Of all the questions we get on diamonds there are many covering this aspect of the stone (the girdle) which I will attempt to answer as we get em, one at a time. Here are some of the more commonly asked questions.
The case of the warped diamond. Is it really warped?
Here is a recent email from a potential client named Eric.
I had a couple questions.
On your Sarin report, there looks to be conflicting information. The Girdle max is stated as 1.68% however, the diagram says 2.7%?? Not sure which is correct. However, I believe it is the 2.7%. Also, When I add up the Girdle depth (1.68) + Crown Height percent (15.1) + the Pavil. Depth 43% = 59.78. This is over 1% higher than the total depth. So it sounds like the stone is warped or there is some discrepancy.. Can you please explain. In terms of looks it might not matter, but in terms of price it definitely matters.
For our readers the diamond in question is this one. http://www.goodoldgold.com/1_34ct_g_vvs2_h&a.htm. If you click on the Sarin report you'll see the information Eric is referring to.
Actually in terms of price it does not matter since this diamond is not warped and neither can it warp. Only malleable objects can warp (ie. wood, plastic, perhaps the brain that gave you this warped information ;) etc.)! That diamond happens to be one of the most precision cut diamonds on the planet with variances no greater than .4%/°.
Here is that diamonds min/max report.
As we can see from the above results it's crown angles have only a .2° variance. It's pavilion angles a .4° variance and it's table a .2% variance. How can anyone in the world conclude that such a stone is warped? Here's how.
There is a certain diamond "guru" selling a book available on the net that states... If the average girdle thickness + the average crown height + the average pavilion depth does not add up to the total depth then the diamond is "warped".
So if we take that formula and apply it to the above diamond we have
15.1% crown height
+1.68% max girdle thickness
+43% pavilion depth
59.78% total depth
Actual total depth % is 60.9%
Over 1% discrepancy. So either the diamond is supposedly warped or there is a grave misunderstanding concerning the information being published by the "guru". First of all the common misunderstanding lies in the fact that there are 3 areas around the girdle that are measured. Those areas are:
the bezel and
These 2 graphics show what identifies the girdle thickness at it's respective points.
When you see the girdle thickness as listed on AGS Reports, Sarin Reports or OGI Reports the girdle thickness listed in the description is the girdle thickness in the Valley. The valleys lie between the bezel and the halves and are generally always the thinnest points on the girdle. Knowing whether these areas are too thin or too thick can affect both the cut grade and the potential durability of the diamond. If the valley is too thin the diamond can is susceptible to chipping.
Here is an example from an AGS Report stating the diamonds girdle thickness. In the valleys this diamonds girdle thickness ranges from 1.3-1.9%. Anything under .5% or over 3% is not considered to be ideal.
Here is a MegaScope report showing this data as listed in the details column. Note the girdle thickness states 1.3 - 1.9% with an average of 1.6% girdle thickness. THIS IS THE MIN/MAX/AVG girdle thickness in the VALLEYS. Now note in the graph on the right it says 3.2%. THAT IS THE AVERAGE GIRDLE THICKNESS AT THE BEZELS. If a person is even going to come close to making any kind of addition to crown height, pavilion depth and girdle thickness the measurement they would need to use is the AVERAGE GIRDLE THICKNESS AT THE BEZEL ... NOT THE VALLEY. So if all you had was an AGS Report forget about trying to get that.
Now add up your average crown height, pavilion depth and AVERAGE GIRDLE BEZEL THICKNESS.
15.2 crown height
+ 3.2% bezel girdle thickness
+ 42.6% average pavilion depth
61.0% total depth %
Actual total depth % is exactly 61.0%
Here is this same diamonds full girdle report listing the girdle thickness all the way around the stone. This graphic is self explanatory. Note that the girdle thickness at the bezels and halves are always thicker than they are at the Valley.