Certificates and Accuracy?

[canadiangrrl]

Hi everyone,

I am wondering if someone can tell me how often AGS certificates are accurate, specifically in regards to crown and pavillion angles.

I''ve noticed while looking online for a diamond that Sarin and Megascope results on angles/percentages sometimes differ from what is printed on the certificate. I am at a loss to understand why this is - and, I have found that even tiny variances can affect the stone''s results on the HCA.

This is frustrating.

Can anyone explain why this happens? Does AGS not use the same equipment as diamond vendors to determine a stone''s measurements? And - my original question - how often are certificates (specifically AGS) "off" on this information? Thanks in advance.

 

[niceice]

The measurements provided on the AGS Diamond Quality Document are much more likely to be more accurate than the numbers provided by dealer Sarin or OGI computerized proportions analysis simply because the labs use a more precise version of the equipment. Let's face it, the labs have more operating capital to work with and thus they can afford to plunk down $65K on a machine that does nothing but measure diamonds... This is not to say that accurate measurements can not be obtained by dealers using the less expensive equipment, we calibrate our machine weekly using a master stone and frequently obtain measurements quite close to those indicated on the lab reports... We also clean the lenses on our machine weekly and sometimes more often depending on how many diamonds are being measured because dust and lint can affect the readings... We often get different measurements than the cutters provided us with prior to sending the diamonds to us for physical evaluation and thus we often end up rejecting diamonds which displayed one set of proportions on the cutter's machine and a different set of proportions on our machine... We suppose that what we're trying to say is that the proportions analysis is only as accurate as how well a machine has been calibrated and maintained, we would be inclined to trust the measurements obtained by the lab over those obtained by a dealer.

By the way, those aren't "certificates" they are lab reports... The labs issue reports indicating their opinion of the characteristics of the diamond at the time of grading, they don't "certify" anything.

 

[canadiangrrl]

Hi Robin & Todd,

Thanks for clearing up my confusion.

Now that I understand the lab process/equipment a little better, it makes perfect sense that the crown/pavillion info supplied by AGS on the document would lean towards accuracy more often than not.