Template of Diamond Info

[pricescope]

David Atlas (aka Oldminer) posted a template of what you need to be told about a diamond, especially one you are not looking at, but attempting to purchase sight unseen:
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Rounds:
measurements: min and max diameter and depth in mm
table%
crown angle avg or every crown angle (slight overkill)
crown height%
pavilion angle or pavilion%
All angles are great but rarely given
Girdle thickness: maximum and minimum.
Total depth% may be calculated or given to you, but it is important.
Polish
Symmetry
The name of the Laboratory that performed the grading should be known and considered.

Fancy shapes:
Pretty much the same things
Measurements so you can determine squareness or L:W ratio
Table%
Crown Height% The angles mean little on fancy shapes.
Girdle thickness: Max and Min as well as the location and amount of very thin girdle areas.
Total Depth% which may be given or readily calculated.
Polish
Symmetry
The name of the Laboratory that performed the grading should be known and considered.

In-House grading may be very accurate, but who knows?

If you can obtain all these facts, you will be best able to make some valuable judgements on the diamond. Without some of these facts, there is much more degree of error involved in any advice you may receive.

David S. Atlas
GG(GIA), ASG
Sr. Mbr. NAJA

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[Garry H (Cut Nut)]

Well done Dave

But please people - demand ANGLES for round stones if you want to use HCA!!!
%'s are next to useless - light refracts and reflects according to angles - and things like culets etc are very poorly measured by proportion devices - the result is pavilion angles are usually understated by 0.2 to 0.4 degrees and this means your HCA score can be out by a whooping 1.0!!!!

Hands up all those who would be prepared to pay for a system that helps you narrow down the best stones so that when you make a request, you are more likely to find a stone (1 in 10) that will have the data that you want.

 

[niceice]

Any dealer actually in possession of the diamond being considered with a Sarin or OGI machine can provide full facet-by-facet evaluation of the diamond, we can provide it for any diamond in our inventory or any diamond which we bring in on behalf of a client for evaluation. The problem is that so many of the internet dealers don't bother to personally evaluate the diamonds that they offer for sale - they drop ship direct from their suppliers and so many of the suppliers don't even have Sarin or OGI machines... They run the stones down the hall to another dealer and who knows the last time the machine was calibrated or whether the diamond was clean when it was measured... So many of the "reports" we see don't even come close to the measurements displayed on the lab reports... The lab reports indicates that the diamond has a total depth of 60.3% and the "report" says it is 60.9% but here the client is wanting us to compare the diamond for them site unseen to ours (based solely on the numbers) because "it scored well on the HCA" - well, we have to ask - if the total depth is off, what makes people think the rest of the measurements are accurate? Hey, we can accept 60.2 or 60.4% but to be off 5/10th's of a percent is a good indicator that the rest of the measurements may be off as well... We see this so much that we've stopped buying diamonds from our suppliers based on their Sarin / OGI measurements - we make them send us the diamonds to be measured on our own machine and we send them back everything that we don't like... So please, pay attention to the measurements being produced by the machine in relationship with what is given for the diamond by the lab for total depth and table... It is a good indicator of whether the measurements for the crown angle and pavilion angle are accurate. If you want an accurate HCA score you need to begin with accurate measurements!

 

[niceice]

We thought it might be beneficial to show what the full facet by facet report for the crown and pavilion angles looks like... It is not the little sticker that is usually seen on the lab reports, it provides a facet-by-facet comparison and looks like this:
http://www.niceice.com/certcopies/gia12332890/gia12332890msr.jpg

 

[Garry H (Cut Nut)]

This is a better report if you wish to be really anal

It shows the twist between top and bottom facet alignment.
i have cut a bit off the bottom that displays upper girdle star ratio and some other bits. The new Sarin DiaVision report shows pavilion lower girdle length also.

There are some stones listed on Rapnet with all this data that is avaiable to any dealer.