Sarin or cert more accurate?

[Laila619]

Hi all,

When the Sarin and the AGS certificate differ quite a bit, what is more accurate? What should I go by when evaluating the diamond for purchase?
And does anyone have an idea as to why the Sarin and AGS cert could differ? AGS is supposed to be the stricted and most reliable, so I am surprised that the Sarin report showed different numbers. Thank you!

 

[stone-cold11]

Machines need to be calibrated regularly to prevent drift in measurement.

AGS numbers should be the more accurate ones.

 

[Lorelei]

AGS are the numbers of authority so best to go by those.

 

[Todd Gray]

Date: 9/14/2009 5:05:55 PM
Author:Laila619
When the Sarin and the AGS certificate differ quite a bit, what is more accurate?

Can you further define "differ quite a bit"?

There is a variance between Sarin machines, sometimes this is a matter of calibration (our unit actually self calibrates because it is a lab quality unit) but also there is some variance that can be caused by the user using the wrong lens / platform combination for the diamond size... I had never thought of this before, but I called Fred Fish at Sarin one day because I was trying to figure out why the results I was getting from our Sarin machine were so different than those stated on the lab report and he told me that there were times he''d been standing in the, uh, "###" lab in NYC and watched some of the graders use the wrong Sarin machine to measure diamonds because they didn''t want to wait in line to use the correct machine (there are like 12 of them lined up in a row, each set for specific ranges of carat weight) and I was (disgusted) like "you''ve GOT to be KIDDING me!"

and I''m NOT saying that the AGS would do this because I''ve seen their operation and they seem (a lot) more on the ball than that, but I am saying that if there is an extreme difference, that use of the wrong lens / platform combination is a possible explanation.

 

[Laila619]

Todd,

By quite a bit, here is what was different: the total depth was off 1 %, the crown angles were steeper on the Sarin than on the cert by .3 - .6 degrees, the mm measurements of the stone were smaller on the Sarin, the table was off 1 %, the girdle was thicker on the Sarin than on the cert, and the lower girdle facets were off 1 %.

It also changed the HCA from ex/ex/ex to vg/vg/vg once I plugged in the new numbers.

 

[Todd Gray]

Date: 9/15/2009 1:03:32 PM
Author: Laila619
Todd,
By quite a bit, here is what was different: the total depth was off 1 %, the crown angles were steeper on the Sarin than on the cert by .3 - .6 degrees, the mm measurements of the stone were smaller on the Sarin, the table was off 1 %, the girdle was thicker on the Sarin than on the cert, and the lower girdle facets were off 1 %.

It also changed the HCA from ex/ex/ex to vg/vg/vg once I plugged in the new numbers.

Personally, I''d re-run the Sarin. Is the stone still loose?

 

[stone-cold11]

depth difference is too much I think. Since depth is just a simple % of the depth to the diameter of the stone, they should not have much difference.