Sarin vs. AGS measurements

[avalpert]

The more diamonds I look at the more discrepencies I see. When using the numbers in HCA or other calculators the differences between the measurements make huge differences. Which are more reliable, AGS'' reported numbers or Sarin report numbers? Should I not be using hte average Sarin number?

 

[Blueman33]

The AGS report and Sarin are both the same measurement and are both inconsistent.

The same stone ran through the same machine can give different measures. Yeah, i know we can locate a golf ball from a GPS, measure a race car performance in 1/1000 of a second, and split the atom..........but so far we don''t have a consistent way to measure angles on a stone

 

[avalpert]

Is that becuase the Sarin machine takes an average of a selection of facets or because of the impreciseness of the measuring itself? I ask because if it is an average problem then it may be more accuratre to average multiple readings, if it is a measurement issue than I''m not sure what would be the right answer.

 

[JohnQuixote]

Sarin's published accuracy is ± 0.02 mm linear and ± 0.2 degrees angular, so there will be slight discrepancies sometimes. Our usual policy is to go with the numbers on the lab report.

Sarin continues to develop their technology and is releasing new software soon.

Blueman is so right re: what we can and can't yet do, techno-wise. There is a machine by Octonus - a Helium scanner - which is pushing everyone forward. It has not yet been distributed globally.

 

[RockDoc]

Date: 6/19/2005 2:32:35 PM
Author: Blueman33
The AGS report and Sarin are both the same measurement and are both inconsistent.

The same stone ran through the same machine can give different measures. Yeah, i know we can locate a golf ball from a GPS, measure a race car performance in 1/1000 of a second, and split the atom..........but so far we don''t have a consistent way to measure angles on a stone

The tolerances on the Sarin is very small, so are the variances from machine to machine.

2 tenths of a degree of 360 degrees ?
2 hundreths of a mm. of the average diameter?

Aren''t you expecting a bit too much.

Rockdoc

 

[Rhino]

If there is a discrepance between Sarin and AGS results there is a way to be able to distinguish which is more correct. I''m at home so i can''t demonstrate this just now but when I get up to the store on Tuesday I''ll expound further.

 

[avalpert]

Might be expecting too much but that .2 degrees is the difference in the HCA between ex,vg,vg,vg and ex,ex,ex,ex, so if the other tools aviable are that sensitive to the rate of error it seems to matter.

 

[JohnQuixote]

Avalpert, actually the HCA should be used as a tool for rejection, not for splitting hairs between known performers. Once you've established that the proportions are solid, the use of ideal-scope images or other direct measures of performance is advisable.

 

[avalpert]

John,

I understand but take for example this:
Depth 60.7
Table 55.4
Crown 34.6
Pavilion 40.9

Score a 1.5 on the HCA

but if you switch the pavilion to 41.1 you score a 2.4 and would be led to reject it. But that is within the margin of error of Sarin and is a real difference I saw between an AGS report and a Sarin report.

 

[Paul-Antwerp]

There are different versions of Sarins and I think that the more expensive Sarin you have, the less deviation one will encounter.

You can bet that a lab has the most sophisticated machine, while a retailer probably will have the most simple device. This is absolutely normal.

In that case, if there are discrepancies, one can better rely on the lab-report.

Live long,

 

[JohnQuixote]

Date: 6/20/2005 3:10:40 PM
Author: avalpert
John,

I understand but take for example this:
Depth 60.7
Table 55.4
Crown 34.6
Pavilion 40.9

Score a 1.5 on the HCA

but if you switch the pavilion to 41.1 you score a 2.4 and would be led to reject it. But that is within the margin of error of Sarin and is a real difference I saw between an AGS report and a Sarin report.

Avalpert,

Great example. In this case we recommend going with the number on the grading report for reasons Paul alluded to.

If you want to go another layer deep, consider that those numbers you're plugging into the HCA are all averages that don't show variance (recently discussed in this post from another thread). I'm not trying to throw wooden shoes into the machinery

I still think HCA has use. But this is why I like actual imagery - ideal-scope/ASET/etc. - when evaluating sight-unseen.

 

[Garry H (Cut Nut)]

This example clearly shows why HCA should be used as part of your narrowing down process to find stones that can be further examined with ideal-scope, independant appraiser, ASET scope or any other method you choose.

HCA should not be used for selection.
It should be used to reject stones.

If you had rejected a good stone that would be sad - but if the vendor told you that the stone was a keeper and has an HCA of 2.4 - then it should not hurt you to consider the stone. In that case I would simply ask them to send an ideal-scope photo.