proportions on EGL certificate

[momo]

My objective is to get a diamond that is the most brilliant within my budget. The visual performance is the key and I do not care as much for color and clarity.

I have several stones in my mind which all have EGL cerfiticates. They all have "excellent proportions" grading. I was wondering what are the criteria for the "proportions" grading on EGL cerfiticates?

I asked the vendor for crown/pavillion data and ran the HCA, then the results were far from excellent (despite the excellent proportions grade on the certificate). So I am a bit confused.

I believe EGL certificate usually do not have crown/pavillion angles (just %), so it might be difficult to be precise, I guess?? I now started thinking if you are very concerned with cut, then it is safer to go with GIA/GIS stones that come with Sarin? Am I correct???

 

[Garry H (Cut Nut)]

GIA give even less data.
The %'s are rounded and not as accurately stated for pavilion as angles. But you can narrow down the stones with HCA and %'s and then ask only for a Sarin on the best stones.
Also ask the vendors if they have an ideal-scope photo or they can examine the stones with one and comment - this will ensure there are no obvious symmetry defects etc which HCA will not be able to predict.
But contrary to some beliefs - if HCA predicts the stone is >3 from % data you will not be missing anythin worth loooking at.
As always - if you are buying unseen then have the stone shipped first to one of the appraisers on the list - this also sends the message to the vendor that they will be audited

 

[Brian Knox]

Hi,

You asked:

I now started thinking if you are very concerned with cut, then it is safer to go with GIA/GIS stones that come with Sarin? Am I correct???


Yes, absolutely !

I would recommend AGS or GIA with a sarin.

Also, it sounds like you might be looking at a foreign EGL report (does it say EGL-USA?)

Foreign EGL reports are notoriously "weak" with respect to color and clarity.


Brian

 

[valeria101]

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On 3/26/2004 10:27:30 PM brianknox wrote:



Foreign EGL reports are notoriously 'weak' with respect to color and clarity.

----------------

Yeah, but the stones are discounted as such. An EGL piece with good HCA and Iscope results would be quite a find. It is good idea - I think - to compare the price with GIA grade stones with either one color or clarity grade LOWER. But since GIA does not give any proportions on the cert, and AGS certerd stines cary a premium, I surely agree that EGL + extra light return test is a good receipe for success.

I would drop the Sarin: once you get it all you can do more than just with the numbers on the cert is another HCA using angles. The reading would a tad more precise (and probably better) but many other features of the cut would still not be accounted for by your analysis. An Iscope pic would give a realistic representation of light return - all that remains to be known. Asking for Sarin you would still have reason to use the Iscope, so why not take a shortcut?

What size do you have in mind?

 

[LadyJ]

OK I am not an expert on this at all. All I know is what I read here and other places.

My findings, and as I said based on what others told me, were that EGL can SOMETIMES be wrong but can SOMETIMES be right. They are not as consistent as GIA. I wanted a GIA for this reason. Like I said this is info I read from others posts so that is why I wanted a GIA. Also I had an expert confirm this for me stating that to put it nicely the standards they have are sometimes not as high. A nice way of saying that it is sometimes an integrity issue. I am sure this is debatable. But he did add that he recently saw an EGL the matched the cert perfectly and was a beautiful stone. So I guess there are wonderful EGL's to be found and I am sure that you can't paint them all with the same brush. There are probably people here at pricescope who have great EGL stones. I was just put off by some of the comments I read and that is why I did not consider an EGL. You'll notice most mall stores have EGL. Not being an experienced diamond buyer was another reason I felt safer with GIA.

For my piece of mind I went with GIA.

 

[Brian Knox]

Well done,

You made the right move.

Brian

 

[valeria101]

Agreed with Brianknox. GIA has lots of clutter, AGS carved it's reputation with the cut grades but NO lab's certs are robust to recertification. If one submits a diamond to the same lab repeatedly, it will return with different grades up to a certain probability). Variations of one grade are expected in both color and clarity.

This has been tried on very small samples, but all labs would more or less agree to it in some ways: the grades are not guaranteed. With GIA certs you buy the credibility created by market share - not absolute grading precision (technically impossible until present). The discount applied to diamonds certified by smaller labs or known 'lenient' already takes into account their market position and reputation. Again, variations of one color and clarity grades are expected. So you can compare prices with GIA/AGS stones graded one grade higher. Foe AGS comparisons cut is a factor - so these are not as tell-tale.

Why such approximations are acceptable? Because adjacent diamond color grades are not distinguishable 'face up' and appraisals or grading of stones 'in mounting' are also done with one grade tolerance. So? the 'look' of the stone is less dependent on that one-grade shift than is it's price. the above-mentioned discount takes care of this.

You like?

 

[fire&ice]

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On 3/26/2004 11:09:05 PM valeria101 wrote:

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On 3/26/2004 10:27:30 PM brianknox wrote:



Foreign EGL reports are notoriously 'weak' with respect to color and clarity.

----------------

Yeah, but the stones are discounted as such. An EGL piece with good HCA and Iscope results would be quite a find. It is good idea - I think - to compare the price with GIA grade stones with either one color or clarity grade LOWER. But since GIA does not give any proportions on the cert, and AGS certerd stines cary a premium, I surely agree that EGL + extra light return test is a good receipe for success.

----------------

Ana, you are correct. This is something that people fail to recognize. EGL stones, in general (even the USA ones) are discounted and can be good values as long as one is paying the correct amount for the proper specs.

It is a foolish argument to get a GIA/AGS stone because it may be easier to sell. First, one doesn't plan on selling a stone. Second, if one is in the position of having to sell, GIA certs can be had.

As long as one verifies the specs w/ an appraiser, it really doesn't matter what cert a stone has. I've got an EGL, GIA, AGS & now an IGI stone. Except for the IGI stone which was purchased for nothing, my EGL stone represented the best value.

 

[hoorray]

Agreed F&I and AnA. To me the cert is good for 3 things: 1. helping make a buying decision buy listing specs from an unbiased source, 2. helping sell the stone (becoming #1 for the potential buyers) and 3. helping identify a stone. There is no reason an independant appraiser can't do #1 & 3 for you. I wouldn't worry about selling ths stone until it becomes an issue. So, if the EGL stones are discounted, and an appraiser accurately evaluates the stone for you, you have the opportunity to find a better value. I wouldn't buy an EGL stone without an appraisal and good return policy tho!

 

[fire&ice]

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On 3/27/2004 11:07:20 AM lop wrote:

I wouldn't buy an EGL stone without an appraisal and good return policy tho! ----------------

But, I wouldn't buy any diamond regardless of cert w/o it (not for a small purchase - a big one).

 

[hoorray]

good point -- neither would I.

 

[momo]

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On 3/26/2004 10:27:30 PM brianknox wrote:

Hi,

Also, it sounds like you might be looking at a foreign EGL report (does it say EGL-USA?)


Foreign EGL reports are notoriously 'weak' with respect to color and clarity.



Brian----------------

How can you tell which EGL issued the certification? Does it say on the cert?

It seems lots of people agree EGL grading is not as consistent as GIA grading, but it affects only color and clarity? In other words, when it comes to numeric data such as table, depth, crown and pavillion, then can we be pretty much sure that they are accurate?

The stone I am interested has the following data;

0.76ct G VVS2
5.96*5.91*3.51
depth 59.10
table 58
crown 15
pavillion 46
girdule mid
culet none

EGL cert says the proportions are "excellent". But when I run the HCA, it says the girdle might be dangerously thin. Is this because the rounding effect of crown and pavillion %? Or is this because the data itself might be an error? What would you say?
Another question of mine is if an independent appraisal is worthwhile for a stone of this size?

 

[strmrdr]

leaving the egl cert aside for a second.
You say your looking for a well cutt diamond top performing diamond.
That one is a largesh table shallow stone they arent known for being top performers.

Id say yes that the thin girdle warning is because of the rounding the egl cert says med. and Id trust that over the hca warning.

It really depends on what you want but if you want to buy based on cut then the tutorial here and the one at www.goodoldgold.com are the places to start.

goodoldgold.com

 

[momo]

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On 3/27/2004 3:01:28 PM strmrdr wrote:



That one is a largesh table shallow stone they arent known for being top performer
----------------

I read somewhere if depth is from 58.7 to 62.4 and table is from 53 to 58, then it is ultra^ideal??

 

[strmrdr]

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On 3/27/2004 3:20:52 PM momo wrote:

----------------

On 3/27/2004 3:01:28 PM strmrdr wrote:




That one is a largesh table shallow stone they arent known for being top performer

----------------

I read somewhere if depth is from 58.7 to 62.4 and table is from 53 to 58, then it is ultra^ideal?? ----------------

It depends on whose idea of ideal your looking at.
The problem is that a lot of different groups consider different things ideal some are stricter than others.
As more science is applied to diamonds the ranges change slightly and that results in some of the confusion.
Also what is considered ideal and super-ideal here is much stricter than at other places.
We tend towards the very top performing diamonds and insist on the information to make that determination.
We are also willing to pay and recommend others pay when needed a slight premium to get it.
The tutorials will explain why we recommend the ones we do and why we are picky about cut.

 

[Brian Knox]

Hi Momo

You asked :

How can you tell which EGL issued the certification? Does it say on the cert?

Yes, EGL USA will say "EGL USA"

EGL foreign will just say "EGL"

BTW I have seen EGL foreign certs that have been off by two grades

 

[Magnum]

Did you actually see the EGL report, or did the vendor read the numbers to you? The reason I ask is because all the numbers look good accept for the pavilion depth percentage. If it really was 46%, than it suggests a very deep pavilion. However when you plug the numbers into the HCA, it says

"The total depth % you entered suggests the girdle is dangerously thin, or the data you entered is incorrect."

I think it may be the second case because if you look at all three depth percentages, the numbers don't look right.
46% pavillion + 15% crown should give you a total depth closer to 63% with a medium girdle, and even if the girdle was a knife-edge (0%) that would still be 61%, which is almost 2% more than the 59.1% you listed.

I'm definitely not an expert, so maybe someone else can chime in, but my guess is that the 46% pavillion depth was either misread to you or may be a misprint.

Magnum

 

[Garry H (Cut Nut)]

Magnum your interpretation is very good (and welcome).
No more to add, except that some people are unaware that HCA does consider the girdle thickness which it calculates from the data entered.
We have a desk top model that accepts direct entry of girdle data but we think it is too dangerous for consumers to enter it since most can not get it from the available sources and there are 2 different places different las use to measure girdle.

 

[valeria101]

The girdle would be up to 2% or so... but not constant. The other mesures are themselves averages of numbers 1% or so apart. SO the puny girdle numbers are of the same order of magnitude as the measurement error for the crown and pavilion depths. Conclusion? The HCA works better for stones with thin-medium girdle and somewhat worse for the others. Thin-medium girdle is already desirable... I would not discount the use of the HCA for this issue: given the same consideration - the measure of the girle is swamped in the error level of the model anyway