crown angle vs. percent

[targa]

this site is great- for a 1 week novice looking into buying his first stone, i no longer feel intimidated when talking to merchants!

I have an EGL report from a vendor who says he can''t get me the sarin.

1. how much more accurate is the hca with angles vs. percent?
2. what do people think about the following stone?- got 1.4 on hca using percent.
3. should i worry about the thin girdle- faceted?


price $10,442

EGL cert
1.76 carat
round brilliant
7.92-7.85 x 4.69
total depth= 59.5%
table width= 60%
crown height= 13%
pavilion depth= 43%
girdle= thin, faceted
polish= vg
symmetry= vg
culet= none
clarity= si1
grain= none
color= f
fluoro= mod blue

thanks for the expert help!
targa

 

[RockDoc]

Targa

It depends on what you want. Have you spent time looking at stones, so you can determine what your real preferences are?

If not you might want to peruse the jewelers in your area and do some research.

If you''re looking for a diamond that is Ideal Cut, the one you posted is probably not what you want.

The HCA favors stones that are shallow...

If the seller wont get you a Sarin report, find one who will.... if this concerns you.

You might want to consider GIA or AgS as the lab of choice...Depending on which one it is, separate EGL labs can vary..
AGS and GIA have far better consistency in grading.

Rockdoc

 

[pqcollectibles]

The diamond you''ve posted is very close to a 60/60. You can read about them in the Tutorial by using the Knowledge link at the top of the page. You''ll have the look of a heavier carat weight because of the spread. This diamond will probably tend to be more brilliant in performance. Meaning more white light than flashes of color.

Rock Doc is right, tho. If the Vendor won''t get a Sarin run for you, find a Vendor who will. A Sarin is very inexpensive to run and doesn''t take long either. Even if the Vendor has to ship the diamond to a lab. Most larger metropolitan areas in the US have a Sarin available right in town.

The HCA tends to be much more accurate when using angles. Your score can be right on or it could vary by maybe as much as double if you had the actual angles. Currently, similar EGL Certed diamonds are being offered by PS Vendors for $800 to $1,000 more in price than you''ve been quoted.

 

[targa]

thanks rockdoc, but without the crown angles how can you tell it wouldn''t fall into an ideal cut (ags 0)? my personal preference is for extreme brilliance, it appears that this stone is quite brilliant. would you consider it a good buy/quality for what it is?
thanks

 

[targa]

btw, i also forgot to ask about the fluorescence- other than blue fluorescence in the dark, will it affect the F colorless appearance in normal lighting situations?
thanks

 

[Garry H (Cut Nut)]

just a couple of points

1. EGL USA has a better rputation than EGL in other countries (confirmed from my personal experiance)
2. The stone will probably be a better buy than an AGS orGIA - read the lab survey on the front page. (You too Rocdoc)
3. HCA is best used to narrow donw possible nice stones - it likes this one - you can delve further - like appraiser or more info from vendor etc
4. Rocdoc says some silly things. HCA does not "The HCA favors stones that are shallow", it includes stones that are shallow as well as those with all the proportions that have been favored by all the latest researchers including GIA and AGS.
5. AGS and GIA will include 61% table sizes in their new ideal round candidates.

 

[valeria101]

Looking at that HCA score this is one of the good 60/60. Just fine!

Not only the score is high, but the combination of crown and pavilion angles falls right among the best awarded for this set of proportions - this simply means that even if those percentages are not very precise it woul d tage some outrageous level of error to push the true score down to bad.

About "faceted girdle" - that's the usual way only the word "faceted" does not appear on other lab reports.

About fluorescence - well, that is blue ("moderate bleu") so if anything it would make this cherry even brighter white when the lighting conditions turn fluorescence on, IMO. This has been debated allot around here, so you will find dozens of threads about fluorescence. As far as I remember, it usually turned out a keeper.

Of course the stone remains to be seen. It is SI1 so it does matter what and where the inclusions are. Do you have at least a copy of the clarity plot on the lab report ? I guess you will see this one anyway during the return period, one picture just makes the process faster.

Just my 0.2 worth, as usual...


Now, I am not sure about HCA being more or less in favor of shallow depths. I remember it took a while for someone to find a H&A with "FIC" proportions a bit back, perhaps these are just fewer out there for the HCA to judge. It would be interesting to se this on a chart

 

[valeria101]

Perhaps there is some intricacy not showing here ? Not being that involved with diamonds, all I see is the chart... much easier to read. If the HCA favored shallow over deep, more high scores would be awarded to combinations of angles that correspond to shallower depth - on the chart, the red/orange area above the diagonal would be larger. It doesn't appear that way.

So... there is one place left for the bias to hide: as is, "average depth" is given by the combinations of angles on the diagonal. If that is considered shallower than some standard, than, yes, the HCA has the respective bias pro shallow diamonds.

The chart is the version for 60% table - so the old AGS standard does not apply.

When it does (taking another chart, pinned on a different table diameter) indeede there are more HCA winners above the old AGS0 line than below. The revised AGS ideal zone expanded upwards (LINK to chart). Obviously any institution can and does change it's policies just like AGS does and GIA is with their prospective cut grades.

(btw. this is classic thread hijaking - if anything on this post applies to the diamond discussed here, I really did not intend it so!)

 

[targa]

thank you all for the info. i do have the egl cert with the chart and will attach it for inclusion review. I still have some uncertainty about girdle thickness, when i read the tutorials i get a sense that thin to med is a good range to be in- but many of the posts talk about the danger of thin girdles with respect to chipping of the diamond in a solitaire setting any thoughts?

 

[targa]

attached is the egl cert to look at the inclusions- thanks

 

[Garry H (Cut Nut)]

Forget about smart analysis from clarity plots.

The thin girdled EGL standard = more like medium on GIA standards - not a worry at all.

The diamond is not EGL USA certed - I would expect it to be softer than most USA certs would give it, but if the price is OK then the fluoro will help the color - it would be well worth having an appraisers opinion on the stone.

I modeled it on DiamClac and it seems to have a high probability to fall in a sweet spot