Find your diamond
Find your jewelry
shape
carat
color
clarity

Question about HCA

junhox212

Rough_Rock
Joined
May 15, 2012
Messages
73
Hello,

My search so far has been E-F color stones with SI1, SI2 clarity with zero fluorescence, excellent cut grade by GIA, putting in the range for table and depth provided some and I have been using the HCA to rule out which stones to consider and which ones not to among the GIA excellent cut stones. While doing this I have asked for help from a fairly well known person in the industry asking for advice on some stones that are spot on in the proportions but have cloud inclusion with SI clarity, and she recommended me stones that all score 4.0 and above and when i asked if this should be a concern, the person responded with:

"We don't put much stock in the HCA tool. This is why we don't like it.
It's not that it isn't accurate, but that it's poorly used. Let's say
you would give a diamond a point system. Out of a hundred, this is how
I would weight it.
1) Diamond's general cut (a decently cut diamond that is proportionate
and brilliant) - 25pts
2) Diamond Size - 25pts
3) Eye cleanliness- 25pts
4) Color - 13 pts
5) Fluorescence, girdle, polish, symmetry, etc - 7pts
6) detailed cut (what the HCA would be useful for) - 5pts

So HCA can help you figure out how to differentiate between diamonds
that are equal on the first 95pts. The problem is that the HCA is a
cool tool that gives you nice neat numbers to make a decision. People
start to focus on it and end up sacrificing on far more important
issues."

Is using the HCA to rule out bad vs good among GIA excellent cut with no fluorescence a bad idea or what is going on?
 

ecf8503

Ideal_Rock
Premium
Joined
Feb 14, 2005
Messages
3,741
GIA's "excellent" cut category is very broad - some not so great stones get through. AGS is much tighter, and they actually evaluate the light performance. The HCA is useful for weeding out those GIA stones that may be poor performers.

All of the things she mentioned are valid points, BUT if it isn't cut correctly it will not sparkle regardless of anything else.

Is HCA perfect? No. Is it useful? Yes. As a tool. Aim for under 2(lower is not better), then ask for ASET / Idealscope images to look at light performance.

Or look at AGS Ideal cuts. :)
 

tyty333

Super_Ideal_Rock
Premium
Joined
Dec 17, 2008
Messages
21,660
Ah, so she gives details on the cut the lowest amount of points (5). I guess it depends what you consider important. I guess she thinks
size, color and cleanliness is more important than cut. Sounds like mall store thinking to me.

Does the vendor provide idealscope images for all their stones?
 

Texas Leaguer

Ideal_Rock
Trade
Joined
Jul 27, 2009
Messages
3,188
I cannot agree with the 100 point system as given to you by your expert mainly because it mixes attributes that are really independent of one another. The concept has some value in constructing a general decision-making matrix, but it should be weighted more to what is most important to YOU on a personal level.

With regard to cut quality and the HCA tool in particular, I also think the advice is faulty. The HCA does not provide detail about a particular diamond. In fact, it often obscures details due to the limited number of inputs which are averaged and rounded. However, it is a very good remote tool for filtering out diamonds from a field of many which may have basic proportions that don't work well together. That is why the tool is designed for rejection rather than selection.

Depending on what your are trying to do, the HCA tool can be very helpful or it can be essentially useless. While the rule of thumb that most people use is to only consider diamonds with scores of 2 or less, it is quite possible for a stone to score over 2 and have outstanding light performance. Conversely, there are stones that happen to score 2 or less that are not precision cut that you may want to reject.That is why light performance images such as ASET, Ideal-scope, and H&A are important diagnostics for final decisions.

Also, when shopping for SI diamonds, there are sometimes issues with transparency that can undermine light performance. While the matrix does apportion a full 25 points for "eye-clean", that does not tell the whole story on clarity.
 

flyingpig

Ideal_Rock
Premium
Joined
Nov 7, 2015
Messages
2,171
HCA is not perfect. In fact, it has many limitations, thus if used improperly, it may mis-guide consumers.
AT the same time, I do not fully agree with the diamond expert you talked to either. She/he is not necessarily wrong.

HCA is "A" tool, nothing more nothing less. Other tools may include ideal proportions guide, GIA/ASG proportion and cut grading charts, GIA/AGS report, IS/ASET image, actual image, PS forum members' inputs, and/or expert's' opinion and visual inspection for a complete assessment and the most informed decision.

There are some industry members who completely bash HCA for its flaws. If so, GIA/AGS (especially GIA cut grading system) needs to be ditched, because they are flawed as well. But this is incorrect, You just need to understand each tool and use them accordingly.
 

ChristineRose

Brilliant_Rock
Premium
Joined
Aug 5, 2012
Messages
926
The HCA is her item #1. It is not her item #6.

Higher clarity is better, but after a point it makes no difference in the visuals. Some people do want to get the higher clarity for various reasons.

Color and size are a matter of taste. Many people would not wear a 4 carat or even a 2 carat diamond no matter how rich they were.

Fluorescence is more of a scare tactic than a real problem. Truly problematic fluorescence is rare, and the most fluorescent stones are also called out as fluorescent for people who seek that out.

Finish, polish, girdle, and symmetry are indications of poor craftsmanship and/or cutting tricks being used to nudge up the weight of a stone. The nudging doesn't make the stone look any better. Unless you are looking at something truly unique (like an antique) you should be able to find a similar stone which is better crafted. So there's rarely a reason to even consider these stones.

All factors need to be balanced against price and availability and grandma's beloved ring and where to give is a matter of taste as well. That said, cut contributes more to the overall appearance than any other factor, assuming you stay away from extremes like horrible inclusions and fancy colors.
 

fair75

Rough_Rock
Joined
May 28, 2015
Messages
87
Like what others have said here, HCA is only a rejection tool. It is designed to reject most of the poorly cut diamonds that are out there. Although HCA is a rejection tool, it is known that it favors shallow crown angles. But if you have ideal scope/ASET scope images, you don't need HCA. For me, I favor diamonds with crown angles between 34 and 35 degrees and pavilion angles between 40.6 and 40.8 degrees. Why? The main reason is that I like to purchase diamonds that have ideal proportions but not true H&As. This can be a bit inconvenient because most on-line vendors do not provide ideal scope/ASET scope images. To be on the safe side, I stick to the very narrow ranges. To my understanding, all the vendors that sell true H&As charge premiums over near H&As (which are the ones I like). They provide very detailed information on the specs and give you scope images that verify the stones that they sell. However, I just can't justify the premium and can't really see major differences.

What I am trying to say is that ideal scope/ASET scope images are really the key to buying good diamonds, in addition to the GIA/AGS grading reports. Do not discard angles that are out of the super ideal (H&A) ranges if you can get your hands on the scope images. They will tell you if these diamonds are still good choices or not. These images reveal the quality of the cut. Remember, CUT IS KING! For example, I bought a diamond that has all the ideal numbers except the crown angle. The crown angle is 36 degrees and I wouldn't normally consider such a diamond. But since I had the opportunity to examine the diamond in the store and use my ideal scope to verify the light performance, I bought it. Why? The ideal scope image is great. The light leakage under the table is minimal, which is a surprise to me given that the crown angle is 36. Most of the time, CA 36 would have significant light leakage. I was very happy because the diamond is a strong performer and the price is good. Therefore, do not let some people tell you that cut should be the least important factor or should be considered last. I attached the images of the diamond I bought to give you an idea. By the way, I wouldn't consider this diamond to be super ideal, a.k.a. true H&A, but it is certain very well-cut. Moreover, it is an eye clean SI1 (feather and cloud are the inclusions) and sparkles like crazy.

ideal_scope_5.jpg

_38092.jpg

_38093.jpg
 

Diamond_Hawk

Brilliant_Rock
Trade
Joined
Apr 8, 2014
Messages
1,221
junhox212|1472152015|4070020 said:
"We don't put much stock in the HCA tool. This is why we don't like it.
It's not that it isn't accurate, but that it's poorly used. Let's say
you would give a diamond a point system. Out of a hundred, this is how
I would weight it.
1) Diamond's general cut (a decently cut diamond that is proportionate
and brilliant) - 25pts
2) Diamond Size - 25pts
3) Eye cleanliness- 25pts
4) Color - 13 pts
5) Fluorescence, girdle, polish, symmetry, etc - 7pts
6) detailed cut (what the HCA would be useful for) - 5pts

So HCA can help you figure out how to differentiate between diamonds
that are equal on the first 95pts. The problem is that the HCA is a
cool tool that gives you nice neat numbers to make a decision. People
start to focus on it and end up sacrificing on far more important
issues."
All of the answers so far have given a really good synopsis of the usefulness of the HCA. In my reading of this advice it appears that by using these 6 points, one would include the HCA in the SELECTION process, and it is not intended for that - as others have pointed out it is primarily a rejection tool. BUT, the HCA also gives you a nice rubric of 'worth further consideration' and 'good, only if price is your main criterion,' etc... Use it as intended and it can be very informative.
 

Wink

Ideal_Rock
Trade
Joined
May 3, 2001
Messages
7,472
junhox212|1472152015|4070020 said:
Hello,

My search so far has been E-F color stones with SI1, SI2 clarity with zero fluorescence, excellent cut grade by GIA, putting in the range for table and depth provided some and I have been using the HCA to rule out which stones to consider and which ones not to among the GIA excellent cut stones. While doing this I have asked for help from a fairly well known person in the industry asking for advice on some stones that are spot on in the proportions but have cloud inclusion with SI clarity, and she recommended me stones that all score 4.0 and above and when i asked if this should be a concern, the person responded with:

"We don't put much stock in the HCA tool. This is why we don't like it.
It's not that it isn't accurate, but that it's poorly used. Let's say
you would give a diamond a point system. Out of a hundred, this is how
I would weight it.
1) Diamond's general cut (a decently cut diamond that is proportionate
and brilliant) - 25pts
2) Diamond Size - 25pts
3) Eye cleanliness- 25pts
4) Color - 13 pts
5) Fluorescence, girdle, polish, symmetry, etc - 7pts
6) detailed cut (what the HCA would be useful for) - 5pts

So HCA can help you figure out how to differentiate between diamonds
that are equal on the first 95pts. The problem is that the HCA is a
cool tool that gives you nice neat numbers to make a decision. People
start to focus on it and end up sacrificing on far more important
issues."

Is using the HCA to rule out bad vs good among GIA excellent cut with no fluorescence a bad idea or what is going on?
I am not as inclined as most of the excellent posters here who are not expressing the outrage here that I am feeling about this type of advice.

First off, shame on her for not recommending some properly cut diamonds to you. All stones above a 4, well of course she needs to belittle the HCA.

Most people can not distinguish between two or more color grades face up.

Most people can not distinguish (even professionals with many years of experience) between an IF and a SI1 and in most cases an SI2 face up.

Diamond size is not a 25% value, even if I agreed with 100 points, which I do not. A poorly cut 1 carat can often face smaller than a well cut 0.80 ct diamond, and actually look smaller than well cut diamonds which actually measure slightly smaller than they do. Light return really can make a smaller diamond look bigger than a bigger but more poorly cut diamond.

The following is my opinion only, others may disagree. Cut is KING! Exclamation Point, Period!

It is the end all and be all of the beauty of your diamond. For example, a D-IF can be a lifeless window in a scientific instrument, or a dazzling fireball of incredible brilliance and dispersion. The only difference is how it is cut. To me, it is the ONLY diamond quality issue as it is the only issue that is under man's control. Color, clarity and carat weight are rarity issues. True, they have a HUGE influence on the price, but only until the lowest clarities and colors do they influence the beauty. Even a lower color can be incredible so long as it is not a yucky color. Dingy brownish-yellow is not going to be beautiful no matter how it is cut.

Back to your original question, the HCA is a nice tool for helping you to reject the sight unseen diamonds and indicating which might be worthy of further investigation. I have seen a few, VERY few HCA four and above diamonds that were beautiful, but they were exceptions that were crafted by a master cutter working with the limitations of the starting crystal, not the norm. (No, not diamonds from Paul either, they are not in his cutting universe!)

Phone ringing, gotta go.

Wink
 

junhox212

Rough_Rock
Joined
May 15, 2012
Messages
73
I have received the following images of the diamond i have placed on hold before ordering. Can you guys analyze it for me? I am not an expert. Thank you. (I don't have enough money to buy a super ideal cut from vendors that specialize in it but I have found .4 carat F SI1 that are within preferred proportions; the stone costs $670) Thank you.

8386225_-_idealscope_image.jpg

8386225_-_aset.jpg
 

fair75

Rough_Rock
Joined
May 28, 2015
Messages
87
The scope images look decent, but not great. What are the specs of the diamond? The light leakage from 2 to 4 o'clock is somehow more than I would expect from an ideally cut diamond (top performing GIA triple ex or AGS triple zero, but not super ideal) Most people may not be able to detect this, but the price of the diamond certainly reflects the quality of the cut and the eye cleanliness. I can see that there are some dark inclusions in the images, which may be visible to the naked eye. The most concerning inclusions are the ones located in the table of the diamond. What kind of inclusions are they? Moreover, the inclusions on the edges of the diamond look to be quite visible as well. Did you ask the vendor if the diamond is eye clean? Did you ask them about their definitions of eye clean? You mentioned that the price for this 0.4 ct F, SI1 is $670, which is a steal for retail diamonds this size and color/clarity. In many cases, the discounted price most likely reflects the quality of the diamond. That's why I wonder about the proportions in the grading report and the eye cleanliness. You said the diamond have preferred proportions but the scope images suggest otherwise.
 

junhox212

Rough_Rock
Joined
May 15, 2012
Messages
73
Bc2 jewels said it is one of cleanest si1 and should not be sitting in inventory long?
 

fair75

Rough_Rock
Joined
May 28, 2015
Messages
87
I just checked the GIA report with the certificate number listed on their site. The clarity setting inclusion is twinning wisps, which may or may not pose a problem. Too many twinning wisps in even SI1 diamonds may cause the diamond to look hazy/cloudy, sometimes they are even visible. Did they say what their definition of eye clean is? 6 to 10 inches from the eyes or 12 inches away? Different vendors have different definitions of eye clean. It would be a good idea to clarify that with them. You have to understand that you ability to spot inclusions depends on your vision and the distance. Have you been to stores and asked to see some GIA SI1 or SI2 diamonds? That would be a great way to gauge how comfortable you are with SI1-SI2 diamonds. Remember, looking at non-GIA or AGS SI1-SI2 diamonds isn't reliable since the grades are mostly inflated.

If you can't see that diamond in person, can you ask the vendor and see if they can take pictures of the diamond, preferably both magnified and non-magnified ones? I am not saying that the diamond won't be eye clean to you, but the limited amount of information and the scope images you provided aren't enough for me or many others on here to make reasonable and educated guess on that. People on here simply need more information, especially some good photos to help you. Of course, the best way to verify the eye cleanliness will be you seeing the diamond in person. Nobody knows your own vision and your comfort zone with inclusions but you. All we can do is try to give you some advice so you can make informed decisions. $670 is not bad for the quality of this diamond based on the GIA report. A retail diamond that is 0.41 carat, F, eye-clean SI1, GIA triple ex with all ideal proportions will most likely not be around $670.

We all want the best diamonds at best prices, but most of the time we have to compromise because of the budget.
 

fair75

Rough_Rock
Joined
May 28, 2015
Messages
87
Also, is there a reason why you insist on E or F color? An ideal-cut G or H color diamond around 0.4 carat will look almost no different from E or F diamonds when set in white gold or platinum setting. You would most likely get a better price or better quality if you go down to G or H.
 

flyingpig

Ideal_Rock
Premium
Joined
Nov 7, 2015
Messages
2,171
35/40.8 can show light leakage like this with washed out arrows, depending on the actual angles.
I think it is more like 35.2/40.9 ish.. or it may be due to the obvious painting and digging (leakage, washed out arrows, and large amount of green around the edge) or both.

If I were the OP, I would keep shopping.

It may be a decent stone at a reasonable price. Combined with very good polish, I just don't stones like this and poor craftmanship/philosophy went into it.
 

junhox212

Rough_Rock
Joined
May 15, 2012
Messages
73
Thank you all so much for your feedback. I am not so sure about the stone anymore. My wife and I have looked at many stones at the malls (ags ideal) and feel that we want minimum f color. Plus the color grade didn't make much of a difference I felt at that carat weight in the clarity grade I am looking at. Can anyone recommend me a stone in the range I am looking for? (F to D color, eye clean SI clarity, .38 to .41 carat, max budget 750 per stone, preferably 700)?
 

AdaBeta27

Brilliant_Rock
Premium
Joined
Sep 7, 2004
Messages
906
I don't know anything about this Jann Paul guy, and his videos seem to cover material that probably has already been covered in videos made by PS vendors. That said, watch this video that visually compares 3 "similar on paper" diamonds side by side.
https://www.youtube.com/watch?v=Cz3qn2Tx6oI

If I ran the HCA numbers right (and I did this hastily so you might want to verify), these are the HCA scores: 2, 1.1, and 4.9.
diamond A
Tbl 59
depth 60.2
ca 32.0
pa 41.2
culet 0
VG, VG, VG, Ex
HCA 2.0 buy if price is right


diamond B
Tbl 58
depth 60.7
ca 33.5
pa 41.0
culet 0
Ex, Ex, Ex, VG
HCA 1.1, TIC range


diamond C (looks like a real dud)
Tbl 58
depth 62.1
ca 35
pa 41.4
culet 0
Good, Fair, Fair, very good
HCA 4.9 - Good only if price is your main concern
 

junhox212

Rough_Rock
Joined
May 15, 2012
Messages
73
I apologize for a late reply. The person just helps and advices which stones to pick from many vendors. =)
 

junhox212

Rough_Rock
Joined
May 15, 2012
Messages
73
Hi everyone who gave me awesome feedbacks =)

I went ahead and looked at couple 4 prong earrings at Tiffany's & Co., one was a D color VVS1 and the other a G color VS2 and i honestly could not tell the difference in color or the difference in sparkle with the diamonds facing up.

Upon getting home i found G, SI2 true hearts at James Allen that were priced similar to the stones i have been looking at and feeling pretty good about ordering them as of now. They were $720 each minus $50 coupon code ($670 each) I have already ordered them but i want to hear your thoughts on these. Do you perceive any of the inclusions can make the diamond cloudy?
Thank you all =)

https://www.jamesallen.com/loose-diamonds/round-cut/0.38-carat-g-color-si2-clarity-excellent-cut-sku-1099771

https://www.jamesallen.com/loose-diamonds/round-cut/0.38-carat-g-color-si2-clarity-excellent-cut-sku-1099772
 
Be a part of the community It's free, join today!
    Vintage OEC Bracelet
    Vintage OEC Bracelet
    June’s Birthstone Trinity
    June’s Birthstone Trinity
    Memorial Day Jewelry 2020
    Memorial Day Jewelry 2020

Need Something Special?

Get a quote from multiple trusted and vetted jewelers.

Holloway Cut Advisor



Diamond Eye Candy

Click to view full-size image.
Top