Shouldn't an ideal cut stone score well on HCA?

[ice empress]

I decided to use the HCA tool for fun, and am quite confused by the score...

Though the diamond in question has been rated as having an "ideal" cut by 2 independent labs (EGL-Canada and GemScan), it rated a dismal 4.6-Good (with the GemScan numbers) and 6.3-Fair (with the EGL numbers) on the HCA scale. My question is... shouldn't an ideally cut diamond almost automatically score well?

I know the diamond sparkles, fires, and scintillates like crazy in real life, so perhaps an abstract number on a scale is unimportant... but I was disappointed nonetheless. I plugged the numbers in and thought the score would definitely be <2.

Here are the stone's measurements, which differ slightly between appraisals:

As per EGL:
- Measurements: 7.66 x 7.63 x 4.72mm
- Depth: 61.7%
- Table: 59%
- Crown: 34º
- Pavilion: 41.8º
- Cutlet: none

As per GemScan:
- Measurements: 7.67 x 7.63 x 4.75mm
- Depth: 62%
- Table: 56.3%
- Crown: 34.4º
- Pavilion: 41.4º
- Cutlet: very small

 

[thediamondshopper]

From the info you provided one or both of their machines aren't calibrated properly. There are large differences in the proportions.

This diamond definitely would not make GIA excellent or AGS ideal which are much more accurate and reputable cut grades. Where this diamond suffers in in the Pavilion angle, it is too steep to be called an ideal cut, but if you like the look end of the day that's all that matters.

 

[diamondseeker2006]

Unfortunately, EGL isn't reliable grading, so their "ideal" designation doesn't really mean much. I agree that one of the measurements is really off or either these are measurements for two different stones!

 

[ice empress]

I wonder if it's worth me revisiting the appraisers to address the differences in measurements... sigh.

I don't think I will, mostly because I don't live in the city and it's a huge inconvenience to make an appointment, drive into the city, and essentially waste an entire day over this. Plus, the diamond is back with the jeweller already, so that it can go into the setting. I got the appraisals mostly so I could have a record of the inclusions. I inspected the diamond (with 10x loupe) in front of each appraiser, and again upon pick-up, so I would hope that the measurements are for the same stone.

Upon seeing the numbers, I naively believed that some discrepancy must be normal. Like thediamondshopper stated, perhaps one of their machine's calibrations were off? Disappointing and frustrating given that each assessment costed me $70-100!

 

[thediamondshopper]

Likely they use a Sarin or OGI scanner, I have seen both produce different results for the same stone, even when both calibrated properly. Then there are different levels of scanners, going from a 6k desktop model to a super accurate 40k model, Im not entirely sure which they use as I work near both labs and dont use either. It is very very important that these machines are calibrated properly. I tried to have a fancy yellow brown recut recently and got two different suggestions from two different local cutters. Coincidentally one had their machine calibrated by OGI and the other did it him self, I later found out that the they cutter who saved a few bucks by calibrating the machine him self would have cut my 2.09 to a 1.9 instead of an outstandingly well cut 2.01.

At the end of the day you could have sent the stone to AGS or GIA for the same price as both appraisals.

 

[ice empress]

Sending the stone to the states for a GIA assessment sounds like a lot of trouble, so perhaps next time I will try Harold Weinstein.

Using AGS' proportion charts (http://www.agslab.com/docs/pbcg/AGSLProportionCharts.pdf), this diamond rates as
- Excellent, using the GemScan measurements
- Very good, using the EGL measurements

I'm tempted to go with the GemScan assessment, given that I feel their VS-2 clarity assessment is more accurate. Also, they noted a "very small" cutlet versus "none" as per EGL. I would imagine that it is more likely that a very small cutlet exists and was missed by EGL, than GemScan saw a cutlet that wasn't there...

 

[ecf8503]

Ultimately it doesn't matter what the numbers say if you love it in real life. But it sounds like you want a mind-clean top performer, so I'd start with GIA and AGS. Are you open to buying online?

 

[ice empress]

Ultimately it doesn't matter what the numbers say if you love it in real life. But it sounds like you want a mind-clean top performer, so I'd start with GIA and AGS. Are you open to buying online?

In the future, I would definitely be open to buying online.

Just to clarify though, the stone in question has already bought by my FI, and is the engagement stone he proposed with. I am currently having it re-set in a halo, and so took the opportunity to get the loose diamond independently appraised and plotted.

I really do love the diamond, and was just curious about its performance "on paper". Pricescope has truly been both a blessing and a curse, and though knowledge is power, sometimes I wish I was still naively ignorant about everything diamonds.

 

[soxfan]

Ultimately it doesn't matter what the numbers say if you love it in real life. But it sounds like you want a mind-clean top performer, so I'd start with GIA and AGS. Are you open to buying online?

In the future, I would definitely be open to buying online.

Just to clarify though, the stone in question has already bought by my FI, and is the engagement stone he proposed with. I am currently having it re-set in a halo, and so took the opportunity to get the loose diamond independently appraised and plotted.

I really do love the diamond, and was just curious about its performance "on paper". Pricescope has truly been both a blessing and a curse, and though knowledge is power, sometimes I wish I was still naively ignorant about everything diamonds.

I feel the same way about PS being a blessing and a curse. My diamond scored a 3.4 on the HCA (very good), but I compared it in the store in all different lighting conditions to an excellent cut and I couldn't tell the difference. Mine also sparkles like crazy.

So the PS "curse" is I MAYBE could have had a better performing diamond, and the "blessing" is that I would NEVER have found my dream setting without it.

Now I just enjoy my ring.... Keep in mind that no one that sees your ring is going to know that it scored a 4 on the HCA. All they are going to see is a sparkly diamond....

 

[soxfan]

What kind of halo are you getting???

 

[ice empress]

What kind of halo are you getting???

Soxfan, I read all about your dilemmas pre-VC and followed your journey closely. The ring he created for you is drop-dead GORGEOUS!!! You must be absolutely thrilled!

I'm quite excited about the transformation my ring will undergo. It will have a single halo (a titch more substantial than the VC Emilya micro-halo, similar to bastetcat's) with curved flush-fitting stems and cathedral shoulders. The shank is also being made thinner, from 2.8mm bright-cut to 2mm shallow-u cuts. It's quite the makeover

 

[soxfan]

What kind of halo are you getting???

Soxfan, I read all about your dilemmas pre-VC and followed your journey closely. The ring he created for you is drop-dead GORGEOUS!!! You must be absolutely thrilled!

I'm quite excited about the transformation my ring will undergo. It will have a single halo (a titch more substantial than the VC Emilya micro-halo, similar to bastetcat's) with curved flush-fitting stems and cathedral shoulders. The shank is also being made thinner, from 2.8mm bright-cut to 2mm shallow-u cuts. It's quite the makeover

LOL! quite the novel, huh? I LOVE Bastecat's halo!!!! I can't wait to see it!

 

[AprilBaby]

I have never run my original diamond thru the HCA because I don't want to know the result. Bought in 1979 it's now in a pendant so it doesn't matter!

 

[ice empress]

I have never run my original diamond thru the HCA because I don't want to know the result. Bought in 1979 it's now in a pendant so it doesn't matter!

I should've known better too...

 

[ChristineRose]

EGL is very inconsistent in its use of terms like VS2 and G but generally they get the measurements right. There are other folks on Pricescope who found their Gemscan measurements not to match their other labs. Still a mistake is a mistake and somebody made a mistake.

I'd give more weight to an AGSL excellent than to anything the HCA says but if the numbers are off, who knows? It looks like it may qualify for a GIA excellent as well. The main reason that GIA excellent is a broader range than AGSL 0 is that GIA showed people a bunch of supposedly less than ideal cut stones and they liked them better than the ideals. It has to do with sacrificing face up white light for colored lights, larger flashes, and more interesting scintillation if you tilt from side to side. So yes, it's possible it's a GIA excellent that you like better than an AGS ideal.

Of course it's all irrelevant if you like the stone, but if you want the peace of mind go ahead and send it to AGS or GIA. It's not the biggest deal in the world and I would say it's not worth wondering all your life. Get it done and move on.