Can you see difference; VG - EX - ID polish, etc

[kirk]

This is my first posting to this site. It is amazing what I have learned from everyone''s various entries these past few months. GREAT SITE!!!

Question - is there a visual difference between a ''VG'' versus ''EX'' versus ''ID'' Polish and Symmetry ratings for a brilliant cut - approx .80cts?
I suspect the symmetry differences between the three ratings could be detectable with the unaided eye - but not sure.

I have narrowed my search to various center stones that primarily differ by these two characteristics (Polish , Sym).

Also - is there a significant visual (unaided eye) difference between a Flourescence rating of ''N'' versus ''F'' versus ''MB'' - given the ring is in everyday conditions of sunlight and typical indoor lighting?

Thanks to everyone for their candid comments and interest to provide useful info on this site.

 

[WinkHPD]

Sometimes it will take an expert a LONG time with a microscope to detect the tiny drag line or missalignment of facet junctions to drop the stone from ideal to excellent or vg. You definately can not see this with they eye and the difference is more for those buying paper than those buying beauty.

There are those things in the cutting of a diamond that make a visible difference, like the combination of pavilion and crown angles and the total depth and table sizes that are largely a result of those angles. A poorly cut stone with excellent excellent is indeed a thing of ugliness while a Hearts and Arrows cut or an EightStar with a very good polish and symmetry is still a joy to your eyes.

Wink

 

[hoorray]

On the flouresence issue, it usually will discount the price of the stone because it is not as in favor right now as it was 15 years ago. On lower colored stones it can make them look more white, so it's a good thing. Lots of people actually prefer the look of a stone with some flouresence. The only negative is that a small percentage of stones will get a milky or oily/hazy look in direct sunlight as a result of the flour. Check out the look of the stone in various lighting situations -- particularly direct sunlight, looking for a hazy or milky look. If this doesn't happen, the flour can be a good thing. (You didn't mention what colors these stones are.)

 

[valeria101]

Here comes worse...

Most mortals would agree that "none" and "faint" fluorescence are about the same. You may see the word "neglijable" on a cert standing for... either.

MB is a little more, but not enough for the vast majority of people with or without experience to deterct. While stats are tricky to apply to individual cases, it may help to keep in mind the result of a GIA panel: none of the inexperienced viewer selected could detect any visual effect of fluorescence in normal light, and among experts 50% did see "something" in some stones but could not consistently tell those with fluorescence apart.

This being said, it is still true that fluorescence makes a more or less strong pricing factor, you would need to take into account when buying. More often it des discount a D-F stones and sometimes bring a premium for an I-J. In theory, blue fluorescence should make a stone look whiter when UW is present in the light source. In practice... it's too faint an effect to really work. If you do decide to value a stone based on looks rather than paper, than fluorescence below "strong" should not be of concern. About 3% of the stones with "strong" fluorescence would have it strong enough to show some visual effect of it in daylight.

 

[fire&ice]

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On 5/22/2004 11:48:31 AM valeria101 wrote:


Here comes worse...

In theory, blue fluorescence should make a stone look whiter when UW is present in the light source. In practice... it's too faint an effect to really work. src="https://www.pricescope.com/idealbb/images/smilies/read.gif">


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Ana, you keep saying this and I have to disagree. I always can pick out the stone w/ bl. fluor. And, more often than not, a stone with at least med blue *will* face up whiter in *most* lighting conditions. Every one of my stones have bl. fluor in at least medium.
Also, the jeweler in the GIA study *did* pick the stones w/ Bl. Fluor as the prefered rock.

That said, no, one's eye can not tell the difference between the VG to EX polish & sym. grades. Though it does go to issue of the care in which the stone has been cut.

 

[WinkHPD]

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That said, no, one's eye can not tell the difference between the VG to EX polish & sym. grades. Though it does go to issue of the care in which the stone has been cut.

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Minor dissagreement on this comment.

Often it goes to the issue of the graining or crystal orientation of the stone. Some diamonds just do not want to take a high polish on some facets, and the best cutter in the world can not make it perfect with such a stone.

This is especially true with diamonds that have enveloped smaller diamond crystals within them. Those facets that touch the included crystal can be a nightmare for the cutter. Cutting can be an extremely tedious job on some diamonds, and over in only a short time for others.

Wink

P.S. I share your enjoyment of fluoresent stone. All but two of the stones in this ring have fluoresence, one a strange chalky yellow and the rest various shades of blue, it is a really COOOOLLLL ring to wear at a night club. I have worn it for more than twenty years now and alternate it with a couple of other very beautiful and also fun rings.

 

[Garry H (Cut Nut)]

Just for fun, Peter Yantzer the director of the AGS lab, can not tell the difference between ID, EX or Good polish with his naked eye.
These are craftsmanship awards for a job well done, but have little effect on the diamonds face up appearance.

 

[zeytoun]

I worked in the GIA diamond grading lab for a while. Me, and most people there, could not tell the difference between good, very good, and excellent polish with the naked eye. Fair, yes. Symmetry, yes. As for flourescence, most of us could often pick out high end of medium blue flourescence with the naked eye, before verifying with the UV box. Low end of medium blue, it was iffy. Most other colors, probably not. Strong Blue flourescence, almost certainly. Although, probably you wouldn't notice a medium blue fluorescence in regular light.

 

[Garry H (Cut Nut)]

Interesting Zeytoun, so you could pick a diamond with stroung fluoro: what sort of lighting environment? And what you were seeing - was it bad, just a feature or good?

 

[zeytoun]

The light in the GIA's New York lab was rather subdued, with a small lamp on my desk. Looking back, I'd say that I was maybe 50/50 accurate when I guesses a stone had medium flourescence, and perhaps 75/25 when I thought it was strong. Officially, we just considered flourescence a characteristic, with no affect on any other grades, but you know how often they're considered less desireable. I always thought they were cool, and my favorite was a fancy pinkish-orange with strong orange flourescence we had in once. If I were in the market for an expensive stone, I would have been sold in a heartbeat by the strong orange flourescence (and of course, the very nice fancy color).

 

[eyesoftexas]

Gary,
Was there any discussion regarding your friends research into the different grade polishes and its effect upon light return. Was this disscussed in Moscow?

 

[Rhino]

Welcome to the forum zeytoun. Glad to have an ex-GIA grader around.

I would concur with what has been said here. The polish factor is perhaps the one aspect that has the least impact on the visual appearance of the diamond although I have come to appreciate the high gloss sheen of GIA Ex/Ex's and AGS 0's.

Having said this however *most* stones I've seen that are GIA VG or G with polish/symmetry had optical symmetry that is would best be described as CHAOTIC.

 

[Garry H (Cut Nut)]

Good point E'sof T.

Really bad polish has little effect on percieved brightness etc. But it made inclusions look larger. We suppose it is the effect that makes those sheets of plastic magnifyers. It is 5.30am and the word escapes me.

 

[zeytoun]

Fresnel?

And thanks for the welcome guys. Re: Rhino's comment on the GIA's recent grading.... without saying too much, there have been some interesting developments at GIA's New York lab the last couple years that might explain. I only worked there for a little over a year from July '02 to August '03, so I'm no expert. But I was priveleged to see quite a few unusual stones close up; fancy colors of all shades and large stones, including a 100+ carat IF, a few flawlesses where we had to plot 30x pinpoints for ident.

 

[Garry H (Cut Nut)]

Yup Zeytoun, that is the word i was looking for (with sleep in eyes). Newsagents and staioners sell page sized plastic sheets with circular grooves that can magnify a whole page at a time. These same fresnel grooves can magnify inclusions if they are posilshed onto a diamond. (but I doubt we would manage 30X for ID purposes

)

Your comments have been appreciated. Welcome aboard. You would be surprised at the lurkers who can never post on this forum, but watch and read and occasionally communicate in private, and maybe we all learn a little more from each other.