HRD reports - how do they stack up?

[Upgradable]

My jeweler is on his biannual buying trip to Antwerp. The diamonds he returns with have HRD certifications. Cut stats are all present with the exception that pavilion measurements are in % instead of angle.

How do HRD certs stand up against GIA or AGS? I like patronizing the local establishment (economically stabilizing and all that PC crapola) but want to know that I''m getting quality goods at a fair price too.

 

[Modified Brilliant]

Although HRD diamond grading reports are not as prevalent here in the US, it is a respected lab, nonetheless.

I have no issues with their grading or accuracy from what I've seen.

This might be helpful: https://www.pricescope.com/community/threads/hrd-vs-gia.2840/ (some of the info is slightly outdated)


Jeff Averbook, GG Graduate Gemologist/Appraiser

www.metrojewelryappraisers.com

 

[Regular Guy]

Date: 10/26/2007 11:10:20 AM
Author: Modified Brilliant

This might be helpful: https://www.pricescope.com/community/threads/hrd-vs-gia.2840/ (some of the info is slightly outdated)

It could be nice if Garry returned to address the point he''s made in the last post in the linked thread...and which upgradeable raises a question for (is this a dangling participle?).

Though the pavilion is the most critical measure, JQ''s recently pointed out that % should (or at least could) be as good as an angle measure. The confound exists with the less important crown measure, since the detail for that will be different, depending on the table measure...so % simply isn''t that helpful for crown vs pavilion.

At least...if the theory is that rounding is the culprit and problem with any use of %...that could be explicated. Why is % more susceptible to rounding? Decimals used with angles, and not with %?

 

[JohnQuixote]

HRD is a strong lab with regard to color & clarity.

Date: 10/26/2007 12:23:10 PM
Author: Regular Guy

Date: 10/26/2007 11:10:20 AM
Author: Modified Brilliant

This might be helpful: https://www.pricescope.com/community/threads/hrd-vs-gia.2840/ (some of the info is slightly outdated)

It could be nice if Garry returned to address the point he's made in the last post in the linked thread...and which upgradeable raises a question for (is this a dangling participle?).

Though the pavilion is the most critical measure, JQ's recently pointed out that % should (or at least could) be as good as an angle measure. The confound exists with the less important crown measure, since the detail for that will be different, depending on the table measure...so % simply isn't that helpful for crown vs pavilion.

At least...if the theory is that rounding is the culprit and problem with any use of %...that could be explicated. Why is % more susceptible to rounding? Decimals used with angles, and not with %?

Correct. Angles are more precise, though GIA rounds angles a bit too. Always remember the culet: If no culet is present you can correlate Y pavilion depth % to X pavilion angle. If there's a notable culet it's not possible to do this. If you want to split hairs, many diamonds have just a tiny bit of culet that's not visible at 10X (no-one panic it affects nothing) which is why angles are better in general.

The HCA was designed with a built-in adjustment per the above, along with the fact that scanners have a hard time judging pavilion depth. As a result the HCA # is slightly different when using % as opposed to the corresponding angle.

 

[Regular Guy]

JQ

Thanks as always.

Still, returning to the question of rounding...

Back when I rode a bicycle in high school...I used to know on a 10 speed where one speed was with respect to another...you know...6th gear vs 7th. You might have to switch the one in front to get there.

Likewise...since GIA rounds...doesn''t it become a practical question...forgetting other differences between the labs...as to which is worse rounding?

GIA because they explicitly round.

Or with anyone that presents percents, since that measurement automatically includes rounding?

Is that clear?

 

[JohnQuixote]

You're welcome. And I understand, but we're sort of splitting already-split hairs... Especially when we remember (a) assume a bit of scan error (b) the stated CA or PA is an average of eight measurements already.

But, as long as your noodle is baking on a Friday, here's more sauce for the goose.

> GIA/DC pavilion depth % ... corresponding GIA pavilion angle ... corresponding DC pavilion angle (Modern Tolk)

PD% . GIA PA . DC PA
42.0 ... 40.0 ... 40.03
42.5 ... 40.4 ... 40.36
43.0 ... 40.8 ... 40.70
43.5 ... 41.0 ... 41.02
44.0 ... 41.4 ... 41.35

(As Ira is sure to see, GIA rounds a tiny bit even with angles for sake of brevity. Again, waay hair-splitting)