particular diamond.

Hello Indira!

I am confident that the jeweller (I am actually not sure whether I use this term correctly, it is a renowned jewellery trader but not specifically specialized in diamonds) would have opened the seal for me if I had insisted on it. However, I felt that she was just not sure whether she was actually allowed to do so and I did not want her to run into any trouble. She does not usually sell loose diamonds and unless she is lying to me, she is selling the stone to me at the price she pays to the Antwerp trader (as said in an earlier post, I have been knowing her for quite some time). This is why I suggested clarifying whether the case is actually permeable to UV light. Unfortunately, I have not yet managed to get anyone on the phone at HRD. I hoped that someone here could know but it is probably a very specific / extraordinary question. I will post the answer that I (hopefully) get from HRD.

Thank you and best regards
David

 

[Indira-London]

Hello David
I did not realise that you were trying to phone them today - it is their national holiday in Belgium today so the HRd will have been shut!

Thanks for explaining re. your jeweller.

 

[michaelgem]

Re: Thus, I have two questions:

1. Is the HRD casing permeable to UV light?
2. If it is not, would an HRD certificate indicate if a stone, in particular due to its strong fluorescence, had a milky/hazy appearance when looked at in bright sunlight?

Just stumbled onto this thread, too late to help.

But you should check the diamond in sunlight absent the plastic casing, because plastics definitely block UV, some more then others.

Polycarbonate plastic such as lexan plastic or plastic, polycarbonate (PC) eyeglass lenses almost completely block all UV, so no fluorescence will be observed with the PC plastic shielding the diamond.

No grading report including HRD's makes any judgment call as to whether a diamond has a milky/hazy appearance when viewed in sunlight, so its buyer beware.

On the other hand if the stone has only strong, not very strong, blue fluorescence it seldom in my experience exhibits this appearance in sunlight.

A more significant concern I would have is the possible overgrading by a grade or two that is common with all the labs following the GIA practice of grading under unfiiltered, UV-containing, fluorescent illumination.

I always check the color in lighting absent UV. If the color is correct, I love a strong blue fluorescent diamond, as in daylight it often looks a grade or two whiter. On top of that I get the stone 5-10 percent cheaper, due to trade perception of value.

Michael D. Cowing

 

[Garry H (Cut Nut)]

Hmm, tricky issue

Michael may be right, however the lexan needs to be much thicker I think to screen much UV

You were probaby looking for blueishness - Michael and I would be looking for haziness.

I am wrtiing an article for the Aust Gemmologist - the editor, a power house - died and it is the memeorial issue. Grahame Brown liked to challenge stoopidity - and fluoro is our achillies heel of it.

I have asked and recieved responses to this qestion:

Please estimate / guesstimate the % of hazy / oily diamonds where transparency is reduced "when viewed in shaded daylight"?

That was followed by VS, Strong, Medium etc

The answers from senior to top people from almost every lab on earth ranged in VS from very few to + or - 90%. If there is an average consensus for strong it would be that maybe 20% of strong blues are hazy to some extent - that is supported from information t=from the best lab in the world - Venus Jewel - who unfortunately only grade their own diamonds and refuse to use commercial labs even if they miss a sale.

As to colour changing / grading - that is even more stoopid.

I think you would be pretty safe and if you send a link to this an good retailer will help you compare the stone - but not in direct sunlight -- never!!!

 

[michaelgem]

Garry always has good advice to add to any subject on diamonds.

Re: I think you would be pretty safe and if you send a link to this an good retailer will help you compare the stone - but not in direct sunlight -- never!!!

Direct sunlight is a terrible illumination to view any aspect of diamond beauty, as this single point source is of such high intensity that it swamps all the other angles of light entering the diamond preventing them from contributing to its beauty. To say nothing about the problem and possible danger of looking at a direct reflection of the sun in the diamond. My retina says Ouch!!!

The examination in sunlight/daylight should be done as follows:

Look at the diamond face up toward the open sky in daylight with your back to the sun and your head shielding the diamond from the direct sun, but not shielding the daylight surrounding the sun. If the diamond appears hazy/oily/milky in this lighting, look for another diamond.

The fluorescence issue as it pertains to the overgrading of blue fluorescing diamonds was a hot issue in 1998 after the GIA came out with a study, which in essence concluded that they were not overgrading color in blue fluorescing diamonds, as their fluorescent illumination contained a similar amount of UV as Northern Daylight through the glass windows of the diamond grading houses and bourses around the world.

That was a cute finesse of the issue, as the trade and GIA have always taught to grade the diamond''s "true body color" in daylight illumination absent UV.

The issue has resurged in 2008 in Tuscon and later in the JCK show in Las Vegas when the desk lamp manufacturer, Dazor, delivered a paper and talk showing that there is little to no UV in indoor situations. The UV in fluorescent lighting and that coming through a window from daylight, falls off rapidly with distance from the light source. On the other hand GIA grading was being done within inches of fluorescent lighting where the UV content was substantial and clearly stimulating blue fluorescence in diamonds. This made them appear, and be graded, whiter than they look in lighting absent UV.

Garry''s information : "The answers from senior to top people from almost every lab on earth ranged in VS from very few to + or - 90%. If there is an average consensus for strong it would be that maybe 20% of strong blues are hazy to some extent

From this information you can see the general trade perception and perhaps misperception that very strong blue fluorescence is either a. no problem or b. almost always to be avoided.

However, there is more of a concensus when it comes to strong blue. And that is what we believe: As long as a strong blue fluorescent diamond has no hazy/milky appearance in daylight, and it has not been overgraded due to the blue fluorescence whitening the yellow body color, strong blue fluorescing diamonds are fine and often a bargin due to what Garry calls trade stoopidity.

Michael D. Cowing

 

[Garry H (Cut Nut)]

Date: 8/2/2008 1:24:07 PM
Author: michaelgem


That was a cute finesse of the issue, as the trade and GIA have always taught to grade the diamond''s ''true body color'' in daylight illumination absent UV.

There in lies the real source of confusion Michael - there never was any agreement about lighting and all the texts and info i have found from ''experts'' shows conflict within the same books.
Daylight was always used - North daylight in your hemisphere, southern in mine. But daylight does have some UV, and so I believe it is reasonable that a standard is applied to how much UV is the right amount - that means corrected tubes and regulated distances from grading lamps etc.

But better still - the same rules for digital color grading devices. And then color can be graded face upp which makes even more sense - a I radiant will look the same colour to a consumer as an I well cut round then

 

[glitterata]

Does AGS exclude fluorescence when grading color? I''m about to buy an AGS J with strong blue fluorescence. What are the chances it''s really a lower color? Is it a better bet than a GIA J with SB fluorescence?

 

[michaelgem]

Date: 8/3/2008 6:37:23 PM
Author: glitterata
Does AGS exclude fluorescence when grading color? I''m about to buy an AGS J with strong blue fluorescence. What are the chances it''s really a lower color? Is it a better bet than a GIA J with SB fluorescence?

For a period of time a few years ago AGS, EGL LA and others used a lexan filter, (the thickness and look of window glass), to remove the UV from the fluorescent grading lights. Lexan virtually illiminates all long and short wave UV. So they were doing what the trade and GIA''s founder Shipley admonished: Grade in daylight equivalent illumination, absent UV.

Because GIA did not go the Lexan route, AGS gave up on filtering out the UV with Lexan to avoid getting results at odds with GIA. Today, in order to be compatible with GIA, AGS is using the GIA Diamond Dock which the GIA currently uses for color grading.

It too has no filter for the UV, but the prescribed working distance from the fluorescent lighting in the Diamond Dock may be sufficiently far that the UV is not stimulating much blue fluorescence.

So the chances that an AGS J with strong blue is really a lower color is exactly the same a GIA J with SB fluorescence. That chance was almost a certainty when the color was graded in the Diamondlite at about a 1" distance. With the current Diamond Dock working distance to the tray the chances may have very much diminished.

Michael D. Cowing

 

[glitterata]

I see. Thanks for the clear answer.

 

[Garry H (Cut Nut)]

Thanks Michael, excellent info
Regards