Should I pull the trigger?Very confused. HCA 1.6, but AGA 3A

[akfong26]

Hi,

I need some professional help. I just put this stone on hold and almost purchased the stone for an engagement ring. The HCA grade is 1.6, but the AGA/NAJA total grade is 3A. How can the HCA and AGA/NAJA grade vary by so much? I would have purchased the stone by looking at the HCA grade of 1.6 if I did not check the AGA/NAJA grade. I am very close to buying. Should I pull the trigger?

Here are the specs:

GIA Certified
Round Brilliant
Measurements:7.16x7.20x4.45
Carat: 1.41
Color: F
Clarity: VS1
Table%: 56
Depth%: 62
Crown Ht%: 15.5
Crown Angle: 35
Pav Angle: 40.8
Cut: Excellent
Polish: Excellent
Symmetry: Excellent
medium-slightly thick

 

[slg47]

Re: Should I pull the trigger?Very confused. HCA 1.6, but AG

Hi,

I need some professional help. I just put this stone on hold and almost purchased the stone for an engagement ring. The HCA grade is 1.6, but the AGA/NAJA total grade is 3A. How can the HCA and AGA/NAJA grade vary by so much? I would have purchased the stone by looking at the HCA grade of 1.6 if I did not check the AGA/NAJA grade. I am very close to buying. Should I pull the trigger?

Here are the specs:

GIA Certified
Round Brilliant
Measurements:7.16x7.20x4.45
Carat: 1.41
Color: F
Clarity: VS1
Table%: 56
Depth%: 62
Crown Ht%: 15.5
Crown Angle: 35
Pav Angle: 40.8
Cut: Excellent
Polish: Excellent
Symmetry: Excellent
medium-slightly thick

The numbers look good. The issue is that the AGA/NAJA cut class tool uses pavilion %, not pavilion angle.

 

[akfong26]

Re: Should I pull the trigger?Very confused. HCA 1.6, but AG

Thank you for the reply... I was very confused...

From the GIA report, the Pav Depth% is 43%. After imputing the correct PAv Depth%, AGA/NAJA grades the stone: 1A.

I can now feel comfortable about purchasing this diamond. THANK YOU!

 

[slg47]

Re: Should I pull the trigger?Very confused. HCA 1.6, but AG

Thank you for the reply... I was very confused...

From the GIA report, the Pav Depth% is 43%. After imputing the correct PAv Depth%, AGA/NAJA grades the stone: 1A.

I can now feel comfortable about purchasing this diamond. THANK YOU!

no problem! please post pictures once you get it

 

[oldminer]

Re: Should I pull the trigger?Very confused. HCA 1.6, but AG

I know that it has been often stated that one ought to use the angle rather than the percentage when calculating with HCA. In theory, these numbers should be equally reliable since they are based on geometry and vary identically with one another. In reality, the measuring devices do a bit better in measuring angles than "calculating" percentages. A bit more machine error or rounding issues, I suppose. I have no control of how scanner software calculates with increased error. Logically, there should be no reason, but we live with it.

Now that you found using the percentage came out a 1A it would appear that the AGA/NAJA cut class tool does work as I believe it should. I put this tool together almost 20 years ago although it has been modified and improved by various participants over the years. The trade often prefers to say you can't pick a stone by any set of numbers. In one limited way this might be true. If a cutter went out of the way to make a diamond using opposite extremes from the cut grade charts it would be possible to cut an ugly cut grade 1 diamond. However, since diamond rough is so costly, and since so much is known about how to cut a beautiful diamond, no expert cutter would ever do such a thing. Therefore, a cut grade of 1A, 1B, or 2A pretty much assure consumers that a diamond is extremely likely to be a beautiful, durable, and sufficiently large in appearance for its carat weight.

You need not pick your final choice based on any tool or report. It is best to inform yourself, let your eyes do the work of seeing the beauty in person, and allowing the best computer of all, your own brain, do the calculating.....

 

[akfong26]

Re: Should I pull the trigger?Very confused. HCA 1.6, but AG

Thank you everyone for the advice.

After hours and hours of research on PriceScope, I know not to only go by the HCA report and AGA/NAJA grade when purchasing a diamond. However, I have found the HCA tool extremely useful when weeding out stones. I found this diamond on b2cjewels.com and they don't provide Ideal-scope images or Sarins report. B2C jewels said they don't actually have the diamond in house and needs to obtain it from an overseas vendor.

I took a chance and ordered the diamond anyways because the HCA and AGA/NAJA grade looked very promising, the angles and table/depth are desirable according to many members in the forums, and the price was cheaper then other online vendors. The return policy is 30 days.

I'm crossing my fingers, but hopefully all my research on this site pays off, and i'll end up with a great engagement diamond at a good price.

What are things I should definitely do when I receive the diamond to make sure it's legit?

 

[Christina...]

Re: Should I pull the trigger?Very confused. HCA 1.6, but AG

You need to take it to an appraiser during your return period and have it evaluated. Ask them to make sure that the diamond matches the report, it's also a good time to have an appraisal done for your insurance company. After that's finished make plans to propose! Congratulations!

 

[Dreamer_D]

Re: Should I pull the trigger?Very confused. HCA 1.6, but AG

Hi,

I need some professional help. I just put this stone on hold and almost purchased the stone for an engagement ring. The HCA grade is 1.6, but the AGA/NAJA total grade is 3A. How can the HCA and AGA/NAJA grade vary by so much? I would have purchased the stone by looking at the HCA grade of 1.6 if I did not check the AGA/NAJA grade. I am very close to buying. Should I pull the trigger?

Here are the specs:

GIA Certified
Round Brilliant
Measurements:7.16x7.20x4.45
Carat: 1.41
Color: F
Clarity: VS1
Table%: 56
Depth%: 62
Crown Ht%: 15.5
Crown Angle: 35
Pav Angle: 40.8
Cut: Excellent
Polish: Excellent
Symmetry: Excellent
medium-slightly thick

You have three pieces of information about cut: The GIA cut grade, the HCA, and the AGA. In my opinion, the GIA cut grade is the most important since they have actually seen the diamond. The others are estimates based on the rounded numbers GIA reports on its certificates, and thus are prone to a measure of error and so need to be considered in light of all the information available. To corroborate the GIA grade, you can request an ideal scope image, photos of the diamond, or look at it in person and compare to other diamonds that perform well on all three tools you are using (cut grade, HCA, and AGA tool)

 

[Karl_K]

Re: Should I pull the trigger?Very confused. HCA 1.6, but AG

Just a small correction.
While GIA has seen the diamond the cut grade information is based on the same flawed numbers you use in the HCA and AGA tools.
None of them measure the actual performance of the diamond, the are making a predictions based on the numbers.
Sometimes those predictions will be right and sometimes wrong.

 

[Dreamer_D]

Re: Should I pull the trigger?Very confused. HCA 1.6, but AG

Just a small correction.
While GIA has seen the diamond the cut grade information is based on the same flawed numbers you use in the HCA and AGA tools.
None of them measure the actual performance of the diamond, the are making a predictions based on the numbers.
Sometimes those predictions will be right and sometimes wrong.

I thought GIA actually looked at the stone to make its cut grade? That is... a crock if they only use the numbers. What is the added value of the GIA grade in that case? I can look at the numbers myself.

 

[Karl_K]

Re: Should I pull the trigger?Very confused. HCA 1.6, but AG

Just a small correction.
While GIA has seen the diamond the cut grade information is based on the same flawed numbers you use in the HCA and AGA tools.
None of them measure the actual performance of the diamond, the are making a predictions based on the numbers.
Sometimes those predictions will be right and sometimes wrong.

I thought GIA actually looked at the stone to make its cut grade? That is... a crock if they only use the numbers. What is the added value of the GIA grade in that case? I can look at the numbers myself.

They run the sarin scan and the computer attached to the scanner spits out the grade based on the severely rounded averages right into their database.

The AGS cut grade is also not based on visual inspection but a computer model of the diamond from sarin data.
However it is 3D and it uses all the facets to create the model instead of rounded then averaged then grossly rounded that GIA does.
The AGS method a much more accurate representation of the diamond is considered for the grade but not perfect either because of scan error/accuracy.
Which is why the ASET printed on the report will rarely look like the actual ASET image.

 

[ChrisES]

Re: Should I pull the trigger?Very confused. HCA 1.6, but AG

What is the added value of the GIA grade in that case? I can look at the numbers myself.

Saving less educated consumers a huge amount of time?

 

[Dreamer_D]

Re: Should I pull the trigger?Very confused. HCA 1.6, but AG

What is the added value of the GIA grade in that case? I can look at the numbers myself.

Saving less educated consumers a huge amount of time?

Of course, but it is still lame.