HCA 0-2 and AGS0

[Regular Guy]

Karl,

Each of the questions above, begun with "a wire?," are genuine questions of mine.

But, fundamentally, I suppose...once again...you have nailed it here...below...

Date: 9/30/2009 8:55:05 AM
Author: strmrdr
As long as cut grading systems have existed there has always been someone pushing the edges and trying to game the system for $$$$.
AGS plat because of the way the grade is calculated is more resistant to this than AGS gold or GIA EX but it is not perfect.
There is no perfect diamond grading tool which is why multiple tools are used.

Like before, where I pinned hope on a system like the HCA...I had come to think that a 0 from AGS'' platinum could be so good as to be defining. But...maybe the cases presented here provide an understanding that this is not the case.

Platinum zero defenders, if you''re out there...you''re welcome to jump in. But, like Stone Cold has previously shown unsatisfactory IS images coming from some of these, like Hagen Daas has shown options here that do not obtain favorable crown & pavilion combinations, and like the example here, despite presenting in your face on the certificate with an ASET image purportedly documenting its zero-ness, but in fact, not doing that at all...for those of us that might have wanted the Platinum zero to be "all that,"...it seems it may not be.

Still, taking an inductive approach, shoppers can look for specimens with credentials like the zero...particularly if off the street, vs. our more well known vendors, to look for evidence of quality. But, as is said here, maybe more evidence than that one document is desirable after all.

 

[John P]

Date: 9/30/2009 8:55:05 AM
Author: strmrdr

As long as cut grading systems have existed there has always been someone pushing the edges and trying to game the system for $$$$.

The platinum report (formerly DQD) was introduced in 2005. Examples like these used to be rare but the longer a system exists the more the boundaries are explored.

AGS plat because of the way the grade is calculated is more resistant to this than AGS gold or GIA EX but it is not perfect.

 

[John P]

On-point for the original poster:

Remember that the HCA is simply drawing an imaginary "chalk outline" based on three main numbers. Of these the pavilion angle is by far the most influential.

Do this experiment: Open the HCA. Enter 61D, 56T, 34.5 CA and 40.8 PA. Now begin increasing PA in 0.1 degree increments and what happens. In five tics (41.3) you reach HCA 3.8. Now reset PA to 40.8. Take CA and increase by 0.1 degrees...keep going...keep going...after twenty tics you still aren''t where the tiny PA adjustments got you in five. Table% has more influence than CA but not as much as PA in the HCA''s predictive metric.

Many "Why is this GIA EX predicted bad on HCA..." threads are because the average PA falls (correctly in my opinion) outside the critical angles required to return light to the viewer''s eye with most efficiency.

 

[John P]

Date: 9/30/2009 11:26:42 PM
Author: Regular Guy

Platinum zero defenders, if you're out there...you're welcome to jump in. But, like Stone Cold has previously shown unsatisfactory IS images coming from some of these, like Hagen Daas has shown options here that do not obtain favorable crown & pavilion combinations, and like the example here, despite presenting in your face on the certificate with an ASET image purportedly documenting its zero-ness, but in fact, not doing that at all...for those of us that might have wanted the Platinum zero to be 'all that,'...it seems it may not be.

Still, taking an inductive approach, shoppers can look for specimens with credentials like the zero...particularly if off the street, vs. our more well known vendors, to look for evidence of quality. But, as is said here, maybe more evidence than that one document is desirable after all.

I'm a fan of your last sentence.

The people I've had the pleasure to work for in this business have always answered to a higher authority than any single metric. Ira, you likely remember that the most discussed current metrics - GIA and AGS light performance - were introduced years after my teachers had firmly established their individual recipes for high performance in RBs; the same recipes they faithfully use today. Recent metrics have consistently validated their vision as cutters, which is terrific. And I feel that on the whole the existence of these systems has had a positive influence on commercial cutting these past several years - thanks to the GIA at least people now know that such a thing as a "cut grade" exists (remember pre-2006?).

Still, my "Evolution" of round brilliant analysis would be something like: Several diamonds in-hand through multiple lighting > One diamond in-hand through multiple lighting > Diamonds in hand single lighting > ASET Photo > AGS Report > 3D Scan > Sarin Averages > HCA Score.

I reserve the right to add/edit that paragraph above. I usually don't throw such lists out, and if you threw me some curves like pixel-counting machines, standardized photos or video, etc. the sourcing would influence where I'd insert them. As a gemologist I'd also like to have a flourescent lamp and a nice loupe in there somewhere... Hey I've been absent from the forum for a while, so you get some rust.

 

[thelvyn123]

I''m fairly new here so my knowledge of what makes for a great diamond is limited at best but I thought I would throw in my 2 cents anyhow.

I''m a huge fan of DIY whether it be pan searing scallops for dinner or putting together a headboard from plywood purchased at Home Depot. However, I do believe that more than a modicum of effort is required to achieve great results with DIY. There is no magic spice which will make homemade scallops taste like restaurant fare (although butter comes close). Likewise, there are no magic tools that will turn a $5 piece of plywood into a beautiful centerpiece. In each of these cases, DIYers need to employ a variety of tools and put forth a significant amount of effort in order to be successful.

I believe diamond selection should be the same way. While it would be great to have a magic bullet report which accurately identified beautiful gems every time, it seems a bit idealistic. I believe we already have a wealth of resources (including this forum) which will provide the discerning buyer with the information they need to locate the stone of their dreams. Individuals who do not have the time or the will to go through this process have the option of paying a premium for an expert selected stone or taking their chances with potentially flawed reports (which are probably still accurate the majority of the time).

 

[zabak80]

That''s exactly it Thelvyn123.

Very well said and sums everything up perfectly.