sarin report - girdle question

[buttercup]

On almost every Sarin or Megascope report I've seen, there seems to conflicting information about the girdle measurement. There is the list of information that contains the range of the table, girdle, crown, and pavilion...and then there is a diagram illustrating these measurements. The girdle measurements seems to differ between these two areas.
For example, take this one from another thread on this board.

The girdle % measurement on the left says 0.7-1.4, while the diagram says 1.9%.

Or this one...

The girdle measurement is listed as 0.9-1.5% but the diagram shows 2.7% Why the different numbers? Which one should I go by?

 

[Garry H (Cut Nut)]

The girdle is a wavy line and is measured at the thinnest point - the .7 to 1.4 is the variation between the girdle at the thinnest point (and is ok unless the stone is say under 1/3rd of ct).
The bigger # is the girdle at the thickest part and is less relevant.

 

[buttercup]

thanks garry!

 

[pyramid]

QUOITE FROM ABOVE:
The girdle is a wavy line and is measured at the thinnest point - the .7 to 1.4 is the variation between the girdle at the thinnest point (and is ok unless the stone is say under 1/3rd of ct).
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This is an old post what would happen if the stone is say under 1/3rd carat, what would the thinnest percent need to be. What if the stone is say 0.18 carats?

 

[Rhino]

Just to clarify even more specifically on the above.

On Sarin Reports and OGI Reports as given in your example the girdle thickness as stated in the measurements (NOT on the graph) are the measurements of the girdle on the perimeter of the diamond known as the "valley". The valley is considered the parts of the girdle that fall between the bezel (or kite facets) and the halves (where upper and lower girdle facets meet).

Here is an OGI Report on a 1.04ct stone pointing out what you already have. The girdle thickness is listed is .8 - 1.5% which is the girdle thickness of the diamond in the "valley" portion of the girdle. The measurement of 3.0% that is listed in graph is the average girdle thickness of the diamond at the bezel or kite facet area.

The next graphic will help put this into better perspective.

 

[Rhino]

Here is a full girdle report on the same stone. In this graphic you can see the girdle measurements as it goes all the way around the stone.

Note the 3 seperate average girdle measurements as indicated in the red, black and blue. Note the average girdle thickness at the bezels. There's your answer.

Hope that helps.

Peace,
Rhino

 

[pyramid]

QUOITE FROM ABOVE:
The girdle is a wavy line and is measured at the thinnest point - the .7 to 1.4 is the variation between the girdle at the thinnest point (and is ok unless the stone is say under 1/3rd of ct).
-----


This is an old post what would happen if the stone is say under 1/3rd carat. What percentages would be normal for a stone say 0.18 carats?

 

[Garry H (Cut Nut)]

A better way to quote girdle thickness would be in mm's.

Marty Haske has shown somewhere on his website that the GIA more or less does this. They use their brains sometimes

.18 = about 3.8mm and .1mm = 2.7%
1ct .1mm = about 1.5%

Both are nice mesurements.
Make sense?

 

[pyramid]

That you CutNut. I think I understand but would a 2.7% girdle not be too thick on a little 0.18 sidestone? I know you said nice measurements just thought is would be 1% or so.

 

[pyramid]

Would that percentage and also less (down to what) be okay on a 0.18 carat diamond?

 

[Garry H (Cut Nut)]

A person with good eye sight should be able to see the girdle.

No one that is sane puts a .18ct diamond on Sarin. If you ask people to do this they might (rightly) double the price.

 

[pyramid]

No one that is sane puts a .18ct diamond on Sarin. If you ask people to do this they might (rightly) double the price

Yes, I didn't think they did it on a Sarin. I suppose there is no way to find out about small diamonds then other than looking to see if one can see the girdle. Do jewellers measure them with something else or how do they accept ones for their stock?


18 = about 3.8mm and .1mm = 2.7%

Would that not be an awful heavy girdle at 2.7% on such a small stone. Is that the normal size of girdles on this size?

 

[pyramid]

Assuming that it can be measured, what would be the thinnest measurement in millimetre or fraction of a millimetre that would be okay on a 0.18 mm diamond? Would all melee use the same measurement?

 

[Garry H (Cut Nut)]

Pyramid hit the "clear default to anal"

 

[pyramid]

Okay, so you are saying CutNut that a 2.7% girdle is the right way to go!

 

[pyramid]

A better way to quote girdle thickness would be in mm's.

Marty Haske has shown somewhere on his website that the GIA more or less does this. They use their brains sometimes

.18 = about 3.8mm and .1mm = 2.7%
1ct .1mm = about 1.5%

Both are nice mesurements.
Make sense?



The HCA and Ideal-Scope Cut Quality Crusader!


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Why does 0.06% show as slightly thick (the pink line) on a 3.8mm diameter diamond on the following chart, so what would 2.7% be?:

2.7% equates to slightly thick on AGS
0.06% equates to slightly thick on GIA mm measurements

Why is this different, what are the different items they are measuring.

http://www.gis.net/~adamas/cut.html#girdle


OH, just noticed it is a quadratic equation understand difference now!

 

[pyramid]

GIA
Extremely thin 0.00 - 0.08 mm
Very thin 0.08 - 0.12 mm
Thin 0.12 - 0.15 mm
Medium 0.15 - 0.20 mm
Slightly thick 0.20 - 0.23 mm
Thick 0.23 - 0.33 mm
Very thick 0.33 - 0.40 mm
Extremely Thick: greater than 0.40 millimeters

AGS
Very thin 0.091 - 0.50%
Thin 0.51 - 1.2%
Medium 1.21 - 1.7%
Slightly thick 1.71 - 2.95%
Thick 2.96 - 4.2%
Very thick 4.21 - 5.7%
Extremely Thick: >= 5.71 %

A 0.1mm girdle on a 1 carat 6.5mm stone is 1.5% which is AGS Medium
A 0.1mm girdle on a 1 carat 6.5mm stone is GIA Very Thin

Why is there such a difference does GIA not approve of AGS Very Thin and Thin grades or do they measure the girdle differently e.g. valleys and bezel/kite area?