GIA/AGS and Sarin

[ib40.5]

Hi folks,
Does the GIA- GTL use direct measurement (i.e. mm gauge) when grading diamonds, or do they use a Sarin type machine? How about AGS? I ask because I obtained different table percentages and girdle thickness by using my local B&M''s sarin. Can this machine be calibrated? Thanks.

 

[denverappraiser]

Both labs are using Sarin type equipment.

These machines aren't always in identical callibration.

Neil Beaty, GG ISA
Independent Appraisals in Denver

 

[Garry H (Cut Nut)]

I believe all labs currently use Sarin for all mm's measurements and proportions.

But they will likely use the correct magnification and better callibrated and maintained scanners than most dealers etc.

If you scan a 5mm diamond in a window that takes up to a 20mm diamond - then you only use 1/4 of the machines capacity.

 

[niceice]

----------------
On 10/22/2004 2:55:07 AM Garry H (Cut Nut) wrote:


But they will likely use the correct magnification and better callibrated and maintained scanners than most dealers etc.

If you scan a 5mm diamond in a window that takes up to a 20mm diamond - then you only use 1/4 of the machines capacity.

----------------

You would think, but often our very well maintained and calibrated unit gets results completely different than what is stated on the lab reports, this is particularly true with GIA graded diamonds. We were speaking with one of the reps from Sarin about this and he indicated that he has been standing in the GIA Laboratory discussing some of the "calibration problems" that they were having with their Sarin when one of the technicians walked up to a machine, dropped a stone on it of the wrong size for the lens set-up and scanned a stone... "And there is your problem" he pointed out to the Lab Director

Like you said Garry, if you scan a 5 mm diamond on a window that takes a 20 mm diamond, you're going to get the wrong results! This is not a problem that is restricted to the GIA, we've had it happen with several of the major gemological laboratories and the problem is often resolved to our satisfaction when we return the diamond to the lab with a copy of our own proportions analysis - our machine is calibrated using a set of three master stones at least once per week. Other responsible dealers do the same with their machines...

None of the technology is perfect. A speck of dust can throw all of the measurements off. If the scanning platform on the machine is not kept clean, if the lid on the machine is not kept closed when it is not in use, if the diamond was not cleaned before it was scanned, the results will be off - even from the presence of a fingerprint! And the machines have a natural variance, so the results can be slightly different every time a diamond is scanned, even if the diamond is not removed from the machine or moved around on the platform between scans. Set the diamond down, press the button to scan the diamond, get one set of results. Press the button again, get similar, but slightly different results. So it goes with the Sarin / OGI animal.

It is our understanding that the AGS Laboratory just bought a couple of the

 

[niceice]

----------------
On 10/22/2004 2:55:07 AM Garry H (Cut Nut) wrote:


But they will likely use the correct magnification and better callibrated and maintained scanners than most dealers etc.

If you scan a 5mm diamond in a window that takes up to a 20mm diamond - then you only use 1/4 of the machines capacity.

----------------

You would think, but often our very well maintained and calibrated unit gets results completely different than what is stated on the lab reports, this is particularly true with GIA graded diamonds. We were speaking with one of the reps from Sarin about this and he indicated that he has been standing in the GIA Laboratory discussing some of the "calibration problems" that they were having with their Sarin when one of the technicians walked up to a machine, dropped a stone on it of the wrong size for the lens set-up and scanned a stone... "And there is your problem" he pointed out to the Lab Director

Like you said Garry, if you scan a 5 mm diamond on a window that takes a 20 mm diamond, you're going to get the wrong results! This is not a problem that is restricted to the GIA, we've had it happen with several of the major gemological laboratories and the problem is often resolved to our satisfaction when we return the diamond to the lab with a copy of our own proportions analysis - our machine is calibrated using a set of three master stones at least once per week. Other responsible dealers do the same with their machines...

None of the technology is perfect. A speck of dust can throw all of the measurements off. If the scanning platform on the machine is not kept clean, if the lid on the machine is not kept closed when it is not in use, if the diamond was not cleaned before it was scanned, the results will be off - even from the presence of a fingerprint! And the machines have a natural variance, so the results can be slightly different every time a diamond is scanned, even if the diamond is not removed from the machine or moved around on the platform between scans. Set the diamond down, press the button to scan the diamond, get one set of results. Press the button again, get similar, but slightly different results. So it goes with the Sarin / OGI animal.

It is our understanding that the AGS Laboratory just bought a couple of the
Helium machines from Octonus and needless to say that we are waiting to see how the machine works for them on a regular basis... By "just" we mean "just" so it is too soon to make a decision...

The problem with the variance in results is one of the reasons we urge people to purchase their diamonds on-line from reputable dealers who physically examine the diamonds that they sell. If you could see the dust piled up on some of the Sarin / OGI machines on the desks of the diamond cutters in their dusty old offices, you wouldn't trust the results!