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Help Deciding Between 2 Gia Diamonds!


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Hi guys, your forum has been so helpful to me in narrowing down to the following 2 diamonds. They both have their positives, but I just can't work out which is the better option? I have seen them both in person but they are from different stores so I can't see them side by side. They are relatively the same price ($300 difference), both look eye clean in the shop. Both pass the HCA test, one is better than the other, but both under 2, however the other has a slightly bigger spread, again probably not noticeable. Any feed back on either of these stones would be very much appreciated. My partner wants me to choose by the morning and I can't decide!!


Option one

GIA dated July 2012


.9 carat

Excellent cut

6.18-6.23 x 3.83mm



Polish excellent

Symmetry VG

Fluorescent none

Depth 61.7 %

Table 55%

Crown angle 35 degrees

Crown height 15.5%

Pavilion angle 40.6 degrees

Pavilion height 43%

Star 50%

Lower half 75%

Girdle thin to slightly thick 3.5%

Cutlet none

Inclusions - feather, crystal (I believe on the table)


Option 2

April 2014 GIA cert


.9 carat

Excellent cut

6.27 - 6.30 x 3.78mm



Polish excellent

Symmetry VG

Fluorescent none

Depth 60.1%

Table 57%

Crown angle 32 degrees

Crown height 13.5%

Pavilion angle 41.2 degrees

Pavilion height 43.5%

Star 50%

Lower half 80%

Girdle thin to slightly thick 3.5%

Cutlet none

Inclusion characteristics feather (near the edge but apparently not touching)


What are your thoughts? Size spread vs better crown angle? Old GIA vs new? I'm scared there is something I am missing with option 1 which is why it hasn't sold?


The jeweller also told me he didn't like option 1 as much as a different one which I walked away from (poor angles). The arrows were very thick and not sharp - not sure if that is good or not?


I want something that will sparkle like crazy out side the jewellery store and without inclusions that can be seen.


Appreciate your feed back!

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FWIW, #1 looks better on paper for me: I like smaller tables and higher crowns, and it's more likely that an SI1 will be eye-clean than an SI2. This said, this is on paper; once you see the diamonds everything may change.


Is there any way in which you can get ASET or other reflector images for the diamonds?

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Thanks for your input davidelevi, I was thinking the same on paper and in person it's to hard to tell from shop to shop, except the 2 year old certificate concerns me. Should I be worried about this? Do you think the inclusion in the table would matter in an SI1 away from jewellery lights?

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The 2 year-old report may mean nothing, or it may mean there is an issue with the stone - quite what the issue is, no-one can know without more information. Four possibilities that come to mind:


1. The inclusion is easily visible

2. The stone is not transparent because of strain or lattice distortion

3. The stone is not particularly well cut, even though it comes up with perfectly acceptable average values (which is what we see on the report)

4. It's priced out-of-market


#4 you can easily rule in or out, since you know the prices; for the other 3, the only solution is seeing the stone or at least several good quality images of it.


The fact that the vendor of #1 has mentioned "thick and not sharp arrows", but nothing to do with the inclusion, makes me think it's not a huge issue, but you never know; these things are also highly subjective: what seems like a totally minor and invisible thing to me may stand out like a sore thumb to you!


BTW - on spread, bear in mind that while it is "real" and measurable, 0.08 mm will effectively be invisible unless you have the two loose stones right next to each other.

Edited by davidelevi
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If GIA deem the diamond an excellent cut, do you often get diamonds that aren't an excellent cut? I understand that they don't take brightness, fire, scintillation into consideration?

Simple answer: neither is the case.


This is a short description of how GIA has developed its cut grading system, and it most definitely takes brightness, fire and scintillation into account; see last paragraph on the first column of page 14 here: http://diamondcut.gia.edu/pdf/cut_uncovered_winter_05_loupe.pdf


I can also honestly say that I have never seen a bad looking GIA-excellent diamond (except when the "bad look" is due to inclusions/transparency, but that's not what we are discussing).


[geek section below - feel free to skip]


However, things get a little more complex and contentious than a "simple" assessment of how much fire, brilliance and scintillation exists in a diamond: GIA also complemented the "objective" measurements of light reflection, refraction and patterning with what is effectively an extensive market research study on people's preferences (both consumers and industry experts), and then had to decide on a grading scale and set boundaries for the grades.


0. A more in-depth primer article on how the GIA cut system was developed: diamondcut.gia.edu/pdf/cut_fall2004.pdf


1. Independently of the choice of scale and how it is quantised, this automatically created stones "at the boundary" of the grades. They may or may not be visibly more or less beautiful than those just on the other side, but they end up being graded differently.


2. GIA decided on a 5-point grading scale, which intrinsically limited the ability to differentiate the "best" stones, since GIA also decided to have "fair" and "poor" grades at the bottom end. This was further compounded by the trade actually improving the average cut quality very considerably over the past 7-8 years, with the result that now about 90% of GIA-graded rounds are either "Excellent" or "Very Good". While none of the X/VG look bad, there's definitely those that look better than others, yet the consumer is locked within what is effectively a 2-grade scale.


3. The broad market research (and some suggest a lot of commercial pressure from industry insiders) resulted in a broad set of different looks, including some that are quite far away from the (old-stlye AGS) notion of an "ideal" set of proportions. For example, GIA allows "excellent" for stones that have quite a steep pavilion and thus have significantly less brightness and more contrast than typical "ideal" stones. However GIA can legitimately say that enough people liked those and put them to the top of their aesthetic preferences to justify including them into "excellent".


4. GIA (and AGS) also decided to use girdle thickness as a parameter influencing the cut grade, even though the effect girdle thickness has on light reflection, refraction and patterning is minimal, particularly within the boundaries of "normal" girdle thickness (say below 5% of diameter). As a result, you can get a diamond that is penalised into "very good" (or AGS "excellent") because of girdle thickness even though the light return - largely determined by pavilion and crown angles - is better than that of a diamond with a poorer combination of angles but a thinner girdle.


5. The methodology used by GIA to grade cut uses as input averages of pavilion and crown angles measured over the 8 main facets of the cut. This is fine, but it provides little indication of the consistency of those angles (except in as much as some is provided by the "symmetry" grade), and the resulting appearance of stones with the same grade and the same reported angles can vary quite a bit from totally symmetrical to rather asymmetrical. Does it make the diamond more or less beautiful? It may - however the lack or presence of symmetry beyond a certain level is (in my opinion) a totally personal decision.

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