Why is my new diamond not sparkly?

[John P]

...To achieve GIA Excellent symmetry the stone must have reasonably tight variations in angular differences...

Looser than you might think Garry? Human eye symmetry judgments at 10X don't pick up 1-2 degree variations in facet angles, much less 3/4 or half degrees.

A couple of years ago in a class I was teaching, I passed the attendees three diamonds: All had EX lab symmetry; great meet-point and twist, but one had huge swings in CA/PA, up to a degree on the PA. With 10X magnification no one spotted the angular issues. I did that exercise to illustrate this very point, btw.

That diamond woua .SRN file, and it's likely to be teased out in a H&A viewer. But typical human 10X symmetry inspection will still miss it. That may be conquered as we rely more and more on mechanical scans for the 2D sym grade.

 

[Garry H (Cut Nut)]

...To achieve GIA Excellent symmetry the stone must have reasonably tight variations in angular differences...

Looser than you might think Garry? Human eye symmetry judgments at 10X don't pick up 1-2 degree variations in facet angles, much less 3/4 or half degrees.

A couple of years ago in a class I was teaching, I passed the attendees three diamonds: All had EX lab symmetry; great meet-point and twist, but one had huge swings in CA/PA, up to a degree on the PA. With 10X magnification no one spotted the angular issues. I did that exercise to illustrate this very point, btw.

That diamond woua .SRN file, and it's likely to be teased out in a H&A viewer. But typical human 10X symmetry inspection will still miss it. That may be conquered as we rely more and more on mechanical scans for the 2D sym grade.

Most of the diamonds coming out of GIA that we are talking about are now being scanned on Helium John.
The criteria is strict enough that a stone like this is now right on the border of VG EX.
Now this is clearly not even a C grade H&A's (the arrows side is very nice though) but its also not a train wreck. I bet if we included this in our 10 stones for a visual only comparison that some experts would pick it as a nice stone by chance.

 

[Laila619]

A combination of the small table combined with 50 star instead of 55 and shorter lower girdle halves ?

Yes, definitely a possibility.

 

[Laila619]

Laila, can you post a picture of the ring?

Yes, I'll be posting a new thread soon with all my goodies. I was a busy girl!

 

[Laila619]

The diamond has very clear arrows but it was not sold as a hearts and arrows. Does a stone having a lovely cut but not being a true hearts and arrows really make a big and visible difference?

 

[John P]

Garry, understood... I can't sustain an extended technical exchange right now, I simply meant to share how stones that are identical on lab-paper can appear differently when seen IRL: Main causes are clarity, cleanliness & cut details.

The diamond has very clear arrows but it was not sold as a hearts and arrows. Does a stone having a lovely cut but not being a true hearts and arrows really make a big and visible difference?

I don't know about "big." The difference may be negligible or it may be notable, depending on fine details. But any experienced diamantaire sometimes encounters two diamonds that appear the same on paper, including basic proportions-numbers, but one sings while the other seems sleepy.

 

[Dreamer_D]

The diamond has very clear arrows but it was not sold as a hearts and arrows. Does a stone having a lovely cut but not being a true hearts and arrows really make a big and visible difference?

Not really.

I am wondering if your expectations were just out of line? Expecting the moon? You had a much larger stone before, which will look more impressive because of larger facets. And your original stone was a very unique cut. Go to Tiffany or Hearts on Fire and compare perhaps to see if its you or the stone that is off?

 

[Garry H (Cut Nut)]

The diamond has very clear arrows but it was not sold as a hearts and arrows. Does a stone having a lovely cut but not being a true hearts and arrows really make a big and visible difference?

Not really.

I am wondering if your expectations were just out of line? Expecting the moon? You had a much larger stone before, which will look more impressive because of larger facets. And your original stone was a very unique cut. Go to Tiffany or Hearts on Fire and compare perhaps to see if its you or the stone that is off?

Great idea Dreamer - same light in a side by side comparison.

 

[treasurehunter]

http://www.youtube.com/watch?v=MC4-hIhRoo4

heres a video of it .

 

[Texas Leaguer]

There are technical differences between a diamond with top basic proportions, and one with top proportions that also has a level of 3D optical precision to make the qualities 'pop.' When all else is equal, precise alignment of all 57 facets in 3D space promotes larger virtual facets - creating larger dispersive fans - which allows the human eye to see more/larger bursts of color. Sharper precision also promotes purer spectral hues, with less pastels, and a crisper on/off to the quality of scintillation.

John, this is a most eloquent explanation of the practical implications/benefits of top optical precision.

As others have speculated, the problem with this diamond might be a residue of some sort (needs cleaning), optical precision may be causing some loss of performance, a clarity feature may be impeding light (maybe one not listed on the cert), or perhaps a combination of minor effects from more than one of these factors.

The suggestions already made are great: Make absolutely sure the diamond itself is clean. Send it to knowledgeable appraiser to verify the cert and study the stone, get side by side with a comparable stone.

With regard to the possibility of clouds or other potential clarity issues, the labs generally plot that which will support the clarity grade and positively identify the stone. Normally additional clouds would at least be mentioned in comments. But, because the grade setting inclusion was the crystal, the grader may have neglected to plot or mention something else that would be relevant to performance, though not necessary to identify the stone or support the grade.

 

[Laila619]

So you're saying there could be clouds but they were not mentioned? I believe they have to at least mention it on the report, i.e. "clouds not shown." This stone is completely clean save for that one lone black crystal.

I have concluded that it is a nice and pretty stone. It's just too small and that is why it's hard for me to see the fireworks and the light play. Like Dreamer said, I am used to a much bigger stone and to the more unique and fiery cut of the Leo I used to have, which had a 36 something crown angle.

 

[Dreamer_D]

So you're saying there could be clouds but they were not mentioned? I believe they have to at least mention it on the report, i.e. "clouds not shown." This stone is completely clean save for that one lone black crystal.

I have concluded that it is a nice and pretty stone. It's just too small and that is why it's hard for me to see the fireworks and the light play. Like Dreamer said, I am used to a much bigger stone and to the more unique and fiery cut of the Leo I used to have, which had a 36 something crown angle.

That seems quite possible! So are you going to keep it or send it back?

 

[Texas Leaguer]

So you're saying there could be clouds but they were not mentioned? I believe they have to at least mention it on the report, i.e. "clouds not shown." This stone is completely clean save for that one lone black crystal.

I have concluded that it is a nice and pretty stone. It's just too small and that is why it's hard for me to see the fireworks and the light play. Like Dreamer said, I am used to a much bigger stone and to the more unique and fiery cut of the Leo I used to have, which had a 36 something crown angle.

Yes, I was suggesting that, as one of the possibilities in this mystery, there could be a clarity feature at play that is not mentioned on the cert. That is why evaluation by a really good gemologist is a good idea.

It certainly could be a matter of expectations and have nothing to do with anything physical. That's why the side by side is a good idea.

 

[MissGotRocks]

Laila, can you post a picture of the ring?

Yes, I'll be posting a new thread soon with all my goodies. I was a busy girl!

Good! Can't wait to see! At this point I'm sort of in the camp that it's the diamond size throwing you off as you're not going to get those big flashes like you would with a larger stone. I'm still thinking it must be pretty though!

 

[Rhino]

Dreamer, it is set.

I've been wearing it out and about in public and I'm just not that impressed. I haven't seen a ton of ideal cut diamonds in person before, so maybe I am just expecting too much, but I wonder if it wouldn't make AGS0 for light performance.

It has to be that lone crystal if I had to guess.

I've had and shot video of GIA Ex's with these proportions that get AGS 3 in light performance. Numbers on a GIA Report is no guarantee of anything Laila.

Regards,
Jonathan

 

[Laila619]

Dreamer, it is set.

I've been wearing it out and about in public and I'm just not that impressed. I haven't seen a ton of ideal cut diamonds in person before, so maybe I am just expecting too much, but I wonder if it wouldn't make AGS0 for light performance.

It has to be that lone crystal if I had to guess.

I've had and shot video of GIA Ex's with these proportions that get AGS 3 in light performance. Numbers on a GIA Report is no guarantee of anything Laila.

Regards,
Jonathan

Interesting, Rhino. But what causes this? I thought light performance was determined by cut.

Dreamer, not sure yet, I'm thinking about it.

 

[Dreamer_D]

Dreamer, it is set.

I've been wearing it out and about in public and I'm just not that impressed. I haven't seen a ton of ideal cut diamonds in person before, so maybe I am just expecting too much, but I wonder if it wouldn't make AGS0 for light performance.

It has to be that lone crystal if I had to guess.

I've had and shot video of GIA Ex's with these proportions that get AGS 3 in light performance. Numbers on a GIA Report is no guarantee of anything Laila.

Regards,
Jonathan

Interesting, Rhino. But what causes this? I thought light performance was determined by cut.

Dreamer, not sure yet, I'm thinking about it.

I think Rhino is suggesting that with rounding on the cert, its still possible your diamond would score poorly on other physical measures of optical performance.

 

[Garry H (Cut Nut)]

Dreamer, it is set.

I've been wearing it out and about in public and I'm just not that impressed. I haven't seen a ton of ideal cut diamonds in person before, so maybe I am just expecting too much, but I wonder if it wouldn't make AGS0 for light performance.

It has to be that lone crystal if I had to guess.

I've had and shot video of GIA Ex's with these proportions that get AGS 3 in light performance. Numbers on a GIA Report is no guarantee of anything Laila.

Regards,
Jonathan

I think you are stretching the numbers Jonathon?
Do you have a real example with these numbers and GIA X for cut and symmetry?

 

[Rhino]

Dreamer, it is set.

I've been wearing it out and about in public and I'm just not that impressed. I haven't seen a ton of ideal cut diamonds in person before, so maybe I am just expecting too much, but I wonder if it wouldn't make AGS0 for light performance.

It has to be that lone crystal if I had to guess.

I've had and shot video of GIA Ex's with these proportions that get AGS 3 in light performance. Numbers on a GIA Report is no guarantee of anything Laila.

Regards,
Jonathan

I think you are stretching the numbers Jonathon?
Do you have a real example with these numbers and GIA X for cut and symmetry?

No stretching Garry. I believe the diamond also scored a 1.7 vis HCA. I'll see if I can hunt down the material. I know the video though for sure which has all the data in it.

Laila it is true light performance and beauty is determined by cut. When it comes to optical performance and particularly as it is examined via AGS's system it performs and optical analysis based on the actual model of the diamond being scanned and examines all it's nuances including how the half facets impact the contrast, the dispersion, etc. This also includes if facets are oriented or skewed in the east/west direction as opposed to the north/south direction.

Ie. When you see crown/pavilion angles on a diamond those are considered to be the "slope" angles which are oriented in the north/south direction. Since diamond is a 3 dimensional object, if the facets in the east/west orientation are skewed it can cause unwanted light leakage in a diamond, thus impacting it's optical grade in the AGS system. I can't say for sure that is the case with your diamond but I would know for sure with a physical inspection of it. It is also why I never ever purchase off of paper alone.

Kind regards,
Rhino

Edited to add: Found the vid. The data on the GIA Report is as follows...

1.13ct H SI1 with

Total Depth: 60.7%
Table: 59%
Crown >: 34.5
Pavilion >: 40.8
Girdle: thin to medium
Stars: 60%
Lower halves: 80%

A combination of numbers any seasoned PriceScope prosumer would give a hearty two thumbs up on. And at the time of shooting did score a 1.7 on the HCA although it may have changed since that time.

 

[Garry H (Cut Nut)]

Edited to add: Found the vid. The data on the GIA Report is as follows...

1.13ct H SI1 with

Total Depth: 60.7%
Table: 59%
Crown >: 34.5
Pavilion >: 40.8
Girdle: thin to medium
Stars: 60%
Lower halves: 80%

A combination of numbers any seasoned PriceScope prosumer would give a hearty two thumbs up on. And at the time of shooting did score a 1.7 on the HCA although it may have changed since that time.

Not comparable, mainly because of the star's and table size - what about sharing the full reports Jon, GIA and AGS-PGS?
If you have the .gem or .srn please send it to me for a Helium report.

Here is what we are comparing:
The stone's stats are as follows:
Cut grade: Excellent
Table: 55 %
Depth: 61.4 %
Crown: 34.5 degrees (15.5 %)
Pavilion: 40.8 (43 %)
Star: 50 %
LGF: 75 %
Girdle: Thin to Medium
Polish: Excellent
Symmetry: Excellent
Fluor: Medium Blue

 

[Laila619]

I wouldn't have bought that one with a 59% table! I swear I can see a difference in diamonds with even a 54/55 table compared to a 57/58 table.

 

[Rhino]

Edited to add: Found the vid. The data on the GIA Report is as follows...

1.13ct H SI1 with

Total Depth: 60.7%
Table: 59%
Crown >: 34.5
Pavilion >: 40.8
Girdle: thin to medium
Stars: 60%
Lower halves: 80%

A combination of numbers any seasoned PriceScope prosumer would give a hearty two thumbs up on. And at the time of shooting did score a 1.7 on the HCA although it may have changed since that time.

Not comparable, mainly because of the star's and table size - what about sharing the full reports Jon, GIA and AGS-PGS?
If you have the .gem or .srn please send it to me for a Helium report.

Here is what we are comparing:
The stone's stats are as follows:
Cut grade: Excellent
Table: 55 %
Depth: 61.4 %
Crown: 34.5 degrees (15.5 %)
Pavilion: 40.8 (43 %)
Star: 50 %
LGF: 75 %
Girdle: Thin to Medium
Polish: Excellent
Symmetry: Excellent
Fluor: Medium Blue

LOL... I didn't say it was *exactly* identical. Of all proportional measurements there will be bigger notable differences in crown/pavilion/lower half data than a couple % in table size. The point being there is nothing alarming about the numbers on the GIA Report or the HCA score. I see similar diamonds recommended all the time. The table could have been 57% instead of 59% and it would have still gotten AGS 3. If I locate the file I'll send it to you Garry.

Kind regards,
Jonathan

Edited to add: One correction. I found the video and watched it again. It actually got an AGS 2 instead of the 3 I had thought. In either case the diamond did suffer in it's optics of brightness, fire and sparkle.

 

[Rhino]

My first instinct (SI2) was potential clouds. I know others asked but I'd ask again, any chance there is a comment about clouds on the report? ... My second instinct was to ask if it's clean and that's been covered from here to yonder (which is Texan for 'there').

Also, what is the optical symmetry like in this stone? Perhaps you are used to a more random type of patterning and this one has more precise symmetry, or vice versa?

It's a cut-nerd topic, but certainly worth consideration. There are technical differences between a diamond with top basic proportions, and one with top proportions that also has a level of 3D optical precision to make the qualities 'pop.' When all else is equal, precise alignment of all 57 facets in 3D space promotes larger virtual facets - creating larger dispersive fans - which allows the human eye to see more/larger bursts of color. Sharper precision also promotes purer spectral hues, with less pastels, and a crisper on/off to the quality of scintillation.

The basic numbers are great, but remember that '40.8' and '34.5' both stand for 8 separate measurements. We don't know what the deviation from those averages is. 40.8 could imply 40.6, 40.6, 40.7, 40.8, 40.8, 40.9, 41.0, 41.0 / or it could imply 40.2, 40.3, 40.5, 40.6, 40.9, 41.2, 41.3, 41.4 / which is a different prospect with less 'pop'. 34.5 also represents 8 different measurements, and 75% stands for 16 different measurements.

Going farther, GIA reports round the given averages. So where you see '34.5 degrees' printed, the actual average was rounded to the nearest 0.5 degree, meaning the real number could be 34.3-34.7 (cut-nerds will say 34.26-34.74). And where you see 75% it was rounded to nearest 5%, so the actual number could be 73-77%. The good news, in this case, is that the averages are so centrally positive that the true numbers will not be straying into areas which cause any reduction in brightness. We just don't know the level of cut-consistency or optical precision here.

I wonder if you are used to a stone with longer lower halves and thus quicker scintillation?

This is also valid, especially with the rounding aspect possibly making the number 73%. Candidly, I'd hope shorter LH would promote larger visual events in this size, which could be a positive? But what's being seen could either be either deviations from average numbers or sub-par optical precision coupled with size, since a 0.77s dispersive fans are smaller than 1.00+ to begin with.

On the whole, with all the above said, the basic numbers are nice. In my experience that's enough for most people, but not necessarily for everyone. You may have very astute eyes and expectations for a certain 'pop' which aren't being fulfilled. No problem with that, I know many people who occupy that niche. Or, it could simply be as others have suggested, and you may prefer a different flavor than the modern RBC. Either way, you're not wrong for wanting what you want.

Was thinking about this and these are precisely my thoughts too and which I had brought out in my own example. Excellent points John.

Rhino