HCA vs CUT

[ame]

Hermesaholic - I totally agree! Ame is the expert in diamond!

Ame - What is the most important in a diamond? Are the words in HCA more important or the certificate showing excellent cut, excellent polish & excellent symmetry?

lilmountaingirl- May i know what features / proportions you are attracted to?

Sorry guys, very fresh in diamond and would like to know more before investing in it.

Thanks!

The most important factor to get a beautiful diamond is the cut quality. That's all in the proportions and angles. Unless it's an AGS cert which truly does officially and effectively grade cut, which it doesn't sound like it is based on using Excellent as the cut quality, I go based on numbers and not what they call Excellent because GIA has a pretty wide margin for what they consider Excellent and I have seen some serious dogs that get called Excellent, and some amazing ones they only call Very Good. Excellent Symmetry is obviously great, but you really want the proportions to be right because the angles are where the cut quality really lies.

In diamond #1 every one of those numbers is truly ideal. A "true ideal" would be around a 55% table, and around a 61% depth with the 34ish crown angle and 40.7ish crown angle. These are like magic numbers.

A 57% table does still fall under "ideal" but it changes the crown angle just enough (in this case into the 35 degree area) sometimes that you lose a little fire return and get more white light return than if you have a 55% table. A bigger table changes the look overall, and changes the fire return vs the white light return. A smaller table gives more color light, a larger one more white light. Some people don't mind that change. Me personally, I like the smaller table.

Another reason I selected 1 over 2 is the girdle, that diamond is "thicker in the middle" meaning more of it's weight is in the middle and it will not face up as large as one with a thin or thin to medium girdle, which is preferred. So it's smaller in diameter than it "should be" vs. the first one. Not by a lot, but it could make the difference.

Not sure who the seller is, but I would seriously ask for an ASET and or IdealScope image and photos if at all possible. I assume you're outside of the US, and working with a vendor IN the US. I know Blue Nile doesn't do that, but there are many online vendors that will.

As far as HCA goes, that is really only a tool to help start weeding out stones that would have angles that would in theory produce a less beautiful stone. Its a PS/Garry Holloway thing, not developed by AGS/GIA or any other lab. But it has its uses in selecting a stone based strictly on paper, and not on visual. The best tool for selection is the eyes!

 

[Kathd]

^^ Thanks, Ame! Great info! I've learned so much from you!

 

[ame]

 

[tbbbjb]

The most important factor to get a beautiful diamond is the cut quality. That's all in the proportions and angles. Unless it's an AGS cert which truly does officially and effectively grade cut, which it doesn't sound like it is based on using Excellent as the cut quality, I go based on numbers and not what they call Excellent because GIA has a pretty wide margin for what they consider Excellent and I have seen some serious dogs that get called Excellent, and some amazing ones they only call Very Good. Excellent Symmetry is obviously great, but you really want the proportions to be right because the angles are where the cut quality really lies.

In diamond #1 every one of those numbers is truly ideal. A "true ideal" would be around a 55% table, and around a 61% depth with the 34ish crown angle and 40.7ish crown angle. These are like magic numbers.

A 57% table does still fall under "ideal" but it changes the crown angle just enough (in this case into the 35 degree area) sometimes that you lose a little fire return and get more white light return than if you have a 55% table. A bigger table changes the look overall, and changes the fire return vs the white light return. A smaller table gives more color light, a larger one more white light. Some people don't mind that change. Me personally, I like the smaller table.

Another reason I selected 1 over 2 is the girdle, that diamond is "thicker in the middle" meaning more of it's weight is in the middle and it will not face up as large as one with a thin or thin to medium girdle, which is preferred. So it's smaller in diameter than it "should be" vs. the first one. Not by a lot, but it could make the difference.

Not sure who the seller is, but I would seriously ask for an ASET and or IdealScope image and photos if at all possible. I assume you're outside of the US, and working with a vendor IN the US. I know Blue Nile doesn't do that, but there are many online vendors that will.

As far as HCA goes, that is really only a tool to help start weeding out stones that would have angles that would in theory produce a less beautiful stone. Its a PS/Garry Holloway thing, not developed by AGS/GIA or any other lab. But it has its uses in selecting a stone based strictly on paper, and not on visual. The best tool for selection is the eyes!

WOW, wonderfully informative. I actually understand it Thanks, AME, you really are an asset to tpf!!!

 

[ame]

Aww thanks!

Also--if you have an AGS0 stone, I wouldn't even bother with an HCA score. Those stones are graded in person, and the HCA is obviously just a model with data.

 

[Yokochic]

Ame, what can I say .... you are a gem! I personally would have no clue at all to the above information.

I will try asking for pictures, but will the pictures refect the light and how sparkle the ring is?

 

[ame]

Depends on the photos, Id want photos in sun/spot lighting, diffused daylight, particularly. At this clarity range you're not likely to need to see the plot.

 

[wantitneedit]

ame, you're ace. You're very generous with info and always give your time to strangers looking to broaden their knowledge on diamonds. thank you

 

[ame]

It's my pleasure, and thank you!

 

[Christiflora]

Hi all,

I have been doing some reading and research and found that HCA score is a good guide as to the quality of diamond.

I am in abit of dilemma and appreciate if you can give me your opinion.

1.06 carat E VVS2. Excellent/very good/very good. HCA score 0.8
Girdle Thickness - Thin / Girdle Finish - Faceted

1.04 carat G VVS1. Excellent / Excellent / Excellent. HCA score 1.9
Girdle Thickess - Medium to slightly thick / Girdle Finish - Faceted

The first one has a super low HCA score but the 2nd one has 3 excellent.

Which is more important - HCA or Cut?

Thanks!!

Personally, I would skip both and look somewhere else for higher cut and better value diamonds. Diamond #1 has only VG symmetry, so I can't 100% trust HCA score that is calculated based on a few measurements on angles and depth/table. I don't like diamond #2 because, as AME pointed out about the "VG" prediction for light return and scintillation. I prefer diamonds with OPTIMUM cut parameters that would yield maximum light return and fire. Furthermore, I would not pay premium for VVS clarity. VS1 or even VS2 are good enough for me to ensure "eye-clean" diamonds. I think you need a high power magnification microscope in order to see the inclusions in VVS stones. As for the color, if you are not color sensitive, G is as good as anything, although I love E/F color stones.

 

[acrowcounted]

Personally, I would skip both and look somewhere else for higher cut and better value diamonds. Diamond #1 has only VG symmetry, so I can't 100% trust HCA score that is calculated based on a few measurements on angles and depth/table. I don't like diamond #2 because, as AME pointed out about the "VG" prediction for light return and scintillation. I prefer diamonds with OPTIMUM cut parameters that would yield maximum light return and fire. Furthermore, I would not pay premium for VVS clarity. VS1 or even VS2 are good enough for me to ensure "eye-clean" diamonds. I think you need a high power magnification microscope in order to see the inclusions in VVS stones. As for the color, if you are not color sensitive, G is as good as anything, although I love E/F color stones.

I agree. This whole HCA calculator trend seems ridiculous to me. How exactly does it calculate Symmetry based on one value of each angle?? For me, this calls the validity of the entire tool into question. I also agree that I personally wouldn't pay the premium for a VVS clarity stone. Unless you know that you are mind-sensitive to clarity ratings, I would definitely look for a VS1/2 stone. Good luck finding your perfect diamond!

 

[ame]

x

I agree. This whole HCA calculator trend seems ridiculous to me. How exactly does it calculate Symmetry based on one value of each angle?? For me, this calls the validity of the entire tool into question. I also agree that I personally wouldn't pay the premium for a VVS clarity stone. Unless you know that you are mind-sensitive to clarity ratings, I would definitely look for a VS1/2 stone. Good luck finding your perfect diamond!

I also addressed the clarity issue, it's probably not a topic for discussion as it was not addressed in my initial comment on it. We don't think it's necessary, but the OP might. If she's willing to reduce her clarity grade or color grade, great, we as a collective can find some more options.






And because this comes up ALL THE TIME, for the record:
I did not base my answer on the HCA scores. I never do. It's a nice tool to use, but it's not exact science or a replacement for actual measurements and proportions.

As I have said MANY times in threads just like this, as well as within this thread, its all about the angles and percentages.

Of the two options presented, stone number 1 has everything going for it, regardless of the HCA score. I selected it of the two proposed options because of the angles and proportions. Those exact proportions, of a 55% table, a depth percentage of around 61, and those angles are damn near ideal of ideal.

And as I also said in several posts, the HCA is not the decider. It's a tool, an "equation" if you will, to help weed out a stone that might not be ideally cut for optimum cut standards. It weeds things out of the cert to help narrow down a selection of stones that the person cannot see in front of them. And like I have said probably hundreds of times on this forum, it is NOT the deciding factor nor is the cert, the proportions and ultimately the eyes are.

 

[acrowcounted]

As I have said MANY times in threads just like this, as well as within this thread, its all about the angles and percentages.

Of the two options presented, stone number 1 has everything going for it, regardless of the HCA score. I selected it of the two proposed options because of the angles and proportions. Those exact proportions, of a 55% table, a depth percentage of around 61, and those angles are damn near ideal of ideal.

And as I also said in several posts, the HCA is not the decider. It's a tool, an "equation" if you will, to help weed out a stone that might not be ideally cut for optimum cut standards. It weeds things out of the cert to help narrow down a selection of stones that the person cannot see in front of them. And like I have said probably hundreds of times on this forum, it is NOT the deciding factor nor is the cert, the proportions and ultimately the eyes are.

Wasn't directing my post at you. In fact, I've noticed and appreciated your attempts to reduce the reliance on the HCA calculator these last few months. I was actually trying to agree with you on this perspective, as well as the clarity perspective which we both agree on. Sometimes hearing the same message from multiple people helps encourage someone to pause and reconsider. That's all I was trying to do.

 

[ame]

Wasn't directing my post at you. In fact, I've noticed and appreciated your attempts to reduce the reliance on the HCA calculator these last few months. I was actually trying to agree with you on this perspective, as well as the clarity perspective which we both agree on. Sometimes hearing the same message from multiple people helps encourage someone to pause and reconsider. That's all I was trying to do.

I appreciate you saying that.

I was only replying about the clarity in reference to your post. I actually just went in and edited the post to add a ton more space between them.

I really like that other people are learning from my posts, and are also interested in making sure that the poster is getting the best she can for her dollar. Or I guess he or she, we never know who we could be helping! I don't care if you want a Tiffany or a non-brand, the same rules apply, you don't want to waste the time or the money if you can get the best bang. I also know that not every "cares" if its the ideal ideal. As weird as that is for me to grasp, some people want size or color or clarity above all other factors.

 

[Christiflora]

Ame, you have been very helpful to many who need diamond buying advice. My post was not directed to anything you said in this thread or any thread. I was merely stating my opinion per my standard.

Among all C's, cut is the most important to me, and whenever I need to skim to meet my budget, I have never compromised my strong desire for best cut diamonds. Therefore, I stay away from anything that has less than a GIA excellent or AGS ideal symmetry round diamonds. I rely heavily on HCA to SCREEN my diamonds before requesting to view diamonds in person. Understanding that HCA is based on an average of a few measurements, I do not want to risk the trouble of paying shipping (can cost up to $200) just to view the diamonds in person in order to confirm their acceptabilty. Yes, I may miss some great looking diamonds that do not meet my excellent/ideal symmetry requirement, but I accept this possibility to err for the safe/sure side. Likewise, I do not mind missing out on this diamond if it turns out to be OK. So if it gives me savings, but I do not mind paying more money. You see, I buy nothing but the premium best cut, ACA diamonds, so I would not mind paying more money. I would rather get the savings from opting with a lower color, lower clarity (but still eye-clean), smaller carat size or even increased budget.

Back to OP, let me repeat, personally, I would continue to look for the best cut diamonds. There are plenty of fish around. Besides, you may not want to trouble yourself with more work/cost associated with pursuing your two diamonds further.